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V˙O2 Kinetics and Performance in Soccer Players after Intense Training and Inactivity
Abstract
The study's purpose was to examine the effects of a short-term period with intensified training or training cessation of trained soccer players on VO(2) kinetics at 75% maximal aerobic speed, oxidative enzymes, and performance in repeated high-intensity exercise.
After the last match of the season, 18 elite soccer players were, for a 2-wk period, assigned to a high-intensity training group (n = 7) performing 10 training sessions mainly consisting of aerobic high-intensity training (8 × 2 min) and speed endurance training (10-12 × 30-s sprints) or a training cessation group (n = 11) that refrained from training.
For the training cessation group, VO(2) kinetics became slower (P < 0.05) with a larger time constant (τ = 21.5 ± 2.9 vs 23.8 ± 3.2 s (mean ± SD, before vs after)) and a larger mean response time (time delay + τ = 45.0 ± 1.8 vs 46.8 ± 2.2 s). The amount of muscle pyruvate dehydrogenase (17%, P < 0.01) and maximal activity of citrate synthase (12%) and 3-hydroxyacyl-CoA (18%, P < 0.05) were lowered. In addition, the fraction of slow twitch fibers (56% ± 18% vs 47% ± 15%, P < 0.05), Yo-Yo intermittent recovery level 2 test (845 ± 160 vs 654 ± 99 m), and the repeated sprint performance (33.41 ± 0.96 vs 34.11 ± 0.92 s, P < 0.01) were reduced. For the high-intensity training group, running economy was improved (P < 0.05), and the amount of pyruvate dehydrogenase (17%) and repeated sprint performance (33.44 ± 1.17 vs 32.81 ± 1.01 s) were enhanced (P < 0.05).
Inactivity slows VO(2) kinetics in association with a reduction of muscle oxidative capacity and repeated high-intensity running performance. In addition, intensified training of already well-trained athletes can improve mechanical efficiency and repeated sprint performance.
... Although the literature that examines how the training process produces physical adaptations in CP footballers is scarce, the training process in CP athletes seems to be crucial to maintain their physical fitness values as the CP disability causes an early decline in motor function, and poor coordination and muscle weakness are the main limitations of CP population (Cans, 2000), as well as of CP football population (Reina et al., 2016) who have lower levels of impairment compared to general population with CP (Palisano et al., 2008). For CP football players, who follow systematic training processes, the effects of a detraining period (e.g., a lockdown) are not known, but the same as in regular football, negative consequences in their physical fitness can be expected (Christensen et al., 2011;Joo, 2018). Due to these expectations of a possible physical fitness detriment during the lockdown period, the main aim of the athletes worldwide during this period was to maintain their general fitness and health (Washif et al., 2021). ...
... The CP football players' physical fitness in the 5, 10 and 20-m sprint, change of direction and dribbling was maintained after the self-training program of this study. A physical fitness decrement after a detraining period has been widely studied in football (Christensen et al., 2011;Joo, 2018;Koundourakis et al., 2014), but in this study, the "detraining" period was a mandatory lockdown in which the technical staff tried to maintain the players' physical fitness through a self-training at home. A previous study by Nakamura et al. (2012) showed no differences in football players' physical fitness after a detraining period between players who did not train, players who performed an endurance training program twice a week and players who performed a plyometric program twice a week (Nakamura et al., 2012). ...
... A previous study by Nakamura et al. (2012) showed no differences in football players' physical fitness after a detraining period between players who did not train, players who performed an endurance training program twice a week and players who performed a plyometric program twice a week (Nakamura et al., 2012). In contrast, Christensen et al. (2011) showed physical fitness maintenance after a 2-week period in which football players performed a high-intensity training program while players who stopped their activity reduced their values in the same variables. However, we cannot compare our results with the mentioned study because in their training program, players performed football-specific tasks (i.e., small-sided games), which the participants of the present study were not allowed to carry out due to the mandatory lockdown. ...
Background The COVID-19 global pandemic caused a complete stop in sport participation which meant a detraining period for athletes. High-level athletes had to train at home guided by their coaches and conditioning trainers in an effort to maintain their physical fitness. The aim of maintaining the training adaptations and physical fitness during the COVID-19 mandatory lockdown was especially important for CP athletes, in which the detraining period was expected to cause early declines in motor function, poor coordination and muscle weakness due to their disability. Methods The present study assessed the effect of a guided self-training program on international CP football players’ physical fitness during the COVID-19 mandatory lockdown. Fifteen CP football players from the Spanish National Team participated in the study. An experimental design with a pre- (T1) and a post-intervention (T2) assessment was carried out, with a 12-week period of players’ self-training (divided in two periods of 6 weeks) which combined strength and endurance training. Physical performance assessment consisted in the free countermovement jump (CMJ), 5, 10 and 20-m sprint, the modified agility T-test (MAT) and a dribbling test. The Kruskal–Wallis test was used for between-group comparisons, while the Student’s paired t test or the Fisher Pitman permutation test, based on the normality of the data, were used for within-group comparisons. Results The results showed no differences between sport classes (FT1, FT2 and FT3) in physical fitness change after the training program (Chi2 = 0.16 to 1.73; p = 0.42 to 0.92). Within-group comparisons showed an increase of jump height in the CMJ (4.19 cm [2.46, 5.93]; p < 0.001) and a maintenance of the 5, 10 and 20-m sprint, MAT and dribbling ability (
... Movement economy has been investigated extensively in endurance athletes, such as runners, cyclists, and triathletes [9,10] indicating a strong ability to predict athletic performance [11,12]. Conversely, consideration of ME in soccer players, despite the prolonged duration of a soccer game, is much scarcer [13][14][15][16][17][18][19], and has yet to be reviewed. Within the current literature on ME in soccer players [13][14][15][16][17][18][19], there is limited data, along with ongoing debates regarding the poor specificity of common ME assessment to team-sports [14,20]. ...
... Conversely, consideration of ME in soccer players, despite the prolonged duration of a soccer game, is much scarcer [13][14][15][16][17][18][19], and has yet to be reviewed. Within the current literature on ME in soccer players [13][14][15][16][17][18][19], there is limited data, along with ongoing debates regarding the poor specificity of common ME assessment to team-sports [14,20]. This article aims to review and summarize the current scientific data of ME in soccer players, while also providing a critique of current methods of assessment and data produced to date, in order to identify ways in which use of ME can be advanced in soccer contexts. ...
... Few studies have provided measures of ME in soccer players in an attempt to investigate the discriminant ability of this parameter [16,18,19,22,28] or evaluate changes following training interventions [13][14][15]17,26]. ...
Soccer is an intermittent team-sport, where performance is determined by a myriad of psychological, technical, tactical, and physical factors. Among the physical factors, endurance appears to play a key role into counteracting the fatigue-related reduction in running performance observed during soccer matches. One physiological determinant of endurance is movement economy, which represents the aerobic energy cost to exercise at a given submaximal velocity. While the role of movement economy has been extensively examined in endurance athletes, it has received little attention in soccer players, but may be an important factor, given the prolonged demands of match play. For this reason, the current review discusses the nature, impact, and trainability of movement economy specific to soccer players. A summary of current knowledge and limitations of movement economy in soccer is provided, with an insight into future research directions, to make this important parameter more valuable when assessing and training soccer players’ running performance.
... In this sense, it has been highlighted the importance that off-season training has to avoid soccer players' deconditioning (6). The effects of short-term detraining on exercise performance during this period have previously been studied (7,29). These studies have shown a significant reduction on RSA performance after a 2-week training cessation in well-trained soccer players (7,29). ...
... The effects of short-term detraining on exercise performance during this period have previously been studied (7,29). These studies have shown a significant reduction on RSA performance after a 2-week training cessation in well-trained soccer players (7,29). However, these studies have reported that a short-term intensified training program at the end of the competitive season might counteract this negative effect (7,29). ...
... These studies have shown a significant reduction on RSA performance after a 2-week training cessation in well-trained soccer players (7,29). However, these studies have reported that a short-term intensified training program at the end of the competitive season might counteract this negative effect (7,29). To the best of our knowledge, no study has analyzed the effects of training cessation during the regular season, nor has this been performed with youth soccer players. ...
The aim of this study was to analyse the effects of two short-term training programs to prevent the negative effect of detraining on repeated sprint ability (RSA) performance. The study was carried out during a 2-wk midseason break without official matches. Forty-five youth soccer players (17.7 ± 0.8 yr, 175.4 ± 5.5 cm and 67.2 ± 5.1 kg) were split into three groups during the intervention period: inactivity group (IN; N = 16), generic high-intensity training group (GG; N = 15) and specific training group (SG; N = 14). IN was instructed to avoid performing physical activity during the 2-wk training intervention. However, GG and SG performed 8 training sessions. GG performed a generic aerobic interval training consisting of 4 repetitions of 4-min of exercise at 90-95% of maximal heart rate. SG performed a specific conditioning through small-sided games (4 vs. 4, 4 × 4-min) and repeated sprints (6 × 30-m). Testing sessions included a RSA test and a Yo-Yo intermittent recovery test level 1 (YYIR1). RSA performance only improved after the training intervention in SG (~2%, P < 0.01, ηp2= 0.23 - 0.25). Both GG and IN declined their performance in post-test (~2%, P < 0.01, ηp2= 0.19 - 0.22). No significant effect, group × time, was analysed for YYIR1 performance. This study suggests that only specific training, based on small-sided games and repeated sprints, leads to short-term improvements on RSA performance in youth soccer players.
... Similarly, a 4-week periodized HIT program demonstrated greater power and enhanced on-ice performance in male collegiate ice hockey players compared with control intervention (29). However, with congested schedules, shorter block periodization such as shock microcycles may be a promising alternative to improve sport-specific performance in a short-term perspective (3,9,18,39). ...
... However, the absence of a control group precludes to draw strong conclusions regarding the interpretation of the results. In other team sports, such as soccer, a 2-week period including HIT (10 sessions consisting of 8 3 2 minutes aerobic high-intensity exercise) and speed endurance (10-12 3 30-second sprints) vs. a training cessation group improved work efficiency during submaximal running and repeated-sprint ability (RSA) performance in Danish second division male soccer players (9). Similarly, 12 sessions of HIT (4 3 4 minutes interval running on a dribbling track or as small-sided games) disseminated over a 2-week period largely improved RSA-related parameters and Yo-Yo intermittent recovery test level 2 (YYIR2) performance in soccer players (39). ...
... Several studies have shown that shock microcycles, including additional HIT sessions, provide a time-efficient way to enhance fitness level in intermittent, high-intensity sports (3,9,18,25,39). To the best of our knowledge, previous ice hockey studies focusing on block periodization used protocols of 4-to 6-week duration (29,33) with the exception of Kinnunen et al. (25) who used an HIT program of 2.5 weeks in elite female ice hockey players. In this latter study, the authors showed positive changes in maximal voluntary plantar flexor torque (111.6%), ...
Elite athletes face congested schedules with increased competition frequency and restricted time for training periods. Therefore, time is lacking to design long-term sport-specific block periodization. This study aimed to investigate the effects of adding a 14-day off-ice high-intensity training (HIT) shock microcycle to the usual training content of the pre-season preparation of high-level male ice hockey players' fitness. Fourteen players were randomly assigned to off-ice HIT (n = 7) or usual pre-season training (control, n = 7). For the HIT group, additional off-ice training content included 2 sessions of repeated-maximal resistance training, 2 sessions of repeated-sprint training, and 2 sessions of high-intensity intermittent training. Control group performed equal number of off-ice sessions using traditional strength and conditioning training. Off-ice Yo-Yo intermittent recovery test level 2 (YYIR2) and on-ice repeated-sprint ability test (RSA) were conducted before (pre-test) and 3 days after the intervention (post-test). Statistical significance was set at p < 0.05. Significant group × time interactions were found for off-ice YYIR2 performance (p < 0.05) and on-ice RSA-cumulated skating time (RSATT; p < 0.05). Compared with pre-test, off-ice YYIR2 distance covered significantly increased (from 708.6 ± 97.2 to 885.7 ± 118.7 m, p < 0.01; +25.8 ± 16.9%, p < 0.05) and on-ice RSATT significantly decreased (from 28.35 ± 0.87 to 28.14 ± 0.84 seconds; -1.7 ± 2.1%, both p < 0.05)] for HIT group. No significant pre-test to post-test changes were found for the control group (+2.7 ± 20.0% for YYIR2 and +0.9 ± 2.2% for RSATT). The implementation of a 14-day shock microcycle (including 6 HIT sessions) significantly improved fitness performance in high-level male ice hockey players. Such HIT block periodization offers a promising way to deal with congested schedules.
... Seven studies were conducted in professional players, three studies were conducted in semi-professional levels, and two in young/youth. Two of the included studies [43,44] applied an intense intervention consisting of five high-intensity sessions per week for two weeks. Both were included as OTP. ...
... The systematic review and meta-analysis revealed significant decreases in YYIRT (Level 1 and 2) distance after training cessation (− 5.2 to − 14.8%) but not after OTPs (Table 6; Fig. 4). The high-intensity nature of the OTP analyzed in this systematic review and meta-analysis [43,44,51] may have helped to avoid a detrimental effect on YYIRT performance. In fact, in several OTPs [43,44,51], meaningful improvements (3.4-6.1%) in YYIRT distance were observed. ...
... The high-intensity nature of the OTP analyzed in this systematic review and meta-analysis [43,44,51] may have helped to avoid a detrimental effect on YYIRT performance. In fact, in several OTPs [43,44,51], meaningful improvements (3.4-6.1%) in YYIRT distance were observed. Such OTPs applied three to five sessions week, with regimens of 3 × 12 min (80-90%HRmax) [51] and 8 × 2 min small-sided games/10-12/25-30 s all-out sprinting (~ 88% HRmax) [43,44]. ...
Background
The off-season period in soccer leads necessarily to changes in fitness status. However, there is a lack of systematization that allows identifying the magnitude of these changes in groups participating in off-season training programs compared with those subjected to training cessation.
Objective
This systematic review with meta-analysis was conducted to assess the effects of training cessation in off-season training programs on men soccer players’ body fat, maximal oxygen uptake (VO2max), yo–yo intermittent recovery test (YYIRT), vertical jump, sprinting time, and repeated-sprint ability.
Methods
To qualify for inclusion in the systematic review, studies must have included: (1) a detraining period of ≥ 2 weeks; (2) controlled trials or cohorts of healthy men soccer players with no restriction on age; and (3) a pre–post training cessation or off-season training programs measure of body fat (%), VO2max (mL kg⁻¹ min⁻¹), YYIRT performance (meters), vertical jump (height), sprinting (time), and repeated-sprint ability (total time).
Results
The electronic search yielded 563 articles, and 12 were subsequently included. Significant (all p < 0.05) detrimental training cessation effects were noted for body fat (ES = 0.26), VO2max (ES = − 1.48), YYIRT (ES = − 0.46), vertical jump (ES = − 0.81), and repeated-sprint ability (ES = 0.68). Similarly, significant (all p < 0.05) detrimental off-season training programs effects were noted for body fat (ES = 0.26), VO2max (ES = − 0.48), vertical jump (ES = − 0.51), and sprinting time (ES = 0.86). When training cessation and off-season training programs effects were compared, greater detrimental effects were noted after training cessation for VO2max (p = 0.002) and repeated-sprint ability (p < 0.001).
Conclusions
Detrimental effects on body composition and physical fitness were observed after both training cessation and off-season training programs. However, off-season training programs seem to ameliorate such detrimental effects on VO2max and repeated-sprint ability to some extent. The results presented here call for the implementation of more effective off-season training programs among male soccer players.
... Buchheit et al. [14] observed that short-term detraining after a competitive season improved levels of strength and cardiorespiratory fitness in Australian football players [14]. In contrast, several studies reported that physical fitness was reduced after a short-term detraining period in elite soccer players [5,15]. The reasons for these contrasting results are not apparent, but may be due to differences in sports and testing methods. ...
... The HAT group that continued to perform high-intensity aerobic exercise after the competitive season maintained their performance level in the Yo-Yo IR2 test over the five week treatment period. These results are supported by previous studies, which indicate that, after the last match of the season, 10 training sessions, consisting of high-intensity training for two weeks, do not change performance in the Yo-Yo IR2 test in elite soccer players [15]. However, Nakamura et al. [23] observed that running and plyometric training for two days per week for three weeks after the completion of a competitive season did not prevent the decrease in performance in The Yo-Yo IR2 test in elite soccer players. ...
... The reason of these differences in results is unclear but it probably related to exercise intensity. Indeed, there was no significant decrease in performance in the Yo-Yo IR2 test during off-season in the present study and Christensen et al. [15]'s study applying high-intensity exercise despite reduced exercise time compared to that in-season. Furthermore, the exercise intensity was higher than that in the previous study conducted by Nakamura et al. [23], which modulated endurance training (70-80% of HRmax). ...
Purpose
The aim of this study was to examine the effects of aerobic high-intensity training with reduced volume and training cessation on body composition and physical fitness after the end of season and the time required to recapture physical fitness with intensified retraining following two weeks of detraining in elite soccer players.
Method
Twenty male semi-professional soccer players participated in this study. The soccer players were assigned to either a group that completed high-intensity aerobic training (HAT, n = 10) or to a detraining and retraining group (DHAT, n = 10) for a 5-week period immediately after the end of the season. The first 2 weeks of the period, members of the HAT group performed high-intensity aerobic exercise (80–90% of HRmax, 12 min × 3, three times per week), whereas members of the DHAT group abstained from any physical activity. During the subsequent 3 weeks, members of both the HAT and DHAT groups completed high-intensity aerobic exercise. Exercise performance testing and body composition analysis were performed before; after 2 weeks of detraining; and at 1, 2 and 3 weeks of retraining.
