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Effects of Training on Sand or Hard Surfaces on Sprint and Jump Performance of Team-Sport Players: A Systematic Review With Meta-Analysis
Abstract
We examined the effectiveness of training on sand and compared the effects of sand and hard surface training programs on the sprint and jump performance of team-sport players. PubMed MEDLINE, SPORTDiscus, and Web of Science databases were used in the literature search. A total of 377 records were initially identified and six studies comprising 136 athletes were included in the meta-analysis. Pre- and post-comparisons showed that sand training interventions were effective at improving both jump and sprint capacities. When comparing sand and hard surfaces, no significant differences in favor of any of the interventions were observed. In summary, this review revealed that sand training is an efficient strategy to improve jump and sprint performances in team-sport players. Moreover, sand surfaces produced similar gains to those observed after hard surface training schemes. Strength and conditioning coaches and sport scientists who work with team-sports can use both sand and hard surface training programs as part of their regular training practices, during distinct phases of the season.
... To prescribe effective PT programs, several variables should be respected, such as the safety, type, number and intensity of jump drills, the overload principle, and the training surface [9][10][11][12]. Considering this, previous studies have indicated that the magnitude of the PT effect on athletic performances is influenced by the amount of energy returned to the athlete from the training surfaces, which mainly depends on the training surface stiffness [9,[13][14][15][16][17]. ...
... To prescribe effective PT programs, several variables should be respected, such as the safety, type, number and intensity of jump drills, the overload principle, and the training surface [9][10][11][12]. Considering this, previous studies have indicated that the magnitude of the PT effect on athletic performances is influenced by the amount of energy returned to the athlete from the training surfaces, which mainly depends on the training surface stiffness [9,[13][14][15][16][17]. Therefore, the surface-type (e.g., hard, grass, sand) is an essential factor that can condition the effectiveness of PT through the stretch-reflex mechanism [18]. ...
... Similar effects were found in the present study when physical fitness 'improvements across PT programs using sand and firm surfaces were compared. The present study reported similar findings to those previously shown in different youth populations [9,[13][14][15]17]. More specifically, four to eight weeks of PT performed on sand produced similar sprint, jump and CODS performance improvements compared to those observed after training on firm surfaces [9,[13][14][15]17]. ...
Short- to middle-term plyometric training has been shown to be an effective method to promote youth fitness and health. However, there is no knowledge of previous studies that investigated the sex and age effects on physical fitness following different PT surfaces (i.e., firm vs. sand) in schoolchildren. This study examined the effects of age and sex on explosive and high-intensity responses following plyometric training (4 weeks, twice/week) performed on firm vs. sand surfaces in untrained schoolchildren. Ninety girls and ninety boys (under 8: age = 7.1 ± 0.5 and 7.1 ± 0.4 years; under 10: age = 9.0 ± 0.4 and 9.0 ± 0.5 years; under 12: age = 11.0 ± 0.5 and 11.0 ± 0.5 years, respectively) participated in a randomized and parallel training design with pre-to-post testing. Participants were allocated (i.e., 30 boys and 30 girls for each group) into either two experimental groups (firm group: performing plyometrics on a clay surface and sand group: performing plyometrics on a dry surface of 20 cm deep sand) or a control group (CG, habitual physical education classes) within their corresponding age groups. Children were tested for sprint, jumping and change of direction speed performances before and after 4 weeks of plyometric training. Both experimental groups induced more significant improvements in all assessed variables than CG (p < 0.0001; effect size > 0.80), whereas both surfaces induced similar improvements (p > 0.05). Older boys achieved better performances than their younger counterparts (p < 0.05) and older girls (p < 0.0001), respectively. This finding showed that age and sex could affect explosive and high-intensity performances during childhood after a short-term plyometric training. In contrast, the training-induced fitness changes were not influenced by the type of surface.
... Prior to measurements, a general and specific warm-up was performed involving light running (rating of perceived exertion [RPE] of 3-4 on a 1-10 scale [18]) for 10 min followed by 3 submaximal jumps, and 2 submaximal sprint trials (~70% of maximal sprint velocity) interspersed by 2 minutes of passive recovery. Finally, session-RPE production [6]. Therefore, soft surfaces might not be "optimal" to activate and potentiate the stretch-shortening cycle [7][8][9][10] and may contribute to higher energy expenditure when compared to sprint or jump tasks performed on harder surfaces at similar speeds or heights, which in turn may potentially impact the subjective perception of effort [6,11,12]. ...
... Finally, session-RPE production [6]. Therefore, soft surfaces might not be "optimal" to activate and potentiate the stretch-shortening cycle [7][8][9][10] and may contribute to higher energy expenditure when compared to sprint or jump tasks performed on harder surfaces at similar speeds or heights, which in turn may potentially impact the subjective perception of effort [6,11,12]. However, somewhat surprisingly, training on a sand surface has been proven to be as efficient as training on harder surfaces in terms of speed-power development (e.g., large effect sizes [> 1.0] and significant changes [P < 0.05] in jump and sprint performance) [6]. ...
... Therefore, soft surfaces might not be "optimal" to activate and potentiate the stretch-shortening cycle [7][8][9][10] and may contribute to higher energy expenditure when compared to sprint or jump tasks performed on harder surfaces at similar speeds or heights, which in turn may potentially impact the subjective perception of effort [6,11,12]. However, somewhat surprisingly, training on a sand surface has been proven to be as efficient as training on harder surfaces in terms of speed-power development (e.g., large effect sizes [> 1.0] and significant changes [P < 0.05] in jump and sprint performance) [6]. In fact, it has been observed that sand training may lead to higher motor unit recruitment in the muscle groups involved in some specific motor tasks (when compared to harder surfaces), which indicates that this training strategy might act as an "alternative way" to increase training load and thus promote positive changes in physical performance [6]. ...
