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Muscular charateristics of detraining in humans
Abstract
Skeletal muscle is characterized by its ability to dynamically adapt to variable levels of functional demands. During periods of insufficient training stimulus, muscular detraining occurs. This may be characterized by a decreased capillary density, which could take place within 2--3 wk of inactivity. Arterial-venous oxygen difference declines if training stoppage continues beyond 3--8 wk. Rapid and progressive reductions in oxidative enzyme activities bring about a reduced mitochondrial ATP production. The above changes are related to the reduction in VO(2max) observed during long-term training cessation. These muscular characteristics remain above sedentary values in the detrained athlete but usually return to baseline values in recently trained individuals. Glycolytic enzyme activities show nonsystematic changes during periods of training cessation. Fiber distribution remains unchanged during the initial weeks of inactivity, but oxidative fibers may decrease in endurance athletes and increase in strength-trained athletes within 8 wk of training stoppage. Muscle fiber cross-sectional area declines rapidly in strength and sprint athletes, and in recently endurance-trained subjects, whereas it may increase slightly in endurance athletes. Force production declines slowly and in relation to decreased EMG activity. Strength performance in general is readily maintained for up to 4 wk of inactivity, but highly trained athletes' eccentric force and sport-specific power, and recently acquired isokinetic strength, may decline significantly.
... Specificity and reversibility training principles are widely reported for peripheral skeletal muscles. 20 While specificity denotes that the nature of changes in muscle structure and function relies on the nature of the applied stimulus, reversibility indicates that when physical training is stopped (training cessation), our body readapt in accordance with the reduced physiological demand. 20 Beneficial adaptations may be lost, 3 but in a three-week break it was not enough. ...
... 20 While specificity denotes that the nature of changes in muscle structure and function relies on the nature of the applied stimulus, reversibility indicates that when physical training is stopped (training cessation), our body readapt in accordance with the reduced physiological demand. 20 Beneficial adaptations may be lost, 3 but in a three-week break it was not enough. ...
... Explained by the reversibility principle, the adaptations provided by training stimulus are reversed in losses when the training is stopped. 20 The decrease in maximum oxygen uptake after short detraining periods is greater in experienced athletes when compared to beginners. 6 Those who work with child athletes usually do not have specific theoretical bases to inform themselves, only general of the individual's motor and maturational development. ...
Objective: to verify if three-weeks of training cessation affects 200 m front crawl performance and kinematics in 12 years old and under age-group swimmers controlling for anthropometric changes.
Method: Sixteen age-group swimmers (11 girls and 5 boys, age: 10.2 ± 1.2 y) performed a 200 m front crawl test (T200) (time trial) PRE- and POST three-weeks (off-season), where performance, kinematics and anthropometrics variables were obtained.
Results: Height increased ~1.0 cm (CI: 0.70 to 1.3 cm; p < 0.001; d = 0.07). Trivial changes were observed for performance (mean diff: 3.3 s CI: -6.7 to 13.9; p = 0.69; d = 0.08) and kinematical variables (p from 0.69 to 0.84; d < 0.001 for all). High intraclass correlations (ICC: 0.69 to 0.84; p < 0.001) were observed for all variables after three-weeks, indicating stability over time.
Conclusion: Three-weeks off-season does not impair swimming T200 performance and kinematic variables in 12 years old and under age-group swimmers.
... After reading full-text copies, 35 studies were excluded from this review due to the following reasons: (i) 20 studies used a within-group design and/or did not include a control group; (ii) 11 studies did not apply traditional RT and/or DT; (iii) two studies investigated clinical populations; (iv) one study performed an indirect assessment of 1RM strength; and (v) one study measured 10RM. At the end of the process, 20 publications meeting the eligibility criteria were included for qualitative analysis: 20 studies related to muscle strength [10,16,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] and seven studies [10,27,28,32,37,43,44] related to muscle hypertrophy. Out of these 20 studies, 18 studies were excluded from the quantitative analysis due to the following reasons: (i) 11 studies applied different maximum strength tests, avoiding a pooled analysis [29][30][31]33,35,36,[38][39][40][41][42]; ...
... After reading full-text copies, 35 studies were excluded from this review due to the following reasons: (i) 20 studies used a within-group design and/or did not include a control group; (ii) 11 studies did not apply traditional RT and/or DT; (iii) two studies investigated clinical populations; (iv) one study performed an indirect assessment of 1RM strength; and (v) one study measured 10RM. At the end of the process, 20 publications meeting the eligibility criteria were included for qualitative analysis: 20 studies related to muscle strength [10,16,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] and seven studies [10,27,28,32,37,43,44] related to muscle hypertrophy. Out of these 20 studies, 18 studies were excluded from the quantitative analysis due to the following reasons: (i) 11 studies applied different maximum strength tests, avoiding a pooled analysis [29][30][31]33,35,36,[38][39][40][41][42]; ...
... (ii) five studies reported information about different hypertrophy outcomes, avoiding a pooled analysis [10,28,32,37,44]; and (iii) two studies did not report muscle hypertrophy data for the control group [27,43]. Therefore, two studies [16,34] were included in the meta-analysis for maximum muscle strength (1RM). ...
A detraining period after resistance training causes a significant decrease in trained-induced muscular adaptations. However, it is unclear how long muscle strength and hypertrophy gains last after different detraining periods. Thus, the present systematic review with meta-analysis aimed to evaluate the chronic effects of detraining on muscle strength and hypertrophy induced by resistance training. Searches were conducted on PubMed, Scopus, EBSCO, CINAHL, CENTRAL, and Web of Science. The difference in means and pooled standard deviations of outcomes were converted into Hedges’ g effect sizes (g). Twenty randomized and non-randomized trials (high and moderate risks of bias, respectively, and fair quality) were included for qualitative analysis of muscle strength and hypertrophy, while only two studies were included in the meta-analysis for maximum muscle strength. The resistance training group presented a significant increase in one-repetition maximum (1RM) chest press (g: 4.43 [3.65; 5.22], p < 0.001) and 1RM leg press strength (g: 4.47 [2.12; 6.82], p < 0.001) after training. The strength gains observed in the resistance training group were also maintained after 16–24 weeks of detraining (g: 1.99 [0.62; 3.36], p = 0.004; and g: 3.16 [0.82; 5.50], p = 0.008; respectively), when compared to the non-exercise control group. However, 1RM chest press and leg press strength level was similar between groups after 32 (g: 1.81 [−0.59; 4.21], p = 0.139; and g: 2.34 [−0.48; 5.16], p = 0.104; respectively) and 48 weeks of detraining (g: 1.01 [−0.76; 2.79], p = 0.263; and g: 1.16 [−1.09; 3.42], p = 0.311; respectively). There was not enough data to conduct a meta-analysis on muscular hypertrophy. In conclusion, the present systematic review and meta-analysis demonstrated that, when taking random error into account, there is no sufficient high-quality evidence to make any unbiased claim about how long changes in muscle strength induced by RT last after a DT period. Moreover, the effect of different DT periods on muscle hypertrophy induced by RT remains unknown since there was not enough data to conduct a meta-analysis with this variable.
... The principle of reversibility training states that stopping or reducing training causes partial or complete reversal of previously developed adaptations. The principle of reversibility, also known as detraining, refers to the total or partial loss of adaptation caused by training achieved through training [23]. It is common for athletes to transition throughout their sporting careers, usually at the end of a competition period or due to illness, injury, or other factors. ...
... The FT became more susceptible to periods of inactivity than ST types [36]. Even when the training period did not exceed two weeks, changes in the distribution of muscle fibers were not seen in long-distance runners or the strength and power of athletes [23]. After the first 15 days, there was a decrease in the area of the transverse fibers by about 0.6% per day [37]. ...
... A decrease in fiber FT content has been observed in soccer players and weightlifters [38], and decreased ability to apply force to the water has been found in swimmers [39]. Likewise, conversion of FTN fibers to FT fibers has been observed in long-distance runners and cyclists [23]. Inactivity also caused a decrease in collagen synthesis in human tendons, with a progressive decrease in collagen synthesis between 10 and 21 days without complete activity [40]. ...
There was an outbreak of severe acute respiratory syndrome by SARS-CoV-2 or COVID-19 in China. The virus spread quickly throughout the world, including in Indonesia. The government has taken many steps to reduce the spread of COVID-19, namely the Stay at Home phase, the Large-Scale Social Restrictions phase, and the New Normal phase. The entire process has affected sports by imposing Training from Home (TFH) for 14 national male athletes and 11 female national athletes for rowing in preparation for the Asia Cup. The athletes' seriousness in exercising for seven weeks was shown from recorded data during the New Normal. The purpose of this research is to see the effect of TFH on athlete detraining. The absence of specific research related to this is a novelty in this study. The method used is quasi-experimental, by looking at the athletes' seriousness in doing the exercises independently without direct assistance from the coach. The coaches could only assist online. The instrument used met the standards of validity and reliability of conformity. It was expected that the athletes' performance did not decrease as they entered the next stage of training. The results showed no significant effect of TFH on detraining in the components of Muscle Power, Aerobic Power, Capacity Squat, Deadlift, and Bench Pull in the men's group. In the women's group, there was a significant effect of TFH on detraining in Muscle Power and Women's Aerobic Capacity, and there was an insignificant effect of TFH on detraining in the components of Aerobic Power, Squat, Deadlift, and Bench Pull. This study concludes that TFH has different effects on detraining elite rowing athletes during the COVID-19 pandemic.
... Detraining is a reduction or interruption in the frequency, intensity, or duration of exercise required to maintain physiological and performance gains through training (15,16). It may be caused by injury, illness, or an unplanned periodic transition phase (17). ...
... For example, Gavanda et al. (39) argued that the three-week detraining process did not affect muscle strength or athletic performance. Similarly, scholars observed that the lower extremity isokinetic muscle strength in a four-week detraining process (41), the speed and strength performances after the 26-day training interruption (38), and the studies (15,16,51,52) that physiological adaptations such as decreased blood volume are among the main reason behind the deterioration in cardiovascular function. ...
... More specifically, it is noticed [3] that a prolonged period of rest after the competitive season causes the partial or complete loss of training-induced physiological and performance adaptations, in response to an insufficient training stimulus, which is defined as detraining. Decreases in physical fitness are inevitable after two to six week period of detraining in athletes [4][5][6][7][8]. The detraining can impair cardiovascular and neuromuscular performance [6]. ...
... Decreases in physical fitness are inevitable after two to six week period of detraining in athletes [4][5][6][7][8]. The detraining can impair cardiovascular and neuromuscular performance [6]. When lockdown started, it was unclear how long the players would be out of organized team training sessions. ...
Objectives: Decreases in physical fitness are inevitable after two to six week period of detraining in athletes. Lockdown period changed the characteristics of soccer players’ training.
Aim of the study: The aim of our study was to apply a HIIT shock-microcycle (SM) after return to training and assess its effect on players’ performance.
Equipment and methods: Nineteen elite professional soccer players during the lockdown period (LP) from March to May 2020 (8 weeks) performed 3-4 individual training sessions per week. The training sessions included running boots of anaerobic short and aerobic prolonged duration intervals. Intensity was determined according to lab ergospirometry test 2 weeks before LP. All the players followed an indoor program, 3-6 sessions per week consisted of core, balance and flexibility exercises (∼45 minutes). SM training content was same for both groups and took place the first two weeks after LP, consisted by eight high intensity interval training sessions (HIIT), two technique, two tactical sessions and two days off.
Results: Repeated sprint ability mean time (RSAMeanTime) and Repeated sprint ability performance – sprint no 4,5,6 (RSA4,5,6S) improved after SM (p=0.025, Effect size:r²=0.331, p=0.010, Effect size:r²=0.411, p=0.009, Effect size:r²=0.418, p=0.037, Effect size:r²=0.293, respectively. Yo-Yo intermitted recovery test level 2 (YYIR2TotalDistance) that covered by players during the 2nd measurement was 10.8% longer (p=0.004, Effect size:r²=0.483). Also, the YYIR2HeartRateRecovery percentage was lower during the 2nd measurement (p=0.014, Effect size:r²=0.107).
Conclusions: These results indicate that SM can improve YYIR2 and RSA performance thus it is a useful tool to regain physical attributes in a short period.
... Prolonged home stays may result in increased sedentary behaviour-spending long periods of the day sitting or lying down [5]. Periods of detraining longer than four weeks have shown a marked decline in VO 2 max, while fewer impairments have been concluded in strength performance [6,7]. This situation leads to an impaired health status and might lead to worse chronic conditions [8]. ...
... Muscle/tendon injuries are among the most common in sport and require a mean of 15 days (SD = 17) to rehabilitate [25]. A period of insufficient training stimulus derives in muscular negative adaptations, fibre distribution, cross-sectional area, force production, power or isokinetic strength [7]. These mechanisms place individuals at a higher risk of sustaining an injury if the return to sporting activity is not managed properly [37]. ...
The lockdown due to the COVID-19 pandemic inherently changed people’s lifestyles. Forty-eight days of isolation led to worsening physical fitness in addition to the development of other unhealthy habits. The aim of this study was to describe sport-related injuries in the active general population. Physical therapy centres and sports medicine clinics were contacted via e-mail, seeking patients who had sustained an injury during or immediately (up to two weeks) after the lockdown. Patients who agreed to participate completed an online survey that followed the International Olympic Committee Statement. The questionnaire focused on physical exercise habits, type of injury, location and tissue affected. A total of 51 females and 67 males (30.5, SD = 8.8 years) participated in the study. Eighty percent of the participants performed aerobic training sessions, while the rest dedicated their workouts to strength training. Two in every three injuries were located in the lower limbs, and 80% affected the musculoskeletal tissue. Of all the injuries recorded, 67% occurred during the first week after lockdown. The number of aerobic exercise sessions was positively correlated with lower limb injuries (χ2 = 17.12, p < 0.05). Exercise habits should be considered when planning to return to a sport after a period of confinement to avoid injury.