Results
Intensified high-intensity training for 5 weeks maintained the performance in the Yo-Yo Intermittent Recovery level 2 test (Yo-Yo IR2) and repeated sprints at any time point (P > 0.05). However 2 weeks of detraining resulted in significant decreases in the performance on the Yo-Yo IR2 (P < 0.01) and repeated sprints test (P < 0.05). Performance on the Yo-Yo IR2 enhanced after 2 weeks of retraining and was maintained up to 3 weeks after retraining, with no significant differences between conditions (P > 0.05). In addition, repeated sprint performance markedly decreased after the detraining period (P < 0.05) and was continuously lower compared to the baseline at 2 weeks after retraining (P < 0.05). Furthermore, this value reached baseline level at the end of the experimental period (P > 0.05). There were no significant differences between conditions in body composition, performance of agility, or sprint ability throughout the 5-week experimental period (P > 0.05).
Conclusions
The present data suggest that short-term detraining after the competitive season can markedly decrease performances in the Yo-Yo IR2 test and repeated sprints. To return to a previous level of ability on the Yo-Yo IR2 and/or sprint test with retraining through high-intensity aerobic training after a period of detraining, a similar or longer period of retraining is required. However, the high-intensity training with reduced amount of training after competitive season can prevent reductions in physical fitness.
... Nonetheless, lactate threshold is likely to have been the main adaptation and contributor to changes in power output at fixed working intensities. With the exception of Christensen et al. (13), who found movement economy improved after an HIIT SM in soccer players, no other studies have observed improvements in movement economy within an intense HIIT period when directly assessing crosscountry skiers or cyclist (40,41). These findings, along with evidence that a high volume of training is the main stimulus for improving movement economy (7), might suggest that only specific athletic groups who are not commonly exposed to high volume of continuous activity, such as team sport athletes, might obtain further movement economy improvements after an HIIT SM . ...
... A possible reason why this study did not find a significant improvement in YYIR2 is that it implemented the HIIT SM immediately after the in-season period, with players already exhibiting high YYIR2 scores compared with those in the literature (5), suggesting that these players may have reached their peak performance already. In addition, this study (13) used methodology that included a postintervention test after 36 hours, and as discussed previously, a longer period of recovery may be necessary to accommodate adaptation and improve test scores after such an intense period of training (10 HIIT sessions over 14 days). Improvements in intermittent endurance performance observed in most of the other studies have been shown to occur by performing $5 HIIT sessions per week over periods ranging from 10 to 28 days (13,18,19,46) and also when HIIT activity involved small-sided game format (38). ...
... In addition, this study (13) used methodology that included a postintervention test after 36 hours, and as discussed previously, a longer period of recovery may be necessary to accommodate adaptation and improve test scores after such an intense period of training (10 HIIT sessions over 14 days). Improvements in intermittent endurance performance observed in most of the other studies have been shown to occur by performing $5 HIIT sessions per week over periods ranging from 10 to 28 days (13,18,19,46) and also when HIIT activity involved small-sided game format (38). However, it is worth noting that only 1 study included a control group performing regular training and HIIT (38); so, although the literature supports fast improvements in intermittent endurance performance after an HIIT SM compared with baseline, further research is required to verify the superiority of such a training strategy approach vs. traditional HIIT periodization on intermittent running performance tests. ...
Dolci, F, Kilding, AE, Chivers, P, Piggott, B, and Hart, NH. High-intensity interval training shock microcycle for enhancing sport performance: A brief review. J Strength Cond Res XX(X): 000-000, 2019-High-intensity interval training (HIIT) is a powerful strategy to develop athletes' fitness and enhance endurance performance. Traditional HIIT interventions involve multiple microcycles (7-10 days long) of 2-3 HIIT sessions each, which have been commonly supported to improve athletic performance after a minimum period of 6 weeks training. Regardless of the efficacy of such an approach, in recent years, a higher frequency of HIIT sessions within a unique microcycle, commonly referred to as an HIIT shock microcycle, has been proposed as an alternative HIIT periodization strategy to induce greater and more efficient endurance adaptation in athletes. This review article provides an insight into this new HIIT periodization strategy by discussing (1) HIIT shock microcycle format and design; (2) the sustainability of this training strategy; (3) effects on performance and physiological parameters of endurance; and (4) potential mechanisms for improvements. Evidence advocates the sustainability and effectiveness of HIIT shock microcycle in different athletes to improve intermittent and continuous running/cycling performance and suggests mitochondria biogenesis as the main acute physiological adaptation following this intervention.
... Although studies have elaborated on the effectiveness of intense intermittent training 17 and sprint training on performance in football players, 18,19 the mechanisms underlying performance enhancements remain poorly understood. 8 In a recent study, speed endurance training, consisting of 6-10 × 30-second all-out runs with 3-minute recovery, improved shuttle run performance and repeated sprint ability, as well as increased abundance of muscle proteins regulating ion transport and oxidative metabolism. ...
... The importance of using appropriate exercise: recovery ratio in augmenting training-induced enhancements in intense intermittent running performance has been highlighted by Iaia et al, showing greater enhancement in Yo-Yo IR2 performance in young professional football players when 6-8 × 20-second allout sprints were interspersed by 120 vs 40 seconds of recovery. 4,9 Intensified training with a concomitant reduction in training time enhances intense intermittent exercise performance in football players, 18,19 cyclists, 31 and runners. 32,33 Studies comparing intense intermittent training, differing in intensity and/or exercise and rest duration, show that training affects football-specific performance in a modality-dependent manner. ...
... 4,11 However, discrepancies exist, in that 2 weeks of intensified training consisting of 10-12 × 30 seconds sprints with 3-minute recovery enhanced repeated sprint ability but not Yo-Yo IR2 performance in sub-elite football players. 18,19 This discrepancy may be related to the relatively short intervention of only two weeks in players already accustomed to intense training or that the Yo-Yo IR2 has higher variability than the Yo-Yo IR1 (CV: 9.6% vs 4.9%). 24,34 Thus, it cannot be excluded that players in the latter studies improved their intermittent endurance performance. ...
This study investigated the in‐season effect of intensified training comparing the efficacy of duration‐matched intense intermittent exercise training with sprint interval training in increasing intermittent running performance, sprint ability, and muscle content of proteins related to ion handling and metabolism in football players. After the first two weeks in the season, 20 sub‐elite football players completed either 10 weeks of intense intermittent training using the 10‐20‐30 training concept (10‐20‐30, n=12) or sprint interval training (SIT, n=10; work/rest‐ratio: 6‐s/54‐s) three times weekly, with a ~20% reduction in weekly training time. Before and after the intervention, players performed a Yo‐Yo intermittent recovery test level 1 (Yo‐Yo IR1) and a 30‐m sprint test. Furthermore, players had a muscle biopsy taken from the vastus lateralis. Yo‐Yo IR1 performance increased by 330 m (95%CI: 178–482, P≤0.01) in 10‐20‐30, whereas no change was observed in SIT. Sprint time did not change in 10‐20‐30, but decreased by 0.04 s (95%CI: 0.00–0.09, P≤0.05) in SIT. Muscle content of HADHA (24%, P≤0.01), PDH‐E1α (40%, P≤0.01), complex I‐V of the electron transport chain (ETC) (51%, P≤0.01) and Na⁺,K⁺‐ATPase subunits α2 (33%, P≤0.05) and β1 (27%, P≤0.05) increased in 10‐20‐30, whereas content of DHPR (27%, P≤0.01) and complex I‐V of the ETC (31%, P≤0.05) increased in SIT. Intense intermittent training, combining short sprints and a high aerobic load, is superior to regular sprint interval training in increasing intense intermittent running performance during a Yo‐Yo IR1 test and muscle content of PDH‐E1α and HADHA in sub‐elite football players.
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... Previous studies have shown no effects of detraining after one week in the Yo-Yo Intermittent Recovery Test, level 2 [11]. However, significant (p < 0.01) detrimental effects of~5 and~22% after three days and 2-weeks of inactivity, respectively, was reported in a study [12]. Aside from the lack of agreement across studies, to our knowledge, no study has analyzed the effects of short-term detraining after an in-season break using the YYIR1 as a marker of performance. ...
... However, the impact of in-season unloading or detraining on RSA in soccer players remains unresolved. For instance, previous studies have analyzed the effects of 1- [11] or 2-week [12,18] off-season detraining periods on RSA (complete interruption of training), showing detrimental effects of~2% after two weeks for RSA total time and~3% for sprinting speed in the last five repetitions during a 20-m RSA test with a total of 10 repetitions [18]. However, RSA best time and RSA fatigue index were not affected after 2-weeks of inactivity [12,18]. ...
... For instance, previous studies have analyzed the effects of 1- [11] or 2-week [12,18] off-season detraining periods on RSA (complete interruption of training), showing detrimental effects of~2% after two weeks for RSA total time and~3% for sprinting speed in the last five repetitions during a 20-m RSA test with a total of 10 repetitions [18]. However, RSA best time and RSA fatigue index were not affected after 2-weeks of inactivity [12,18]. Possibly, the loading pattern (e.g., deliberate overload leading to overreaching) and the athlete's performance level previous to detraining might modulate such changes. ...
To better understand the detraining effects in soccer, the purpose of the study was to analyse if performance level of soccer players modulate repeated-sprint ability (RSA) and intermittent endurance changes during 2-weeks of detraining (i.e., in-season break). Seventeen professional and sixteen young elite soccer players of two different teams performed, before and after 2-weeks of detraining, the RSA test and the Yo-Yo Intermittent Recovery Test, level 1 (YYIR1). Before detraining, professional players perform better (p < 0.05) RSA best time (RSAbest) than young players. A decrease (p < 0.05) in RSAbest, RSA total time (RSAtotal) and mean time (RSAmean) performance was observed in both teams, without changes in RSA fatigue index (Sdec). No significant changes in distance covered during YYIR1 was observed in any team. Before detraining, faster players from both teams (FG) (following the median split technique, soccer players with RSAbest ≤ 3.95 s) performed better (p < 0.01) in RSAtotal, RSAmean and RSAbest, but worse (p < 0.01) in Sdec. Although FG and the slower players (SG, RSAbest > 3.95 s) showed a worse (p < 0.05) RSAtotal, RSAbest and RSAmean performance after detraining (ES = 1.5, 1.4 and 2.9; ES = 0.6, 1.2 and 0.6; for FG and SG, respectively), the deterioration was greater in the FG for RSAbest (p < 0.05) and RSAtotal (ES = 1.46). After detraining, FG improved (p < 0.05) Sdec performance. In conclusion, a 2-week in-season break (detraining) period induced a worse RSA, with no effect on intermittent endurance in professional and elite young soccer players, with greater detrimental effects on RSAtotal and RSAbest in FG. In addition, Sdec does not seem to be sensitive to changes in RSA after a 2-week in-season break.
... The training of footballers is also focused on this important aspect of faster removal of lactate by using lactate as a potential source of energy. A number of studies [15][16][17][18][19] have concluded that the level of aerobic efficiency determines the limits of the intensity of work. Oxygen insufficiency in working muscle is considered to be a regulatory factor of the metabolic changes that cause the exhaustion of muscle glycogen resources and the inhibition of the activity of glycolytic enzymes. ...
... Like real match play, an efficient physiological response in AST and CST depends on the appropriate training and running economy of the players. The dominant role of the aerobic energy system in football games has been suggested by many researchers [15,17]. High VO 2max allows athletes to run intermittently, with brief pauses, more efficiently than athletes with low aerobic capacity. ...
In this study, the Ajax Shuttle Test (AST) and the Curved Sprint Test (CST) were conducted on semiprofessional football players to evaluate (1) their test performance, (2) the extent of anaerobic glycolysis by measuring blood lactate, (3) performance decrement and onset of fatigue, and (4) the correlation between selected physiological variables and test performance. Thirty-two semiprofessional Polish football players participated in this study. Both AST and CST were conducted on an outdoor football ground and were conducted in two sets; each set had six repetitions. In the case of AST, the total duration for 6 repetitions of the exercise in Sets 1 and 2 were 90.63 ± 3.71 and 91.65 ± 4.24 s, respectively, whereas, in the case of CST, the respective values were 46.8 ± 0.56 and 47.2 ± 0.66 s. Peak blood lactate concentration [La] after Sets 1 and 2 of AST were 14.47 ± 3.77 and 15.00 ± 1.85 mmol/L, and in the case of CST, the values were 8.17 ± 1.32 and 9.78 ± 1.35 mmol/L, respectively. Performance decrement in AST was more than in CST, both after Set 1 (4.32 ± 1.43 and 3.31 ± 0.96 in AST and CST, respectively) and Set 2 (7.95 ± 3.24 and 3.71 ± 1.02 in AST and CST, respectively). Only in a few of the repetitions, pulmonary ventilation (VE) and oxygen uptake (VO2) were found to be significantly correlated with the performance of the volunteers in both AST and CST. Respiratory exchange ratio (RER) was significantly correlated with most of the repetitions of AST, but not with CST. The study concludes that (1) AST shows more dependence on the anaerobic glycolytic system than shorter repetitive sprints (as in CST), (2) there is more performance decrement and fatigue in AST than in CST, and (3) early decrease in performance and fatigue in the semiprofessional football players in AST and CST may be due to the insufficiency of their aerobic energy system.
... In addition, a high number of specific skills are performed with simultaneous cognition efforts such as decision making under high physiological stress. Thus, athletes in complex sports such as football may experience the greatest challenges in relation to maintaining training status during the COVID-19 lockdown (Christensen et al., 2011;Krustrup et al., 2006). Performance in competitive football is governed by different physiological systems. ...
... Depending on the length of the isolation-training period, one may expect a decrease on general fitness that would be related to the lack of high-intensity exercise performed during this period (Christensen et al., 2011;Krustrup et al., 2006;Thomassen et al., 2010). Training contents (i.e. in the single session), sequence (i.e. in the session and across the functional micro-cycle) and progression (i.e. ...
The COVID-19 pandemic has changed the conditions for competitive football around the globe dramatically. Several competitions and leagues have been cancelled or postponed. Players have firstly been forced to training in solitude. In a second stage, players start training in small groups with strict contact restriction and return to competitive play might occur after only few weeks of normal team training preparation. These special circumstances are likely to impact football performance and injury risk in the upcoming competitions. Thus, clubs, coaching and medical staff, as well as players are challenged on the prioritization of fitness and performance, which easily can create several “catch-22-dilemmas”. The present article presents views on fitness training, physical preparation and recovery during these uncommon conditions, and how elite football players can return to the competitive field well-prepared for post-crisis football endeavours around the world. Due to the multifaceted physiological demands in elite football, the long recovery requirements after match-play and an upcoming reality with many games within a short period, elite football players, managers and clubs may face extraordinary challenges associated with return to play under the current circumstances.
... Research within adult populations has produced equivocal findings, with some studies demonstrating significant associations between superior VO 2 kinetics and intermittent exercise capacity (Dupont et al. 2005;Rampinini et al. 2009Rampinini et al. , 2010, while others have reported no association between the two (Buchheit et al. 2012b;Christensen et al. 2011;Wells et al. 2012). Research in both male and female adolescents, however, has demonstrated faster VO 2 kinetics in soccer trained individuals in comparison with their untrained counterparts (Marwood et al. 2011;Unnithan et al. 2015). ...
... While the present results provide some evidence for the relationship between physical measures associated with superior soccer performance and VO 2 kinetics, the complex physiology involved during high-intensity intermittent exercise should be acknowledged. As a result, research in this area has produced equivocal results, with some studies finding little or no relationship between VO 2 kinetics and intermittent exercise performance (Buchheit et al. 2012a;Christensen et al. 2011;Wells et al. 2012) and other studies demonstrating significant associations between superior VO 2 kinetics and intermittent exercise capacity (Dupont et al. 2005;Rampinini et al. 2009Rampinini et al. , 2010. Performance during high-intensity intermittent exercise, like that which is experienced during soccer match play, is a product of complex interactions between metabolic, cardiorespiratory and cardiovascular issues. ...
Purpose:
To examine the relationship between oxygen uptake kinetics (VO2 kinetics) and physical measures associated with soccer match play, within a group of highly trained youth soccer players.
Methods:
Seventeen highly trained youth soccer players (age: 13.3 ± 0.4 year, self-assessed Tanner stage: 3 ± 1) volunteered for the study. Players initially completed an incremental treadmill protocol to exhaustion, to establish gaseous exchange threshold (GET) and VO2max (59.1 ± 5.4 mL kg(-1) min(-1)). On subsequent visits, players completed a step transition protocol from rest-moderate-intensity exercise, followed by an immediate transition, and from moderate- to severe-intensity exercise (moderate: 95 % GET, severe: 60 %∆), during which VO2 kinetics were determined. Physical soccer-based performance was assessed using a maximal Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) and via GPS-derived measures of physical soccer performance during soccer match play, three 2 × 20 min, 11 v 11 matches, to gain measures of physical performance during soccer match play.
Results:
Partial correlations revealed significant inverse relationships between the unloaded-to-moderate transition time constant (tau) and: Yo-Yo IR1 performance (r = -0.58, P = 0.02) and GPS variables [total distance (TD): r = -0.64, P = 0.007, high-speed running (HSR): r = -0.64, P = 0.008 and high-speed running efforts (HSReff): r = -0.66, P = 0.005].
Conclusion:
Measures of VO2 kinetics are related to physical measures associated with soccer match play and could potentially be used to distinguish between those of superior physical performance, within a group of highly trained youth soccer players.
... The physical performance decrement after a detraining period has been widely studied in professional football players with different detraining protocols (Christensen et al., 2011;Joo, 2018;Koundourakis et al., 2014). Joo (2018) showed decrements in the players' ability to repeat sprints (RSA) and in the distance covered in an intermittent aerobic test (Yo-YoIR1). ...