This study compared the effects of two sprint-jump training programs, performed on either sand or grass surfaces, on the sprint and jump performance of elite young soccer players over an 8-week training period. Fifteen under-20 soccer players were randomly allocated to sand (n=7) or grass (n=8) groups. Athletes performed 12 training sessions, comprising vertical and horizontal jump exercises, and linear and change-of-direction (COD) sprint drills. Pre- and post-measurements were completed in the following order: vertical jump, sprint speed at 10- and 17-m, curve sprint (CS), and modified Zigzag COD tests. Between-group differences were determined using an ANOVA two-way with repeated measures and effect sizes (ES). No improvements in jump performance were found in any of the groups. Significant increases were observed in the sand group for acceleration in 0-10-m and for 10- and 17-m linear sprint velocity (ES = 1.15, 1.16, and 1.81, respectively; P< 0.05). In contrast, no significant differences were detected for acceleration and linear sprint velocity in the grass group, comparing pre- and post-tests (ES ranging from 0.01 to 0.47; P>0.05). Both sand and grass groups revealed similar increases in the CS and COD velocities after the training period (ES ranging from 0.98 to 1.93; P<0.05). In conclusion, sprint-jump training programs performed on both grass and sand surfaces elicited significant improvements in CS and COD performances, whereas acceleration and linear sprint velocity increased only in the sand group, after a short-term training period. The sand training surface was proven to be a practical strategy to improve sprint performance in all its forms in soccer players, which is of great interest and importance for coaches and sport scientists working in elite soccer.
... Plyometric exercises, for example, are usually performed on harder surfaces (i.e., vinyl, concrete, or grass) (9,17,34), with the rationale that compliant surfaces (e.g., sand) result in greater energy cost and dissipation of stored elastic energy, thus impairing the functionality of the stretch-shortening cycle and force production (2,5,6,38). However, a recent metaanalysis (33) demonstrated that sand surfaces are as efficient as hard surfaces to improve sprint and jump capacities in team-sport players. Moreover, although it was not part of the meta-analysis, some of the included studies also showed positive effects of sand training on COD ability (4,15). ...
... Moreover, although it was not part of the meta-analysis, some of the included studies also showed positive effects of sand training on COD ability (4,15). From a neuromechanical perspective, the enhanced performance induced by plyometric sand training seems to be related to higher motor unit recruitment in the muscle groups involved in the movements, which acts as an "alternative way" to increase the training load (17,33). Although previous investigations have demonstrated the efficiency of sand training in improving physical performance (1,33,34), the low number of controlled trials of high methodological quality with elite athletes and the heterogeneous approaches of these studies preclude more robust conclusions on this issue. ...
... From a neuromechanical perspective, the enhanced performance induced by plyometric sand training seems to be related to higher motor unit recruitment in the muscle groups involved in the movements, which acts as an "alternative way" to increase the training load (17,33). Although previous investigations have demonstrated the efficiency of sand training in improving physical performance (1,33,34), the low number of controlled trials of high methodological quality with elite athletes and the heterogeneous approaches of these studies preclude more robust conclusions on this issue. ...
The aims of this study were to: 1) examine the effects of a 6-week sand training program including both sprint and jump exercises on the speed-related and vertical jump performance of elite young soccer players; and 2) compare the changes induced by a sand training scheme with those induced by a similar training program (in terms of volume, intensity, and exercise types) performed on grass. Twenty-four under-20 soccer players were randomly allocated to two training groups, as follows: “sand” (n = 12) or “grass” (n = 12) groups. Athletes performed squat and countermovement jumps, linear sprints, and Zigzag change-of-direction (COD) speed tests at pre-, mid- (after 6 training sessions), and post-intervention (after 12 training sessions). Both groups exhibited similar increases in the vertical jump and Zigzag performance after the 6-week training period (P-values ranging from 0.0001 to 0.025; effect size ranging from 1.05 to 3.78, for main effect of time). No significant changes were detected for the linear sprint velocity for both groups (P-values ranging from 0.079 to 1.00; effect size ranging from 0.07 to 0.65, for main effect of time). In summary, training on sand or grass surfaces resulted in similar improvements in the physical performance of elite young soccer players. This study confirms the current evidence on the effectiveness of both soft and harder training surfaces in improving the sprint and jump performance of team-sport athletes.
... Therefore, it remains unclear whether chronic plyometric training on a particular surface confers more significant benefits to physical performance. It is one of the least studied aspects of plyometric training (Ramirez-Campill, et al., 2018a) and is limited primarily to understanding of the acute response (Pereira et al., 2021); consequently, it merits further study. In addition, physical adaptations to plyometric training would be influenced in a specific manner considering the exercise nature (i.e., drop jump vs. CMJ) depending on the surface used. ...
... In this sense, this is in the same direction as indicated by Ramírez-Campillo et al. (2018a) because the type of surface can affect the speed of the stretch-shortening cycle (e.g., fast vs. slow), implying different biomechanical and physiological effects and different adaptations. Proposed mechanisms that could improve jumping performance on softer surfaces such as sand would include increased muscle activity of the muscle groups, increased motor unit recruitment, and neurological drive, reduced joint impact on tendons, and muscle-tendon unit stiffness (Pereira et al., 2021). ...
... Particularly, it focused on exploring the effect of the surface at the chronic level on jump-related performance, one of the least studied aspects of plyometric training, according to Ramírez-Campillo et al. (2018b) in their recent scoping review. This was also noted by Pereira et al. (2021). In practical terms, coaches could use softer surfaces in sports with similar characteristics when weather conditions are adverse to reduce the probability of injury and optimize physical adaptations related to jumping in plyometric training. ...
The aim of this study was to compare jump-related performance after plyometric training on harder vs. softer surfaces in rugby sevens players. Fourteen players were randomly assigned into harder surface group (H-G, n = 7) and softer surface group (S-G, n = 7). Three times per week, in the morning, the players performed a plyometric training on different surfaces and strength training in the afternoon. Before and after 4-week intervention period, were assessed with squat jump (SJ), countermovement jump (CMJ), and CMJ with arms (CMJA) tests to measure vertical jump displacement (d), rate of force development (r), and power (p). The main results indicated a significant improvement in S-G for CMJd (∆% = +8.2%; p = 0.029; ES = 0.59) and for CMJAp (∆%= +8.7%; p = 0.035; ES = 0.44). These improvements were significant compared to H-G for CMJAd (F1,12 = 8.50; p = 0.013; η2p = 0.41; ES = 0.83) and CMJAp (F1,12 = 7.69; p = 0.017; η2p = 0.39; ES = 0.79). This study reveals that performance related to countermovement jump with arms on softer surface after 4-week of plyometric training was effective in improving vertical jump displacement and lower body power in rugby sevens players.
... Plyometric training is commonly performed on hard surfaces [8,11,12], with the rationale that more compliant surfaces (e.g., sand) usually store the generated muscle energy and, hence, reduce the elastic rebound force [13]. In contrast, previous studies have suggested using a sand surface as an effective strategy to enhance neuromuscular performance, as it may potentially increase the activation of the stressed muscles in the target motor task [14][15][16]. In this context, findings from prior investigations have shown that the level of PT effect on physical fitness is influenced by the type of training surface (e.g., grass, sand, or firm) [17][18][19]. ...