... These results are in line with those reported in previous systematic reviews conducted in youth and adults soccer players (Silva et al., 2016;Clemente, 2021). These impairment can be caused, among others, by the decreases in muscle capillary density and oxidative enzymes resulting in reduced mitochondrial adenosine triphosphate production after training cessation, which in combination with a reduced arterial-venous oxygen difference may explain the decrements in aerobic fitness observed in our study (Mujika & Padilla, 2001). Moreover, although short term detraining does not significantly change muscle fiber distribution, it may influence fiber cross-sectional area. ...
... Moreover, although short term detraining does not significantly change muscle fiber distribution, it may influence fiber cross-sectional area. This may compromise force production, accompanied by a reduction in electromyographical activity, which can be observed in reduced performance of power-related actions like vertical and horizontal jumping, sprinting or change-of-direction (Mujika & Padilla, 2001). Improvements promoted by SSG and HIIT over 5 to 6 weeks, independently or combined, on aerobic fitness have been confirmed previously in youth male soccer players (Arslan, Orer & Clemente, 2020;Arslan et al., 2021bArslan et al., , 2021a. ...
Background
The aim of this study was two-fold: (i) analyze the within-group physical fitness adaptations promoted by a detraining period (4 weeks) followed by an intervention period (4 weeks) using small-sided games (SSGs) or running-based high intensity interval training (HIIT); and (ii) analyze the between-group differences aiming to identify the effectiveness of each training intervention on the physical fitness of youth male soccer players.
Methods
This study followed a randomized parallel study design. Forty male soccer players (age: 16.4 ± 0.5 years old) were assessed three times: (i) baseline; (ii) after 4 weeks of detraining; and (iii) after a retraining period of 4 weeks. After returning from detraining, players were randomized to an SSG-based training intervention ( n = 20) or running-based HIIT ( n = 20). Interventions lasted 4 weeks, with a training frequency of three sessions per week. At all timepoints, players were assessed by: (i) anthropometry (height, body mass, fat mass (FM)), countermovement jump (CMJ), standing broad jump (SBJ), triple hop jump (THJ), linear sprint test (5-, 10-, and 20-m), zig-zag test with (ZZwB) and without (ZZwoB) ball, three corner run test (3CRT), Y-balance test and the Yo-Yo intermittent recovery test level 1 (YYIRT). Mixed ANOVA (time * group) was conducted for testing interactions between the three timepoints of repeated measures and the two groups. Effect size (ES) for pairwise comparisons was calculated using Cohen’s.
Results
Between-group analysis revealed significantly smaller SBJ ( t = −2.424, p = 0.020, d = −0.767 small ES) and THT ( t = −4.353, p < 0.001, d = −1.376 large ES) in the SSG group after the retraining period. At the same time, SSG presented significantly greater FM after retraining compared to HIIT ( t = 3.736, p < 0.001, d = 1.181 large ES). Additionally, SSG had significantly smaller values than HIIT in the ZZwB ( t = −3.645, p < 0.001, d = −1.153 large ES), but greater times in the ZZwoB ( t = 2.679, p = 0.011, d = 0.847 large ES) and 3CRT ( t = 3.126, p = 0.003, d = 0.989 large ES).
Conclusions
Although SSG and HIIT interventions improved physical fitness outcomes after a period of detraining, they were not able to effectively restore body composition, CMJ, 20-m sprint, ZZwB, and YYIRT compared with the baseline assessments (before detraining). Only HIIT was significantly effective for restoring SBJ, short linear sprin speed, and change-of-direction compared with baseline. HIIT was also significantly better than SSG in improving SBJ and ZZwoB. Although the small sample, the non determination of maturation status and the need to be cautious regarding generalization, HIIT appears to be more beneficial than SSG after a detraining period for recovery of body composition and physical fitness qualities in this specific context of youth soccer players.
... Ponieważ trening fizyczny jest procesem, w którym następują obciążenia prowadzące do przystosowania się mięśni do większego wysiłku fizycznego 11 , ograniczenie treningów jedynie do warunków domowych doprowadziło do odtrenowania (ang. detraining), czego konsekwencją jest obniżenie poziomu wyników sportowych (Mujika, Padilla 2001). W treningu sportowym nawet okres zawieszenia lub rozluźnienia (do czterech tygodni) zmniejsza korzyści, które z treningu czerpią młodzi ludzie, niezależnie od tego, jak intensywny trening był wcześniej. ...
... Jest to proces odwracalny, zgodnie z zasadą odwracalności treningu, według której zatrzymanie lub wyraźne zmniejszenie treningu prowadzi do częściowego lub nawet całkowitego odwrócenia adaptacji, które były wywołane treningiem(Mujika, Padilla 2001). ...
Subject competitions provide valuable support to the teaching / learning process. Particular attention should be paid to competitions recommended by pedagogical supervision bodies, which should be very popular, both among students and teachers. The
aim of the article was to investigate trends in the participation in Polish competition miniLogia. The contest is organized for children from the Mazovian primary schools and is aimed at revealing and developing computing talents, and raising the level of informatics education. The quantitative research exploited data from the thirteen years,
from school year 2006/2007 to 2018/2019. In particular, the results obtained by 850 students in the third level of each year of the competition were analysed. The results show the decreasing participation of students, especially from the towns outside Warsaw.
There is also an increasing share of non-public school students among finalists. The proportion of girls who advance to the highest level of the competition is still significantly lower than the corresponding percentage of boys. Moreover, the results show male participants still score higher than girls. The findings indicate the need for change in Polish computing education on the primary level and suggest a direction for future research.
... The consequences of typical breaks between seasons (with their duration defined as ca. 4 to 6 weeks for elite athletes) are not well defined and may be related to the strategy adopted during the recovery period and the baseline level of fitness [3,4]. However, some of the changes occurring in the cardiorespiratory, neuromuscular, and metabolic systems have been characterized [5]. There are studies in the literature showing both a significant decrease in VO 2 max in well-trained athletes who stopped training for 3-6 weeks [6,7] and a reduction in capillary density, oxidative capacity [5], mean cross-sectional area of muscle fibers [8], EMG activity, and changes in fiber type [9]. ...
... However, some of the changes occurring in the cardiorespiratory, neuromuscular, and metabolic systems have been characterized [5]. There are studies in the literature showing both a significant decrease in VO 2 max in well-trained athletes who stopped training for 3-6 weeks [6,7] and a reduction in capillary density, oxidative capacity [5], mean cross-sectional area of muscle fibers [8], EMG activity, and changes in fiber type [9]. According to Kuipers and Keizer, the complete cessation of training in a well-trained, competitive athlete can result in a 2 of 11 syndrome of detraining, relaxation, exercise abstinence, or exercise addiction [10]. ...
This study aims to evaluate the effects of a prolonged transition period (detraining) on the physical capacity, power, and speed parameters of elite swimmers. Fourteen swimmers (seven females and seven males) aged 20.4 ± 1.7 years participated in the study. The athletes were subjected to two rounds of identical tests at 12-week intervals during the detraining period (DP), which consisted of an evaluation of the athletes’ body weight and composition, a measurement of the power of their lower limbs (Keiser squat, countermovement jump (CMJ), akimbo countermovement jump (ACMJ)) and upper limbs (Keiser arms) on land, and 20-m swimming using the legs only (Crawl Legs test), arms only (Crawl Arms test), and full stroke (Front Crawl test). An analysis of variance revealed a significant effect of the main factor, Gender, on all the measured parameters, while for the factor Detraining, except for Front Crawl (W) (F = 4.27, p = 0.061), no significant interaction effect (Gender × Detraining) was revealed. Among both the male and the female participants, a reduction in lactate-threshold swimming speed (LT Dmax) and a reduction in swimming speed and power on the Crawl Arms, Crawl Legs, and Front Crawl tests was observed after 12 weeks. There were also statistically significant reductions in ACMJ and CMJ jump height and upper-limb power (Keiser squat) among the female and male swimmers. There were no significant changes in body weight or body composition. The study showed a clear deterioration in results for most of the parameters, both for those measured on land and for those measured in water.
... Since high-intensity performance is required in soccer, home confinement has produced harmful effects of greater magnitude on the specific physical conditioning of soccer players than on athletes from other types of sports [3]. Practitioners in soccer are worried about the long-term impact of detraining caused by the home confinement since previous researches showed that detraining longer than 4 weeks resulted in a significant decrease in performance in professional soccer players [2,5,[7][8][9]. ...
... However, decreases in physical fitness are inevitable after >4 weeks of detraining in welltrained elite soccer players who have a relatively higher level of fitness compared to recreational players [24]. In elite athletes, eccentric muscle strength can decrease remarkably after 4-week detraining [9]. In current study, the players performed 8-week home-based exercise training during home confinement. ...
Objectives
This study aimed to examine the effects of COVID-19 confinement on hamstring eccentric strength, hip adduction-abduction strength and posterior chain flexibility in professional male soccer players. We also aimed to investigate whether muscle strength and flexibility would change when the players returned to play after COVID-19 confinement.
Methods
Thirty professional male soccer (Age; 24.9±4.8 yrs, BMI; 22.7±1.4 kg/m²) players participated in this study. Hamstring eccentric strength, hip abduction-adduction strength and posterior chain flexibility (PCF) were measured before (time 1) and after the home confinement period (time 2) and after return to play (time 3). Repeated measures of ANOVA was used for statistical analysis.
Results
PCF decreased from time 1 to time 2 (p=0.005) but it increased from time 2 to time 3 (p=0.03). Hamstring eccentric strength decreased from time 1 to time 2 for both dominant (p=0.002) and non-dominant (p=0.04) limbs and no difference was observed between time 2 and time 3 (p>0.05). Hip abductor and adductor strength did not change between time 1 and time 2 (p>0.05) but they increased from time 2 and time 3 in the dominant limb (p<0.05). Five players (16%) had muscle injuries including hamstrings and adductors when they returned to play.
Conclusion
This study showed that 8-week COVID-19 confinement had an adverse effect on hamstring eccentric strength and PCF and 3 players had hamstring muscle injuries when they returned to play. Therefore, soccer players can be at risk of hamstring muscle injuries due to long-term detraining. Hip abductor and adductor strength seem not to be negatively affected by 8-week COVID-19 confinement. However, 2 players had adductor strain when they returned to play.
... 공정한 경주를 위해 경륜은 선수 개개인의 기량에 따라 슈퍼 특선 (SS급), 특선(S급), 우수(A급), 선발(B급) 총 4개의 등급으로 구분되 며, 경주 성적에 따라 승급 또는 강급이 결정된다 (Lee et al., 2022 (Craig & Norton, 2001;da Rocha Penteado et al., 2010;Driller & Halson, 2013;Malizia & Blocken, 2021 (Park & Seo, 2020;Sakong et al., 2021 (Bassett & Howley, 2000;Mujika & Padilla, 2001a). 또한, 탈진까지의 총 운동시간, 최대 파워 및 안 정 시 혈중젖산 농도는 경륜 선수의 스프린트 성능과 높은 상관성 이 있는 것으로 알려져 있다 (Rosenblat et al., 2022;Støren et al., 2013;Sung et al., 2021 ...
PURPOSE This study aimed to compare body composition, physical fitness, maximum muscle strength, and blood lactate concentration according to the level of aerobic capacity in Keirin cyclists.METHODS Forty-four Keirin cyclists participated in this study and were divided into three groups: the top 20% VO<sub>2</sub>max group (TG, n=9), the middle 20% VO<sub>2</sub>max group (MG, n=9), and the low 20% VO<sub>2</sub>max group (LG, n=9). The study measured body composition, physical fitness, maximum muscle strength, and blood lactate concentration in Keirin cyclists. Differences between groups were determined using one-way ANOVA analysis.RESULTS Body weight, percentage of body fat, and body mass index were significantly higher in the LG than in the TG and MG. The vertical jump and maximum muscle strength were significantly higher in the TG and MG than in the LG. Additionally, blood lactate concentrations immediately after exhaustive exercise and during the 5-minute recovery periods were higher in the LG than in the TG and MG. Moreover, the time to exhaustion, HRmax and maximum power were the highest in the TG.CONCLUSIONS Our findings suggest new information that levels of aerobic capacity in male Keirin cyclists might be a crucial predictor of cycling performance and recovery ability.
... Athletes often experience training cessation because of injury, illness, post-season vacation, or other reasons. The magnitude of a training cessation-induced decline in their physical functions strongly depends on the duration of training cessation and/or the training level of subjects [1][2][3]. Regarding muscle performance, to date, much attention has been paid to notable declines in muscle strength after long-term training cessation (i.e., longer than four weeks) [2]. In contrast, limited information is available, and a scientific consensus has not yet been reached on the effects of short-term (i.e., less than four weeks) training cessation on muscle performance in power-trained athletes [1]. ...
Athletes often experience short-term training cessation because of injury, illness, post-season vacation, or other reasons. Limited information is available about the effect of short-term (less than four weeks) training cessation on muscle strength in athletes. Sprinting athletes must maintain knee extension and flexion strength to reduce the risk of sprint-type hamstring strain injury. This study aimed to identify whether and to what extent knee extension and flexion torque in concentric and eccentric contractions is reduced by two weeks of training cessation in sprinters. Before and after the training cessation, maximal voluntary isokinetic knee extension and flexion torque in slow and fast concentric (60 and 300°/s) and slow eccentric (60°/s) contractions were assessed in 13 young male highly trained sprinters (average World Athletics points = 978). Knee flexion torque during the bilateral Nordic hamstring exercise (NHE) was also measured. After the training cessation, isokinetic concentric at 300°/s and eccentric torque were significantly reduced in both knee extension and flexion. There was no difference in the magnitude of reduction between isokinetic knee extension and flexion torques in all conditions. The relative changes were more notable in eccentric (-15.0%) than in concentric contraction at 60°/s (-0.7%) and 300°/s (-5.9%). Knee flexion torque during the NHE also declined (-7.9% and -9.9% in the dominant and non-dominant legs, respectively). There was no significant correlation between the relative reductions in isokinetic knee flexion torque and knee flexion torque during the NHE. The findings suggest that sprinters and their coaches should focus on recovering fast concentric and slow eccentric knee extension and flexion strength after two weeks of training cessation.