... In this regard, a previous study by Nakamura et al., (2012) showed no differences in aerobic and anaerobic fitness after a detraining period among players who did not train, players who performed 30-min of running at 70-80% HRmax twice a week, and players who performed a plyometric program twice a week (Nakamura et al., 2012). In contrast, Christensen et al., (2011) showed physical and physiological maintenance after a 2-week period in which football players performed a high-intensity program while players who stopped their activity reduced their values in the same variables. However, the results of the current study cannot be compared with the mentioned study because in their high-intensity program, players performed footballspecific tasks (i.e., small-sided games), which the participants of the present study were not able to perform due to the mandatory lockdown. ...
COVID-19 caused a total halt in sport competition during 2020. The purpose of this study was to analyze the changes between pre- and post-lockdown competitive periods in the players’ workload variables in competition. Seventeen professional football players were monitored using a WIMU PRO® inertial device throughout the 2019-20 season. Anthropometric and physical fitness were assessed with the aim to relate possible associations between these characteristics and the workload changes in the pre- and post-lockdown periods. During the lockdown, players carried out an 8-week guided self-training. There was a general decrement in the players’ physical workload demands in competition, and the parameters related to high-intensity actions as accelerations and decelerations (-8.96% [ES: 0.64] and -11.04% [ES: 0.77] respectively; p < .05), Ind HSR (-35.57% [ES: 0.92]; p = .002), HMLD (-8.58% [ES: 0.66]; p = .016), PLOAD (-7.03% [ES: 0.54]; p = .047) and Vmax (-3.80% [ES: 0.65]; p = .016) can be highlighted. The results showed high negative correlations between match workload variables prior to the lockdown and the percentage of change in these variables after the lockdown period. Individual percentages of change showed high variability in players’ changes. Individual self-training programs should be reviewed to minimize the impact of a “detraining” period in players’ physical performance during possible new lockdown periods.
... Detraining in team sport players after an offseason (≥4 weeks) causes reductions in maximal oxygen uptake ( _ VO 2max ; 0.8% to 21.2%; Caldwell and Peters 2009;Sotiropoulos et al. 2009;Koundourakis et al. 2014;Melchiorri et al. 2014), which are associated with reductions in blood and plasma volume (5-12%), increases in heart rate during submaximal and maximal training (5-10%), and lower stroke volume (10-17%) (Mujika and Padilla 2000;Silva et al. 2016). .6%) in intermittent running capacity have also been reported after short-term (~2 weeks) detraining periods (Thomassen et al. 2010;Christensen et al. 2011;Joo 2018), suggesting study of the effects of longer detraining periods is needed. Likewise, reductions in vertical jumping (2.1-6.3%) and increased sprint times (2.4-3.3%) ...
... Reductions in intermittent endurance performance are likely explained by adaptations such as slower VO 2 kinetics, alterations in oxidative enzymes (e.g. GLUT-4), reduced mitochondrial content and capillary density, higher sub-maximal heart rate, lower stroke volume and a higher respiratory exchange ratio (Mujika and Padilla 2000;Thomassen et al. 2010;Christensen et al. 2011). Increases in body mass (Darrall-Jones et al. 2016) and the impairment in sprint performance over the off-season might also have contributed to the reductions in 30-15 IFT peak speed. ...
Purpose: To determine the changes in physical qualities of academy rugby union players over a 10-week unsupervised off-season period. Methods: Body mass, jump height, sprint performance, and intermittent running (30:15 IFT) of 64 academy rugby union players (age = 17.2 ± 0.4 y) were recorded before and after the off-season. Results: Changes in body mass (+1.4 ± 1.3 kg), countermovement jump (-2.2 ± 1.2 cm), squat jump (-1.5 ± 1.8 cm), 10 m sprint (+0.06 ± 0.05 s), 40 m sprint (+0.13 ± 0.11 s) and 30:15 IFT (-0.8 ± 0.8 km.h⁻¹) were observed (P < 0.001, d = -1.77 to 0.47). Only changes in body mass were greater in forwards than backs (P = 0.036, d = 0.46). Players with higher end-of-season body mass, squat jump and 30:15 IFT had greater off-season changes (P = < 0.001 to 0.044; d = 0.63 to 0.94), whilst the pre-post difference in body mass influenced CMJ (P = 0.005, d = 0.75) and 10 m momentum change (P <0.001, d = 1.61). Conclusion: Understanding the individuality of the changes in physical qualities of academy rugby union players during the off-season is important to ensure players return safely to pre-season training loads.
... However, in line with our results, Buchheit [50] found no correlations between RSA performance and τ phase II , reporting that stepwise multiple regression analysis showed that mean repeated-sprint time, best sprint time and maximal aerobic speed were the only significant predictors of RSA performance. Accordingly, Christensen and associates [51] also found that τ phase II was not associated with better RSA performance in a group of soccer players, although the changes in τ phase II after a speed-endurance training program were associated with changes in RSA performance. ...
... The studies mentioned above [21,50,51] involved running activities, utilizing a different set of muscle groups, in a different set of participants, exposed to very different training regimens compared to the individuals involved in the present study. However, they allow us to make some assertions regarding the observed results. ...
The present study sought to investigate if faster upper body oxygen uptake (VO2) and hemoglobin/myoglobin deoxygenation ([HHb]) kinetics during heavy intensity exercise were associated with a greater upper body repeated-sprint ability (RSA) performance in a group of judokas and in a group of individuals of heterogenous fitness level. Eight judokas (JT) and seven untrained healthy participants (UT) completed an incremental step test, two heavy intensity square-wave transitions and an upper body RSA test consisting of four 15 s sprints, with 45 s rest, from which the experimental data were obtained. In the JT group, VO2 kinetics, [HHb] kinetics and the parameters determined in the incremental test were not associated with RSA. However, when the two groups were combined, the amplitude of the primary phase VO2 and [HHb] was positively associated with the accumulated work in the four sprints (ΣWork). Additionally, maximal aerobic power (MAP), peak VO2 and the first ventilatory threshold (VT1) showed a positive correlation with ΣWork and an inverse correlation with the decrease in peak power output (Dec-PPO) between the first and fourth sprints. Faster VO2 and [HHb] kinetics do not seem to be associated with an increased upper body RSA in JT. However, other variables of aerobic fitness seem to be associated with an increased upper body RSA performance in a group of individuals with heterogeneous fitness level.
... For example, 2-6 weeks of high-intensity intermittent training termed 'speed endurance training' increased mitochondrial protein content and maximal activity of key enzymes (Burgomaster et al. 2008;Gibala et al. 2006), whereas mitochondrial enzyme activity remained constant after 6 weeks of continuous training at a lower exercise intensity (Cochran et al. 2014). Speed endurance training for periods of 2-9 weeks has been extensively studied Christensen et al. 2011;Gunnarsson et al. 2013;Laursen and Jenkins 2002;Mohr et al. 2007; Thomassen et al. 2010) and has been shown to improve high-intensity intermittent exercise performance (Gibala et al. 2012;Iaia and Bangsbo 2010). Improved muscle function may possibly be caused by an increased expression of muscle ion transporters, such as the Na + -K + ATPase, monocarboxylate transporters and the Na + /H + exchanger, which may facilitate ion handling capacity. ...
... The finding of upregulated mitochondrial capacity after SET has been reported in several other studies in both untrained individuals (Burgomaster et al. 2008;Gibala et al. 2006;Nordsborg et al. 2015) and trained athletes (Iaia and Bangsbo 2010;Skovgaard et al. 2016). SET appears to increase muscle oxidative capacity when added to normal training (Gunnarsson et al. 2013), as in the present study, and when performed in conjunction with lowered training volume (Christensen et al. 2011;Nordsborg et al. 2015). Recently, MacInnis et al. (MacInnis et al. 2017) also demonstrated that single-leg cycling performed in an interval compared to a continuous manner elicited superior skeletal muscle mitochondrial adaptations despite equal total work. ...
Purpose:
To examine the skeletal muscle and performance responses across two different exercise training modalities which are highly applied in soccer training.
Methods:
Using an RCT design, 39 well-trained male soccer players were randomized into either a speed endurance training (SET; n = 21) or a small-sided game group (SSG; n = 18). Over 4 weeks, thrice weekly, SET performed 6-10 × 30-s all-out runs with 3-min recovery, while SSG completed 2 × 7-9-min small-sided games with 2-min recovery. Muscle biopsies were obtained from m. vastus lateralis pre and post intervention and were subsequently analysed for metabolic enzyme activity and muscle protein expression. Moreover, the Yo-Yo Intermittent Recovery level 2 test (Yo-Yo IR2) was performed.
Results:
Muscle CS maximal activity increased (P < 0.05) by 18% in SET only, demonstrating larger (P < 0.05) improvement than SSG, while HAD activity increased (P < 0.05) by 24% in both groups. Na(+)-K(+) ATPase α1 subunit protein expression increased (P < 0.05) in SET and SSG (19 and 37%, respectively), while MCT4 protein expression rose (P < 0.05) by 30 and 61% in SET and SSG, respectively. SOD2 protein expression increased (P < 0.05) by 28 and 37% in SET and SSG, respectively, while GLUT-4 protein expression increased (P < 0.05) by 40% in SSG only. Finally, SET displayed 39% greater improvement (P < 0.05) in Yo-Yo IR2 performance than SSG.
Conclusion:
Speed endurance training improved muscle oxidative capacity and exercise performance more pronouncedly than small-sided game training, but comparable responses were in muscle ion transporters and antioxidative capacity in well-trained male soccer players.
... In another study on the subject [41] that evaluated the effects of an intensive training program consisting of highintensity aerobic activities (8x2 min) and resistance speed tasks (10-12x30 seconds) with a complete training interruption, it was observed that soccer players who did not participate in the intensive training showed delayed inertia of VO 2 max associated with reduced muscle oxidative capacity. ...
... In the studies previously mentioned, the effects of a detraining period were analyzed based on the evaluation of different physical and physiological capacities associated with aerobic capacity [2, 15, 17 -19, 42], anaerobic capacity [2,5,11,32,44], speed [41], flexibility [8,9] and body composition [15,18]. Considering that soccer is a game of interaction and collective involvement, in which the performance depends on a set of interactions between the variables, it is essential to perceive and investigate how the techniques and behavioral variables influence the individual and collective performance [2]. ...
Competitive breaks in soccer have been revealed to be detrimental to the individual and collective performance of soccer players and teams. Several studies have been carried out, and the evidence suggests the need to apply specific training programs to avoid a decline in soccer players’ performance. However, the elaboration of these specific programs, in many cases, is essentially focused on physical performance, neglecting the technical and behavioral domain.
In this small review, the competitive breaks and their main effects for detraining were critically analyzed. Concurrently, we analyzed the effects of the use of specific training programs to avoid changes in the performance of soccer players and teams.
It is essential to create guidelines for coaches to apply for specific training programs properly during competitive breaks so that soccer players can maintain their individual and collective performance, considering the physiological, technical, and behavioral domains. Applying of these programs will also contribute to enhancing soccer players’ physical condition, increasing their tolerance to the imposed training loads, and, consequently, reducing the appearance of injuries.
... Computation of YYIR2 test global means, SDs and quantiles (Figure 3) involved 116 studies/subgroups reporting on 2,478 participants (median age = 23.2 years, IQR = 20.7-26.0 years) (Young et al., 2005;De Souza et al., 2006;Krustrup et al., 2006;Thomas et al., 2006;Mohr et al., 2007Iaia et al., 2008Iaia et al., , 2015Iaia et al., , 2017Morton et al., 2009;Rampinini et al., 2010;Rebelo et al., 2010;Thomassen et al., 2010;Christensen et al., 2011;Chuman et al., 2011;Mooney et al., 2011Mooney et al., , 2013aRoberts et al., 2011;Ueda et al., 2011;Gunnarsson et al., 2012;Ingebrigtsen et al., 2012Ingebrigtsen et al., , 2013Ingebrigtsen et al., , 2014Nakamura et al., 2012;Saunders et al., 2012;Wells et al., 2012Wells et al., , 2014Bassini et al., 2013;Buchheit et al., 2013;McGawley and Andersson, 2013;Mohr and Krustrup, 2013Owen et al., 2013;Pivovarniček et al., 2013;Yuki et al., 2013;Fanchini et al., 2014;Karavelioglu et al., 2014;Lollo et al., 2014;Miloski et al., 2014;Nunes et al., 2014;Sampaio et al., 2014;Skovgaard et al., 2014; Brocherie et al., 2015a,b;Cholewa et al., 2015;Coelho et al., 2015;Gatterer et al., 2015; Hogarth et al., 2015a,b;Jamurtas et al., 2015; Krustrup and Mohr, 2015;Leme et al., 2015;Mara et al., 2015;Matta et al., 2015;McLean et al., 2015;Michalsik et al., 2015;Mohr, 2015;Rogan, 2015;Stein et al., 2015;Boer and ...
Background: Although Yo-Yo intermittent tests are frequently used in a variety of sports and research studies to determine physical fitness, no structured reference exists for comparison and rating of test results. This systematic review of the most common Yo-Yo tests aimed to provide reference values for test results by statistical aggregation of published data.
Methods: A systematic literature search for articles published until August 2017 was performed in MEDLINE, Web of Science, SPORTDiscus and Google Scholar. Original reports on healthy females and males ≥16 years were eligible for the analysis. Sub-maximal test versions and the Yo-Yo Intermittent Recovery Level 1 Children's test (YYIR1C) were not included.
Results: 248 studies with 9,440 participants were included in the structured analysis. The Yo-Yo test types most frequently used were the Yo-Yo Intermittent Recovery Level 1 (YYIR1, 57.7%), the Yo-Yo Intermittent Recovery Level 2 (YYIR2, 28.0%), the Yo-Yo Intermittent Endurance Level 2 (YYIE2, 11.4%), and the Yo-Yo Intermittent Endurance Level 1 (YYIE1, 2.9%) test. For each separate test, reference values (global means and percentiles) for sports at different levels and both genders were calculated.
Conclusions: Our analysis provides evidence that Yo-Yo intermittent tests reference values differ with respect to the type and level of sport performed.The presented results may be used by practitioners, trainers and athletes to rate Yo-Yo intermittent test performance levels and monitor training effects.
... week intensified training period with elite soccer players after competition 4 . This may have good carryover to Rugby Union, which has a high number of repeated-sprint requirements 2 . ...
Purpose::
To investigate the effects of repeated-sprint training in hypoxia vs. in normoxia on World-level male Rugby Union players' repeated-sprint ability (RSA) during an international competition period.
Methods::
Nineteen players belonging to an international Rugby Union Senior male national team performed four sessions of cycling repeated-sprints (consisting of 3 × eight 10-s sprints with 20-s passive recovery) either in normobaric hypoxia (RSH, 3000 m, n=10) or in normoxia (RSN, 300 m; n=9) over a 2-wk period. At Pre- and Post-training intervention, RSA was evaluated using a cycling repeated-sprint test (6 x 10-s maximal sprint and 20-s passive recovery) performed in normoxia.
Results::
Significant interaction effects (all P<0.05, η2>0.37) between condition and time were found for RSA-related parameters. Compared to Pre-, maximal power significantly improved at Post- in RSH (12.84 ± 0.83 vs. 13.63 ± 1.03 W.kg-1, P<0.01, η2=0.15) but not in RSN (13.17 ± 0.89 vs. 13.00 ± 1.01 W.kg-1, P=0.45, , η2=0.01). Mean power was also significantly enhanced from Pre- to Post-intervention in RSH (11.15 ± 0.58 vs. 11.86 ± 0.63 W.kg-1, P<0.001, η2=0.26), while it remained unchanged in RSN (11.54 ± 0.61 vs. 11.75 ± 0.65 W.kg-1, P=0.23, η2=0.03).
Conclusion::
As little as four dedicated specific RSH sessions were beneficial to enhance repeated power production in World-level Rugby Union players. Although the improvement from RSA to game behaviour remains unclear, this finding appears of practical relevance since only a short preparation window is available prior to international Rugby Union games.
... Tennis professional tour is characterized by a massive part of season dedicated to the competitions, i.e. tour- naments' participations. With this calendar, optimizing the training time appears particularly determinant with a permanent search for the most specific and effective training methods. 1 In order to overcome the limited time schedule, recent publications on intermittent sports such as football 2 or tennis 3 have shown that the use of shock microcycles leads to sport-specific per- formance improvements. ...
The aim of this case study was to investigate the effects of a shock microcycle of repeated-sprint training in hypoxia (RSH) on physical fitness and tennis performance. One rookie professional tennis player performed repeated-sprint ability (RSA) and Yo-Yo Intermittent Recovery level 2 (YYIR2) tests before and after (+3 days and +21 days) six sessions of RSH (4 sets of 5 × ∼6 s repeated-shuttle sprint interspersed by ∼24 s of passive recovery) practiced during a 14-day “in-season” period. Tennis performance was subjectively measured from match results and Association of Tennis Professionals (ATP) points obtained during four professional tournaments played before and after intervention. While no changes were found at +3 days post-RSH, improvements in physical fitness (single sprint time (−4.5%), RSA total time (−3.1%) and sprint decrement (−16.7%), as well as YYIR2 total distance covered (+21.4%)) were observable at +21 days post-RSH. Tennis performance obtained during the tournaments was better after intervention. From pre to post-RSH, the decreases in opponents’ ATP ranking during matches won (1109 ± 334 points vs. 818 ± 212 points) and lost (499 ± 68 points vs. 256 ± 58 points) revealed a stronger opposition. Consequently, a three-fold increase (from 4 to 12 ATP points gained from pre to post-RSH) in participant’s ATP ranking was recorded. In summary, a 14-day “in-season” shock microcycle including six sessions of repeated-sprint training in hypoxia revealed interesting effects in specific fitness and tennis performance in a rookie professional tennis player.