... The present study showed similar physical performance improvements after PT with sand and firm surfaces. These findings are in line with previous reports indicating that short-to middle-term PT performed on an unstable surface (i.e., sand) produced similar linear running speed, jump, agility, balance, and endurance performance improvements as those observed after training on stable surfaces (i.e., firm) [3,12,14,[17][18][19]. In this regard, it has been reported that performing explosive tasks (i.e., sprinting, jumping) on firm surfaces may improve the muscles' efficiency in utilizing the elastic energy stored during the eccentric phases, generating powerful concentric actions [12,16,59,60]. ...
... In this regard, it has been reported that performing explosive tasks (i.e., sprinting, jumping) on firm surfaces may improve the muscles' efficiency in utilizing the elastic energy stored during the eccentric phases, generating powerful concentric actions [12,16,59,60]. Thus, the plyometric training-induced adaptations on firm surfaces may be attributed to increased efficiency in storing and reusing elastic energy in explosive motions [14]. In contrast, previous studies have reported that sand training may increase the level of muscle activation and energy cost resulting from a considerable amount of elastic energy dissipation [61,62], and it could serve as an alternative way to increase overload during workouts [14]. ...
Plyometric training (PT) has been found to be effective for children’s fitness. However, no study has examined the effects of sex on physical fitness adaptations from surface-type PT in children. This study compared the effects of short-term surface-type PT (firm vs. sand) on the physical fitness of schoolchildren of both sexes. Sixty girls (age = 10.00 ± 1.15 years) and sixty boys (age = 10.02 ± 1.12 years) participated in a short-term (4 weeks), randomized and parallel PT design with pre-to-post measurements. Children were divided into two experimental groups (firm group: PT performed on a clay surface, 20 boys and 20 girls; sand group: PT performed on a dry surface of 20 cm deep sand, 20 boys and 20 girls) and a control group (CG, 20 boys and 20 girls). Squat jump, standing long jump, 20 m sprint, 5-10-5 shuttle, dynamic balance, and maximal aerobic velocity were measured at baseline and after intervention. Both experimental groups showed greater pre-post changes in all assessed variables than the CG (p < 0.0001). No significant differences in pre-post changes were observed relative to surface type or sex (p > 0.05). These findings suggest that a twice-weekly PT program induced physical fitness improvements, which may have transfer to health status during childhood. Additionally, surface type and sex did not affect the training-induced changes in physical fitness.
... For example, Impellizzeri et al. (2008) reported that sand-based PJT is more effective in improving selected sprint and jump outcomes compared to grass-based PJT. The use of sand surface during PJT may enhance neuromuscular performance (Ahmadi et al., 2021;Pereira et al., 2021), and its unstable nature may increase muscle activation (Pereira et al., 2021). There is for instance evidence that running on sand compared with stable ground results in increased muscle activation (Jafarnezhadgero et al., 2022). ...
... For example, Impellizzeri et al. (2008) reported that sand-based PJT is more effective in improving selected sprint and jump outcomes compared to grass-based PJT. The use of sand surface during PJT may enhance neuromuscular performance (Ahmadi et al., 2021;Pereira et al., 2021), and its unstable nature may increase muscle activation (Pereira et al., 2021). There is for instance evidence that running on sand compared with stable ground results in increased muscle activation (Jafarnezhadgero et al., 2022). ...
... Similar to our findings, a study of Granacher et al. (2015) reported a greater countermovement jump improvement after PJT performed on stable (i.e., firm gym floor) versus unstable (e.g., balance pads) surface (12.9% and 4.5%, respectively). Although SLJ improvement was larger after PJT with TT, both intervention groups achieved largemagnitude improvements compared to the control group which can likely be attributed to neuromuscular adaptations primarily induced through PJT (Pereira et al., 2021), including enhanced motor unit recruitment and/or firing frequency (Ramirez-Campillo et al., 2021b). In addition, our results also reported an increase in calf girth (i.e., left and right calf) in both experimental groups undergoing PJT. ...
This study aimed at examining the effects of nine weeks of sand-based plyometric-jump training (PJT) combined with endurance running either outdoor or treadmill surface on measures of physical fitness. Male participants (age, 20.1±1.7 years) were randomly assigned to a sand-based PJT combined with endurance running on outdoor surface (OT, n=25) or treadmill surface (TT, n=25). The endurance running intervention comprised a mixed training method, i.e., long slow distance, tempo, and interval running drills. A control group was additionally included in this study (CG, n=25). Participants in CG followed their regular physical activity as OT and TT but did not receive any specific intervention. Individuals were assessed for their 50-m linear sprint time, standing long jump (SLJ) distance, cardiorespiratory fitness (i.e., Cooper test), forced vital capacity (FVC), calf girth, and resting heart rate (RHR). A three (groups: OT, TT, CG) by two (time: pre, post) ANOVA for repeated measures was used to analyze the exercise-specific effects. In case of significant group-by-time interactions, Bonferroni adjusted paired (within-group) and independent (between-group comparisons at post) t-tests were used for post-hoc analyses. Significant group-by-time interactions were found for all dependent variables (p<0.001–0.002, ɳp2=0.16–0.78). Group-specific post-hoc tests showed improvements for all variables after OT (p<0.001, Hedges´g effect size [g]=0.05–1.94) and TT (p<0.001, g=0.04–2.73), but not in the CG (p=0.058–1.000, g=0.00–0.34). Compared to CG, OT showed larger SLJ (p=0.001), cardiorespiratory fitness (p=0.004), FVC (p=0.008), and RHR (p<0.001) improvements. TT showed larger improvements in SLJ (p=0.036), cardiorespiratory fitness (p<0.001), and RHR (p<0.001) compared with CG. Compared to OT, TT showed larger improvements for SLJ (p=0.018). In conclusion, sand-based PJT combined with either OT or TT similarly improved most measures of physical fitness, with greater SLJ improvement after TT. Coaches may use both concurrent exercise regimes based on preferences and logistical constrains (e.g., weather; access to treadmill equipment).
... Besides the exercise mode and intensity, several other factors may influence PAPE responses, especially in highly-trained subjects (Impellizzeri et al., 2008;Rhea, 2004). For instance, the mechanical properties of landing surfaces can play a critical role when programming and prescribing ballistic and reactive movements such as DJs (Pereira et al., 2021). Although jumping on "hard surfaces" (e.g., vinyl or wood) increases the capacity of muscles to store and reuse elastic energy, movements on "soft surfaces" (e.g., sand) usually have a higher energy cost and can lead to greater muscle activation (Pereira et al., 2021). ...