... It has been proposed that strength-endurance performance is predicated on adaptations including increases in capillarization and mitochondria activity as well as enhanced metabolic enzymatic activity 36 . Interestingly, all these adaptations seem to be negatively impacted by short periods of complete training cessation 37 . Additionally, increases in maximal strength have been speculated to enhance local muscular endurance due to loads used in testing being a lower percentage of an individual's 1RM. ...
Based on emerging evidence that brief periods of cessation from resistance training (RT) may re-sensitize muscle to anabolic stimuli, we aimed to investigate the effects of a 1-week detraining interval at the midpoint of a 9-week RT program on muscular adaptations in resistance-trained individuals. Thirty-nine young men and women were randomly assigned to 1 of 2 experimental, parallel groups: An experimental group that abstained from RT for 1 week at the midpoint of a 9-week, high-volume RT program (DELOAD) or a traditional training group that performed the same RT program continuously over the study period (TRAD). The lower body routines were directly supervised by the research staff while upper body training was carried out in an unsupervised fashion. Outcomes included assessments of muscle thickness along proximal, mid and distal regions of the middle and lateral quadriceps femoris as well as the mid-region of the triceps surae, lower body isometric and dynamic strength, local muscular endurance of the quadriceps, and lower body muscle power. Results indicated similar between-group increases in lower body muscle size, local endurance, and power. Alternatively, TRAD showed greater improvements in both isometric and dynamic lower body strength compared to DELOAD. In conclusion, our findings suggest that a 1-week detraining period at the midpoint of a 9-week RT program appears to negatively influence measures of lower body muscle strength but has no effect on lower body hypertrophy, power or local muscular endurance.
... The MVC torque increased after WB-HIIT, whereas it was reduced in the CTL group. The decrease in the CTL group is most probably due to a slightly lower involvement in physical activity and/or active displacements during the COVID-19 pandemic, 72 despite the instruction to keep physical activity habits stable. The associated EMG activities of the agonist (vastus medialis, vastus lateralis and rectus femoris) and antagonist (biceps femoris) muscles were not modified in any group. ...
Background/objective:
Bodyweight exercises performed at home could be a complementary approach to improve health-related fitness in people having little spare time and during stay-at-home periods. This study then investigated body composition, cardiorespiratory fitness, and neuromuscular adaptations to a home-based, video-directed, whole-body high-intensity interval training (WB-HIIT).
Methods:
Fourteen subjects participated to an 8-week WB-HIIT (6 females, 23 ± 1 years) and fourteen were included in a non-exercise control group (CTL; 6 females, 24 ± 4 years). All took part to pre- and post-intervention assessments of body composition, peak oxygen uptake (VO2peak) and first ventilatory threshold (VT1; index of aerobic capacity), dynamic (leg press 3-repetition maximum) and isometric strength (knee extensors maximal isometric contractions with assessment of voluntary activation), and muscle endurance during an isometric submaximal contraction maintained till exhaustion. WB-HIIT consisted in 30-s all-out whole-body exercises interspaced with 30 s of active recovery. Training sessions were performed at home by means of videos with demonstration of exercises. Heart rate was monitored during sessions.
Results:
WB-HIIT increased VO2peak (5%), VT1 (20%), leg lean mass (3%), dynamic (13%) and isometric strength (6%), and muscle endurance (28%; p < 0.05), while they did not improve in CTL. VO2peak increase was correlated (r = 0.56; p < 0.05) with the time spent above 80% of maximal heart rate during training sessions. Isometric strength increase was correlated with change in voluntary activation (r = 0.74; p < 0.01).
Conclusion:
The home-based WB-HIIT induced concomitant cardiorespiratory fitness and neuromuscular improvements. The predominant effect was observed for aerobic capacity and muscle endurance which could improve exercise tolerance and reduce fatigability.
... 28 Confinement has been shown to be prejudicial for athletes as detraining negatively affects different physiological systems such as neuromuscular, cardiovascular, respiratory and musculoskeletal, as well as physical capacities such as strength, power, endurance and agility that are all essential for athlete's performance. 10,[28][29][30] One positive information from our data is that 64.5% (138/214) were oriented by medical staff during training. It is an important action that was developed during the quarantine period to maintain athletes healthy and active. ...
Background
Social distancing may affect athletes’ training, causing negative effects on mental and physical health.
Objective
This study therefore aimed to characterize the perception of Brazilian athletes about their physical and psychosocial aspects, sleep quality and coping strategies during the quarantine of the coronavirus disease 2019 (COVID-19) pandemic.
Methods
This was a cross-sectional study with online survey, performed with Brazilian athletes (amateur and professional) over 18 years. The main outcomes measures assessed were physical and psychosocial aspects, sleep quality and coping strategies.
Results
A total of 214 athletes were included. The average weekly hours of training during the quarantine was 4.71 ± 3.71 h, of which 64.5% athletes (138/214) were oriented by medical staff during training. For 52.8% (113/214) of athletes, training intensity during the quarantine was different/very different from the intensity before the quarantine. 79.4% athletes (170/214) reported moderate to extreme difficulties in keeping the same level of training during the quarantine. 77.1% athletes (165/214) had moderate to extreme anxiety and each of the athletes had concern about his or her athletic career future, including return to the sport. 72.9% athletes (156/214) reported change in sleep schedule during the quarantine period.
Conclusion
The quarantine period during COVID-19 pandemic negatively affected the athlete's perception about training routine, since athletes reported reduction in training hours and training intensity. Overall, the athletes reported that they were moderately to extremely anxious. They also had concerns about their career in the future, as well as concerns regarding return to sport.
... Athletes usually trained at home DL, focusing on bodyweight-based and weightlifting strength training, as well as cardiovascular endurance conditioning [9,11,35]. However, home-exercise programs (characterized by limited equipment and facilities) do not provide enough stimuli to replicate the conditions of real competitions and usually lead to irregular training loads and a reduction in strength and general fitness levels [2,7,9,11,12,19,36,37]. ...
The COVID-19 lockdown may have had collateral effects on the conditions of athletes, with possible increases in injury risks upon the return to sports. Due to the existence of multiple factors of injury risks based on the lockdown and the return to sports, the aim of this study was to analyze the injury rates after the lockdown in competitive athletes. A non-experimental quantitative design based on a survey was carried out, and 94 athletes (42 males and 52 females; 23.57 ± 6.20 years) participated. Statistical analyses were carried out using non-parametric tests. Injury rates did not increase significantly after the lockdown, and there were no statistical differences between performance levels, types of sports, the design of a specific training program by sports professionals during the lockdown, the moment of injury, and the mechanism of injury. It is important to develop injury prevention protocols to prepare athletes after such a long period of detraining.
... Research regarding humans is incomplete in regards to characterizing the extent of detraining for performance versus muscle size (Bosquet et al., 2013;Coratella et al., 2021;Mujika & Padilla, 2001;Staron et al., 1991). Our study supports the notion that changes in performance are more rapid upon training/detraining than F I G U R E 6 Transverse sections of nontrained (a) and 3 months posttrained (b) muscles of rats were labeled by immunofluorescence for laminin (red) and nuclei (blue). ...
Rodent studies investigating long-term effects following termination of hypertrophy-inducing loading have predominantly involved exposures such as synergist ablation and weighted wheel running or ladder climbing. This research yielded a spectrum of results regarding the extent of detraining in terms of muscle mass and myonuclei number. The studies were also limited in their lack of sensitive performance measures and indirect relatedness to resistance training. Our research group developed and validated a relevant rat model of resistance-type training that induces increased muscle mass and performance. The aim of the present study was to determine to what extent these features persist 3 months following the termination of this training. While performance returned to baseline, muscle mass remained elevated by 17% and a shift in distribution to larger muscle fibers persisted. A 16% greater total RNA and heightened mRNA levels of ribosomal protein S6 kinases implicated preserved transcriptional output and ribosomal content. Remodeling of muscle fiber nuclei was consistent with these findings - increased nuclear number and a distribution shift to a more circular nuclear shape. These findings indicate that muscle mass detrains at a slower rate than performance and implicates multiple forms of myonuclear remodeling in muscle memory.
... Konverze svalových vláken byla sledována u různých sportovních oblastí. Vlivem tréninku nebo naopak detréninku (období s velmi sníženým tréninkovým objemem i intenzitou) byly sledovány změny v poměru vláken (Mujika & Padilla, 2001). Konverze byly identifikovány v období od 8 týdnů až po 7 měsíců, změny (z vláken I. na II. ...
Cílem textu je poskytnout vědecky podloženou evidenci k teorii tonických a fázických svalů včetně souvisejících vlastností (tendencí) z různých hledisek. Text je členěn na Rozlišení tonických a fázických svalů, Svalová vlákna, Inervace svalu, Zkrácení svalu, Tonus svalu, Oslabení svalu. Pro hledání relevantních zdrojů byly použity databáze PubMed, Semantic Scholar, Scopus. České zdroje byly hledány prostřednictvím Google Scholar, Theses.cz, případně google.com nebo v knihovních systémech.
... Therefore, the detraining effect on the tongue may be different from that of the limb muscles. It is also generally reported that detraining effects may differ depending on the intensity, number of sessions, frequency, and duration of training (Mujika & Padilla, 2001). Therefore, it is important to investigate the detraining effects associated with TSE considering these conditional differences. ...
Purpose
The purpose of this study was to investigate the effects of tongue-strengthening exercise (TSE) on tongue strength and effortful swallowing pressure in young healthy adults.
Method
Thirteen young healthy volunteers (six men, seven women; M age = 20.5 ± 0.5 years) performed 8 weeks of isometric TSE 3 days per week. A tongue pressure measurement device was used to measure maximum isometric tongue pressure (MITP) and conduct the TSE, and a tactile sensor system attached to the hard palate was used to measure effortful swallowing pressure. MITP and effortful swallowing pressure were measured at baseline, after 4 and 8 weeks of training, and at 4 and 8 weeks after the last training session to examine the detraining effects.
Results
The results indicated that both MITP and effortful swallowing pressure increased significantly from baseline to 8 weeks after training. Although the improved MITP significantly decreased at 4 and 8 weeks after training cessation, no detraining effect was observed for effortful swallowing pressure.
Conclusions
TSE is an effective method for increasing tongue pressure in wide tongue–palate contact areas during effortful swallow. The effortful swallowing pressure gained with TSE appears to be maintained for at least eight nontraining weeks.
... However, these findings are not directly comparable, since the measurement in that study was made through the Nordic flexion exercise, which differs from our study, even though both tests are capable to assess the eccentric strength of the knee flexors. Even though eccentric strength has been shown to be more susceptible to decline compared to other neuromuscular factors [36]. ...
Background:
It is well known that periods of inactivity generate a loss of muscle strength, a fundamental component of sports performance in soccer. However, little information is available on the decrease in strength levels in professional soccer players after the quarantine lockdown that occurred during the COVID-19 pandemic.
Aim:
To compare the isokinetic peak torque profiles of professional soccer players from different teams before and after the quarantine period generated by COVID-19.
Methods:
A retrospective observational study was performed using data collected from two different professional elite-level soccer teams just before and immediately after the COVID-19 quarantine period. One team gave individual instructions to its players for conditioning maintenance at home during the quarantine period, while the other team used regular video calls to maintain the player's conditioning status on home training. The main outcomes were the mean peak torque of knee extensors and flexors, from concentric and eccentric contractions of each playing position. Analysis. A two-way ANOVA analysis was used to compare peak torque before and after the quarantine period and between both teams' strategies, showing a statistically significant reduction in eccentric knee flexor peak torque from the team that did not have remote monitoring.
Conclusions:
Remote monitoring programs are recommended so that athletes are less affected by the deleterious effects of confinement.
... Walaupun masih sulit untuk memprediksi durasi krisis global COVID-19 yang saat ini sedang berlangsung, namun dalam hal memprediksi hilangnya adaptasi yang dipicu oleh pelatihan masih sangat Prayogi Dwina Angga 1) , Deddy Whinata Kardiyanto 2) Jp.jok (Jurnal Pendidikan. Jasmani, Olahraga dan Kesehatan).5(1) 11-25 13 dimungkinkan (Melchiorri dkk., 2014;Mujika & Padilla, 2001;Rodríguez-Fernández dkk., 2018). ...
The COVID-19 pandemic has resulted in the temporary suspension of the training centering system which has resulted in complex decisions relating to the continuation of training activities in accordance with existing circumstances. This paper aims to provide education and guidance in the implementation of regular exercise programs that must be realized as a solution to minimize the occurrence of COVID-19 transmission in the regular training process as well as provide understanding to the main sports branch management, coaches and athletes in carrying out regular training programs. This study uses a literature review method where the researcher conducts a series of studies by reviewing and analyzing various content and data, which involves various kinds of information related to the implementation of the training centering system in the new normal era. There are 4 key principles in the re-implementation of the training process on a regular basis or training camps, including preparation for resumption of training, criteria for training commencement, assessments and guidelines that serve as a reference for the implementation of training camps, as well as management and strategies for mitigating COVID-19 risks at training camps.
... In the present study we showed greater decreases in vertical jumping ability (−13.6% to −15%) and similar impairments in sprint and agility performance (4.7% to 5.5% for 30 m sprint time and 7.9% to 8.3% on the 505 agility test) compared with the study of Salazar et al. [25]. These decrements in speed and power performance in adolescents could be attributed to reductions in muscle fiber cross-sectional area (muscular factor) and to an impaired central activation (neural factor) as a result of inactivity [40], which has been shown to decrease force production and electromyographic activity [41]. On the other hand, Spyrou et al. [23] did not observe significant differences in vertical jump after 70 days of quarantine in futsal elite players. ...
Background:
This study examined the effects of a five-month lockdown due to COVID-19 pandemic on physical fitness parameters in urban adolescent male and female students.
Methods:
Two hundred and ninety-three male and female students (age: 15.8 ± 0.3 years) who attended the fourth grade of the same high school during the years 2016-2017 (first control group), 2018-2019 (second control group) and 2020-2021 (lockdown group) took part in the present study.