... Tome je vjerovatno uzrok različita dinamika rasta i razvoja antropoloških dimenzija kod fudbalera pioirskog uzrasta. Ipak, rezultati ranijih istraživanja (Christensen et al.;Melchiorri et al., 2014;Rodríguez-Fernández et al., 2018) pokazali su značajan negativni uticaj pauze u treningu na aerobnu i anaerobnu izdržljivost mladih fudbalera. ...
Continuity in the training process of the football player is very important from the aspect of maintaining the sports form at the achieved level. Numerous studies have shown that pauses in training have a negative impact on most of the basic motor abilities of the footballer. This research had the main goal of examining the impact of a passive summer break on the basic motor abilities of the pioneer age footballers. On the sample of 85 players of pioneer age living in the area of Montenegro from four football clubs, an average age of 14 years ± 6 months, 16 motor tests were used to evaluate 6 basic motor abilities: explosive power of legs, repetitive forces, speed, agility, and endurance. The tests were conducted at the end of the competition season and before preparing for the next competitive season, and after 45 days of passive summer break. During the summer break, footballers did not have organized training activities. The results of the study showed that in all the analyzed motor abilities, the average results for the soccer players of the pioneer age were reduced. The biggest negative changes were observed in footballers who had the best results before the summer break. This research has confirmed the findings of most of the earlier studies regarding the negative impact of passive breaks in the player's training process. Therefore, it is recommended to train the trainers during the summer break even in the youngest categories of players to organize some activities aimed at maintaining the achieved level of sporting form.
Key words: football, pioneers, summer breaks, motor skills.
... However the suitability and sensitivity of V O2max as a determinant of football work rate has been questioned by some (Edwards et al., 2003. A player's HR during a game is rarely below 65% of maximum, signifying that blood flow to the exercising musculature is continuously higher than at rest (Stølen et al., 2005), indicating that oxygen utilisation by exercising muscles rather than oxygen delivery might be a more important factor (Christensen et al., 2011). ...
The concept of how training load affects performance is founded in the notion that training contributes to two specific outcomes, these are developed simultaneously by repeated bouts of training and act in conflict of each other; fitness and fatigue (Banister et al., 1975). The ability to understand these two components and how they interact with training load is commonly termed the “dose-response relationship” (Banister, 1991). The accurate quantification of training load, fitness and fatigue are therefore of paramount importance to coaches and practitioners looking to examine this relationship. In recent years, the advancement in technology has seen a rise in the number of methodologies used to assess training load and specific training outcomes. However, there is a general lack of evidence regarding the reliability, sensitivity and usefulness of these methods to help inform the training process. The aim of this thesis was therefore to improve the current understanding around the monitoring and prescription of training, with special reference to the relationship between training load, fitness and fatigue.
Chapter 4 of this thesis looked to establish test re-test reliability. Variables selected for investigation were measures of subjective wellness; fatigue, muscle soreness, sleep quality, stress levels and mood state, assessments of physical performance; countermovement jump (CMJ), squat jump (SJ) and drop jump (DJ) and the assessment of tri-axial accelerometer data; PlayerLoadTM and individual component planes anterior-posterior (PLAP), mediolateral (PLML), and vertical (PLV), were collected during a sub-maximal shuttle run. The results from this investigation suggest that a short three minute sub-maximal shuttle run can be used as a reliable method to collect accelerometer data. Additionally, assessments of CMJ height, SJ height, DJ contact time (DJ-CT) and DJ reactive strength index (DJ-RSI) were all deemed to have good reliability. In contrast, this chapter highlighted the poor test re-test reliability of the subjective wellness questionnaire. Importantly, the minimum detectable change (MDC) was also calculated for all measures within this study to provide an estimate of measurement error and a threshold for changes that can be considered ‘real’.
Chapter 5 assessed the sensitivity and reproducibility of these measures following a standardised training session. To assess sensitivity, the signal-to-noise (S: N) ratio was calculated by using the post training fatigue response (signal) and the MDC derived from Chapter 4 (noise). The fatigue response was considered reproducible if the S: N ratio was greater than one following two standardised training sessions. Three measures met the criteria to be considered both sensitive and reproducible; DJ-RSI, PLML and %PLV. All other measures did not meet the criteria. Subjective ratings of fatigue, muscle soreness and sleep quality did show a sensitive response on one occasion, however, this was not reproducible. This might be due to the categorical nature of the data, making detectable group changes hard to accomplish. The subjective wellness questionnaire was subsequently adapted to include three items; subjective fatigue, muscle soreness and sleep quality on a 10-point scale. The test re-test reliability of these three questions was established in Chapter 6, demonstrating that subjective fatigue and muscle soreness have good test re-test reliability.
Chapter 6 was comprised of two studies looking to simultaneously establish the dose-response relationship between training load, measures of fatigue (Part I) and measures of fitness (Part II). In Part I training load was strategically altered on three occasions during a standardised training session in a randomised crossover design. In Part II training and match load was monitored over a 6-week training period with maximal aerobic speed (MAS) assessed pre and post. A key objective for both studies was to assess differences in the training load-fitness-fatigue relationship when using various training load measures, in particular differences between arbitrary and individualised speed thresholds. Results from Part I showed a large to very large relationship between training load and subjective fatigue, muscle soreness and DJ-RSI performance. No differences were found between arbitrary and individualised thresholds. In Part II however, individual external training load, assessed via time above MAS (t>MAS), showed a very large relationship with changes in aerobic fitness. This was in contrast to the unclear relationships with arbitrary thresholds. Taking the results from both studies into consideration it was concluded that t>MAS is a key measure of training load if the objective is to assess the relationship with both fitness and fatigue concurrently with one measure.
Chapter 7 subsequently looked to validate the training load-fitness-fatigue relationships established in Chapter 6 via an intervention study. The aim was to develop a novel intervention that prescribed t>MAS, in order to improve aerobic fitness, based on the findings from Chapter 6. Additionally, the fatigue response following a standardised training session was assessed pre and post intervention to evaluate the effect the predicted improvements in aerobic fitness would have on measures of fatigue. Results from Chapter 7 indicate a highly predictable improvement in aerobic fitness from the training load completed during the study, validating the use of the t>MAS as a monitoring and intervention tool. Furthermore, this improvement in aerobic fitness attenuated the fatigue response following a standardised training session. The final key finding was the very strong relationship between improvements in aerobic fitness and reductions in fatigue response. This further highlights the relationship between t>MAS, fitness and fatigue.
In summary, this thesis has helped further current understanding on the monitoring and prescription of training load, with reference to fitness and fatigue. Firstly, a rigorous approach was used to identify fatigue monitoring measures that are reliable, sensitive and reproducible. Secondly, the relationship between training load, fatigue and fitness was clearly established. And finally, it has contributed new knowledge to the existing literature by establishing the efficacy of a novel MAS intervention to improve aerobic fitness and attenuate a fatigue response in elite youth football players.
... It has been widely used to improve several health and performance indicators [10,12]. It is well-known that HIIT is an exercise model that has been shown to result in similar muscular and cardiovascular adaptations compared to other traditional endurance exercise models [13][14][15][16][17]. HIIT is proposed as an effective training method for trained athletes [18][19][20][21][22], as well as for diseased populations [11,23] and healthy untrained individuals [24,25]. Jacobs et al. [26] determined mechanisms explaining improvements in exercise performance after six sessions of HIIT in untrained young adults. ...
High intensity interval training (HIIT) is widely used to improve VO2max. The purpose of this study was to examine if lower extremity HIIT resulted in improved maximal oxygen uptake (VO2max) and peak power output (PPO) of the upper extremities. Twenty healthy and trained participants (11 female and 9 male, VO2max 3160±1175 ml/min) underwent a 6-week HIIT program of the lower extremities on a cycle ergometer. Before and after the training period a maximal cycle ergometry (CE) and a maximal hand crank ergometry (HCE) were conducted to determine VO2max and PPO. Additionally, hematological parameters were determined. Increases in VO2max of the lower extremities (3160±1175 to 3449±1231 ml/min, p<0.001, η2p=0.779) as well as of the upper extremities (2255±938 to 2377±1015 ml/min, p=0.010, η2p=0.356) from pre- to post-test were found. PPO of the lower extremities increased (243±95 to 257±93 W, p<0.001, η2p=0.491), whereas it remained unchanged for the upper extremities (103±50 to 108±54 W, p=0.209, η2p=0.150). All hematological parameters increased. The results demonstrate that VO2max of the upper extremities increased after 6-weeks of cycling HIIT. However, upper body PPO was unchanged.
... 13,14 This observation indicates that prolonged reductions in-or loss of voluntary muscle activation can convert the type 1 fibers to type 2 fibers. However, in studies of persons with intact nerve supply, decreased physical activity patterns such as detraining and immobilization have reported both reductions, 15,16 increases 17 and no change 11,12 in the type 1 muscle fiber proportion. Presently, it seems uncertain whether changes in the muscle fiber type 1 proportions occur in response to patterns of reduced physical activity under normal physiological conditions. ...
The main objective of this systematic review was to examine the effect of reduced muscle activity on the relative number of type 1 muscle fibers (%) in the human vastus lateralis muscle. Other objectives were changes in type 2A and 2X percentages and muscle fiber cross‐sectional area. We conducted systematic literature searches in eight databases and included studies assessing type 1 fiber percentage visualized by ATPase‐ or immunohistochemical staining before‐ and after a period (≥ 14 days) of reduced muscle activity. The reduced muscle activity models were detraining, leg unloading and bed rest. Forty‐two studies comprising 451 participants were included. Effect sizes were calculated as the mean difference between baseline and follow‐up and Generic Inverse Variance tests with random effects models was used for the weighted summary effect size. Overall, the mean type 1 muscle fiber percentage was significantly reduced after interventions (‐1.94 %‐points, 95 % CI [‐3.37, ‐0.51], p = 0.008), with no significant differences between intervention models (p = 0.86). Meta‐regression showed no effect of study duration on type 1 fiber percentage (p = 0.98). Conversely, the overall type 2X fiber percentage increased after reduced muscle activity (p < 0.001). The CSA of the muscle fiber types decreased after the study period (all p‐values < 0.001) with greater reductions in type 2 than type 1 fibers (p < 0.001). The result of this meta‐analysis display that the type 1 muscle fiber percentage decrease as a result of reduced muscle activity, although the effect size is relatively small.
... Performing speed endurance training (all-out intermittent 30 sec of exercise at an average of~90-95% of maximal intensity) and a basic volume of endurance training for 2-9 weeks has been found to improve short-and long-term performance in runners Iaia et al. 2009), cyclists Gunnarsson et al. 2013), and soccer players (Thomassen et al. 2010;Christensen et al. 2011;Gunnarsson et al. 2012;Nyberg et al. 2016), but no study has investigated the acute response of combining speed endurance exercise with endurance exercise within the same session. ...
The aim of this study was to investigate the mRNA response related to mitochondrial biogenesis, metabolism, angiogenesis, and myogenesis in trained human skeletal muscle to speed endurance exercise (S), endurance exercise (E), and speed endurance followed by endurance exercise (S + E). Seventeen trained male subjects (maximum oxygen uptake (VO2-max): 57.2 ± 3.7 (mean ± SD) mL·min−1·kg−1) performed S (6 × 30 sec all-out), E (60 min ~60% VO2-max), and S + E on a cycle ergometer on separate occasions. Muscle biopsies were obtained at rest and 1, 2, and 3 h after the speed endurance exercise (S and S + E) and at rest, 0, 1, and 2 h after exercise in E. In S and S + E, muscle peroxisome proliferator-activated receptor-γ coactivator-1 (PGC-1α) and pyruvate dehydrogenase kinase-4 (PDK4) mRNA were higher (P < 0.05) 2 and 3 h after speed endurance exercise than at rest. Muscle PGC-1α and PDK4 mRNA levels were higher (P < 0.05) after exercise in S + E than in S and E, and higher (P < 0.05) in S than in E after exercise. In S and S + E, muscle vascular endothelial growth factor mRNA was higher (P < 0.05) 1 (S only), 2 and 3 h after speed endurance exercise than at rest. In S + E, muscle regulatory factor-4 and muscle heme oxygenase-1 mRNA were higher (P < 0.05) 1, 2, and 3 h after speed endurance exercise than at rest. In S, muscle hexokinase II mRNA was higher (P < 0.05) 2 and 3 h after speed endurance exercise than at rest and higher (P < 0.05) than in E after exercise. These findings suggest that in trained subjects, speed endurance exercise provides a stimulus for muscle mitochondrial biogenesis, substrate regulation, and angiogenesis that is not evident with endurance exercise. These responses are reinforced when speed endurance exercise is followed by endurance exercise.
... High-intensity endurance training modes (single and combined forms of HIT, Tables 27.1 and 27.2) have been suggested to better fit in the soccer training periodization puzzle than the adoption of high volumes/low intensity endurance modes [19]. This rational is based on the following observations: (1) the acute anabolic (e.g., growth hormone and insulin-like growth factor-I) [60][61][62][63][64] and redox environment; (2) HIT maintains a muscle fiber phenotype associated with strength and power capabilities [65]; (3) commonality of muscle action (brief and intense muscle contractions) [19]; (4) the adaptations in skeletal muscle and improvements in laboratory and field endurance-related parameters that are comparable to the observed after high-volume endurance training [66][67][68][69][70][71]; (5) increase in endurance and neuromuscular-related outcomes [72]; and (6) may improve muscle power-based actions [71][72][73]. Nevertheless, independent of the HIT training mode, exercise design should recreate the high-impulsive structure/nature of soccer (e.g., acceleration and deceleration, multidirectional running patterns). ...
This chapter discusses the state of research on concurrent endurance and strength training in soccer. The first part of the chapter provides rationales for soccer as a concurrent modality and describes the physiological and performance adaptations to concurrent training in soccer. Thereafter, some considerations for training programs design will be provided, by addressing the role of the different concurrent training variables (within session order, between mode recovery length and intensity and volume) on performance outcomes and likely role on injury prevention. Because each team and athlete constitute a specific case, coaches should adopt an integrated approach when considering the concurrent training design taking into account as many related factors as possible (e.g. individual player profile, period of the season, player returning from injury or not).
... Isolated HIIT-SM have been performed between 9 and 21 days, during which 9 to 24 sessions were conducted [9][10][11][12][13][17][18][19]. This concept is discussed to promise a rapid increase in performance, but usually reduces the total training volume during this period of about 30% compared to regular training weeks, especially for elite athletes [20]. Although multiple studies have demonstrated the effectiveness of HIIT-SM to improve endurance performance [9][10][11][12][13] others have been less conclusive [16][17][18][19]. ...
Background
Performing multiple high-intensity interval training (HIIT) sessions in a compressed period of time (approximately 7–14 days) is called a HIIT shock microcycle (SM) and promises a rapid increase in endurance performance. However, the efficacy of HIIT-SM, as well as knowledge about optimal training volumes during a SM in the endurance-trained population have not been adequately investigated. This study aims to examine the effects of two different types of HIIT-SM (with or without additional low-intensity training (LIT)) compared to a control group (CG) on key endurance performance variables. Moreover, participants are closely monitored for stress, fatigue, recovery, and sleep before, during and after the intervention using innovative biomarkers, questionnaires, and wearable devices.
Methods
This is a study protocol of a randomized controlled trial that includes the results of a pilot participant. Thirty-six endurance trained athletes will be recruited and randomly assigned to either a HIIT-SM (HSM) group, HIIT-SM with additional LIT (HSM + LIT) group or a CG. All participants will be monitored before (9 days), during (7 days), and after (14 days) a 7-day intervention, for a total of 30 days. Participants in both intervention groups will complete 10 HIIT sessions over 7 consecutive days, with an additional 30 min of LIT in the HSM + LIT group. HIIT sessions consist of aerobic HIIT, i.e., 5 × 4 min at 90–95% of maximal heart rate interspersed by recovery periods of 2.5 min. To determine the effects of the intervention, physiological exercise testing, and a 5 km time trial will be conducted before and after the intervention.
Results
The feasibility study indicates good adherence and performance improvement of the pilot participant. Load monitoring tools, i.e., biomarkers and questionnaires showed increased values during the intervention period, indicating sensitive variables.
Conclusion
This study will be the first to examine the effects of different total training volumes of HIIT-SM, especially the combination of LIT and HIIT in the HSM + LIT group. In addition, different assessments to monitor the athletes' load during such an exhaustive training period will allow the identification of load monitoring tools such as innovative biomarkers, questionnaires, and wearable technology.
Trial Registration : clinicaltrials.gov, NCT05067426. Registered 05 October 2021—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT05067426 . Protocol Version Issue date: 1 Dec 2021. Original protocol. Authors: TLS, NH.
... Even though HIIT has been widely used in practice, it is seldom used as a testing protocol [13,14], with INC being used to plan the training calendar. Very few studies with small groups of soccer players have used intermittent running tests (e.g., YO-YO intermittent recovery test) to determine changes in performance after the players followed HIIT training [15][16][17][18]. To date, none have considered the relationship between INC and HIIT protocols in evaluating the performance of professional team players. ...