... For instance, the mechanical properties of landing surfaces can play a critical role when programming and prescribing ballistic and reactive movements such as DJs (Pereira et al., 2021). Although jumping on "hard surfaces" (e.g., vinyl or wood) increases the capacity of muscles to store and reuse elastic energy, movements on "soft surfaces" (e.g., sand) usually have a higher energy cost and can lead to greater muscle activation (Pereira et al., 2021). Somewhat surprisingly, a recent systematic review addressed this issue and revealed that both hard and sand surfaces were equally efficient to chronically improve measures of athletic performance (Pereira et al., 2021). ...
... Although jumping on "hard surfaces" (e.g., vinyl or wood) increases the capacity of muscles to store and reuse elastic energy, movements on "soft surfaces" (e.g., sand) usually have a higher energy cost and can lead to greater muscle activation (Pereira et al., 2021). Somewhat surprisingly, a recent systematic review addressed this issue and revealed that both hard and sand surfaces were equally efficient to chronically improve measures of athletic performance (Pereira et al., 2021). Notably, when it comes to PAPE responses, there is no literature examining which type of the surface is able to promote greater acute increases in both sprinting and jumping abilities following ballistic exercises. ...
This study aimed to compare the post-activation performance enhancement induced by successive drop-jumps performed on hard or sand surfaces in the sprint and jump performance of top-level sprinters. Athletes were tested on 2 occasions. On each visit they were allocated to one of the experimental protocols, which consisted of performing 2x5 drop-jumps from a box height of 60 cm on hard or sand surfaces in a randomized order, 7 days apart. Prior to and 7 and 15 minutes after executing the drop-jumps, the sprinters performed countermovement jumps and 60-m sprint tests. Differences between sprinting splits and surfaces were assessed using a two-way analysis of variance with repeated measures. No significant differences in jump height or sprint time were observed (P> 0.05), regardless of the surface used (i.e., hard or sand) during the conditioning activity (effect sizes [95% confidence intervals] ranging from 0.01 [-0.84; 0.84] to 0.44 [-0.42; 1.27]). Performing drop-jumps on sand or hard surfaces immediately before maximum sprinting bouts does not provide any additional benefit to top-level sprinters. Sprint coaches may prescribe short-plyometric training activities on sand surfaces even close to competitions, bearing in mind that this strategy will not compromise sprint-specific performance.
... Ramirez-Campillo et al. (2020) showed that a multi-surface (including sand) plyometric training led to greater improvements in neuromuscular performance compared with grass surface training in soccer players. A recent systematic review with metaanalysis also showed that sand training programs are able to induce positive changes in neuromuscular performance in teamsport players and that both training surfaces (sand and grass) are equally effective to improve sprint and jump performances (Pereira et al., 2021). Nevertheless, it should be noted that training exclusively on the sand was revealed to be detrimental to stretch-shortening cycle development, but tended to improve squat jump height more than grass surface (Impellizzeri et al., 2008). ...
... Sand training also reported to induce lower exercise-induced muscle damage, soreness, and associated negative side effects (e.g., reduced performance), thereby demonstrating a decreased neuromuscular strain (Miyama and Nosaka, 2004). In addition, some changes in kinematic parameters (e.g., decrements in sprint speed and stride length) when running on sand (Pinnington et al., 2005;Alcaraz et al., 2011;Gaudino et al., 2013) has been similar to those observed when performing resisted sprints on grass surface using loads inferior to 20% of the body mass of the athletes (Pereira et al., 2021). Therefore, the compliant nature and unstable characteristics of sand could serve as a practical way to increase overload during workouts, without the need for using additional resistance or supplementary equipment (e.g., elastic bands) (Pereira et al., 2021). ...
... In addition, some changes in kinematic parameters (e.g., decrements in sprint speed and stride length) when running on sand (Pinnington et al., 2005;Alcaraz et al., 2011;Gaudino et al., 2013) has been similar to those observed when performing resisted sprints on grass surface using loads inferior to 20% of the body mass of the athletes (Pereira et al., 2021). Therefore, the compliant nature and unstable characteristics of sand could serve as a practical way to increase overload during workouts, without the need for using additional resistance or supplementary equipment (e.g., elastic bands) (Pereira et al., 2021). This information has relevance for training load prescription optimization across the soccer competitive season. ...
This study aimed to examine the acute physiological effect of shuttle-run-based high-intensity intermittent exercise (HIIE) performed at the same relative speed (i. e., 100% PST−CAR) on sand (SAND) and grass (GRASS) in male junior soccer players. Seven Under-23 Brazilian national league (“Série A”) soccer players completed four testing sessions in either SAND or GRASS surface condition. The first two testing sessions consisted of performing a maximal progressive shuttle-run field protocol until volitional exhaustion (Carminatti's test, T-CAR), whereas the third and fourth sessions comprised a HIIE session on each ground surface. The HIIE session consisted of three 5-min bouts [12 s shuttle-run (with a direction change every 6 s)/12 s of passive rest] performed at 100% of T-CAR peak speed (PST−CAR) with 3 min of passive recovery between sets. Measurements of oxygen uptake (VO2), heart rate (HR), blood lactate concentration ([La]), and rating of perceived exertion (RPE) were performed during all conditions. The SAND condition elicited significantly higher %VO2peak (94.58 ± 2.73 vs. 87.45 ± 3.31%, p < 0.001, d = 2.35), %HRpeak (93.89 ± 2.63 vs. 90.31 ± 2.87%, p < 0.001, d = 1.30), RPE (8.00 ± 0.91 vs. 4.95 ± 1.23 a.u., p < 0.001, d = 2.82), and [La] (10.76 ± 2.37 vs. 5.48 ± 1.13 mmol/L, p < 0.010, d = 2.84). This study showed that higher internal workloads are experienced by the players during a single HIIE session performed on a softer surface as SAND, even when the exercise intensity was individualized based on 100%PST−CAR.