Results:
The percentage of overweight and obese students, according to body mass index, increased in males from 16.0% (2016-2017) and 14.6% (2018-2019), to 36.7% in 2020-2021 (p < 0.01), and in females from 8.6% (2016-2017) and 7.0% (2016-2017), to 25.6% in 2020-2021 (p < 0.01). Lower body fitness, as assessed by jumping, sprinting and agility tests, was impaired for both males and females after the lockdown compared with the 2016-2017 and 2018-2019 cohorts (vertical jumps: 10.4-15.1%; p < 0.01; d = 0.58-1.01, 30 m sprint: 3.7-4.9%; p < 0.01; d = 0.62-0.74; 505 agility test: from 6.1% to 9.4%; p < 0.01; d = 0.80-1.04). However, flexibility and performance in upper-body fitness tests (handgrip maximum isometric strength and medicine ball throws with different loads) was significantly reduced only in males after the lockdown (p < 0.05 to 0.01).
Conclusions:
These results suggest that a five-month lockdown negative influenced the physical fitness of adolescent students. Notably, greater reductions were observed in upper body strength, power and flexibility in males than in females. These results highlight the need to maintain strength, power and body mass during long periods of inactivity in adolescent populations.
... The present study demonstrated a progressive increase in the rate of maximal isometric torque during the acquisition phase of testing (sessions 1-3). The increase was then retained over the 2-week rest interval on session 4, when any gains associated with physiological adaptations due to a limited number of contractions would have dissipated over the 2-week interval (Häkkinen and Komi, 1983;Mujika and Padilla, 2001). ...
Background: The proprioceptive neuromuscular facilitation (PNF) reciprocal contraction pattern has the potential to increase the maximum rate of torque development. However, it is a more complex resistive exercise task and may interfere with improvements in the maximum rate of torque development due to motor skill learning, as observed for unidirectional contractions. The purpose of this study was to examine the cost-benefit of using the PNF exercise technique to increase the maximum rate of torque development.
Methods: Twenty-six participants completed isometric maximal extension-to-flexion (experimental PNF group) or flexion-only (control group) contractions at the wrist. Ten of the assigned contractions were performed on each of three sessions separated by 48-h for skill acquisition. Retention was assessed with 5 contractions performed 2-weeks after acquisition. Torque and surface electromyographic (sEMG) activity were analyzed for evidence of facilitated contractions between groups, as well as alterations in muscle coordination assessed across test sessions. The criterion measures were: mean maximal isometric wrist flexion toque; the maximal rate of torque development ( d τ/ d t m a x ); root-mean-square error (RMSE) variability of the rate of torque versus torque phase-plane; the rate of wrist flexion muscle activation ( Q 30 ); a coactivation ratio for wrist flexor and extensor sEMG activity; and wrist flexor electromechanical delay (EMD).
Results: There were no significant differences between groups with respect to maximal wrist flexion torque, d τ/ d t m a x or RMSE variability of torque trajectories. Both groups exhibited a progressive increase in maximal strength (+23.35% p < 0.01, η ² = 0.655) and in d τ/ d t m a x (+19.84% p = 0.08, η ² = 0.150) from the start of acquisition to retention. RMSE was lowest after a 2-week rest interval (−18.2% p = 0.04, η ² = 0.198). There were no significant differences between groups in the rate of muscle activation or the coactivation ratio. There was a reduction in coactivation that was retained after a 2-week rest interval (−32.60%, p = 0.02, η ² = 0.266). Alternatively, EMD was significantly greater in the experimental group (Δ 77.43%, p < 0.01, η ² = 0.809) across all sessions. However, both groups had a similar pattern of improvement to the third consecutive day of testing (−16.82%, p = 0.049, η ² = 0.189), but returned close to baseline value after the 2-week rest interval.
Discussion: The wrist extension-to-flexion contraction pattern did not result in a greater maximal rate of torque development than simple contractions of the wrist flexors. There was no difference between groups with respect to motor skill learning. The main adaptation in neuromotor control was a decrease in coactivation, not the maximal rate of muscle activation.
... The concept of detraining has been described in previous literature as "the partial or complete loss of training-induced anatomical, physiological, and performance adaptations, as a consequence of training reduction or cessation." [6], p.80. Historically, research has mainly focused on the physiological effects of detraining after strength or resistance training, e.g., [7,8], but very little is known about detraining in balance skill [9]. The current study assumes that a sudden stop in balance training might induce detraining effects that could increase the risk of falls in older adults. ...
Since the COVID-19 pandemic hit, lockdowns have been implemented to fight off infections in countries around the world. Whilst this measure is without a doubt effective against spreading infection, it might also decrease participation in exercise. For older adults, exercise is particularly important in the prevention of falls, and sudden detraining because of a lockdown or due to other causes might have detrimental consequences. This systematic review study aims to assess what is currently known on detraining effects for balance outcomes. Nine studies were included within this review. Results suggest that detraining effects could already be significant as early as 4 weeks after stopping the intervention. Programs that specifically focus on improving balance were more robust against detraining, with most positive effects still being present after 8 weeks. However, even with a specific focus on balance, studies started to show some signs of detraining. The current study is limited by the low number of included studies in the review, indicating a need to further confirm these results.
... Furthermore, research demonstrated that athletes could maintain their strength levels for up to 3 weeks of detraining, but decay rates increase thereafter (between 5-16 weeks) [20]. Others indicated that strength could be maintained for up to 4 weeks of inactivity, whereas highly trained athletes' eccentric force, sport-specific power, and recently acquired isokinetic strength, may decline significantly [21]. ...
During the COVID-19 lockdown, professional soccer players ceased their regular team training sessions and were provided with exercise programs to follow independently. This investigation assessed the impact of a 7-week COVID-19 lockdown and home-based individual physical training on professional soccer players' body composition and physical fitness. The study consisted of nineteen division 1 elite soccer players (age 27.68 ± 5.99 years, height 178.47 ± 5.44 cm) and compared the anthropometric and physical fitness parameters obtained post-transition period to those obtained post-COVID-19 lockdown. The statistical analysis indicated that body fat percentage was significantly higher after the lockdown period [t(18) = -5.59, p < 0.01, d = 0.56]. Furthermore, VO2max [t(17) = -11.54, p < 0.01, d = 0.57] and running time [t(17) = 3.94, p < 0.01, d = 0.76] values were significantly higher after the COVID-19 lockdown than those obtained after the transition period. In addition, significantly higher level of performance was demonstrated on squat jump [t(18) = -4.10, p < 0.01, d = 0.30], countermovement jump [t(18) = -7.43, p < 0.01, d = 1.11] and sit and reach tests [t(19) = -5.33, p < 0.01, d = 0.32]. Concurrently, lower body strength was indicated to be significantly greater (p < 0.01) following the COVID-19 lockdown. The training protocol provided during the confinement, due to the COVID-19 outbreak, was effective in keeping physical fitness at a significantly higher level compared to the transition period. Coaches and trainers are encouraged to examine the effectiveness of this protocol, as it may help them develop effective periodization programs during the transition period. This protocol may aid in the development of effective periodization programs that require minimal equipment and can be followed in similar situations.
... Interestingly, detraining did not result in losing performance following HIIT training. Previous studies reported that the reversibility of neuromuscular adaptation is slower than cardiovascular and metabolic adaptations [51]. Therefore, HIIT training, in which neuromuscular adaptation is more prominent, and combined training protocol, including HIIT training, experienced no significant or lower decreases following 2 weeks of detraining. ...
Neuromuscular adaptations are essential for improving athletic performance. However, little is known about the effect of different endurance training protocols and their subsequent detraining on the gene expression of critical factors for neuromuscular synaptic transmission. Therefore, this study investigated the effects of endurance training (high-intensity interval training [HIIT], continuous [cEND], mixed interval [Mix], and all protocols combined [Comb]) and detraining on performance and gene expression (GE) of the alpha-1a, synaptotagmin II (Syt-II), synaptobrevin II (Vamp2), and acetylcholinesterase (AChE) in the gastrocnemius and soleus of Wistar rats. Eighty rodents were randomly divided into control, HIIT, cEND, Mix, Comb, and detraining groups. The rodents trained for 6 weeks (5 × /week), followed by 2 weeks of detraining. Performance improved in all training groups and decreased following detraining (p < 0.05), except HIIT. In the gastrocnemius, alpha-1a GE was upregulated in the Mix. Syt-II and AChE GE were upregulated in HIIT, Mix, and Comb. Vamp2 GE was upregulated in all groups. In the soleus, alpha-1a GE was upregulated in HIIT, Mix, and Comb. Syt-II and Vamp2 GE were upregulated in all groups. AChE GE was upregulated in cEND, Mix, and Comb. Detraining downregulated mostly the gene expression in the skeletal muscles. We conclude that training intensity appears to be a key factor for the upregulation of molecules involved in neuromuscular synaptic transmission. Such changes occur to be involved in improving running performance. On the other hand, detraining negatively affects synaptic transmission and performance.
... The time required to recover pre-detraining neuromuscular and cardiorespiratory levels may highly vary among athletes based on several factors, including time of training stimuli cessation or reduction, amount of individual detraining-induced effects, individual fitness levels, and sport-specific requirements (Girardi et al., 2020). Regarding the pause time, some studies found reductions in physical performance after four weeks of detraining (Fleck and Kraemer, 2006;Raso et al., 2001), while in others, between 2 and 4 weeks of detraining, no differences were found (Carneiro et al., 2016, Gasparete et al., 2010, Michelin et al., 2008, Mujika and Padilla, 2001. ...
This investigation aimed to compare the level of physical performance of the military of the 3rd Military Police Battalion before and during the COVID-19 pandemic. The participants were 82 military personnel (76 men) who were submitted to the Physical Fitness Test (PFT) in November 2019 and repeated it in September 2020. The 12-minute and VO 2 max tests were selected for cardiorespiratory evaluation and push-ups and sit-up tests to assess localized muscle resistance. The results showed a decrease in the performance of these soldiers, both in cardiorespiratory variables and in localized muscular resistance (p ≤ 0.05). The pandemic may have negatively influenced the physical performance of the military.
... The resistance training-induced adaptations include both neuromuscular and musculoskeletal changes (43), and a detraining period could possibly affect both. The posttraining effects may be transitory, and their persistence depends on the continuity of the training stimuli (36) and the duration of the detraining period, without any sex difference (7). The literature reports many cases where the resistance training-induced adaptations were retained. ...
Coratella, G, Beato, M, Bertinato, L, Milanese, C, Venturelli, M, and Schena, F. Including the eccentric phase in resistance training to counteract the effects of detraining in women: a randomized controlled trial. J Strength Cond Res XX(X): 000-000, 2021-The current study compared the effects of concentric-based (CONC), eccentric-based (ECC), and traditional concentric-eccentric (TRAD) resistance training on muscle strength, mass, and architecture and the postdetraining retention of the training-induced effects in women. Sixty women were randomly assigned to unilateral volume-equated CONC, ECC, or TRAD knee extension training or control (N = 15 per group). Before training, after an 8-week intervention period, and after an 8-week detraining period, isokinetic concentric, eccentric, and isometric torque were measured. In addition, thigh lean mass was assessed by dual X-ray absorptiometry and vastus lateralis thickness, pennation angle, and fascicle length by ultrasound. After training, concentric and isometric torque increased (p < 0.05) similarly in all groups, whereas eccentric torque increased more in ECC than that in CONC (+13.1%, effect size (ES): 0.71 [0.04-1.38]) and TRAD (+12.6%, ES: 0.60 [0.12-1.08]). Thigh lean mass increased in ECC (+6.1%, ES: 0.47 [0.27-0.67]) and TRAD (+3.1%, ES: 0.33 [0.01-0.65]). Vastus lateralis thickness and pennation angle increased (p < 0.05) similarly in all groups, whereas fascicle elongation was visible in ECC (+9.7%, ES: 0.92 [0.14-1.65]) and TRAD (+7.1%, ES: 0.64 [0.03-1.25]). After detraining, all groups retained (p < 0.05) similar concentric torque. ECC and TRAD preserved eccentric torque (p < 0.05), but ECC more than TRAD (+17.9%, ES: 0.61 [0.21-1.21]). All groups preserved isometric torque (p < 0.05), but ECC more than CONC (+14.2%, ES: 0.71 [0.04-1.38]) and TRAD (+13.8%, ES: 0.65 [0.10-1.20]). Thigh lean mass and vastus lateralis fascicle length were retained only in ECC (p < 0.05), pennation angle was preserved in all groups (p < 0.05), and thickness was retained in CONC and ECC (p < 0.05). Including the eccentric phase in resistance training is essential to preserve adaptations after detraining.
... It is also important to know how long the adaptations produced by resistance exercise training could be maintained after detraining [27]. However, limited information is available for the effect of detraining after ET versus CT training on the trained and contralateral non-trained muscles. ...
Abstract Background Unilateral resistance training increases the strength of the contralateral non-trained homologous muscles known as the cross-education effect. We tested the hypothesis that unilateral eccentric resistance training (ET) would induce greater and longer-lasting cross-education effect when compared with concentric resistance training (CT). Methods Young (20–23 y) participants were allocated to ET (5 males, 4 females) or CT (5 males, 4 females) group that performed unilateral progressive ET or CT of the elbow flexors, twice a week for 5 weeks (10 sessions) followed by a 5-week detraining, and control group (7 males, 6 females) that did not perform any training. Maximum voluntary isometric contraction torque of the elbow flexors (MVIC), one-repetition maximum of concentric dumbbell curl (1-RM), and biceps brachii and brachialis muscle thickness (MT) were measured from the trained and non-trained arms before, several days after the last training session, and 5 weeks later. A ratio between the trained and non-trained arms for the change in MVIC or 1-RM from pre- to post-training (cross-body transfer ratio) was compared between ET and CT groups. Results The control group did not show significant changes in any variables. Both ET and CT increased (P 0.05) after ET and CT, and MVIC returned to the baseline after detraining, but 1-RM was maintained for both groups. An increase (P
Objective
The objective of this study was to determine the effect of intensity dosing during tongue exercise on tongue pressure generation, adherence, and perceived effort.
Design
This was a five-site, prospective, randomized clinical trial. Outcome measures were obtained across multiple baselines, biweekly during exercise, and 4-weeks post-intervention.
Setting
The general community at each study site.