This descriptive study aimed to explore the physiological factors that determine tolerance to exertion during high-intensity interval effort. Forty-seven young women (15–28 years old) were enrolled: 23 athletes from Taiwan national or national reserve teams and 24 moderately active females. Each participant underwent a maximal incremental INC (modified Bruce protocol) cardiopulmonary exercise test on the first day and high-intensity interval testing (HIIT) on the second day, both performed on a treadmill. The HIIT protocol involved alternation between 1-min effort at 120% of the maximal speed, at the same slope reached at the end of the INC, and 1-min rest until volitional exhaustion. Gas exchange, heart rate (HR), and muscle oxygenation at the right vastus lateralis, measured by near-infrared spectroscopy, were continuously recorded. The number of repetitions completed (Rlim) by each participant was considered the HIIT tolerance index. The results showed a large difference in the Rlim (range, 2.6–12.0 repetitions) among the participants. Stepwise linear regression revealed that the variance in the Rlim within the cohort was related to the recovery rates of oxygen consumption (), HR at the second minute after INC, and muscle tissue saturation index at exhaustion (R = 0.644). In addition, age was linearly correlated with Rlim (adjusted R = −0.518, p < 0.0001). In conclusion, the recovery rates for and HR after the incremental test, and muscle saturation index at exhaustion, were the major physiological factors related to HIIT performance. These findings provide insights into the role of the recovery phase after maximal INC exercise testing. Future research investigating a combination of INC and HIIT testing to determine training-induced performance improvement is warranted.
... Therefore an intermediate muscle typology might be expected in these sports. Multiple investigations on the muscle fiber typology in sub-elite soccer players, confirm a rather intermediate average muscle fiber type composition, as the mean percentage of ST fibers ranges between 40 to 62% ST fibers (J.L. Andersen et al., 1994;Christensen et al., 2011;Gunnarsson et al., 2012;Kuzon et al., 1990;Nyberg et al., 2016;Reilly et al., 2000). Nevertheless, data on elite soccer players is still missing. ...
The human skeletal muscle consists of two major cell types, slow-twitch fibers (also called type I fibers) and fast-twitch fibers (or type II fibers). These fibers have distinct characteristics, as fast-twitch fibers are able to generate a large amount of power at high shortening velocities, while slow-twitch fibers have a better energy efficiency, a higher resistance to fatigue and a more robust structural integrity. On average, most humans will dispose of a 50% slow-twitch and a 50% fast-twitch distribution. However a big heterogeneity exists, what results in people with predominantly slow or fast muscle fibers. The typology of a person is mostly genetically determined and is present across most muscles of the body. Taken together, the fact that muscle fibers have distinct characteristics and that muscle typologies range over the whole continuum from predominantly slow to fast in human, will have important implications for sports performance. Nevertheless, these typologies are currently not used in the daily coaching practice. This is probably due to the invasiveness of the current ‘gold’ standard to measure the muscle typology: a muscle biopsy, which is a labor intensive method and harbors a low generalizability. In 2011, our group introduced a non-invasive way to estimate the muscle fiber type composition through the measurement of carnosine – a metabolite which is abundantly available in fast-twitch fibers – using proton magnetic resonance spectroscopy (1H-MRS). The non-invasiveness of this technique enables the use in both the sports practice and science, and renews the interest of the muscle typology in sports. In the first study, the 1H-MRS method to determine the muscle typology was further optimized with the ultimate goal to make it applicable on various scanner systems of multiple vendors. 1H-MRS was found to be a reliable method to quantify carnosine in the muscle. Furthermore, best practices were proposed to prevent often encountered methodological problems and step by step guidelines were developed to allow broader utilization of this technique. Secondly, we investigated if pre-puberty carnosine measurements could give insights in the post-puberty carnosine concentrations, which would allow application of this technique in early specialization sports (study 2). Carnosine was shown to be a trackable metabolite through the disruptive puberty period (R2=0.249-0.670), which confirms the potential of the current technique to scan both future talents and elite athletes. Next to the methodological optimization, the relevance of the muscle typology for talent identification was examined. Before the start of the thesis, the construct validity of our method was already confirmed in athletics, in which clear differences were determined in the muscle typology of either sprint or endurance disciplines. Despite the fact that a comparable distribution of the muscle typologies could be expected in other cyclic sports such as cycling and swimming, this was not yet investigated in elite athletes. Therefore, study 3 established the muscle typologies of 80 world-class cyclists. Clear differences were found in the muscle typology between cycling events. Keirin, bicycle motocross racing (BMX), sprint and 500 m to 1 km time trial cyclists can be considered as fast typology athletes. Time trial, points race, scratch, and omnium consist of intermediate typology athletes, while most individual pursuit, single-stage, cyclo-cross, mountain bike, and multistage cyclists have a slow typology. Nevertheless, this distribution was not present in 73 elite swimmers (study 4), as no clear differences in the muscle typology were detected between short and long distance swimming events in the different strokes. However, there was some evidence to suggest that truly world-class sprint swimmers had a faster muscle fiber type composition when compared to elite swimmers competing at the international level. Moreover, breaststroke swimmers were identified to have a faster muscle typology in comparison to the either freestyle, backstroke or butterfly swimmers. Elite soccer players (n=118) were found to have an on average intermediate typology, which matches with the intermittent nature of this sport (study 6). In contrary to our hypothesis, no differences in the muscle typology were detected between different positions (keeper, defender, midfielder and striker). A big heterogeneity was established over all positions, indicating that the muscle typology is not of major importance for talent identification in soccer. To determine the influence of the muscle typology on individualized training and recovery cycles, we investigated if fatigue and recovery were different when both slow and fast typology subjects were exposed to the same high-intensity training (study 5). Fatigue during three Wingate tests, determined by the power drop, was 20% higher in fast typology athletes. Even though the same work was done during these Wingate tests, also the recovery from these Wingate tests was found to be 15 times slower in fast typology athletes (20 min in slow typology vs. longer than 5 h in fast typology). If a training plan would be composed with a minimum of recovery in between the training sessions, recovery might be insufficient for fast typology athletes, possibly rendering them with a higher risk for muscle strains. In study 6, we studied if the muscle typology is a risk factor for muscle strains in elite soccer players. We discovered that fast typology soccer players had a 5.3 times higher chance to get a hamstring injury, when compared to slow typology soccer players during a prospective longitudinal follow-up study over three seasons. Next to a higher accumulation of fatigue, a higher vulnerability in fast typology players could be expected due to the lower structural integrity in fast fibers. Bringing together, the muscle typology is an important characteristic, which could be non-invasively monitored using 1H-MRS. This technique could help athletes to make a scientific based decision on their ideal discipline during talent orientation. Moreover, it could help coaches tailoring training to enlarge the athletes’ muscle potential and to prevent fatigue accumulation. This endeavor might partly prevent fast typology athletes to be at a higher risk for strain injuries. Consequently, we believe that measuring the muscle fiber typology of athletes should be considered as a valuable procedure to help athletes to fully develop their potential based on the smart use of muscle profiling.
... 10,31 Indeed, increases in skeletal muscle mitochondrial biogenesis and mitochondrial enzyme activity (e.g., citrate synthase activity) have been observed after 2 weeks of HIIT in normal healthy individuals, 7À10,39 unhealthy populations, 31 and even highly trained athletes. 40 Considering that a single session of HIIT activates adenosine monophosphate-activated protein kinase and p38 mitogen-activated protein kinase, 41 which phosphorylate and activate PGC-1a and turns on mitochondrial biogenesis, 16,41 it will be important to determine if there are increases in mitochondrial biogenesis and mitochondrial enzyme activities even after the second day of 5 days of HIIT-D. ...
High-intensity interval training (HIIT) induces similar or even superior adaptations compared to continuous endurance training. Indeed, just 6 HIIT sessions over 2 weeks significantly improves VO2max, submaximal exercise fat oxidation and endurance performance. Whether even faster adaptations can be achieved with HIIT is not known. Thus, we aimed to determine whether 2 sessions of HIIT per day, separated by 3 h, every other day for 5 days (double HIIT, HIIT-D, n = 15 participants) can increase VO2max, submaximal exercise fat oxidation and endurance capacity as effectively as 6 sessions of HIIT over 2 weeks (single HIIT, HIIT-S, n = 13). Each training session consisted of 10*60 s of cycling at 100% of VO2max interspersed with 75 s of low-intensity cycling at 60 W. Pre- and post-training assessments included VO2max, time to exhaustion at ∼80% of VO2max and 60-min cycling trials at ∼67% of VO2max. Similar increases (p < 0.05) in VO2max (HIIT-D 7.7% vs. HIIT-S 6.0%, p > 0.05) and endurance capacity (HIIT-D 80.1%, HIIT-S 79.2%, p > 0.05) were observed in the 2 groups. Submaximal exercise CHO oxidation was reduced in the 2 groups after exercise training (HIIT-D 9.2%, p = 0.14 vs. HIIT-S 18.8%, p = 0.14) while submaximal exercise fat oxidation was significantly increased in HIIT-D (15.5%; p = 0.048) but not in HIIT-S (9.3%; p = 0.290).
In summary, 6 HIIT sessions over 5 days was as effective in increasing VO2max and endurance capacity and was more effective in improving submaximal exercise fat oxidation than 6 HIIT sessions over 2 weeks.
... For this reason, football players have been provided with different strategies, both for training and recovery, to reduce the negative impact of the confinement period on their fitness and endurance capacity. Training sessions combining multi-vector strength exercises involving eccentric contraction with a high speed of execution [4] and High Intensity Interval Training (HIIT) seems to be efficient to maintain physical fitness [5]. Tools such as individual questionnaires could be used to control the rated perceived exertion (RPE) or wellness [6][7][8]. ...
Background
Coronavirus disease 2019 (COVID-19) has restricted freedom of movement with several countries ‘locked down’ worldwide. During this isolation period or quarantine, habits have been modified. This might have had negative effects on physiological variables but also influenced numerous emotional aspects, especially in elite athletes, which can have a negative impact on training and sleep quality, affecting their performance.
Methods
175 Spanish professional and non-professional association football players answered an online survey about demographic and training habits, as well as two validated questionnaires to assess psychological variables (POMS and WLEIS-S).
Results
The results showed that the confinement period reduced the load of training (p < 0.01), and modified the sleeping behaviour (both, sleep time (p < 0.05) and quality (p < 0.001)) across soccer players. Higher emotional intelligence (EI) values were positively related to training variables and strongly correlated with the mood. Interestingly, athletes’ mood was affected differently depending on gender.
Conclusion
We found that confinement period affects both, training load and recovery process and that mood states and EI could predict the training variables and performance of top-level football players.
... Es un deporte de habilidades abiertas de colaboración-oposición e invasión, por lo que entrenar con otros es parte esencial de su significado y hacerlo de manera aislada del contexto del juego, no es coherente y además alejado de las exigencias de la competencia real (Martín-Barrero y Martínez-Cabrera, 2019). Para mantener la capacidad de resistencia y de fuerza y reducir el impacto negativo del período de confinamiento, se han dispuesto distintas estrategias tanto de entrenamiento como de recuperación (Domínguez et al., 2020;Christensen et al., 2011). Sin embargo, un período inusual sin entrenamiento o competencia también podría presentar un importante efecto sobre los estados emocionales o mentales de los jugadores (Jukic et al., 2020). ...
Resumen. En respuesta a la aparición del COVID 19 y la pandemia ocasionada, los países tomaron medidas para manejar las curvas de infección. Han obligado a permanecer en confinamiento y esta estrategia afectó a diversos contextos, dentro de los cuales, se encuentra el ámbito deportivo, suspendiendo competiciones, partidos oficiales, entrenamientos en cancha, transmisiones deportivas, etc. Sin embargo, en el caso de los profesionales del fútbol, se mantuvieron en preparación física a través de plataformas tecnológicas. El objetivo de este trabajo es explorar los niveles de ansiedad rasgo, de sensación de bienestar y la relación entre ambas variables en futbolistas profesionales de cuatro clubes de Chile con el fin de contribuir al diagnóstico sobre cómo la crisis de Covid-19 puede haber afectado a la realidad deportiva en cuanto a la salud mental y emocional. Para ello se aplicó el STAI y el PERMA. Como resultados, los futbolistas investigados muestran niveles promedio de ansiedad rasgo y buen nivel de bienestar general. También se encuentra correlación entre ambos. Este estudio permite concluir que si bien la situación actual puede verse como amenazante, mantener las condiciones laborales y en actividad para un deportista parece ser clave para sentir cierto grado de control frente a la incertidumbre, así como estrategias de afrontamiento que permitan tener una alta sensación de bienestar. Palabras clave: Emociones, Coronavirus, Pandemia, Futbolista profesional. Abstract. In response to the emergence of COVID 19 and the resulting pandemic, countries took steps to manage infection curves. They have forced them to remain in confinement and this strategy affected various contexts, within which is the sports field, suspending competitions, official matches, training on the field, sports broadcasts, etc. However, in the case of soccer professionals, they remained in physical preparation through technological platforms. The objective of this work is to explore the levels of trait anxiety, feeling of well-being and the relationship between both variables in professional soccer players from four clubs in Chile in order to contribute to the diagnosis of how the Covid-19 crisis may have affected sports reality in terms of mental and emotional health. For this, the STAI and PERMA were applied. As results, the investigated soccer players show average levels of trait anxiety and a good level of general well-being. There is also a correlation between the two. This study allows us to conclude that although the current situation can be seen as threatening, maintaining working and active conditions for an athlete seems to be key to feeling a certain degree of control in the face of uncertainty, as well as coping strategies that allow having a high sensation of wellness.
... Thus, exploration of training regimes allowing training quality to be upheld while residing at terrestrial altitude, i.e. 'live high-train high', is warranted. In normoxia, various protocols of high-intensity interval training have continuously proven efficient for improving aerobic and anaerobic exercise capacity in both healthy [5,6] and trained [7,8] individuals. Specifically, sprint-interval training (SIT) performed as four to six 30 s Wingate sprints performed in cycle-ergometers interspersed with 2-4 min of passive recovery [9] is a highly efficient training paradigm to improve maximal oxygen uptake ( _ VO 2max ) and anaerobic performance both in healthy and untrained individuals [10][11][12] as well as trained individuals [13,14]. ...
Sprint-interval training (SIT) is efficient at improving maximal aerobic capacity and anaerobic fitness at sea-level and may be a feasible training strategy at altitude. Here, it was evaluated if SIT intensity can be maintained in mild to moderate hypoxia. It was hypothesized that 6 x 30 s Wingate sprint performance with 2 min active rest between sprints can be performed in hypoxic conditions corresponding to ~3,000 m of altitude without reducing mean power output (MPO). In a single-blinded, randomized crossover design, ten highly-trained male endurance athletes with a maximal oxygen uptake ( V ˙ O 2max ) of 68 ± 5 mL O 2 × min ⁻¹ × kg ⁻¹ completed 6 x 30 s all-out Wingate cycling sprints separated by two-minute active recovery on four separate days in a hypobaric chamber. The ambient pressure within the chamber on each experimental day was 772 mmHg (~0 m), 679 mmHg (~915 m), 585 mmHg (~ 2,150 m), and 522 mmHg (~3,050 m), respectively. MPO was not different at sea-level and up to ~2,150 m (~1% and ~3% non-significant decrements at ~915 and ~2,150 m, respectively), whereas MPO was ~5% lower (P<0.05) at ~3,050 m. Temporal differences between altitudes was not different for peak power output (PPO), despite a main effect of altitude. In conclusion, repeated Wingate exercise can be completed by highly-trained athletes at altitudes up to ~2,150 m without compromising MPO or PPO. In contrast, MPO was compromised in hypobaric hypoxia corresponding to ~3,050 m. Thus, SIT may be an efficient strategy for athletes sojourning to moderate altitude and aiming to maintain training quality.
... Short-term (1 and 2 weeks) detraining appears not to have any significant effects on Yo-Yo intermittent test in professional soccer players (Joo, 2016;Rodríguez-Marroyo et al., 2018). In contrast, other studies found that the short-term detraining period (2 weeks) decreased performance in the Yo-Yo test (Thomassen et al., 2010;Christensen et al., 2011;Joo, 2018). This contradiction may be due to the expertise level of players (Joo, 2018). ...
The present study aimed to verify the quarantine's effects during a serious viral outbreak on the cardiovascular and performance associated with the Yo-Yo test in a sample of professional soccer players. 20 high-level soccer players (n = 20; age: 26 ± 4 years-old; weight: 76.85 ± 6.7 kg; height: 179 ± 6 cm) participated in this study. The intermittent Yo-Yo test was performed pre-and post-COVID-19 quarantine in a random order. During each test, the soccer players' running performance outcomes were monitored using a portable 5-Hz GPS with a 100 Hz accelerometer and a paired t-test was conducted at a p-value of ≤ 0.05. The main results demonstrated significant differences between pre-versus post-COVID-19 quarantine in the following variables: relative distance (161.7 ± 5.9 > 141.1 ± 33.8 m/min), maximal speed (18.7 ± 0.9 > 18.2 ± 0.6 km/h), acceleration (60 ± 20 frequency > 52 ± 16 frequency), deceleration (34 ± 13 frequency > 27 ± 6 frequency), sprints > 19 km/h [0.8 (0.2;3)% >0.5 (0;0.5)%], and in high intensity running distance [16.48 (2.68;41.64)m > 0.827 (0.164;3.0)m]. We concluded that COVID-19-related restrictions and quarantine COVID-19 demonstrated adverse effects on professional soccer players' Yo-Yo tests performance.
... Accordingly, a higher reliance on carbohydrate (i.e., higher RER) may at least in part explain the lower V̇O 2 during post-training submaximal exercise testing because oxidation of 100% carbohydrate (RER 5 1.0) relative to 100% fat oxidation (RER 5 0.7) per se would lead to higher energy turnover (21.1 vs. 19.6 kJ per liter V̇O 2 ) during exercise, as supported by observations in persons ingesting high fat diets before exercise (14). The potential mechanism(s) responsible for the higher RER remains speculative because a higher RER during exercise typically is associated with endurance training cessation (16) or detraining (36). Consequently, the presence of measurement noise could also be a plausible cause for the present gains in RER. ...