... With all these changes, the conclusion was that intermittent exposure to hyperbaric hypoxia did not accelerate erythropoiesis despite the increase in serum EPO [14]. Some studies show physiological changes similar to those produced by altitude training [15][16][17]. Man, M.C. et al. present an alternative, although less explored, that has the potential to positively influence performance while avoiding some of the negative physiological consequences of hypoxia being sand training. Increases in VO2max and VMA after sand training were high (1.3 ± 0.1%; p < 0.001 and 1.2 ± 0.1%; p < 0.001), and the hemoglobin values also increased (3.3 ± 1.1%; p = 0.035) [15]. ...
... km r. various land, segment strength and r.l.-70% VMA 1410 S.T.15 14 km r. various land-75% VMA/S.T.16 8 km e.r., 3 series of ex. for strength22 11 S.T.17 12 km r. uniform tempo, 70% VMA/S.T.18 10 km r. uniform tempo, 10 × 100 m r.l.-70% VMA 22 12 S.T. 19 14 km r. uniform tempo, 75% VMA 14 13 S.T. 20 12 km r. progressive various land 75-83% VMA/S.T. 21 10 km r. uniform tempo, 70% VMA and 3 series of ex. for strength 22 14 S.T. 22 6 km r. uniform tempo, 65% VMA, 30 × 100 m r. accelerated (100% VMA) with connection 100 m e.r. 4 km/S.T. 23 10 km r. uniform tempo, stretching 24 15 S.T. 24 8 km e.r., stretching 75% VMA/S.T. 25 40 min r. (2min r. tempo sustained + 1 min conn. ...
Training above 1800 m causes increases in hemoglobin, erythropoietin and VO2max values in the bodies of athletes. The purpose of this study is to prove that living at an altitude of 1850 m and training at 2200 m (LHTH+) is more effective than living and training at 2000 m (LHTH). Ten endurance athletes (age 21.2 ± 1.5 years, body mass 55.8 ± 4.3 kg, height 169 ± 6 cm, performance 3000 m 8:35 ± 0:30 min) performed three training sessions of 30 days, in three different situations: [1] living and training at 2000 m altitude (LHTH), [2] living at 1850 m and training at 2200 m (LHTH+), and [3] living and training at 300 m (LLTL). The differences in erythropoietin (EPO), hemoglobin (Hb) concentration, and VO2max values were compared before and at the end of each training session. Data analysis indicated that LHTH training caused an increase in EPO values (by 1.0 ± 0.8 mU/mL, p = 0.002 < 0.05.); Hb (by 1.1 ± 0.3 g/dL, p < 0.001); VO2max (by 0.9 ± 0.23 mL/kg/min, p < 0.001). LHTH+ training caused an increase in EPO values (by 1.9 ± 0.5 mU/ML, p < 0.001); Hb (by 1.4 ± 0.5 g/dL, p < 0.001); VO2max (by 1.7 ± 0.3 mL/kg/min, p < 0.001). At the LLTL training, EPO values do not have a significant increase (p = 0.678 > 0.050; 1 ± 0.1 mU/mL, 0.1 ± 0.9%.), Hb (0.1 ± 0.0 g/dL, 0.3 ± 0.3%), VO2max (0.1 ± 0.1, 0.2 ± 0.2%, p = 0.013 < 0.05). Living and training at altitudes of 2000 m (LHTH) and living at 1850 m training at 2200 m (LHTH+) resulted in significant improvements in EPO, Hb, and VO2max that exceeded the changes in these parameters, following traditional training at 300 m (LLTL). LHTH+ training has significantly greater changes than LHTH training, favorable to increasing sports performance. The results of this study can serve as guidelines for athletic trainers in their future work, in the complete structure of multi-year planning and programming, and thus improve the process of development and performance training.
... The focus ranges, for example, from notational analysis (Iannaccone et al., 2022;Navarro, Morillo, Reigal, & Hernandez-Mendo, 2018), player profiling (Lemos et al., 2020), skill and position specific analyses (Lemos et al., 2021;Navarro et al., 2018;Zapardiel & Asín-Izquierdo, 2020), load measures (Iannaccone et al., 2022;Muller, Willberg, Reichert, & Zentgraf, 2022), physiological and kinematic requirements of beach handball (Pueo, Jimenez-Olmedo, Penichet-Tomas, Ortega Becerra, & Agullo, 2017), and energy cost considerations on sand surfaces (Balasas et al., 2013). In addition, a recent meta-analysis indicated that training sessions on sand can improve sprinting and jumping performance on firm ground as much as training on firm ground (Pereira et al., 2021). ...
... Yet, coaches and athletes may be reluctant to add training on sand surfaces for fear that it will negatively affect performance on rigid surfaces and is time consuming, even though performanceenhancing training on sand surfaces can improve results on both surfaces (Ahmadi et al.;Hammami et al., 2020;Pereira et al., 2021). From that viewpoint, an optimal training intervention is one that can increase jump, sprint, and agility performance on rigid and sand surfaces and whereby the proportion of sand exercises in training sessions should increase over time. ...
Beach handball athletes experience an overlap during their preparation phase for the beach and the indoor season for several weeks. This transition phase from playing on an indoor surface to a sand surface is crucial for players’ performance levels both on the sand and indoor surfaces, but coaches and athletes alike are concerned about possible performance impairments when training on a sand surface while still playing indoors. Therefore, we aimed to evaluate the effects of a specific transition phase from the indoor to the beach season in elite beach handball athletes. With 29 elite athletes participating in the study, we evaluated their jumping (countermovement and drop jump) and sprinting (5–10–20 m) performances and conducted a handball-specific agility test on both rigid and sand surfaces. In addition, we evaluated a drop long jump on a sand surface. Vertical jumping performance was analyzed using a 3D marker-based system on both rigid and sand surfaces under standardized laboratory conditions. All tests took place directly before and after a 6-week intervention program. The results showed that athletes in the intervention group significantly improved their performance in jumping (countermovement and drop long jump) compared to the control group. Furthermore, performance on a rigid surface was not only maintained for all tests but also significantly increased for the countermovement jump. Therefore, the intervention program is effective at improving performance during the transition from indoor to beach seasons without impairing indoor performance.
... The lower horizontal speed on the sand surface means the athlete takes longer to make a move, hence having a longer time in contact with the sand surface [48]. The high shock absorptive qualities of sand can also limit maximal movement speed in sprint training and jumping performance [49]. This means that sand therapy can also reduce the pressure (resistance) caused by a hard footing, such as when exercising on a hard-textured court here, where the sand absorbs more pressure on the joints which usually occurs in hard-textured courts. ...
... The sand exercise training method is higher (better) than the water exercise training method on the agility of basketball athletes. 49 Health, sport, rehabilitation Здоров'я, спорт, реабілітація Здоровье, спорт, реабилитация 8(2) ...