Participants
Typically aging adults between 55–82 years of age with no history of neurological or swallowing disorders. Eighty-four volunteers completed the study.
Interventions
Participants were randomly assigned to one of four exercise groups: (a) maximum intensity/no biofeedback, (b) progressive intensity/no biofeedback, (c) maximum intensity/biofeedback, and (d) progressive intensity/biofeedback. Half of the participants completed a maintenance exercise program.
Outcome Measures
Maximum isometric pressure (MIP), regular effort saliva swallow pressure, adherence, and the Borg Rating of Perceived Exertion Scale.
Results
All exercise protocols were efficacious for gains in MIP (large effect sizes; Cohen's d ). Group 3 made gains in regular effort saliva swallow pressure (medium effect size). There was a significant change in perceived exertion for regular effort saliva swallow pressure at 8 weeks. Tongue pressure gains were maintained at 1 month, regardless of maintenance group status. Mean adherence across groups was high.
Conclusions
All groups improved pressure generation. Intensity dosing differences did not affect strength gains, adherence, or detraining. Regular effort saliva swallow pressure may be most responsive to maximum intensity with biofeedback. The findings suggest flexibility in approach to tongue exercise protocols. Tongue muscles may differ from limb muscles in terms of dose response and neuroplasticity principles.
Objective: To analyze the influence of exergaming (EXE) quality of life, cancer-related fatigue (CRF), electromyography, and strength and endurance muscle in a randomized crossover trial. Methods: We conducted a single-blinded, randomized, and crossover trial, which included 38 cancer volunteers undergoing chemotherapy (Age = 60.07 ± 12.10 years; body mass index = 26.79 ± 5.33 kg/m2). All volunteers were randomized into two intervention moments: EXE and without intervention (WI) and after 1-month washout period of crossing of the evaluated moments. The intervention was performed on an EXE protocol using Xbox 360 Kinect®, with the game "Your Shape Fitness Evolved 2012" two to three times per week for 20 sessions. All volunteers were assessed the CRF and quality-of-life levels through the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) questionnaire, the median frequency (MDF) by surface electromyography, maximal voluntary isometric contraction (MVIC), and the muscle endurance time at 80% MVIC of the dorsiflexors and plantar flexors using dynamometer. Results: In the comparison between EXE and WI moments, were observed increase in the scores for quality of life (P < 0.001), subscale fatigue (P < 0.001), in the MDF values of right lateral gastrocnemius muscles: P = 0.017, muscle endurance time (left dorsiflexion [LDF]: P < 0.001; right dorsiflexion [RDF]: P < 0.001; left plantar flexion [LPF]: P < 0.001; RPF: P = 0.039), and muscle strength (LDF: P < 0.001; RDF: P < 0.001; LPF: P = 0.002). Conclusion: The crossover study, the EXE protocol promoted improvement in cancer-related fatigue (CRF) and quality of life, increased MVIC, endurance time, and MDF values of the dorsiflexor and plantar flexor muscles of cancer volunteers undergoing chemotherapy.
Trainingsprinzipien gelten als Handlungsorientierungen für die Gestaltung des Trainingsprozesses. In den letzten Jahrzehnten haben sich eine Vielzahl dieser Prinzipien etabliert. Je nach Bezugssystem und Sprachraum existieren in der Literatur bis zu 20 dieser Prinzipien. Deren wissenschaftliche Evidenz und die Bedeutung für den Trainingsprozess ist nicht immer klar belegt. Einige dieser Prinzipien sind zudem unscharf von anderen abgrenzbar. Eine integrative und evidenzbasierte Berücksichtigung relevanter Prinzipien sollte im Planungs-, Umsetzungs- und Auswertungsprozess des Trainings unter effizientem Mittel- und Methodeneinsatz im Sinne eines optimalen Anpassungsprozesses gefördert werden. Diese intendierten Anpassungsreaktionen sind reizspezifisch, individuell und müssen unter Berücksichtigung des progressiven Overloads sowie der Belastungsnormativa (Frequenz, Intensität, Typ und Zeit) sorgfältig geplant und überwacht werden. Dieser Beitrag ist Teil der Sektion sportmotorische Fähigkeiten und sportliches Training, herausgegeben vom Teilherausgeber Michael Fröhlich, innerhalb des Handbuchs Sport und Sportwissenschaft, herausgegeben von Arne Güllich und Michael Krüger.
Objective
The objectives of this study were to quantify training adherence and exercise compliance during a workplace-based strength training intervention delivered to office workers over a 12-week period and to analyze the association with clinically relevant pain reductions.
Methods
A subsample of 269 participants completed a training diary from which measures of training adherence and exercise compliance (training volume, load, and progression) were calculated. The intervention consisted of 5 specific exercises targeting the neck/shoulder area (neck, shoulders, and upper back). The associations of training adherence, quitting time, and measures of exercise compliance with 3-month pain intensity (on a scale from 0 to 9) were analyzed for the whole sample, pain cases (reporting pain of ≥3 at baseline), participants attaining/not attaining clinically relevant pain reductions (≥30%), and participants meeting/not meeting per-protocol training adherence of ≥70%.
Results
Participants reported reduced pain in the neck/shoulder area after 12 weeks of specific strength training, especially women and pain cases, with the caveat that attaining clinically relevant pain reductions depended on the levels of training adherence and exercise compliance attained. Over the 12-week intervention, 30% of the participants were absent for a minimum of 2 consecutive weeks (quitting time), with the median quitting time being around weeks 6 to 8. With a threshold of 70% training adherence, a total training volume of approximately 11,000 kg (only in women) and progressions of 1 to 2 times baseline values were shown to be significant for clinically relevant pain reductions.
Conclusion
Strength training produced clinically relevant reductions in neck/shoulder pain when appropriate levels of training adherence and exercise compliance were attained. This finding was particularly evident for women and pain cases. We advocate for the inclusion of both training adherence and exercise compliance measures in future studies. To optimize intervention benefits, motivational activities after 6 weeks are needed to avoid participants quitting.
Human skeletal muscle demonstrates remarkable plasticity, adapting to numerous external stimuli including the habitual level of contractile loading. Accordingly, muscle function and exercise capacity encompass a broad spectrum, from inactive individuals with low levels of endurance and strength, to elite athletes who produce prodigious performances underpinned by pleiotropic training-induced muscular adaptations. Our current understanding of the signal integration, interpretation and output coordination of the cellular and molecular mechanisms that govern muscle plasticity across this continuum is incomplete. As such, training methods and their application to elite athletes largely rely on a "trial and error" approach with the experience and practices of successful coaches and athletes often providing the bases for "post hoc" scientific enquiry and research. This review provides a synopsis of the morphological and functional changes along with the molecular mechanisms underlying exercise adaptation to endurance- and resistance-based training. These traits are placed in the context of innate genetic and inter-individual differences in exercise capacity and performance, with special considerations given to the ageing athletes. Collectively, we provide a comprehensive overview of skeletal muscle plasticity in response to different modes of exercise, and how such adaptations translate from "molecules to medals".
Objective
To examine the prospective associations between physical activity trajectories, measured from repeated assessments over time, and cognitive function.
Method
A total of 2972 participants aged 45 years old and over (median age: 56.0 [interquartile range - IQR 50.0–62.0], 50.8% males]) from the Chinese Health and Retirement Longitudinal Study (CHARLS) study were included. First, our study used the growth mixture modeling to identify physical activity trajectories from the first three surveys of the CHARLS. Second, we performed regression analysis to explore the associations of the trajectories with 3-year cognitive function.
Results
We identified four physical activity trajectories, characterized by persistently low (N = 1880), initially low then increasing (154), initially moderate then decreasing (584), and initially high then decreasing (354). After 3-year follow-up, compared to individuals with persistently low trajectory, those with initially moderate then decreasing (β = −0.74, 95% CI = (−1.38, −1.10), p = 0.024) and initially high then decreasing (β = −1.12, 95% CI = (−1.91, −0.33), p = 0.005) were significantly associated with cognitive decline. The effects of the decline in physical activity on cognitive function varied by sex. Females’ cognitive function (β = −1.79, 95% CI = (−2.82, −0.77) was more likely to be influenced by decreasing physical activity, but this association was not significant in males. We did not find the significant effect of initially low then increasing trajectory on cognitive function.
Conclusions
Fast decline in physical activity is related to a higher risk of cognitive decline, especially in females.
During the pandemic period, football referees, like professional athletes, had to take a break from training for a long time. “Repetitive sprinting skill”, “high-intensity repetitive running performance” and “high aerobic power” have an important place in the performance of the referees, and it has been observed that the developments gained after 2 weeks in detraining situation begin to be lost. On the other hand, increased fat ratios and strength differences between the extremities are considered to be the risk of disability and low performance. The aim of this study is to ensure that the performances of elite athletes are preserved with resistance training when they are away from field training for a long time, such as during mandatory situations during the pandemic period, end of seasons, and during injury periods. Participants performed a study consisting of 24 AMRAP-style functional resistance training, limited to a maximum of 9 m ² area, with the aim of metabolic conditioning, and 12 injury-preventing exercises in 42 days. Age, height, body weight, and fat ratios were 35.6 ± 5.01 years, and 184.65 ± 4.42 cm, respectively. A total of 38 elite referees, 8 of whom were FIFA licensed, with a weight of 80.88 ± 7.12 kg and 12.9 ± 3.08%, participated. When the participants' pre-and post-exercise measurements were compared, post-exercise body weight (p = 0.017), fat percentage (p = 0.000), jump performance (p = 0.000), doggy running (p = 0.000), MaxVO 2 value (p = 0.000) and warm-up While there was a statistically significant difference in the RPE value after the procedure, no statistically significant difference was found in other parameters. As a result, it was found that planned functional strength training focused on metabolic conditioning significantly reduced anaerobic capacity and aerobic power losses in elite athletes. Accordingly, it is seen that home/hotel room training, which will be planned in holiday periods ranging from 1 to 3 months before starting the beginning of the season training, can be a simple and effective method for the athletes to start the next season in the readiest way.
Purpose: The purpose of this study was to investigate the impact on health-related fitness resulting from COVID-19 lockdowns on male high school students in Melbourne, Australia. Method: A total of 146 students completed fitness testing in February and retesting in November following 7 months of remote learning. Fitness tests conducted were 20-m shuttle run (Beep Test), flexed arm hang, body mass index, push-ups, sit-ups, and sit and reach. Results: The mean fitness levels of this cohort decreased across the health-related fitness components. Decreases were varying in magnitude, body composition ( d = 0.3), flexibility ( d = 0.56), muscular strength ( d = 0.64), muscular endurance ( d = 0.39 and d = 0.26), and cardiovascular endurance ( d = 0.96). Discussion: The impact on students’ fitness levels was noteworthy, and the long-term impacts of this decrease are yet to be seen. This research brings focus to what can be done to maintain adolescent fitness when their usual exercise opportunities are not available.
Captivity presumably challenges physiological equilibrium of birds and thus influences flight ability. However, the extent to which captive birds exhibit altered features underpinning maximum flight performance remains largely unknown. Here, we studied changes in physiological condition and load-lifting performance in the Eurasian tree sparrow (Passer montanus) over 15, 30, and 45 days of captivity. Sparrows showed body mass constancy over time but also an increased hematocrit at 15 days of captivity; both relative pectoralis mass and its fat content increased at 30 days. However, maximum takeoff speed and maximum lifted load remained largely unchanged until 45 days of captivity. Wingbeat frequency was independent of captivity duration and loading condition, whereas body angle and stroke plane angle varied only with maximum loading and not with duration of captivity. Overall, these results suggest that captive birds can maintain maximum flight performance when experiencing dramatic changes in both internal milieu and external environment.
This chapter discusses basic principles that appear to be useful in the treatment and rehabilitation of musculoskeletal injuries. It provides some specific advice for reducing the risk of developing musculoskeletal disorders in the occupational setting. The chapter describes procedures that may help reduce the pain and promote the healing process when an injury does occur. It then focuses on some of the lifestyle habits that have been shown to be of benefit to musculoskeletal health. Dietary factors appear to be important with respect to musculoskeletal health. Obesity is a risk factor for musculoskeletal disorders in general. There are many ways in which cumulative damage may accrue. The cumulative damage development might be the result of a mono‐task job, or more often, jobs comprised of multiple tasks. Adoption of non‐neutral postures may have an important role in increasing stress on musculoskeletal tissues, which has an important impact on the fatigue life of tissues.
Training sollte bestimmten Prinzipien folgen. Die Wissenschaft zeigt, dass sie auch in nicht-leistungssportlichen Settings, wie der klinischen Bewegungstherapie, relevant sind und zunehmend gefordert werden. Die Sportwissenschaftler Lars Donath und Oliver Faude haben die wichtigsten Prinzipien einem aktuellen Prüfstand unterzogen.
Z Detraining, antrenmanlar ile elde edilen fizyolojik ve performans özelliklerinin kazanımları korumak için gerekli olan antrenman sıklığı, yoğunluğu veya süresindeki bir azalma veya kesilmesi olarak ifade edilmektedir. Antrenmanla oluşan fizyolojik adaptasyonların geri dönüşlülük miktarı; kişinin antrenman durumuna, genetik özelliklerine, antrenmanın şiddet, yoğunluk ve sıklık bileşenlerinin ne kadar azaltıldığına ve antrenmana ne kadar süre ara verildiğine bağlıdır. Detraining döneminin sporcuların dayanıklılık, kuvvet, sürat, denge ve esneklik gibi performans özellikleri üzerinde önemli etkileri bulunmaktadır. Bu dönemde sporcuların performans seviyelerinde büyük düşüşler yaşanmaktadır. Bu düşüşler, antrenmanlı sporcularda, antrenmansız sporculara göre daha fazla olmaktadır. Yoğun antrenmanlar ile kazanılan özellikler, antrenmanlara verilen kısa bir ara ile hızla gerilemeye başlamaktadır. Kondisyonel özellikler ne kadar uzun süreç içerisinde kazanılırsa kayıpları da o kadar geç olmaktadır. Sporcuların performanslarında büyük düşüşler yaşanmaması için antrenörlerin detraining dönemini çok dikkatli bir şekilde planlamaları gerekmektedir. Yapılan bu çalışmada detraining'in temel fizyolojik sistemler üzerindeki etkileri incelenmiştir. ABSTRACT Detraining is expressed as a decrease or interruption in the frequency, intensity or duration of training necessary to maintain the gains in physiological and performance characteristics obtained by training. The amount of reversibility of physiological adaptations that occur with training; depends on the person's training status, genetic characteristics, how much the intensity and frequency components of the training are reduced, and how long the training is interrupted. The detraining period has important effects on the performance characteristics of the athletes such as endurance, strength, speed, balance and flexibility. During this period, the performance levels of the athletes decrease greatly. These decreases are higher in trained athletes than in untrained athletes. The features gained through intense training begin to regress rapidly with a short break in training. The longer the conditional properties are gained, the later the losses are. Coaches need to plan the detraining period very carefully so that the performance of the athletes does not decrease significantly. In this study, the effects of detraining on the major physiological systems were investigated.