Bláfoss, R, Rikardo, J, Andersen, AØ, Hvid, LG, Andersen, LL, Jensen, K, Christensen, PM, Kvorning, T, and Aagaard, P. Effects of resistance training cessation on cycling performance in well-trained cyclists: an exploratory study. J Strength Cond Res 36(3): 796-804, 2022-Supplementary (i.e., concurrent) resistance training can enhance cycling performance among competitive cyclists. However, a lack of knowledge exists about the retention (decay profile) in mechanical muscle function and cycling performance after concurrent resistance and endurance training. The present exploratory intervention study investigated the effect of 6 weeks of resistance training cessation when preceded by 8 weeks of concurrent resistance and endurance training on mechanical muscle function and cycling performance in 9 male well-trained competitive cyclists (V̇o2max = 66 ± 7 ml·min-1·kg-1). Cyclists performed periodized resistance training targeting leg and core muscles for 8 weeks as a supplement to their normal endurance (cycling) training. This was followed by 6 weeks of endurance training only (retention period) leading up to the start of the competitive season. Maximal leg extensor power, isometric leg extensor strength (maximal voluntary contraction [MVC]), rate of force development (RFD), and long-term cycling performance (2-hour submaximal cycling at 55% of Wmax), followed by 5-minute max cycling were evaluated. After 8 weeks of concurrent resistance and endurance training, leg extensor power, MVC, and RFD increased by 12, 15, and 17%, respectively while mean power output (W) during 5-minute max cycling increased by 7% (p < 0.05). Training-induced gains in MVC and 5-minute max cycling power were retained after 6-week cessation of resistance training (p < 0.05). These findings indicate that competitive cyclists can focus on cycling training alone for at least 6 weeks leading up to competition without losing attained gains in maximal muscle strength and cycling performance achieved by preceding periods of concurrent resistance training.
... Desde el punto de vista del rendimiento la evaluación constante de RSA a lo largo de la temporada puede proporcionar información valiosa a los entrenadores y atletas. De manera similar a las pausas fuera y dentro de la temporada, pueden conducir a un desentrenamiento a corto plazo, esto puede inducir un desacondicionamiento cardiovascular y neuromuscular (Christensen et al., 2011;Mujika y Padilla, 2001), que potencialmente puede alterar el RSA, el índice de fatiga o la puntuación de disminución porcentual (Sdec) (Glaister, 2009). El conocimiento del alcance de las respuestas de la fatiga durante un RSA puede ayudar a los preparadores físicos a prever cambios eventuales durante los descansos de la temporada y a implementar estrategias de entrenamiento adecuadas para optimizar los niveles de condición física. ...
Introducción: El desarrollo de dispositivos portátiles de espectroscopia de infrarrojo cercano no invasivo (NIRS) ha permitido que las mediciones de oxígeno muscular se realicen fuera de un entorno de laboratorio para investigar cambios musculares locales en pruebas campo para guiar el entrenamiento. En general, durante el ejercicio los NIRS portátiles utiliza la saturación de oxígeno muscular (SmO2) como parámetro principal para el estudio de la hemodinámica porque proporciona información sobre el rendimiento y el metabolismo muscular durante el ejercicio. Un uso novedoso de NIRS portátil, es la medición de la oxigenación muscular en reposo a través del método de oclusión arterial (AOM). AOM consiste en realizar breves oclusiones arteriales para conocer el consumo de oxígeno muscular en reposo (mVO2). En la actualidad, AOM es una técnica para obtener información de la capacidad oxidativa del músculo en reposo, lo cual significa que el atleta no realiza ningún esfuerzo físico. Sin embargo, existe poca literatura científica de cómo está implicado el mVO2 en el proceso de entrenamiento.
Por otro lado, el monitoreo de la acumulación de fatiga pre y post competencia es importante dentro de la planificación del entrenamiento. Uno de los roles de los científicos del deporte es conocer el perfil de fatiga y recuperación con el fin de optimizar los procesos de entrenamiento para buscar un mejor rendimiento deportivo. Pero existen limitaciones, debido a que el estudio de la fatiga es un fenómeno multifactorial que envuelve diferentes mecanismos fisiológicos. En cuanto a la relación que pueda tener NIRS portátil y la medición de SmO2 con la fatiga dentro de un contexto deportivo se desconoce, debido a que es una variable que no se ha puesto en práctica en el deporte, pero con un gran potencial.
En el contexto de la salud, existen numerosas investigaciones que han asociado la SmO2 a enfermedades cardiovasculares, respiratorias y metabólicas como el sobrepeso y obesidad, que son patologías que afectan la entrega de oxígeno durante la actividad física. Uno de los factores claves para prescribir el ejercicio físico es conocer las zonas de metabólica, es decir la intensidad de ejercicio donde existen cambios metabólicos y que se aplica según el objetivo de la sesión de entrenamiento en personas que realizan actividad física para la salud.
Por último, existen algunos vacíos científicos de la aplicación de NIRS portátil en contextos de fatiga, rendimiento y salud. Por lo tanto, con esta tesis podemos brindar nuevos aportes científicos del metabolismo muscular a través de la medición de la SmO2 en reposo y durante el ejercicio, necesario para conocer estados de condición física de un deportista, fatiga, recuperación y la prescripción de ejercicio de ejercicio físico.
Objetivos: La tesis presenta como objetivo general: Utilizar la saturación de oxígeno muscular y estudiar su implicación en la fatiga, rendimiento y salud.
Para realizar el objetivo general se llevó a cabo los siguientes objetivos específicos: 1. Examinar la relación de la saturación de oxígeno muscular en reposo con marcadores de fatiga en futbolistas femeninos. 2. Interpretar el rol de la saturación de oxígeno muscular como un marcador de rendimiento deportivo durante una prueba de alta intensidad (sprint-repetidos) en futbolistas femeninos. 3. Evaluar los cambios de oxigenación muscular en reposo después de un periodo de entrenamiento y correlacionarlos con la composición corporal y la potencia de salto en futbolistas. 4. Comparar y correlacionar los parámetros fisiológicos en función de la saturación de oxígeno muscular por zonas metabólicas durante una prueba de esfuerzo en personas con sobrepeso/obesidad y normo-peso.
Métodos: Los cuatro objetivos de esta tesis fueron investigados con cuatro estudios científicos. Los participantes fueron futbolistas femeninos y masculinos que competían en segunda y tercera división respectivamente, y mujeres con sobrepeso/obesidad y normo-peso. En todas las pruebas se utilizó un NIRS portátil marca MOXY colocado en el músculo gastrocnemio y músculo vasto lateral. El primer estudio consistió en medir marcadores de fatiga neuromuscular, escalas psicológicas y marcadores sanguíneos utilizados para medir fatiga a nivel biológico. En conjunto se midió la prueba de oxígeno muscular en reposo (mVO2 y SmO2) mediante la técnica AOM. Todas las mediciones se realizaron pre, post y post 24 h tras un partido de futbol femenino. El segundo estudio consistió en que los futbolistas femeninos realizaran una prueba de sprint repetidos, donde se evaluó la frecuencia cardiaca, velocidad y SmO2 en conjunto. El tercer estudio consistió en observar cambios de SmO2 en reposo después de un periodo de pretemporada en jugadores de futbol y relacionarlo con la composición corporal y la potencia de salto. El cuarto estudio consistió en realizar una prueba de esfuerzo incremental con detección de zonas metabólicas: fatmax, umbrales de entrenamiento VT1 y VT2 y potencia aeróbica máxima para compararlo y relacionarlo con la SmO2.
Resultados y Discusión: En base a los objetivos de la tesis: Primero, en las jugadoras de futbol se encontró un aumento de mVO2 y SmO2 en reposo a las 24 h post partido oficial [(mVO2: 0.75 ± 1.8 vs 2.1± 2.7 μM-Hbdiff); (SmO2: 50 ± 9 vs 63 ± 12 %)]. Principalmente, este aumento es resultado de la correlación de la vasodilatación mediada por el flujo sanguíneo y el trasporte de oxígeno muscular que es un mecanismo implicado en los procesos de recuperación de la homeostasis del músculo esquelético y la restauración del equilibrio metabólico. El aumento del consumo de oxígeno se relacionó con la disminución de la potencia de salto (r= −0.63 p <0.05) y el aumento del lactato deshidrogenada (LDH) (r = 0.78 p <0.05) como marcadores de fatiga. Seguidamente en el segundo estudio, encontramos que la disminución del rendimiento durante una prueba de sprint repetidos, comienza con el aumento gradual de la SmO2, debido al cambio de la presión intramuscular y la respuesta hiperémica que conlleva, mostrando una disminución en la respuesta inter-individual [desaturación desde el cuarto sprint (Δ= 32%) y re-saturación después del sexto sprint (Δ= 89%)]. Además, la extracción de oxígeno por parte del músculo tiene una asociación no-lineal con la alta velocidad (r = 0.89 p <0.05) y con la fatiga mostrada el % decremento del sprint (r = 0.93 p <0.05).
En el estudio 3 se encontró que la dinámica de SmO2 en reposo es sensible a cambios después de un periodo de pretemporada (SmO2-Pendiente de recuperación: 15 ± 10 vs. 5 ± 5). Asimismo, se mostró que la SmO2 en reposo está relacionado paralelamente con el porcentaje de grasa del cuerpo (r= 0,64 p <0.05) y una relación inversa con la potencia de salto a una sola pierna (r = -0,82 p<0.01). Esto significa que a través del entrenamiento se mejoró el metabolismo y hemodinámica muscular con un tránsito más rápido del oxígeno muscular, y se asoció a las mejoras del peso corporal, somatotipo, CMJ y SLCMJ.
En el cuarto estudio, basado en los parámetros fisiológicos de una prueba de esfuerzo para prescribir ejercicio: se encontró una relación entre la SmO2 y el VO2max durante la zona fatmax y VT1 (r=0,72; p=0,04) (r=0,77; p=0,02) en mujeres con normo-peso. Sin embargo, en el grupo sobrepeso obesidad no se encontró ninguna correlación ni cambios de SmO2 entre cada zona metabólica.
Conclusión: La investigación de esta tesis ha demostrado avances en la medición de la SmO2. El uso de mVO2 y SmO2 en reposo es una variable de carga de trabajo que se puede utilizar para el estudio de la fatiga después de un partido de futbol femenino. Asimismo, la SmO2 en reposo puede ser interesante tomarlo en cuenta como un parámetro de rendimiento en futbolistas. Siguiendo el contexto, en el rendimiento durante una prueba de sprint repetidos, la SmO2 debe interpretarse basado en la respuesta individual del porcentaje de extracción de oxígeno muscular (∇%SmO2). El aporte de ∇%SmO2 es un factor de rendimiento limitado por la capacidad de velocidad y soporte de la fatiga de los futbolistas femeninos. Respecto a los aspectos de salud y prescripción del ejercicio, proponemos utilizar la SmO2 como un parámetro fisiológico para controlar y guiar el entrenamiento en zonas fatmax y VT1, pero solo en mujeres normo-peso. En patologías metabólicas como el sobrepeso y obesidad se necesitan más estudios. Como conclusión general, esta tesis muestra nuevas aplicaciones prácticas de cómo utilizar la SmO2 y su implicación en la fatiga, en contraste la adaptación al entrenamiento, pruebas de rendimiento y prescripción de la actividad física para la salud.
... The fitness level of the players participating in this experiment was lower than that of the professional soccer players that were included in a previous study (Bradley et al., 2013). The Yo-Yo IL 2 results were lower than those of European professional soccer players (Christensen et al., 2011). These differences in fitness levels can be attributed to differences in league levels, measurement timing, and conditions. ...
Exercise performance is reduced in hot environments due to physiological responses caused by increased body temperature. A proper residential environment is important for improving the performance and maintaining physical condition of soccer players in the summer. The purpose of this study was to determine the effect of indoor temperature of the resting space during the summer on the fitness and condition of soccer players. A total of 12 K-3 League semiprofessional players without serious injuries in the last 3 months voluntarily participated in the study. Participants performed speed (10 m, 20 m, and 30 m), soccer-specific coordination skill (dribbling), agility, repeated sprints, Yo-Yo intermittent level 2, vertical jump, and questionnaire (fatigue, sleep quality, muscle soreness, stress, and mood) after staying indoor temperature at 20°C, 26°C, and 30°C for one night, respectively. There was no difference among groups in physical fitness (speed, agility, jump, coordination, Yo-Yo intermittent level 2, and repeated sprints). The differences in fatigue and sleep quality were not statistically significant among groups, but they tended to be different. Muscle soreness was similar among all groups. Significant differences were observed between the 20°C and 30°C groups in stress and mood levels. The present study concluded that, while the physical fitness did not differ among groups, the 30°C residential environment was shown to have a negative psychological effect. Considering that many diseases associated with hot weather occur in low residential temperatures, a room temperature of 26°C is recommended for elite soccer players in hot summer weather.
... En un interesante estudio (Christensen et al., 2011), se valoró los efectos del desentrenamiento comparando un grupo de futbolistas profesionales, que en la postemporada realizaron entrenamientos de alta intensidad y un grupo de cesación del entrenamiento, en este segundo grupo la cinética del VO2 se volvió más lenta, se redujo la cantidad de piruvato deshidrogenasa muscular y la actividad máxima de citrato sintasa y 3-hidroxiacil-CoA, todos factores que pueden explicar los resultados del presente estudio. El DES provoca importantes modificaciones fisiológicas como reducciones significativas en el volumen de plasma (Grivas, (Bangsbo & Michalsik, 2002). ...
The fact that soccer requires an aerobic base verified through a test of maximum oxygen consumption and identification of the appearance of ventilatory thresholds one and two is recognized. The SARCoV- 2 virus pandemic significantly affected professional football, generating a detraining situation in many clubs. The objective of the present study is to describe the effect of total and partial detraining for 11 weeks, on cardirespiratory parameters. The sample consisted of 26 soccer players belonging to a professional first division club in Paraguay. An ergometry with gas analysis was performed before and after the detraining period associated with the confinement of the pandemic. The results showed a 0.4% increase in body weight. -14.9% decrease in oxygen consumption in the first threshold; -17.4% in oxygen consumption in second threshold; -15.4% in maximum oxygen consumption; no significant changes in heart rate in first and second threshold as in maximum oxygen consumption (0.1, -0.2, 0.6 respectively); -4.7% in maximum aerobic speed and 13.5% in muscle efficiency. Detraining induced by quarantine can produce a significant loss of aerobic performance; detraining at the cardiorespiratory level seems to be more relevant than at the muscular level, based on the muscle efficiency parameter presented.
... It is a general observation that a period of intensified training enhances performance during intense exercise in endurance-trained individuals, despite the fact they experience no training-induced changes inVo 2max , aerobic capacity, Vo 2 -kinetics, capillarization, blood volume, hemoglobin mass, and muscle metabolic enzymes (117,119,304,318,(647)(648)(649)(650). In fact, performance enhancements are occasionally observed in these studies despite detriments in muscle oxidative enzymes (117,650) and capillarization (534) during the training period. ...
Exercise causes major shifts in multiple ions (e.g., K+ , Na+ , H+ , lactate- , Ca2+ , and Cl- ) during muscle activity that contributes to development of muscle fatigue. Sarcolemmal processes can be impaired by the trans-sarcolemmal rundown of ion gradients for K+ , Na+ , and Ca2+ during fatiguing exercise, while changes in gradients for Cl- and Cl- conductance may exert either protective or detrimental effects on fatigue. Myocellular H+ accumulation may also contribute to fatigue development by lowering glycolytic rate and has been shown to act synergistically with inorganic phosphate (Pi) to compromise cross-bridge function. In addition, sarcoplasmic reticulum Ca2+ release function is severely affected by fatiguing exercise. Skeletal muscle has a multitude of ion transport systems that counter exercise-related ionic shifts of which the Na+ /K+ -ATPase is of major importance. Metabolic perturbations occurring during exercise can exacerbate trans-sarcolemmal ionic shifts, in particular for K+ and Cl- , respectively via metabolic regulation of the ATP-sensitive K+ channel (KATP ) and the chloride channel isoform 1 (ClC-1). Ion transport systems are highly adaptable to exercise training resulting in an enhanced ability to counter ionic disturbances to delay fatigue and improve exercise performance. In this article, we discuss (i) the ionic shifts occurring during exercise, (ii) the role of ion transport systems in skeletal muscle for ionic regulation, (iii) how ionic disturbances affect sarcolemmal processes and muscle fatigue, (iv) how metabolic perturbations exacerbate ionic shifts during exercise, and (v) how pharmacological manipulation and exercise training regulate ion transport systems to influence exercise performance in humans. © 2021 American Physiological Society. Compr Physiol 11:1895-1959, 2021.
... The "signal" or the usually observed change following a training program in soccer players is also generally greater in the distance-related tests than in the speed-related tests. Namely, the mean change following training programs comprised of different HIIT formats [18] (i.e., long interval HIIT, short interval HIIT, repeated sprint training (RST), sprint interval training (SIT) and small-sided games (SSG)) lasting from 2 to 12 weeks in soccer players averages 2.7% for UMTT or Vam Eval test [80][81][82][83][84][85] (Table 1), 6.7% for 20mSRT [67,68,[86][87][88][89] (Table 2), 18.8% for Yo-YoIRT1 [58,68,74,85, (Table 3), 16.5% for Yo-YoIRT2 [74,77,[111][112][113][114][115][116][117] (Table 4) and 9.1% for 30-15IFT [58,84,[118][119][120][121] (Table 5). Although solid conclusions cannot be made due to the differences in duration and experimental designs of the studies it is interesting to notice that training programs comprised of short interval HIIT offered the greatest improvements in UMTT, 20mSRT and 30-15IFT. ...