Purpose: The author tried to examine the water and sand exercise models to maximize athletes’ training ability as exercise media.
Material and Methods: This research is experimental research with a “Two Groups Pretest-Posttest” design that includes a pre-test before the subjects are given treatment and a post-test after the treatment. The research populations were twenty male athletes from a basketball club in Yogyakarta, selected using a random sampling technique. All samples were subjected to a pre-test to determine the treatment group, ranked by their pre-test scores, then matched with the A-B-B-A pattern in two groups with ten athletes each. The sampling technique used in this dividing step was ordinal pairing. This research was conducted 18 times in treatment. The instrument used was an agility test using the Lane agility test. The movements for each number are as follows, (1) Sprint, stunt step, (2) Right slide (running with a guard position to the right side), (3) Run backwards, (4) Left slide, (5) Right slide, (6) Sprint, stunt step, pivot, (7) Right slide, (8) Sprint.
Results: The research used normality, homogeneity, and hypothesis testing. To test the hypothesis, the researchers used the two types of t-tests, namely paired sample test and the independent sample test. The T-test is a statistical analysis technique that can be used to determine whether there is a significant difference between two sample means or not. The results revealed that the t count was 2,335 with a p significance value of 0.031. Because the t-count was 2.335 and the significance value was
... The high shock absorption capacity of sand may decrease the impact forces experienced during high-intensity activities, which may lead to a reduction in muscle lesions and pain and improve recovery time between sessions [10,11]. Considering these differences, recent evidence supports the use of sand as a training means to improve the performance of team sports athletes [12]. Binnie et al. [7] have reported that for training, the use of sand instead of grass training surfaces elicits a relatively higher training intensity, without causing any additional decrement in performance the following day (24 h post exercise). ...
... Recently, more complex research exploring specific mechanisms that may lead to greater adaptations with sand versus more traditional training surfaces has emerged [7,[12][13][14]. Such studies have quantified the contributions of energetic uptake (aerobic and anaerobic) during short-term exercising in the sand (namely 10 min) [14]. ...
Altitude training increases haemoglobin, erythropoietin values among athletes, but may have negative physiological consequences. An alternative, although less explored, that has the potential to positively influence performance while avoiding some of the negative physiological consequences of hypoxia is sand training. Ten endurance-trained athletes (age: 20.8 ± 1.4, body mass: 57.7 ± 8.2 kg, stature: 176 ± 6 cm; 5000 m 14:55.00 ±0:30 min) performed three 21-day training camps at different locations: at a high altitude (HIGH), at the sea-level (CTRL), at the sea-level on the sand (SAND). Differences in erythropoietin (EPO) and haemoglobin (Hb) concentration, body weight, VO2max and maximal aerobic velocity (VMA) before and after each training cycle were compared. Data analysis has indicated that training during HIGH elicited a greater increase in VO2max (2.4 ± 0.2%; p = 0.005 and 1.0 ± 0.2%; p < 0.001) and VMA (2.4 ± 0.2%, p < 0.001 and 1.2 ± 0.2%; p = 0.001) compared with CTRL and SAND. While increases in VO2max and VMA following SAND were greater (1.3 ± 0.1%; p < 0.001 and 1.2 ± 0.1%; p < 0.001) than those observed after CTRL. Moreover, EPO increased to a greater extent following HIGH (25.3 ± 2.7%) compared with SAND (11.7 ± 1.6%, p = 0.008) and CTRL (0.1 ± 0.3%, p < 0.001) with a greater increase (p < 0.01) following SAND compared with CTRL. Furthermore, HIGH and SAND elicited a greater increase (4.9 ± 0.9%; p = 0.001 and 3.3 ± 1.1%; p = 0.035) in Hb compared with CTRL. There was no difference in Hb changes observed between HIGH and SAND (p = 1.0). Finally, athletes lost 2.1 ± 0.4% (p = 0.001) more weight following HIGH vs. CTRL, while there were no differences in weight changes between HIGH vs. SAND (p = 0.742) and SAND vs. CTRL (p = 0.719). High-altitude training and sea-level training on sand resulted in significant improvements in EPO, Hb, VMA, and VO2max that exceeded changes in such parameters following traditional sea-level training. While high-altitude training elicited greater relative increases in EPO, VMA, and VO2max, sand training resulted in comparable increases in Hb and may prevent hypoxia-induced weight loss. Citation: Man, M.C.; Ganera, C.; Bărbule, G.D.; Krzysztofik, M.; Panaet, A.E.; Cucui, A.I.; Tohănean, I.; Alexe, D.I. The Modifications of Haemoglobin, Erythropoietin Values and Running Performance While Training at Mountain vs. Hilltop vs. Seaside. Int. J. Environ. Res. Public Health 2021, 18, 9486. https://
... Often, this is achieved through maximum voluntary contractions as a condition activity (CA) with similar biomechanical demands as a subsequent explosive task, e.g., performing a back squat exercise before vertical jumping (42). Usually, studies are focused on examining the effectiveness of a wide variety of CAs for contraction types, intensities, and volumes, along with different rest intervals (8,29,36,42,44), in inducing improvements in subsequent activities. Moreover, it seems that the magnitude of the PAPE effect may differ depending on the primary task because the literature reveals that the greatest increases in performance are noted in sprints and somewhat less in jumping tasks (42). ...
The effects of conditioning activity (CA) on muscle stiffness are currently unknown, suggesting that maximum CA effort can increase or decrease the stiffness of involved muscle groups. Therefore, this study aimed to investigate the effect of maximal isometric half-squats on the viscoelastic properties of muscles and postactivation performance enhancement (PAPE) in sprints and jumps. Twelve handball players underwent a standard warm-up and baseline assessment of muscle stiffness and tone of vastus lateralis and gastrocnemius medialis muscle, followed by 20-m sprint with intermediate measures at 5 and 10 m and countermovement jump. The PAPE was assessed by repeating the tests (at 4th, 8th, and 12th minute post-CA) after a CA protocol consisting of 3 sets of 3-second maximal isometric half-squats (EXP) or a control condition (CTRL) without any CA. The vastus lateralis stiffness in the 4th and 12th minute and muscle tone in the 4th minute post-CA significantly decreased compared with baseline (p 5 0.041, ES 5 0.57; p 5 0.013, ES 5 0.52; p 5 0.004, ES 5 0.81, respectively) in the EXP condition. The 20-m sprint time significantly decreased at all post-CA time points compared with the baseline for the EXP condition (p , 0.033) and the after values in the CTRL condition (p , 0.036). In comparison to baseline, the 10-m sprint time decreased in the eighth minute post-CA (p 5 0.021; ES 5 0.82) in the EXP condition. Moreover, it was significantly lower at the 8th and 12th minute post-CA (p 5 0.038; ES 5 0.71 and p 5 0.005; ES 5 1.26) compared with that time points in the CTRL condition. The maximal isometric half-squats effectively improved sprint performance and significantly decreased vastus lateralis tone and stiffness. These findings offer new insights into the assessment of viscoelastic properties for evaluating the fatigue or potentiation state, which requires further investigation.