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.
Introduction: Current practice in coaching track cycling sprint athletes is a focus on a very narrow band of power output from 1-4 seconds. However, there is a small oxidative contribution to sprint performance as short as 10-s, and this contribution increases as a rider competes in multiple events. All Olympic track cycling events demand repeated sprint performance! Purpose: This study models sprint-cycling performance to investigate the role of durations requiring a high oxidative contribution to energy supply and their relationship to sprint-cycling power durations. It hypothesizes power at endurance durations are strongly related to power at sprint durations, and further, these relationships may be nonlinear and saturable. Methods: Power meter data was used from 89 participants (192 datasets) to model fit the data using 4 different models (exponential, linear, parabolic, and power) using total least-squares. All data was based on a (0,0) start point acknowledging neither glycolytic or oxidative pathways operate independently. Dependent variables were 15 and 30 second power, and predictor variables 2, 8 and 20 minute power. Results: All four models yielded high r2 values (r2 > 0.81), and the exponential and linear models in particular. Strong correlations for all models demonstrates the role of oxidative power duration on performance over short durations. The linear model was the best model based on consistent, high r2 values and model simplicity, validating the first hypothesis, but nullifying the second. Conclusion: The results show maximal performance in sprint-cycling durations of 15 and 30 seconds are strongly related to maximal performance in 2, 8, and 20 minute power, and training at these durations does not diminish performance, and with a season, training maximally at these durations complements performance. These results match physiological studies showing oxidative pathways play a major role in sprint and repeated sprint efforts.
Guiding cyclists in their return from illness and injury can be managed in many ways. Understanding how cyclists use power-derived training metrics can give care providers a common language to aid in this return. A general understanding of these metrics may be used to monitor cyclists for signs of nonfunctional overreaching or overtraining. Understanding aspects of training and detraining, particularly hematological, is helpful in communicating fitness expectations. Three populations of cyclists are discussed in terms of their expected knowledge of these metrics, typical training volume and intensity, and relationship with a coach or coaches.
The aim of this research was to analyse the capacity of a home-based training programme to
preserve aerobic capacity and jumping performance in top-level handball players during the COVID-19 lockdown.
Eleven top-level male handball players from the same team participated in the study. A submaximal shuttle run
test and a counter-movement jump test were used to measure the players’ aerobic fitness and lower limb
explosive strength, respectively. A 9-week home-based training programme was followed during lockdown.
Pre-test measurements were assessed before the pandemic on 29 January 2020 and ended on 18 May 2020.
Moderate significant mean heart rate increases were found in the late stages of the submaximal shuttle run
test after the lockdown (stage 5, 8.6%, P = 0.015; ES = 0.873; stage 6, 7.7%, P = 0.020; ES = 0.886; stage
7, 6.4%, P = 0.019; ES = 0.827). Moderate significant blood lactate increases were observed immediately
after the submaximal shuttle run test following the lockdown (30.1%, P = 0.016; ES = 0.670). In contrast, no
changes were found in jump performance. A structured home-based training programme during the
COVID-19 lockdown preserved lower limb explosive strength but was an insufficient stimulus to maintain aerobic
capacity in top-level handball players.
Mat Pilates has become an attractive alternative exercise among older women, however, despite knowing the importance of regular exercise, interrupting training is a common issue in this population. The aim of the current study was to evaluate the effects of 6-weeks of detraining after a period of 12-weeks of training with Mat Pilates on the functional capacity and neuromuscular performance of the knee extensor muscles in older women. Ten older women (62.6 ± 2.6 years; 1.57 ± 0.05 m height; 69.3 ± 9.2 kg; 27.8 kg/m² body mass index) volunteered to participate in this study. The study was divided into three periods: a 4-week control period, followed by 12 weeks of Mat Pilates intervention, and a 6-week detraining period. During the intervention, the results showed significant improvements in functional capacity tests (time up and go, time up stairs, time down stairs, and chair sit-and-reach), rate of torque development, and impulse (p < 0.05). After the detraining period, a decrease was observed in the chair sit-and-reach test (p < 0.05) and contractile impulse at intervals 0–30 and 0–50 ms (p < 0.05). We conclude that a 6-week detraining period after a Mat Pilates training protocol was sufficient to cause declines in the chair sit-and-reach test and in the contractile impulse of the knee extensors in the early phase of the torque-time curve (0–30 and 0–50 ms), but not in the other functional capacity tests and neuromuscular parameters evaluated.
Objectives
The COVID-19 pandemic changed daily routines, including physical activity, which could influence physical and mental health. In our study, we describe physical activity and sedentary behaviour patterns in relation to the pandemic and estimate associations between anxiety and physical activity and sedentary behaviour in community-dwelling adults.
Design
Cross-sectional study.
Setting
Calgary, Alberta, Canada.
Participants
Between April and June 2020, a random sample of 1124 adults (≥18 years) completed an online questionnaire.
Primary and secondary outcomes
The online questionnaire captured current walking, moderate intensity, vigorous intensity and total physical activity and sedentary behaviour (ie, sitting and leisure-based screen time), perceived relative changes in physical activity, sedentary and social behaviours since the pandemic, perceived seriousness and anxiety related to COVID-19, and sociodemographic characteristics. Differences in sociodemographic characteristics, perceived relative change in behaviour and current physical activity and sedentary behaviour were compared between adults with low and high anxiety.
Results
Our sample (n=1047) included more females (60.3%) and fewer older adults (19.2%). Most participants (88.4%) considered COVID-19 as extremely or very serious and one-third (32.9%) felt extremely or very anxious. We found no differences (p>0.05) in current physical activity or sedentary behaviour by anxiety level. The largest perceived change in behaviours included social distancing, driving motor vehicles, use of screen-based devices, watching television and interactions with neighbours. We found anxiety-related differences (p<0.05) in perceived changes in various behaviours.
Conclusions
Changes in physical activity, sedentary behaviour and social behaviour occurred soon after the COVID-19 pandemic was declared, and some of these changes differed among those with low and high anxiety.
1 Finland HÄKKINEN K., KOMI P.V. & TESCH P.A. Effect of ccmbined concentric ard eccentric strength training and detraining on force-time, muscle fiber-and metabolic characteristics of leg extensor muscles. Scand. J ,Sports Sci. 3 (2): 50-58, 1981. Prog¡essive strength training of combined concentric and eccentric contractions were performed three times a week for 16 weeks by 14 males {20-30 yrs of age) accustomed to weight training. The training peeriod was iollowed bv 8 weeks of detraining. The training program consisted mainly of dynamic exeicises for the ieg-extensovs with loads of 80 to 120 of one maximum repetition The training caused significant improvements in-maximal force (p < 0.001) and various force-time (p (0.05-4.01) para¡àeters. Du¡ing thg I'ast trarning àionìh tbe inãrease in force was gireatly tri¡nited' and there was ¿ decrease in th,e force-time parameters. The marked improvements in mwcle strength were accompanied by ccnsiderable intemål qdaptatioos ,Ín-ttre tnaCned muscle, as Judged from l¡rcreases (p < 0-001) ,iqr. the fibet ãeas ôt tËe Ïast fi¡¡itch (FT) and slow twitch (ST) fibers. Durlng early conditioning improvement i! the qqgs! jump w,as related to tl.e relãtive hypertrop]ty of tr1l ii¡eis fo <0.01). No sier¡j-Êi,cå,r¡t ct¡anges ,in tJre er¡zyme aittv¡tiês oi mÍoki¡¡ase-a¡¡d creatine kirmse were found as a result of-tra¡rrir}g, but i,ndividt¡al charrges in my-o-kinase activity $/ere related to the relative. hypertrop'hy of FT fibers-(p ç 0.05) and Improvernent i+ the squat jump (p < O.Of)-during early conditiontuag. All the ada,p-iatlo:ns'-incilcating musõle hypertrophy occurred. prtm@lv during the last two training mo¡rths. Decreases (p (0.001) in maxirnal force during the detrairring were accompâ-nied bv a sisrificår¡t rediuction in the fi¡b,er areas of ttle fC tp < 0.01) and ST (p < 0.05) tvpes end by a change in bödy-antliropometry.-A periodiè-and partial usage. of àccentr-ic contráctions,-together with conèentric training' is suggested to be effectiùe in training for-maximal force and äso for force-time eharacteristics. In training of longer durations the specific effects of strength trainlng are-obviot¡s and explaiñable by adaptatlons in the trained muscle. Keg tenns: erìzJûne actlvities, muscle mechanics, muscle metabollsn, muscle streng:th.
The effects of an 8-week strength training program followed by an 8-week detraining period were evaluated in 11 boys and 4 girls, ages 7 to 12 years. Three boys and 6 girls matched for age and level of maturity served as controls. Progressive strength training was performed twice a week on child-size equipment. Subjects were tested on the following measures: 6 repetition maximum (RIM) leg extension, 6-RM chest press, vertical jump, and flexibility. Strength training significantly (p < 0.05; ANOVA) increased 6-RM strength on the leg extension (53.5%) and chest press (41.1%), whereas control group gains averaged 7.9%. Strength training did not significantly affect other variables. Detraining resulted in a significant loss of upper (-19.3%) and lower body (-28.1%) strength in the experimental group. The results suggest that participation in a short-term strength training program will increase the strength of children; however, strength gains regress toward untrained control values during the detraining period.
(C) 1996 National Strength and Conditioning Association
The adaptation of mitochondrial ATP production rate (MAPR) to training and detraining was evaluated in nine healthy men. Muscle samples (approximately 60 mg) were obtained before and after 6 wk of endurance training and after 3 wk of detraining. MAPR was measured in isolated mitochondria by a bioluminometric method. In addition, the activities of mitochondrial and glycolytic enzymes were determined in skeletal muscle. In response to training, MAPR increased by 70%, with a substrate combination of pyruvate + palmitoyl-L-carnitine + alpha-ketoglutarate + malate, by 50% with only pyruvate + malate, and by 92% with palmitoyl-L-carnitine + malate. With detraining MAPR decreased by 12-28% from the posttraining rate (although not significantly for all substrates). No differences were found when MAPR was related to the protein content in the mitochondrial fraction. The largest increase in mitochondrial enzyme activities induced by training was observed for cytochrome-c oxidase (78%), whereas succinate cytochrome c reductase showed only an 18% increase. The activity of citrate synthase increased by 40% and of glutamate dehydrogenase by 45%. Corresponding changes in maximal O2 uptake were a 9.6% increase by training and a 6.0% reversion after detraining. In conclusion, both MAPR and mitochondrial enzyme activities are shown to increase with endurance training and to decrease with detraining.
Four male subjects aged 23-34 years were studied during 60 days of unilateral strength training and 40 days of detraining. Training was carried out four times a week and consisted of six series of ten maximal isokinetic knee extensions at an angular velocity of 2.09 rad.s-1. At the start and at every 20th day of training and detraining, isometric maximal voluntary contraction (MVC), integrated electromyographic activity (iEMG) and quadriceps muscle cross-sectional area (CSA) assessed at seven fractions of femur length (Lf), by nuclear magnetic resonance imaging, were measured on both trained (T) and untrained (UT) legs. Isokinetic torques at 30 degrees before full knee extension were measured before and at the end of training at: 0, 1.05, 2.09, 3.14, 4.19, 5.24 rad.s-1. After 60 days T leg CSA had increased by 8.5% +/- 1.4% (mean +/- SEM, n = 4, p less than 0.001), iEMG by 42.4% +/- 16.5% (p less than 0.01) and MVC by 20.8% +/- 5.4% (p less than 0.01). Changes during detraining had a similar time course to those of training. No changes in UT leg CSA were observed while iEMG and MVC increased by 24.8% +/- 10% (N.S.) and 8.7% +/- 4.3% (N.S.), respectively. The increase in quadriceps muscle CSA was maximal at 2/10 Lf (12.0% +/- 1.5%, p less than 0.01) and minimal, proximally to the knee, at 8/10 Lf (3.5% +/- 1.2%, N.S.). Preferential hypertrophy of the vastus medialis and intermedius muscles compared to those of the rectus femoris and lateralis muscles was observed.(ABSTRACT TRUNCATED AT 250 WORDS)
After 5 months of intense training, eight male swimmers were studied during 4 wk of inactivity. Biopsy specimens from the deltoid muscle revealed that its respiratory capacity (QO2) decreased by 50% (5174 to 2559 microliter X h-1 X g-1) after 1 wk of inactivity. Subsequent weeks of detraining did not change the QO2. Although the trained swimmers' muscle phosphofructokinase and phosphorylase activities were significantly higher (P less than 0.05) than those from a group (N = 8) of untrained men, 4 wk of detraining had no effect on these enzyme activities. Mean (+/-SE) resting muscle glycogen concentrations were significantly higher (P less than 0.05) for the trained swimmers (153 +/- 3 mmol X kg-1) than for the untrained men (85 +/- 7.5 mmol X kg-1). Over the 4 wk of inactivity, the swimmers' muscle glycogen progressively decreased from 153 (+/- 3) to 93 (+/-7) mmol X kg-1. After a standard 183-m swim at 90% of the swimmer's best time for that distance, blood lactate rose from a mean of 4.2 (+/-0.8) at week 0 to 9.7 (+/-0.8) mmol X 1(-1) at week 4. These observations demonstrate dramatic changes in the metabolic characteristics of the swimmer's muscle with a 1-4-wk interruption in training.