A desire to make fitness testing cheaper and easier to conduct in a team-sport setting has led to the development of numerous field aerobic fitness tests. This has contributed to a growing confusion among strength and conditioning coaches about which one to use. The main aim of this narrative review was to examine the reliability, validity, sensitivity and usefulness of the commonly used field aerobic fitness tests and to provide practical guidelines for their use in soccer. The University of Montreal track test (UMTT) and Vam Eval test seem the best options for estimation of maximal oxygen uptake (VO2max) while the highest signal-to-noise ratio of the 30-15 intermittent fitness test (30-15IFT) suggests its superior sensitivity to track changes in fitness. The UMTT and 30-15IFT are the best solutions for prescription of long and short high-intensity interval training sessions, respectively. All field tests mostly present with marginal usefulness, but the smallest worthwhile change for UMTT or Vam Eval test, Yo-YoIRT2 and 30-15IFT are smaller than their stage increment making the improvement of only one stage in the test performance already worthwhile. Strength and conditioning coaches are advised to choose the test based on their specific purpose of testing.
Background:
It is unknown whether a concentrated period of small-sided games and high intensity training is an effective training approach in youth soccer players. The aim of the study was to examine the effect of a concentrated period of soccer specific training on physical fitness in youth players.
Methods:
Nineteen male soccer players, from two teams, participated (mean ± SD age: 16.2 ± 0.8 years; body mass: 58.2 ± 7.6 kg; height: 170.8 ± 7.7 cm). One team performed 5 days of small-sided games and high intensity training (SSG & HIT; n = 12) and the other team regular soccer training with 1 day of SSG and HIT (REG; n = 7) weekly for 4 weeks. The 30-15 intermittent fitness test (30-15 IFT), countermovement jump (CMJ) and change of direction (COD) performance were measured pre and post intervention. Heart rate (HR) and rating of perceived exertion (RPE) were recorded and session load calculated (RPE x minutes).
Results:
Average % of maximum HR and session load were 83% and 344 AU for the SSG & HIT vs 73% and 253 AU for the REG (P< 0.05). 30-15 IFT improved for the SSG & HIT (from 17.0 ± 1.1 to 18.4 ± 0.8 km/h; p< 0.05; ES = 0.57) with no difference for the REG group (Pre: 17.9 ± 1.3, Post: 18.2 ± 1.6 km/h, ES= 0.10). CMJ and COD were unchanged in both groups and no injuries were reported.
Conclusions:
A 4-week concentrated period of daily SSG & HIT is effective for improving endurance performance in youth soccer players. This was without injuries and without negating performance in power and change of direction.
Background and Study Aim. The COVID-19 pandemic has caused many athletes to interrupt their regular training programme. The change-of-direction performance is a highly critical parameter for fencing. This study aims to investigate the effects of the detraining process caused by the COVID-19 pandemic on the change-of-direction performance of fencers.
Material and Methods. The study sample comprised 15 fencers (11 males, 4 females) who were competitors in the U17-20 age categories (mean age: 15.75±1.51 years; height: 170.30±7.68 cm; weight: 65.16±10.83 kg) in Turkey. All participants were high school students. Branch-specific change-of-direction tests (4-2-2-4-m shuttle and 7-m repeat lunge ability) were measured in the middle of the competition season and after the detraining period. The detraining period lasted 31 weeks due to the pandemic process.
Results. The results showed that participants were slower in the post 7-m repeat lunge ability test (23.32±2.21 sec.) compared with the pre-test (22.38±1.58 sec.) and participants were slower in the post 4-2-2-4-m shuttle test (6.43±0.54 sec.) compared with the pre-test (5.84±0.33 sec.) (p
Intensified training may lead to fatigue or even a state of overreaching with temporary reductions in performance. Any aid helping to prevent these consequences and to better tolerate such a training regime would be of great importance. 5-hydroxymethylfurfural (5-HMF) and α-ketoglutaric acid (α-KG) supplementation has been suggested to support favorable training outcomes but its effectiveness to facilitate adaptations during an intensified training period has never been investigated. During an in-season competition break (2 weeks), seventeen young outfield soccer players (age:14.7 ± 0.4 yr) performed a 9-day lasting shock microcyle including 5-7 repeated sprint exercise sessions in addition to the regular training (∼6 sessions/wk) and match (1-2 matches/wk) schedule. Before the training period a treadmill test to exhaustion, a YOYO intermittent recovery level 2 (YYIR2) and a repeated sprint ability (RSA) test were performed. The treadmill test was repeated 3 days after the shock microcycle whereas the YYIR2 and the RSA test on day 10 after the training. Magnitude based inference analysis showed likely positive effects of the 5-HMF/α-KG compared to the control group for changes in the maximal running velocity (+0.3 ± 0.7 vs. -0.3 ± 0.8 km/h) and running velocity at lactate turn-point 1 (+0.2 ± 0.4 vs. -0.2 ± 0.6) and lactate turn-point 2 (+0.4 ± 0.4 vs. -0.2 ± 0.6 km/h, for the 5-HMF/α-KG and placebo group, respectively). Training improved YYIR2 performance (+180 ± 67 vs. +200 ± 168m) and RSA (mean time: -0.1 ± 0.1 vs. -0.1 ± 0.1s, for the 5-HMF/α-KG and placebo group, respectively) in both groups and to the same extent. In conclusion, an in-season shock microcyle including repeated sprint training improves YYIR2 performance and RSA in youth soccer players. Supplementation with 5-HMF/α-KG did not modify training adaptations but led to likely positive exercise performance responses shortly after the intensified training regime.
In 2020, the world is suffering an unprecedented pandemic (coronavirus or COVID-19) that it is eliciting devastating consequences. This article has gathered the opinions of international soccer experts about the short-term and long-term effects of coronavirus quarantine on physical performance and injury incidence in high-level soccer players, by means of open-ended questions encouraging the expression of unrestricted opinions. In this way, the text aims to provide the reader with a compilation and comparison of knowledge from a practical perspective in order to understand how the coronavirus quarantine may affect the high-level players’ physical performance from the extensive experience and broad career of conditioning area professionals in top-level soccer teams around the world together with the knowledge provided by research.
This study aimed to evaluate the effect of high-intensity interval training shock microcycles (HIITSM) on endurance, running economy and change of direction economy in female soccer players. Nineteen sub-elite female soccer players were randomised to two groups: HIITSM (10 HIIT sessions over 13 days) or HIITTRAD (4 HIIT sessions over 13 days) interventions. Endurance performance was evaluated through the 30–15 intermittent fitness test (30–15IFT); running economy over a 5-min treadmill run; and change of direction economy over two conditions: (1) 5-min 20m shuttle run, and (2) 5-min 10m shuttle run. HIITSM significantly improved 30–15IFT scores compared to baseline (+4.4%, p=0.009; d=0.96) and 30–15IFT scores relative to HIITTRAD (p=0.002; d=2.01). There was no significant interaction (group×time) for running economy and change of direction economy. Pre- to post- intervention there was a significant main time effect for blood lactate over 20m and 10m shuttle runs (p<0.001 and p=0.037, respectively), with large (d=0.93) and moderate (d=0.53) changes observed for the HIITSM over the two distances, respectively. HIITSM may be more effective than HIITTRAD to improve 30–15IFT over shorter training periods but may not affect running economy and change of direction economy.
BACKGROUND: High-intensity interval training (HIIT) is an important training component to improve aerobic and anaerobic exercise capacity. Higher HIIT workloads in general may generate additional effects on the improvement of exercise capacity, while missing adherence to more strenuous training regimes may affect training success. This study investigated if higher training workload generated by progressive HIIT (proHIIT) is superior to HIIT when used in an uncontrolled setting.
METHODS: Thirty-four moderately trained females and males performed a 4-week training intervention with three exercise sessions per week. Participants were randomized into two HIIT groups using the individual lactate threshold at baseline: Group 1 (n = 17), HIIT, 4 runs at maximal speed (all-out) with 30 s active recovery (total = 48 runs), Group 2 (n = 17), proHIIT, 4 runs at maximal speed (all-out) with 30 s active recovery with one extra repetition every week (up to 7 runs, total = 66 runs). An incremental field test protocol with standard blood lactate (LA) diagnostic and heart rate monitoring was used to access changes in exercise capacity.
RESULTS: Overall, power output (running speed) at LA threshold (baseline LA+1.5 mmol∙L-1) increased by +3.6% (p = 0.004, effect size [ES] = 0.38) after 4 weeks of HIIT. However, no significant between-group differences pre- vs post-intervention were detected.
CONCLUSIONS: Our data suggest that proHIIT does not provide additional improvement of running speed at individual lactate threshold over HIIT in an uncontrolled setting.
Beard, A, Ashby, J, Chambers, R, Millet, GP, and Brocherie, F. Wales Anaerobic Test (WAT): Reliability and fitness profiles of international rugby union players. J Strength Cond Res XX(X): 000-000, 2019-To provide strength and conditioning coaches a practical and evidence-based test for repeated-sprint ability (RSA) in rugby union players, this study assessed the relative and absolute test-retest reliability of the Wales Anaerobic Test (WAT) and its position-specific association with other fitness performance indices. Thirty-four players (forwards: n = 19; backs: n = 15) of the Welsh rugby union male senior national team performed the WAT (10 × 50-m distance, 25-30 seconds of passive recovery) twice within 4 days. Time for each repetition was recorded, with the best (WATBest) and total time (WATTT) retained for analysis. Relative (intraclass correlation coefficient [ICC]) and absolute (SEM) reliability of the WAT indices were quantified. Furthermore, association (Pearson's product-moment correlations and stepwise backward elimination procedure) with other fitness performance indices (10- and 40-m sprinting times, 30-15 intermittent fitness test [30-15IFT] and the Yo-Yo intermittent recovery test level 2 [YYIR2]) was investigated. Pooled values revealed "moderate" to "high" ICCs for WATBest (ICC = 0.89, p = 0.626) and WATTT (ICC = 0.95, p = 0.342). Good test sensitivity was reported for forwards and backs' WATTT (p > 0.101). Both WATBest and WATTT correlated with 10-m and 40-m sprinting times (r > 0.69, p < 0.001) as well as with 30-15IFT (r < -0.77, p < 0.001) and YYIR2 (r < -0.68, p < 0.001) for pooled values. The WAT proved to be a reliable and sensitive test to assess the rugby union specific RSA-related fitness of international players.
Purpose: To describe the effects of COVID-19 lockdown and a subsequent retraining on the training workloads, autonomic responses and performance of a group of elite athletes.
Methods: The training workloads and heart rate variability (HRV, assessed through the LnRMSSD) of seven elite badminton players were registered daily during 4 weeks of normal training (baseline), 7-10 weeks of lockdown, and 6-8 weeks of retraining. Physical performance was assessed at baseline and after each phase by means of a countermovement jump (CMJ) and the estimated squat 1-repetition maximum (1RM).
Results: A reduction in training workloads was observed in all participants during the lockdown (-63.7%), which was accompanied by a reduced HRV in all but one participant (-2.0%). A significant reduction was also observed for CMJ (-6.5%) and 1RM performance (-11.5%), which decreased in all but one participant after the lockdown. However, after the retraining phase all measures returned to similar values to those found at baseline. At the individual level there were divergent responses, as exemplified by one athlete who attenuated the reduction in training workloads and increased her performance during the lockdown, and another one who markedly reduced his workload and performance and got injured during the retraining phase.
Conclusions: Although there seems to be a large inter-individual variability, COVID-19 lockdown is likely to impose negative consequences on elite athletes, but these detrimental effects might be avoided by attenuating reductions in training workloads and seem to be overall recovered after 6-8 weeks of retraining.
This study investigated the repeated-sprint ability (RSA) physiological responses to a standardized, high-intensity, intermittent running test (HIT), maximal oxygen uptake (VO(2) (max)) and oxygen uptake (VO(2)) kinetics in male soccer players (professional (N = 12) and amateur (N = 11)) of different playing standards. The relationships between each of these factors and RSA performance were determined. Mean RSA time (RSA(mean)) and RSA decrement were related to the physiological responses to HIT (blood lactate concentration ([La(-)]), r = 0.66 and 0.77; blood bicarbonate concentration ([HCO(3)-]), r = -0.71 and -0.75; and blood hydrogen ion concentration ([H(+)]), r = 0.61 and 0.73; all p < 0.05), VO(2) (max) (r = -0.45 and -0.65, p < 0.05), and time constant (tau) in VO(2) kinetics (r = 0.62 and 0.62, p < 0.05). VO(2) (max) was not different between playing standards (58.5 +/- 4.0 vs. 56.3 +/- 4.5 mL.kg(-1).min(-1); p = 0.227); however, the professional players demonstrated better RSA(mean) (7.17 +/- 0.09 vs. 7.41 +/- 0.19 s; p = 0.001), lower [La-] (5.7 +/- 1.5 vs. 8.2 +/- 2.2 mmol.L(-1); p = 0.004), lower [H+] (46.5 +/- 5.3 vs. 52.2 +/- 3.4 mmol.L(-1); p = 0.007), and higher [HCO3-] (20.1 +/- 2.1 vs. 17.7 +/- 1.7 mmol.L(-1); p = 0.006) after the HIT, and a shorter in VO2 kinetics (27.2 +/- 3.5 vs. 32.3 +/- 6.0 s; p = 0.019). These results show that RSA performance, the physiological response to the HIT, and differentiate between professional- and amateur-standard soccer players. Our results also show that RSA performance is related to VO(2) max, tau, and selected physiological responses to a standardized, high-intensity, intermittent exercise.
The physiological determinants of performance in two Yo-Yo intermittent recovery tests (Yo-YoIR1 and Yo-YoIR2) were examined in 25 professional (n = 13) and amateur (n = 12) soccer players. The aims of the study were (1) to examine the differences in physiological responses to Yo-YoIR1 and Yo-YoIR2, (2) to determine the relationship between the aerobic and physiological responses to standardized high-intensity intermittent exercise (HIT) and Yo-Yo performance, and (3) to investigate the differences between professional and amateur players in performance and responses to these tests. All players performed six tests: two versions of the Yo-Yo tests, a test for the determination of maximum oxygen uptake (V(O)(2)(max)), a double test to determine V(O)(2) kinetics and a HIT evaluation during which several physiological responses were measured. The anaerobic contribution was greatest during Yo-YoIR2. V(O)(2)(max) was strongly correlated with Yo-YoIR1 (r = 0.74) but only moderately related to Yo-YoIR2 (r = 0.47). The time constant (tau) of V(O)(2) kinetics was largely related to both Yo-Yo tests (Yo-YoIR1: r = 0.60 and Yo-YoIR2: r = 0.65). The relationships between physiological variables measured during HIT (blood La(-), H(+), HCO(3) (-) and the rate of La(-) accumulation) and Yo-Yo performance (in both versions) were very large (r > 0.70). The physiological responses to HIT and the tau of the V(O)(2) kinetics were significantly different between professional and amateur soccer players, whilst V(O)(2)(max) was not significantly different between the two groups. In conclusion, V(O)(2)(max) is more important for Yo-YoIR1 performance, whilst tau of the V(O)(2) kinetics and the ability to maintain acid-base balance are important physiological factors for both Yo-Yo tests.
The present study examined muscle adaptations and alterations in work capacity in endurance-trained runners as a result of a reduced amount of training combined with speed endurance training. For a 6- to 9-wk period, 17 runners were assigned to either a speed endurance group with a 25% reduction in the amount of training but including speed endurance training consisting of six to twelve 30-s sprint runs 3-4 times/wk (SET group n = 12) or a control group (n = 5), which continued the endurance training ( approximately 55 km/wk). For the SET group, the expression of the muscle Na(+)-K(+) pump alpha(2)-subunit was 68% higher (P < 0.05) and the plasma K(+) level was reduced (P < 0.05) during repeated intense running after 9 wk. Performance in a 30-s sprint test and the first of the supramaximal exhaustive runs was improved (P < 0.05) by 7% and 36%, respectively, after the speed endurance training period. In the SET group, maximal O(2) uptake was unaltered, but the 3-km (3,000-m) time was reduced (P < 0.05) from 10.4 +/- 0.1 to 10.1 +/- 0.1 min and the 10-km (10,000-m) time was improved from 37.3 +/- 0.4 to 36.3 +/- 0.4 min (means +/- SE). Muscle protein expression and performance remained unaltered in the control group. The present data suggest that both short- and long-term exercise performances can be improved with a reduction in training volume if speed endurance training is performed and that the Na(+)-K(+) pump plays a role in the control of K(+) homeostasis and in the development of fatigue during repeated high-intensity exercise.
Beat-by-beat \( \dot{Q} \)
aO2 and breath-by-breath \( \dot{V} \)O2 were assessed in ten male subjects (24 ± 3.5 years; 78 ± 7.7 kg; 182 ± 5.6 cm) during cycling exercise at 50 W before and after a 14-day period of head-down tilt-bed rest (HDTBR). O2 deficit (DefO2) was calculated as the difference between the volume of O2 that would have been consumed if a steady state had been immediately attained minus that actually taken up during exercise. \( \dot{Q} \)
aO2 kinetics was described fitting the data with a non-linear mono-exponential model with time delay. Mean response times (MRT) of \( \dot{V} \)O2 and \( \dot{Q} \)
aO2 kinetics were then calculated. DefO2 and MRT of \( \dot{V} \)O2 response did not change after HDTBR, whereas MRT of \( \dot{Q} \)
aO2 kinetics increased. The invariance of \( \dot{V} \)O2 kinetics after HDTBR suggests that, although \( \dot{Q} \)
aO2 response became slower after HDTBR, it did not affect the kinetics of peripheral gas exchange, which probably remained under the control of local muscular mechanisms.