... We understand related theories' research status and development trends. 4 These data provide specific materials and basis for this study to determine the research direction, formulate the research plan design, and the overall structure of the thesis. ...
Introduction
Muscle strength training can increase the strength of the phasic muscles, aiding in balance and body stability. Running is a physical-dominant speed sport where strength-speed is two crucial quality in the athletic training of its practitioners. It is believed that training muscle strength at high-intensity intervals can increase athletic speed performance. However, there is no determinant point to determine the peak of this relationship.
Objective
The purpose of this study is to examine the effect of high-intensity interval muscular strength training on the physical conditioning of athletes. This paper also examines the relationship between muscular strength training and performance training in sprinters.
Methods
Twenty sprinter volunteers were randomly selected as research subjects, divided without discrepancies into control and experimental groups, with ten people each. Mathematical statistics were used to analyze the physiological indicators of the subjects before and after muscle strength training. At the same time, the statistical correlation method was applied to analyze the performance changes of athletes before and after the exercise cycle.
Results
After muscle strength training, the athletes in the experimental group were better than those before the training. The data were statistically significant (P<0.05).
Conclusion
Muscle strength training can promote the physical conditioning of sprinters. At the same time, the training mode can also improve the athlete’s performance. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.
Keywords:
Sports; Athletes; Resistance Training; High-Intensity Interval Training
... Training on SAND was found to be effective for improving sprinting, jumping and balance ability of team sport players [14,20,[66][67][68], and that there is a significant association between specific agility and vertical jump tests on SAND [46]. Additionally, the adaptations of jumping, sprinting and agility were found to be transferred on RIGID [13,15,16]. ...
Plyometric training on sand is suggested to result in advanced performance in vertical jumping. However, limited information exists concerning the biomechanics of drop jumps (DJ) on sand. The purpose of the study was to compare the biomechanical parameters of DJs executed on rigid (RIGID) and sand (SAND) surface. Sixteen high level male beach-volleyball players executed DJ from 40 cm on RIGID and SAND. Force-and video-recordings were analyzed to extract the kinetic and kinematic parameters of the DJ. Results of paired-samples t-tests revealed that DJ on SAND had significantly (p < 0.05) lower jumping height, peak vertical ground reaction force, power, peak leg stiffness and peak ankle flexion angular velocity than RIGID. In addition, DJ on SAND was characterized by significantly (p < 0.05) larger rate of force development and knee joint flexion in the downward phase. No differences (p > 0.05) were observed for the temporal parameters. The compliance of SAND decreases the efficiency of the mechanisms involved in the optimization of DJ performance. Nevertheless, SAND comprises an exercise surface with less loading during the eccentric phase of the DJ, thus it can be considered as a surface that can offer injury prevention under demands for large energy expenditure.
... Thus, physical fitness variables such as frequent sprinting, change-of-direction speed (CODS) and anaerobic power can biomechanical variables and physical fitness in female indoor volleyball players. Based on the relevant literature [15,18,19], we hypothesized that PJT in either sand or a rigid court surface would improve jump-related biomechanical variables and physical fitness in female indoor volleyball players, with greater improvements after sand-based PJT. ...
Background:
This study aims to assess the effects of 8 weeks of plyometric jump training (PJT) conducted on sand or a rigid court surface on jump-related biomechanical variables and physical fitness in female indoor volleyball players.
Methods:
Seventeen participants were randomly divided into a sand surface group (SsG, n = 8) and rigid surface group (RsG, n = 9). Both groups completed equal indoor volleyball training routines. Participants were assessed pre and post the 8-week PJT for jump-related biomechanical variables (countermovement jump (CMJ) RSI; drop jump (DJ) reactive strength index (RSI); spike jump (SJ) height; CMJ height; CMJ rate of force development (RFD); CMJ velocity at take-off; DJ height and CMJ peak force), 20 m linear sprint time, t test for change-of-direction sprint (CODs) time, Wingate test peak power (PP), cardiorespiratory endurance, and leg-press one-repetition maximum (1RM).
Results:
A two-way mixed analysis of variance (group × time) revealed that there was a significant group × time interaction between DJ height (p = 0.035) and CMJ peak force (p = 0.032) in favour of RsG and SsG, respectively. A significant interaction was also observed for cardiorespiratory endurance (p = 0.01) and 1RM (p = 0.002), both favouring the SsG. No other group × time interaction was observed.
Conclusions:
The type of surface used during PJT induced specific adaptations in terms of jump-related biomechanical variables and physical fitness in female indoor volleyball players. Based on the individual needs of the athletes, practitioners may prescribe one type of surface preferentially over another to maximize the benefits derived from PJT.
Objective: Although football, futsal, and beach soccer have relatively different physiological requirements and playing on different surfaces is likely to impact dynamic balance at different levels, there is no study evaluating the dynamic balance of football, futsal, and beach soccer players. The objective of the present study is to evaluate the dynamic balance of football, futsal, and beach soccer players.
Material and Methods: A total of 114 amateur male players registered with the Turkish Football Federation participated in the study. They were divided into three sub-groups according to their sports disciplines: football (n=41), futsal (n=39), and beach football (n=34). The modified star excursion balance test with four outcomes for each extremity as anterior (A), posterior lateral (PL), posterior medial (PM), and composite (C) score was used to measure dynamic balance.
Results: Dominant side PL and C scores (p<0.01, ES=0.10; p<0.01, ES=0.11; respectively), and non-dominant side A, PL and C scores of beach soccer players were significantly higher comparing to futsal players (p=0.01, ES=0.07; p<0.01, ES=0.08; p<0.01, ES=0.08; respectively). Also, dominant side C scores of beach soccer players were significantly higher than football players (p<0.02, ES=0.11).