The purpose of this study was to investigate the effects of repeated high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performances. First, nineteen subjects were submitted to a 15-week cycle ergometer training program which involved both continuous and high-intensity interval work patterns. Among these 19 subjects, six participated in a second 15-week training program after 7 weeks of detraining. Subjects were tested before and after each training program for maximal aerobic power and maximal short-term ergocycle performances of 10 and 90s. Muscle biopsy from the vastus lateralis before and after both training programs served for the determination of creatine kinase (CK), hexokinase, phosphofructokinase (PFK), lactate dehydrogenase (LDH), malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH) activities. The first training program induced significant increases in all performances and enzyme activities but not in CK. Seven weeks of detraining provoked significant decreases in maximal aerobic power and maximal 90s ergocycle performance. While the interruption of training had no effect on glycolytic enzyme markers (PFK and LDH), oxidative enzyme activities (HADH and OGDH) declined. These results suggest that a fairly long interruption in training has negligeable effects on glycolytic enzymes while a persistent training stimulus is required to maintain high oxidative enzyme levels in human skeletal muscle. The degree of adaptation observed after the second training program confirms that the magnitude of the adaptive response to exercise-training is limited.
To study the effect of some weeks of rest on three groups of adolescent soccer players, who had undergone systematic training for eleven months.
Experimental design: Retrospective and comparative investigation; duration 4-8 weeks. Setting: young amateur players from a Spanish football club were examined at the beginning and at the end of the summer rest period. Participants: 37 young soccer players aged 14, 15 and 16 years old. They were members of three football teams. Interventions: during the rest period they were free from any training program. Measures: biopsies of M. vastus lateralis were taken immediately after training and after the summer holidays. The type, percentage and diameter of the fibers, as well as the enzymes of glycogen metabolism (glycogen synthase and glycogen phosphorylase), glycolysis (phosphofructokinase and lactate dehydrogenase), oxidative metabolism (succinate dehydrogenase and citrate synthase) and creatine kinase and transaminase (aspartate and alanine aminotransferase) were studied.
Detraining had an adaptation effect, decreasing the cross-sectional area of type I and type II fibers, and decreasing the activities of creatine kinase, citrate synthase, phosphofructokinase, lactate dehydrogenase and aspartate aminotransferase.
The results can help trainers to plan the length of the rest period between training.
Seven endurance exercise-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Maximal O2 uptake (VO2 max) declined 7% (P less than 0.05) during the first 21 days of inactivity and stabilized after 56 days at a level 16% (P less than 0.05) below the initial trained value. After 84 days of detraining the experimental subjects still had a higher VO2 max than did eight sedentary control subjects who had never trained (50.8 vs. 43.3 ml X kg-1 X min-1), due primarily to a larger arterial-mixed venous O2 (a-vO2) difference. Stroke volume (SV) during exercise was high initially and declined during the early detraining period to a level not different from control. Skeletal muscle capillarization did not decline with inactivity and remained 50% above (P less than 0.05) sedentary control. Citrate synthase and succinate dehydrogenase activities in muscle declined with a half-time of 12 days and stabilized at levels 50% above sedentary control (P less than 0.05). The initial decline in VO2 max was related to a reduced SV and the later decline to a reduced a-vO2 difference. Muscle capillarization and oxidative enzyme activity remained above sedentary levels and this may help explain why a-vO2 difference and VO2 max after 84 days of detraining were still higher than in untrained subjects.
Six senior Rugby League players were assessed for changes to their physical and physiological characteristics as a result of six weeks relative inactivity following the completion of the regular playing season and the play-off series, including the Grand Final in which each of the subjects played. The initial tests, performed within 48 hours of the Grand Final, included height, weight and skinfold measures prior to the extraction of a biopsy sample of the lateral head of the right Gastrocnemius. The muscle samples were subjected to determination of Succinate Dehydrogenase (SDH) and Phosphofruktokinase (PFK) activities, fibre type content, and planimetric measurement of fibre areas. Following the biopsy procedure, each subject performed duplicate maximum oxygen uptake (MV̇O2) tests on a bicycle ergometer. These procedures were repeated every two weeks for the following six weeks, with the biopsies being performed alternately on contralateral legs. During the detraining period the total skinfold measures of six sites were relatively constant (55.04 mm to 53.65 mm), body weight demonstrated a non-significant reduction (79.75 kg to 76.04 kg), whereas mean MV̇O2 decreased significantly from 55.80 to 48.98 ml.kg-1.min-1 (4.42 l.min-1 to 3.69 l.min-1). Over the same period SDH activity decreased significantly from 9.10 to 6.81 uM.gm-1.min-1 and PFK demonstrated a significant decrease from 23.15 to 19.52 uM.gm-1.min-1. The mean fibre composition of the lateral head of the gastrocnemius was 48.25% fast-twitch (FT), and 51.75% slow-twitch (ST) fibres. The FT fibres were consistently larger than the ST fibres, with the former being initially 23% larger, decreasing to 9% larger than the ST fibres by the end of the detraining period. The changes in the cross sectional areas of each fibre type and in the contribution of each fibre type to the lateral head of gastrocnemius muscle during the six weeks detraining period were not significant.
Detraining is associated with the reversal of many physiological and biochemical adaptations acquired through chronic aerobic exercise. However, highly conditioned individuals appear to retain some of the benefits derived from endurance training despite remaining inactive for as long as 12 weeks. In particular, training-induced gains in skeletal muscle capillarization, myoglobin concentration, and oxidative enzyme capacity are partially retained by well-trained individuals and appear to be responsible for the long-term maintenance of arterial-venous oxygen difference (a-vO2 difference) and maximal aerobic capacity ([latin capital V with dot above]O2 max) above untrained levels. Conversely, in previously sedentary, moderately trained persons, training related adaptations are completely reversed to pretraining levels after approximately 10 weeks of inactivity.
(C) 1994 National Strength and Conditioning Association
The effects of different types of training and immobilization on muscle tissue have been studied intensively and have been well established. At the beginning of strength or power training, the increase in muscular performance can be explained by neural and psychological adaptation; that is, recruitment of more motor units per time unit, learning of more effective and economical usage of the active motor units and reduction of the inhibitory inputs to the active alpha motor neurons. After 6 to 8 weeks, further progress is due to gradual muscular hypertrophy, that is, a true increase in size of pre-existing fibres. Today, the theory of muscular hyperplasia (new fibre formation by a splitting of existing fibres) is not supported in critical reviews. With endurance training, there is an increased concentration and volume density of muscle mitochondria with corresponding biochemical adaptation, allowing the muscle to produce more mechanical power output aero-bicalry and to be activated for longer periods of time without being fatigued. Immobilization, in turn, atrophies the muscle very quickly, significantly already after one week. The most striking morphological findings are reduction in fibre size and diameter, reduction in the capillary density and a simultaneous increase in intramuscular connective tissue. At the same time, many harmful functional and biochemical effects also occur. Compared with muscle tissue, the knowledge of the effects of training and immobilization on tendon or ligament tissue is scarce and research has not been systematic. In animal experiments the tensile strength, elastic stiffness and total weight of a tendon or ligament have increased due to training (collagen fibre thickening) and decreased due to immobilization (fibre splitting and disorientation). These changes can be explained by an exercise (immobilization-induced increase (decrease) in synthesis of collagen and proteogrycan-water matrix due to increased (decreased) fibroblast activity. The effects of training on the myotendinous junction or proprioceptors (muscle spindles and Golgj tendon organs) are largely unknown. Our recent studies showed that immobilization is very detrimental to these organs morphologically as well as biochemically. Slowly progressing physical exercise causes meaningful adaptive changes in the articular cartilage: the cells and nuclei of chondrocytes enlarge and the proteoglycan content and cartilage thickness increase. However, if training is too strenuous or biomechanically misloading, a degeneration process of the cartilage may begin, which is also the case in an immobilized joint Bone tissue adapts to weight-bearing and muscular work well by increasing bone mass and density, most probably through osteoblast stimulation. The remodelling cycle of bone tissue is, however, a slow process, taking at least several months to occur. The achieved bone mass is also dependent on genetic, nutritional and hormonal factors. Immobilization, on the other hand, causes exactly the reverse effects on bone tissue and may finally (that is, after 5 to 6 months) lead to irreversible osteoporosis.
The effects of 15 days of detraining and 15 days of retraining were studied in 6 well-trained runners. Detraining resulted in significant decreases in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) of 24 % and 13 %, respectively, but no significant increases in these enzyme activities occurred with retraining. Maximal oxygen uptake (VO2 max) decreased by 4% with detraining (p < 0.05), and increased by a similar amount with retraining. Performance time in an intense submaximal run decreased by 25% (p < 0.05) with inactivity, but still averaged 9% below the initial level after retraining. Maximal heart rate and peak heart rate during the performance run were higher after detraining by 4 and 9 beats per min, respectively (p < 0.05). With retraining, these heart rate values were decreased by 7 and 9 beats per min (p < 0.05). Blood lactate concentrations after the VO2 max and performance run were approximately 20% lower after detraining and retraining (p < 0.05). Muscle fibre areas for three subjects tended to be larger in biopsy samples taken after detraining and retraining. These data suggest that even short periods of detraining result in significant changes in indices of physiological capacity and function in subjects near their upper limit of adaptation, and that a longer period of retraining is necessary for muscle to re-adapt to its original trained state.
Sixteen healthy, young women (10 experimental, 6 control) participated in a fourteen week physical conditioning deconditioning program. Seven weeks were spent in training and seven weeks detraining. The conditioning program consisted of 16 min/day three days/week sessions of continuous riding on a stationary bicycle (Monark) ergometer. All exercise was closely monitored with respect to intensity, and elicited an average heart rate that was 73% of maximal HR range. Initial measurements were made on the following dependent variables at rest and during two submaximal (450 and 600 KPM/min) and one maximal work loads: V(o2,) HR, RQ, V(E). From these data oxygen pulse and ventilatory equivalent were calculated. Body composition measurements were also made prior to training using a skinfold technique. A similar series of measurements was made after seven weeks of training and following a seven week detraining period. Evaluation of data revealed that training resulted in substantial gains in cardiovascular efficiency during both submaximal and maximal work. Body composition changes were modest. After seven weeks of detraining all variables approached initial levels. Control subjects remained essentially the same throughout the study. It was concluded that stationay bicycle riding is an effective alternative to other rhythmic exercises in developing cardiovascular efficiency, when training stops one returns rapidly to pretraining levels, and young women respond to endurance training in a manner that is qualitatively similar to young men.
The purpose of the investigation was to study the effects of inactivity periods of 1, 4, 6, and 8 weeks on the retention of recently acquired levels of muscular strength in the ipsilateral and contralateral arms. The aubject8 (80 experimental and 20 control) were right-handed mole volunteers, 18 to 22 yr. The experimental subjects participated three times weekly in a 6-week high-intensity, low-repetition strength conditioning programme. Following training, the trained subjects were randomly divided into four experimental groups and stopped training for 1,4, 6, or 8 weeks. Upon completion of the inactivity periods, a retention test was administered to both arms. The data analysis revealed that all experimental groups enhanced their isometric strength levels significantly in both arms during conditioning, thus demonstrating the phenomenon of cross-transfer of isometric strength. No significant differences were found for the control group. It was also found that all experimental groups retained a significant amount of isometric strength acquisition in both arms following the inactivity periods. No significant amount of strength was lost in the conditioned as well as the unconditioned arm despite 1 week of detraining. However, detraining of 4, 6, and 8 weeks resulted in a significant loss in both arms. Finally, no significant differences were found between the 6- and 8-week inactivity groups in the conditioned as well as the unconditioned arm.
This study examined if measures associated with distance running performance were affected by short-term (14 d) training cessation in 12 distance runners. VO2max decreased by approximately 3 ml.kg-1.min-1 (mean +/- SE, 61.6 +/- 2.0 vs 58.7 +/- 1.8 ml.kg-1.min-1, p < 0.05) with training cessation. Time to exhaustion (TTE) during the incremental VO2max test decreased by 1.2 min (13.0 +/- 0.5 vs 11.8 +/- 0.5 min, p < 0.001) and maximal heart rate increased (p < 0.001) by 9 beats per minute (BPM). No changes in running economy (75 and 90% VO2max) were evident, although submaximal heart rate increased by 11 BPM (p < 0.001) at both running speeds. Other evidence for detraining were decreases in estimated resting plasma volume (-5.1 +/- 1.9%) and muscle citrate synthase activity (-25.3 +/- 2.6%, p < 0.05). Muscular atrophy (muscle fiber cross-sectional area) was not evident. TTE and submaximal heart rate exhibited relatively large percent changes (-9 and +6%, respectively) compared to VO2max (-4%). These findings indicate that the reduction in VO2max with short-term training cessation is relatively small. TTE and submaximal heart rate may be easily measured, yet more sensitive indicators of decrements in distance running performance.
Healthy males were examined before and after 12 weeks of accommodated resistance training (three week ‐1 ) and after 12 weeks of detraining. Training consisted of four to five sets of six coupled maximum voluntary bilateral concentric and eccentric (Grp ECCON; n = 10) or 12 concentric (Grp CON; n = 8) quadriceps muscle actions. Concentric and eccentric peak torque at various constant angular velocities and three repetition maximum half‐squat and vertical jump height were measured.
Grp ECCON showed greater ( P < 0.05) overall increase in peak torque after training and detraining than Grp CON. Thus, concentric peak torque (0.52 rad s ‐1 ) increased more ( P < 0.05) over the experimental period in Grp ECCON and increases in eccentric peak torque were preserved in Grp ECCON only. Increases in peak torque in response to training were greater ( P < 0.05) at 0.52 than at 2.62 rad s ‐1 . Alterations in the torque‐velocity patterns induced by training remained after detraining in Grp ECCON but not in Grp CON. The retained increases ( P < 0.05) in half‐squat were 12 and 18% in Grps CON and ECCON, respectively. Neither group showed increased vertical jump height after detraining.