The physical demands in soccer have been studied intensively, and the aim of the present review is to provide an overview of metabolic changes during a game and their relation to the development of fatigue. Heart-rate and body-temperature measurements suggest that for elite soccer players the average oxygen uptake during a match is around 70% of maximum oxygen uptake (VO2max). A top-class player has 150 to 250 brief intense actions during a game, indicating that the rates of creatine-phosphate (CP) utilization and glycolysis are frequently high during a game, which is supported by findings of reduced muscle CP levels and severalfold increases in blood and muscle lactate concentrations. Likewise, muscle pH is lowered and muscle inosine monophosphate (IMP) elevated during a soccer game. Fatigue appears to occur temporarily during a game, but it is not likely to be caused by elevated muscle lactate, lowered muscle pH, or change in muscle-energy status. It is unclear what causes the transient reduced ability of players to perform maximally. Muscle glycogen is reduced by 40% to 90% during a game and is probably the most important substrate for energy production, and fatigue toward the end of a game might be related to depletion of glycogen in some muscle fibers. Blood glucose and catecholamines are elevated and insulin lowered during a game. The blood free-fatty-acid levels increase progressively during a game, probably reflecting an increasing fat oxidation compensating for the lowering of muscle glycogen. Thus, elite soccer players have high aerobic requirements throughout a game and extensive anaerobic demands during periods of a match leading to major metabolic changes, which might contribute to the observed development of fatigue during and toward the end of a game.
We studied the effect of an alteration from regular endurance to speed endurance training on muscle oxidative capacity, capillarization, as well as energy expenditure during submaximal exercise and its relationship to mitochondrial uncoupling protein 3 (UCP3) in humans. Seventeen endurance-trained runners were assigned to either a speed endurance training (SET; n = 9) or a control (Con; n = 8) group. For a 4-wk intervention (IT) period, SET replaced the ordinary training ( approximately 45 km/wk) with frequent high-intensity sessions each consisting of 8-12 30-s sprint runs separated by 3 min of rest (5.7 +/- 0.1 km/wk) with additional 9.9 +/- 0.3 km/wk at low running speed, whereas Con continued the endurance training. After the IT period, oxygen uptake was 6.6, 7.6, 5.7, and 6.4% lower (P < 0.05) at running speeds of 11, 13, 14.5, and 16 km/h, respectively, in SET, whereas remained the same in Con. No changes in blood lactate during submaximal running were observed. After the IT period, the protein expression of skeletal muscle UCP3 tended to be higher in SET (34 +/- 6 vs. 47 +/- 7 arbitrary units; P = 0.06). Activity of muscle citrate synthase and 3-hydroxyacyl-CoA dehydrogenase, as well as maximal oxygen uptake and 10-km performance time, remained unaltered in both groups. In SET, the capillary-to-fiber ratio was the same before and after the IT period. The present study showed that speed endurance training reduces energy expenditure during submaximal exercise, which is not mediated by lowered mitochondrial UCP3 expression. Furthermore, speed endurance training can maintain muscle oxidative capacity, capillarization, and endurance performance in already trained individuals despite significant reduction in the amount of training.
The rates of increase in O2 uptake (VO2) after step changes in work rate from 25 W to 60% of pretraining peak VO2 (VO2 peak) were measured at various times during an endurance training program (2 h/day at 60% pretraining VO2 peak). Seven untrained males [23 +/- 1 (SE) yr] performed a series of repeated step changes in work rate before training (PRE) and after 4 days (4D), 9 days (9D), and 30 days (30D) of training. VO2 kinetic responses were determined from breath-by-breath data averaged across four repetitions and analyzed using a two-component exponential model. Mean response time (time taken to reach 63% of steady-state VO2) was faster (P < 0.01) than PRE (38.1 +/- 2.6 s) at both 4D (34.9 +/- 2.4 s) and 9D (32.5 +/- 1.8 s) and was faster (P < 0.01) at 30D than at all other times (28.3 +/- 1.0 s). Blood lactate concentrations (after 6 min of cycling) were also lower at 4D and 9D than PRE (P < 0.01) and were lower at 30D than at all other times (P < 0.01). VO2 peak was unchanged from PRE (3.52 +/- 0.20 l/min) at 8D (3.55 +/- 0.20 l/min) but was increased (P < 0.01) at 30D (3.89 +/- 0.18 l/min). Muscle oxidative capacity (maximal citrate synthase activity) was not significantly increased until 30D (P < 0.01). It is concluded that at least part of the acceleration of whole body VO2 kinetics with endurance training is a rapid phenomenon, occurring before changes in VO2 peak and/or muscle oxidative potential.
This study examined the contribution of phosphocreatine (PCr) and aerobic metabolism during repeated bouts of sprint exercise. Eight male subjects performed two cycle ergometer sprints separated by 4 min of recovery during two separate main trials. Sprint 1 lasted 30 s during both main trials, whereas sprint 2 lasted either 10 or 30 s. Muscle biopsies were obtained at rest, immediately after the first 30-s sprint, after 3.8 min of recovery, and after the second 10-and 30-s sprints. At the end of sprint 1, PCr was 16.9 ± 1.4% of the resting value, and muscle pH dropped to 6.69 ± 0.02. After 3.8 min of recovery, muscle pH remained unchanged (6.80 ± 0.03), but PCr was resynthesized to 78.7 ± 3.3% of the resting value. PCr during sprint 2 was almost completely utilized in the first 10 s and remained unchanged thereafter. High correlations were found between the percentage of PCr resynthesis and the percentage recovery of power output and pedaling speed during the initial 10 s of sprint 2 (r = 0.84, P < 0.05 and r = 0.91, P < 0.01). The anaerobic ATP turnover, as calculated from changes in ATP, PCr, and lactate, was 235 ± 9 mmol/kg dry muscle during the first sprint but was decreased to 139 ± 7 mmol/kg dry muscle during the second 30-s sprint, mainly as a result of a ~45% decrease in glycolysis. Despite this ~41% reduction in anaerobic energy, the total work done during the second 30-s sprint was reduced by only ~18%. This mismatch between anaerobic energy release and power output during sprint 2 was partly compensated for by an increased contribution of aerobic metabolism, as calculated from the increase in oxygen uptake during sprint 2 (2.68 ± 0.10 vs. 3.17 ± 0.13 l/min; sprint 1 vs. sprint 2; P < 0.01). These data suggest that aerobic metabolism provides a significant part (~49%) of the energy during the second sprint, whereas PCr availability is important for high power output during the initial 10 s.
The main purpose of this study was to investigate the effects of an 8-wk severe interval training program on the parameters of oxygen uptake kinetics, such as the oxygen deficit and the slow component, and their potential consequences on the time until exhaustion in a severe run performed at the same absolute velocity before and after training. Six endurance-trained runners performed, on a 400-m synthetic track, an incremental test and an all-out test, at 93% of the velocity at maximal oxygen consumption, to assess the time until exhaustion. These tests were carried out before and after 8 wk of a severe interval training program, which was composed of two sessions of interval training at 93% of the velocity at maximal oxygen consumption and three recovery sessions of continuous training at 60--70% of the velocity at maximal oxygen consumption per week. Neither the oxygen deficit nor the slow component were correlated with the time until exhaustion (r = -0.300, P = 0.24, n = 18 vs. r = -0.420, P = 0.09, n = 18, respectively). After training, the oxygen deficit significantly decreased (P = 0.02), and the slow component did not change (P = 0.44). Only three subjects greatly improved their time until exhaustion (by 10, 24, and 101%). The changes of oxygen deficit were significantly correlated with the changes of time until exhaustion (r = -0.911, P = 0.01, n = 6). It was concluded that the decrease of oxygen deficit was a potential factor for the increase of time until exhaustion in a severe run performed after a specific endurance-training program.
The purpose of this study was to examine oxygen consumption (VO2) and heart rate kinetics during moderate and repeated bouts of heavy square-wave cycling from an exercising baseline. Eight healthy, male volunteers performed square-wave bouts of leg ergometry above and below the gas exchange threshold separated by recovery cycling at 35% VO2 peak. VO2 and heart rate kinetics were modeled, after removal of phase I data by use of a biphasic on-kinetics and monoexponential off-kinetics model. Fingertip capillary blood was sampled 45 s before each transition for base excess, HCO and lactate concentration, and pH. Base excess and HCO concentration were significantly lower, whereas lactate concentration and pH were not different before the second bout. The results confirm earlier reports of a smaller mean response time in the second heavy bout. This was the result of a significantly greater fast-component amplitude and smaller slow-component amplitude with invariant fast-component time constant. A role for local oxygen delivery limitation in heavy exercise transitions with unloaded but not moderate baselines is presented.
The purpose of this study was to examine the effect of 4 weeks of intense interval-training on the pulmonary off-transient oxygen uptake (V*O2) after running until exhaustion at the same absolute speed. Seven physical education students ran as follows in three maximal tests on a synthetic track (400 m) whilst breathing through a portable, telemetric metabolic analyser: firstly, in an incremental test which determined maximal oxygen uptake (V*O2max), the minimal speed associated with V*O2max (vV*O2max) and the speed at the lactate threshold ( v(LT)). Secondly, in two continuous severe intensity runs at 90% (R90) and 95% (R95) of vV*O2max. After training, the times to exhaustion ( t(lim)) at these two speeds (i.e. the time limits t(lim90) and t(lim95), respectively), were significantly increased at both speeds (+37% and +66% for t(lim90) and t(lim95), P=0.04 and 0.01, respectively) and v(LT) and vV*O2max were increased by 8% and 5%, respectively ( P<0.02). The time constants of the cardio-dynamic added to the metabolic phase (phases I+II) and of the slow phase (phase III) of oxygen kinetics in the on-transient phase decreased significantly after training ( P=0.05). However, the decrease in the time constants of oxygen kinetics in the on-transient phases II and III were not correlated with the improvement in performance (i.e. increase in t(lim)). After training the V*O2 off-transient phase was significantly faster [off-time constant (tau(off)) decreased significantly both after R90 and R95, P=0.03]. This decrease in tau(off) was correlated with the increase in t(lim90) ( r=0.795, P=0.03). The physiological factors best correlated with the increased performance after training were v(LT) for t(lim90) and vV*O2max for t(lim95).
The aim of this study was to assess physical fitness, match performance and development of fatigue during competitive matches at two high standards of professional soccer. Computerized time-motion analyses were performed 2-7 times during the competitive season on 18 top-class and 24 moderate professional soccer players. In addition, the players performed the Yo-Yo intermittent recovery test. The top-class players performed 28 and 58% more (P < 0.05) high-intensity running and sprinting, respectively, than the moderate players (2.43 +/- 0.14 vs 1.90 +/- 0.12 km and 0.65 +/- 0.06 vs 0.41 +/- 0.03 km, respectively). The top-class players were better (11%; P < 0.05) on the Yo-Yo intermittent recovery test than the moderate players (2.26 +/- 0.08 vs 2.04 +/- 0.06 km, respectively). The amount of high-intensity running, independent of competitive standard and playing position, was lower (35-45%; P < 0.05) in the last than in the first 15 min of the game. After the 5-min period during which the amount of high-intensity running peaked, performance was reduced (P < 0.05) by 12% in the following 5 min compared with the game average. Substitute players (n = 13) covered 25% more (P < 0.05) ground during the final 15 min of high-intensity running than the other players. The coefficient of variation in high-intensity running was 9.2% between successive matches, whereas it was 24.8% between different stages of the season. Total distance covered and the distance covered in high-intensity running were higher (P < 0.05) for midfield players, full-backs and attackers than for defenders. Attackers and full-backs covered a greater (P < 0.05) distance in sprinting than midfield players and defenders. The midfield players and full-backs covered a greater (P < 0.05) distance than attackers and defenders in the Yo-Yo intermittent recovery test (2.23 +/- 0.10 and 2.21 +/- 0.04 vs 1.99 +/- 0.11 and 1.91 +/- 0.12 km, respectively). The results show that: (1) top-class soccer players performed more high-intensity running during a game and were better at the Yo-Yo test than moderate professional players; (2) fatigue occurred towards the end of matches as well as temporarily during the game, independently of competitive standard and of team position; (3) defenders covered a shorter distance in high-intensity running than players in other playing positions; (4) defenders and attackers had a poorer Yo-Yo intermittent recovery test performance than midfielders and full-backs; and (5) large seasonal changes were observed in physical performance during matches.
It has frequently been demonstrated that prior heavy cycling exercise facilitates pulmonary O(2) kinetics at the onset of subsequent heavy exercise. This might be due to improved muscle perfusion via acidosis-induced vasodilating effects. However, it is difficult to measure the blood flow (BF) to the working muscles (via the femoral artery) during cycling exercise. We therefore selected supine knee extension (KE) exercise as an alternative, and investigated whether the faster O(2) kinetics in the 2nd bout was matched by proportionally faster BF kinetics to the exercising muscle. Nine healthy subjects (aged 21-44 years) volunteered to participate in this study. The protocol consisted of two consecutive 6-min KE exercise bouts in a supine position (work rate: 70-75% of peak power) separated by a 6-min baseline rest (EX1 to EX2). During the protocol, a pulsed Doppler ultrasound technique was utilized to continuously measure the BF in the right femoral artery. The protocol was repeated at least 6 times to characterize the precise kinetics. In agreement with previous studies using cycling exercise, the O(2) kinetics in the 2nd bout were facilitated compared with that in the 1st bout [mean +/-s.d. of the 'effective' time constant (tau): EX1, 68.6 +/- 15.9, versus EX2, 58.0 +/- 14.4 s. Phase II-tau: EX1, 48.7 +/- 9.0, versus EX2, 41.2 +/- 13.3 s. Empirical index of the slow component (Delta O(2(6-3))): EX1, 78 +/- 44, versus EX2, 57 +/- 36 ml min(-1) (P < 0.05)]. However, no substantial difference was observed for the facilitation of the femoral artery BF response to the 1st and 2nd exercise bouts [i.e. the 'effective'tau of the femoral artery BF: EX1, 40.8 +/- 16.9, versus EX2, 39.0 +/- 17.1 s (P > 0.05)]. It was concluded that the faster pulmonary O(2) kinetics during heavy KE exercise following prior heavy exercise was not associated with a similar modulation in the BF to the working muscles.
The purpose of this study was to test the hypothesis that subjects having a shorter time constant for the fast component of VO2 kinetics in a transition from rest to constant exercise would maintain their speed for a longer time during repeated sprint exercise (RSE). Eleven male soccer players completed a graded test, two constant exercises at 60% maximal aerobic speed and RSE, consisting of fifteen 40-m sprints alternated with 25 s of active recovery. All the tests were performed on the field (200 m indoor track). The parameters of the VO2 kinetics (time delay, time constant, and amplitude of the primary phase) during the two constant exercises were modeled. All subjects elicited VO2 during the RSE. A significant correlation was found between VO2 and the relative decrease in speed during the 15 sprints (r=0.71; p < 0.05), but not between VO2 and the cumulated time for the 15 sprints (r=0.48; p > 0.05). There were significant correlations between the time constant of the primary phase and the relative decrease in speed during the 15 sprints (r=0.80; p < 0.01) and the cumulated time for the 15 sprints (r=0.80; p < 0.01). These results suggest that individuals with faster VO2 kinetics during constant load exercise might also have a faster adjustment of VO2 during RSE leading to a shorter cumulated time and a lower relative decrease in speed during the 15 sprints.
The purpose of the present study was to examine the effect of unilateral lower limb suspension (ULLS) deconditioning on oxygen uptake kinetics. Eight healthy males underwent ULLS for 20 days and performed a series of 6-min square-wave transitions from rest to 60-W single-leg cycling exercises just before and after ULLS. To characterize the kinetics of the oxygen uptake response, a single exponential model was applied to the data until the end of the fast component omitted the first 15 s of the on-transit using a nonlinear least-squares fitting procedure. The following results were found: (i) the time constant of oxygen uptake was unchanged before and after ULLS; (ii) although there was no significant difference in the baseline and the asymptotic amplitude of the fast component, the asymptote, i.e., the absolute asymptotic amplitude of the fast component (the sum of the baseline and the asymptotic amplitude), and the end exercise oxygen uptake were decreased after ULLS; (iii) the contribution of the slow component to the total response of oxygen uptake was unchanged at pre- and post-ULLS. In conclusion, the asymptote in the fast component and the end exercise oxygen uptake were decreased after 20-d ULLS, though the response speed and the amplitude of the slow component of oxygen uptake were not changed. It is suggested that deconditioning as a result of limb disuse affects oxygen uptake response.
To investigate pyruvate dehydrogenase (PDH)-E1alpha subunit phosphorylation and whether free fatty acids (FFAs) regulate PDH activity, seven subjects completed two trials: saline (control) and intralipid/heparin (intralipid). Each infusion trial consisted of a 4-h rest followed by a 3-h two-legged knee extensor exercise at moderate intensity. During the 4-h resting period, activity of PDH in the active form (PDHa) did not change in either trial, yet phosphorylation of PDH-E1alpha site 1 (PDH-P1) and site 2 (PDH-P2) was elevated in the intralipid compared with the control trial. PDHa activity increased during exercise similarly in the two trials. After 3 h of exercise, PDHa activity remained elevated in the intralipid trial but returned to resting levels in the control trial. Accordingly, in both trials PDH-P1 and PDH-P2 decreased during exercise, and the decrease was more marked during intralipid infusion. Phosphorylation had returned to resting levels at 3 h of exercise only in the control trial. Thus, an inverse association between PDH-E1alpha phosphorylation and PDHa activity exists. Short-term elevation in plasma FFA at rest increases PDH-E1alpha phosphorylation, but exercise overrules this effect of FFA on PDH-E1alpha phosphorylation leading to even greater dephosphorylation during exercise with intralipid infusion than with saline.