This study showed greater preservation of concentric and eccentric peak torque after detraining following coupled concentric and eccentric than concentric resistance training. Only the former regime induced a change in the shape of torque‐velocity curves that was manifest after detraining. These results suggest that the performance of eccentric muscle actions is critical to optimize increases in muscular strength in response to heavy resistance training, because it probably induce greater and more long‐lived neural adaptations than the performance of concentric actions.
To elucidate the changes in neuro-muscular function during strength training and detraining, five male subjects underwent progressive isotonic strength training of their calf muscles three times a week for 8 weeks with additional detraining for the same periods. Electrically evoked twitch contractions were induced in the triceps surae muscles of each subject every 4 weeks during the training and detraining periods. At the same time, maximal voluntary isometric contractions (MVC) and the maximal girth of the calf (MGC) were measured. During the training period, MVC increased significantly from 98.4 to 129.6 Nm (31.7%, P less than 0.01) for the first 4 weeks of training but MGC showed little increase. Neither of the changes correlated with each other. Twitch contraction parameters, i.e. maximal twitch torque (Pt), maximal rate of torque development (max dT/dt) and rate of relaxation (relax dT/dt) showed no statistical change. During detraining, on the contrary, a large and significant increase (22.5%, P less than 0.01) was observed in max dT/dt without any changes in Pt and relax dT/dt. The MVC/Pt showed both significant increases during training and decreases during detraining. Our data suggest that short term strength training as employed in the present study does not induce changes in the contractile properties of the muscle during training, but may significantly affect the rate of force development during the subsequent detraining period, indicating the possible existence of complex post-training muscle adaptation.
Seven endurance-trained subjects [maximal O2 consumption (VO2max) 64 +/- 1 (SE) ml.min-1.kg-1] underwent sequential hyperinsulinemic euglycemic clamps on three occasions: 1) in the "habitual state" 15 h after the last training bout (C), 2) after 60 min of bicycle exercise at 72 +/- 3% of VO2max performed in the habitual state (E), and 3) 5 days after the last ordinary training session (detrained, DT). Sensitivity for insulin-mediated whole-body glucose uptake was not affected by acute exercise [insulin concentrations eliciting 50% of maximal insulin-mediated glucose uptake being 44 +/- 2 (C) vs. 46 +/- 3 (E) microU/ml] but was decreased after detraining (54 +/- 2 microU/ml, P less than 0.05) to levels comparable to those found in untrained subjects [Am. J. Physiol. 254 (Endocrinol. Metab. 17): E248-E259, 1988]. Near-maximal insulin-mediated glucose uptake (responsiveness) was higher than in untrained subjects and not influenced by acute exercise or detraining [13.4 +/- 1.2 (C), 12.2 +/- 0.9 (E), and 12.2 +/- 0.3 (DT) mg.min-1.kg-1]. Calculated by indirect calorimetry, the glucose-to-glycogen conversion was not influenced by E but was reduced during detraining (P less than 0.05) yet remained higher than previously found in untrained subjects (P less than 0.05). However, only on E days did muscle glycogen increase during insulin infusion. Glycogen synthase activity was increased on E and decreased on DT compared with C days.(ABSTRACT TRUNCATED AT 250 WORDS)
The adaptability of human skeletal muscle to increased (training) and decreased (detraining) usage was studied in 11 athletes over a 42-month-long observation period. Biopsies were taken from the deltoid and the quadriceps muscle, together with measurements of maximum torque output during voluntary knee extensions at high relative to slow speeds of movement. A 16% and 14% decrease in the proportion of type I fibers was seen in the proximal arm and leg muscles, respectively, in the detraining subjects. This conformed with the changes in muscle function. On the other hand, in the training subjects, who increased their activity level through systematic daily physical training over an almost 4-year-long period, there were no significant changes seen in fiber type proportions of either arm or leg muscles. This was presumably due to the smaller net change in physical activity level caused by training as compared to detraining in the subjects of this study. Thus, the results show that fiber type proportions in intact human skeletal muscle are not exclusively determined by heredity, but may also be influenced by environmental factors, such as physical activity level.
Muscle biopsies were taken from female dancers, aged 24 +/- 2 years, first during an active period and then after 32 weeks of detraining. During the active period, the percentage of type I fibers was 63% +/- 12%, and of the subgroups IIA, IIB, and IIC, 26% +/- 9%, 8% +/- 7%, and 3% +/- 3%, respectively. There was no significant change due to detraining either in the proportion of type I fibers or in the type II subgroups. During the active period, the cross-sectional area of the type I fibers was 3798 +/- 586 micron 2. The areas of the subgroups IIA, IIB, and IIC were 3394 +/- 858, 2497 +/- 530, and 3296 +/- 638 micron 2, respectively. After the detraining period, the area of the type I fibers had increased significantly (P less than 0.05). The areas of the types IIA, IIB, and IIC tended to be increased although not significantly. It is suggested that the comparatively high percentage of type I fibers, which was found in the active dancers, is the result of selection rather than of training, while the small fiber areas seem to be due to training.
Following 5 months of competitive training (approximately 9,000 yards.d-1, 6 d.wk-1), three groups of eight male swimmers performed 4 wk of either reduced training (3,000 yard.session-1) or inactivity. Two groups reduced their training to either 3 sessions.wk-1 (RT3) or 1 session.wk-1 (RT1), whereas the third group (IA) did no training. Measurement of muscular strength (biokinetic swim bench) showed no decrement in any group over the 4 wk. In contrast, swim power (tethered swim) was significantly decreased (P less than 0.05) in all groups, reaching a mean change of -13.6% by week 4. Blood lactate measured after a standard 200-yard (183 m) front crawl swim increased by 1.8, 3.5, and 5.5 mM over the 4 wk in groups RT3, RT1 and IA, respectively. In group RT1, stroke rate measured during the 200-yard swim significantly increased (P less than 0.05) from 0.54 +/- 0.03 to 0.59 +/- 0.03 strokes.-1 while stroke distance significantly decreased (P less than 0.05) from 2.50 +/- 0.08 to 2.29 +/- 0.13 m.stroke-1 during the 4-wk period. Both stroke rate and stroke distance were maintained in group RT3 over the 4 wk of reduced training. Group IA was not tested for stroke mechanics. Whereas maximal oxygen uptake decreases significantly (P less than 0.05) over the 4 wk in group RT1 (4.75 to 4.62 l.min-1), no change in maximal oxygen uptake was observed in group RT3. These results suggest that aerobic capacity is maintained over 4 wk of moderately reduced training (3 sessions.wk-1) in well-trained swimmers. Muscular strength was not diminished over 4 wk of reduced training or inactivity, but the ability to generate power during swimming was significantly reduced in all groups.
Human subjects participated in a training/detraining paradigm which consisted of 7 wk of intense endurance training followed by 3 wk of inactivity. In previously sedentary subjects, training produced a 23.9 +/- 7.2% increase in maximal aerobic power (V02max) (group S). Detraining did not affect group S V02max. In previously trained subjects (group T), the training/detraining paradigm did not affect V02max. In group S, training produced an increase in vastus lateralis muscle citrate synthase (CS) activities (nmol.mg protein-1. min-1) from 67.1 +/- 14.5 to 106.9 +/- 22.0. Detraining produced a decrease in CS activity to 80 +/- 14.6. In group T, pretraining CS activity (139.5 +/- 14.9) did not change in response to training. Detraining, however, produced a decrease in CS activity (121.5 +/- 7.8 to 66.8 +/- 5.9). Group S respiratory exchange ratios obtained during submaximal exercise at 60% V02max (R60) decreased in response to training (1.00 +/- 0.02 to 0.87 +/- 0.02) and increased (0.96 +/- 0.02) after detraining. Group T R60 (0.91 +/- 0.01) was not affected by training but increased (0.89 +/- 0.02 to 0.95 +/- 0.02) after detraining. R60 was correlated to changes in CS activity but was unrelated to changes in V02max. These data support the hypothesis that the mitochondrial content of working skeletal muscle is an important determinant of substrate utilization during submaximal exercise.
Seven endurance-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Heart rate, ventilation, respiratory exchange ratio, and blood lactate concentration during submaximal exercise of the same absolute intensity increased (P less than 0.05) progressively during the first 56 days of detraining, after which a stabilization occurred. These changes paralleled a 40% decline (P less than 0.001) in mitochondrial enzyme activity levels and a 21% increase in total lactate dehydrogenase (LDH) activity (P less than 0.05) in trained skeletal muscle. After 84 days of detraining, the experimental subjects' muscle mitochondrial enzyme levels were still 50% above, and LDH activity was 22% below, sedentary control levels. The blood lactate threshold of the detrained subjects occurred at higher absolute and relative (i.e., 75 +/- 2% vs. 62 +/- 3% of maximal O2 uptake) exercise intensities in the subjects after 84 days of detraining than in untrained controls (P less than 0.05). Thus it appears that a portion of the adaptation to prolonged and intense endurance training that is responsible for the higher lactate threshold in the trained state persists for a long time (greater than 85 days) after training is stopped.
Eleven male subjects (20-32 years) accustomed to strength training went through progressive, high-load strength training for 24 weeks with intensities ranging variably between 70 and 120% during each month. This training was also followed by a 12-week detraining period. An increase of 26.8% (P less than 0.001) in maximal isometric strength took place during the training. The increase in strength correlated (P less than 0.05) with significant (P less than 0.05-0.01) increases in the neural activation (IEMG) of the leg extensor muscles during the most intensive training months. During the lower-intensity training, maximum IEMG decreased (P less than 0.05). Enlargements of muscle-fibre areas, especially of fast-twitch type (P less than 0.001), took place during the first 12 weeks of training. No hypertrophic changes were noted during the latter half of training. After initial improvements (P less than 0.05) no changes or even slight worsening were noted in selected force-time parameters during later strength training. During detraining a great (P less than 0.01) decrease in maximal strength was correlated (P less than 0.05) with the decrease (P less than 0.05) in the maximum IEMGs of the leg extensors. This period resulted also in decreases (P less than 0.05) of the mean muscle-fibre areas of both fibre types. It was concluded that improvement in strength may be accounted for by neural factors during the course of very intensive strength training. Selective training-induced hypertrophy also contributed to strength development but muscle hypertrophy may have some limitations during long-lasting strength training, especially in highly trained subjects.
Male university students (N = 53) participated three times weekly in a 7-week training program. During each session, one all-out bout of right elbow flexion was performed on an arm-lever ergometer at a cadence of 40 repetitions per minute against a 9.60-lb. resistance. Following training, the subjects were randomly divided into three experimental groups and stopped training for 1, 3, or 5 weeks. Upon completion of the inactivity periods, a retention test was administered. The data analysis revealed that all groups enhanced their muscular endurance levels during training and retained a significant amount of the endurance acquisition following the inactivity periods. No appreciable amount of muscular endurance was lost as a result of the 1-week inactivity period, but curtailment of training for at least 3 weeks caused a significant decrement. The 3- and 5-week inactivity periods did not differ significantly, but both resulted in greater endurance decrements than did the 1-week layoff.
The purpose of the present study was to investigate the effects of 3-month sprint and endurance training programs on the vastus lateralis muscle fiber area and the activities of glycolytic (phosphofructokinase; PFK) and oxidative (succinate dehydrogenase; SDH) enzymes of adolescent boys. Enzyme activities were also determined after a subsequent 6-month detraining period. Endurance training resulted in significant increases in VO2max (58.4 to 64.3 ml . min-1 . kg-1), in ST and FTa fiber area (6.0 to 7.3 and 8.0 to 10.4 microns 2 x 10(3), respectively), and in SDH activity (6.4 to 9.1 IU). After detraining VO2max and SDH activity returned to pretraining levels. Sprint training resulted in a significant increase only in PFK activity (28.1 to 33.9 IU), which was also abolished in the detraining period. These data demonstrate that in adolescent boys skeletal muscle enzyme changes are specific to the mode of training and that they are similar in direction but different in magnitude to those found in adults.
Seven endurance exercise-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Maximal O2 uptake (VO2 max) declined 7% (P less than 0.05) during the first 21 days of inactivity and stabilized after 56 days at a level 16% (P less than 0.05) below the initial trained value. After 84 days of detraining the experimental subjects still had a higher VO2 max than did eight sedentary control subjects who had never trained (50.8 vs. 43.3 ml X kg-1 X min-1), due primarily to a larger arterial-mixed venous O2 (a-vO2) difference. Stroke volume (SV) during exercise was high initially and declined during the early detraining period to a level not different from control. Skeletal muscle capillarization did not decline with inactivity and remained 50% above (P less than 0.05) sedentary control. Citrate synthase and succinate dehydrogenase activities in muscle declined with a half-time of 12 days and stabilized at levels 50% above sedentary control (P less than 0.05). The initial decline in VO2 max was related to a reduced SV and the later decline to a reduced a-vO2 difference. Muscle capillarization and oxidative enzyme activity remained above sedentary levels and this may help explain why a-vO2 difference and VO2 max after 84 days of detraining were still higher than in untrained subjects.
Fourteen male subjects (20-30 yr) accustomed to weight training went through progressive strength training of combined concentric and eccentric contractions three times per week for 16 wk. The training was followed by the 8-wk detraining period. The training program consisted mainly of dynamic exercises for leg extensors with the loads of 80-120% of one maximum concentric repetition. Significant improvements in muscle function were observed in early conditioning; however, the increase in maximal force during the very late training period was greatly limited. Marked improvements (P less than 0.001) in muscle strength were accompanied by significant (P less than 0.01) increases in the neural activation (IEMG) of the leg extensor muscles. The relationship between IEMG and high absolute forces changed (P less than 0.01) during the training period. The occurrence of these changes varied during the course of training. It was concluded that the early change in strength may be accounted for largely by neural factors with a gradually increasing contribution of hypertrophic factors as the training proceeds. It was suggested that the magnitudes and occurrence of these changes may vary due to the differences in conditioning periods, in individual muscles of muscle groups, in subject material, and in conditioning methods. During detraining, the decrease in muscle force seemed to be explainable also by the neural and muscular adaptations caused by the inactivity.