Conclusion: Findings demonstrate that the dynamic balance profile of beach soccer players was better compared with futsal players. In light of present study results, it may be beneficial for players from different sports disciplines to train on sand in order to improve dynamic balance.
Purpose:
The purpose of the present study was to investigate the use of sand as an alternative surface for training, injury prevention and rehabilitation interventions in English professional football. A Secondary aim was to explore the potential barriers to implementation.
Materials and methods:
All 92 teams from the male English professional football pyramid during the 2021-22 season were eligible to take part. A cross-sectional survey of the medical personnel (one per club) was conducted between June 2021 and December 2021 based on the RE-AIM framework. A total of 58 respondents (63% of all clubs) completed the survey.
Results and conclusions:
Only 18 (31%) of the clubs surveyed used sand-based interventions across the last 3 seasons. Respondents felt sand-based interventions would be effective at improving physiological gains (median 4, interquartile range [IQR] 4-5) and as part of injury prevention and rehabilitation strategies (4, IQR 3-4) but were indifferent in relation to its potential to improve sporting performance (3, IQR 3-4). Barriers to implementation of sand-based interventions within wider football were a lack of facilities, lack of awareness of its potential benefits, lack of high-quality evidence and the surface not being specific to the sport. Medical staff also did not perceive that coaches' positively viewed sand interventions as a training or injury management strategy.
This study aimed to assess whether post-warm-up body mass only alternate leg bounding performed on grass or a hard surface acutely improves pre-planned change of direction performance in women's team sports players relative to a control condition and, if so, profile the time-course of such changes. On three occasions, 14 amateur women's team sports players performed 20 m pre-planned change of direction ('Pro-Agility') tests at 4 min, 8 min, and 12 min following interventions. Interventions were implemented immediately after a standardized warm-up and consisted of three sets of 10 repetitions of alternate leg bounding (five ground contacts per limb) on a hard indoor surface (HARD) or natural grass (GRASS), or a control condition involving ~75 s of continuous walking with no bounding (CON). Performance was similar between conditions at 4 min post-intervention. Performance at 8 min was greater in HARD (2.9%, p = 0.015), and GRASS (3.8%, p = 0.029) relative to CON, whilst GRASS also exceeded CON at 12 min post-bounding (5.2%, p = 0.004). All effects were large. No differences existed between HARD and GRASS at any timepoint. Alternate leg bounding performed with body mass only can acutely improve indices of change of direction performance in women's team sports players irrespective of the ground surface when an appropriate post-stimulus recovery period is provided. Bounding on grass or a hard surface represents a feasible match-day practice that enhances subsequent change of direction performance and could therefore be used as part of practically applicable pre-match, half-time, and/or pitch-side (re)warm-up activities.
Purpose:
This study aimed to compare the effects of unresisted versus heavy sled sprint training (0% vs 40% body mass [BM]) on sprint performance in women. Moreover, the effects of the aforementioned loads on resisted sprint and jump performance were analyzed.
Methods:
Twenty-eight physically active women were randomly allocated into 2 groups: unloaded sprint training group (G0%, n = 14), and resisted sprint training with 40% BM group (G40%, n = 14). Pretraining and posttraining assessments included countermovement jump, unloaded 30-m sprint, and 20-m sprint with 20%, 40%, 60%, and 80% BM. Times to cover 0 to 10 (T10), 0 to 20 (T20), 0 to 30 (T30), 10 to 20 (T10-20), 20 to 30 (T20-30), and 10 to 30 m (T10-30) were recorded. Both groups were trained once a week for 8 weeks and completed the same training program, but with different loads (0% vs 40% BM).
Results:
No significant time × group interactions were observed. For unloaded sprint performance, G0% showed significant (P = .027) decreases only in T10-20, while G40% attained significant decreases in T30 (P = .021), T10-30 (P = .015), and T20-30 (P = .003). Regarding resisted sprint performance, G0% showed significant (P = .010) improvements only for the 20% BM condition. The G40% group attained significant improvements in all loading conditions (20%, 40%, 60%, and 80% BM). Both groups showed significant improvements (P < .001) in countermovement jump height.
Conclusions:
In physically active women, no significant differences in sprint and countermovement jump performance were detected after 8 weeks of resisted and unresisted sprint training programs. Future studies should, therefore, be devoted to how sprint training should be individualized to maximize performance.
Background:
The effects of 7 weeks plyometric training on a stable surface and on sand were compared in junior male handball players.
Methods:
A team of experienced players was divided randomly between three groups, undertaking a standard in-season regimen (C, n = 10), or supplementing this regimen by plyometric training on sand (PS, n = 11) or a stable surface (P, n = 10) for 7 weeks. Assessments included 20 m sprint times, change of direction tests (Modified change-of-direction T-test and Modified Illinois test), a repeated sprint T-test, jumping ability (squat, countermovement and five jump tests), and static and dynamic balance.
Results:
After the intervention, PS showed significant increases of sprint speed relative to P and C. Change of direction scores were also improved for PS relative to P and C. Both PS and P increased vertical jump performance (squat jump, p = 0.005; ES = 0.170; counter-movement jump p < 0.001; ES = 0.247). Repeated sprint T-test scores improved in PS and P relative to C, with best times of PS > P (p < 0.05). Both plyometric groups improved their dynamic balance (p < 0.05), with three parameters of PS and only one of P being significantly greater than C. Static balance was also enhanced in both experimental groups (PS > P).
Conclusions:
We conclude that for reasons that remain to be clarified, several performance measures in adolescent male handball players were increased more by 7 weeks of PS than by P.
The purpose of this study was to investigate the effect of plyometric training on sand and
wooden parquet training surfaces on the physical performance parameters of young male basketball players.
Twelve well-trained young male basketball players with age 17.58±0.5 years, body mass 87.73±9.82 kg, and
height 193.75±7.02 cm were voluntarily involved in the study. All participants were grouped randomly as
sand and wooden training groups. A six-week plyometric training programme was performed on the sand
and wooden parquet surfaces. Anthropometric measurements and physical performance tests; vertical and
standing long jump, box agility, and 30m sprint tests were performed. Data were collected before and after six
weeks of plyometric training and were analysed using ANCOVA. The results indicated that the plyometric
training programme significantly improved jumping, agility and 30m sprint performance for both groups.
Significant differences were found between the post-test mean values of two groups in the box-drill agility and
30m sprint test scores (p < .05). The results of this study suggest that while the plyometric training performed
on a wooden or sand surface does not cause a different effect on the improvement of jumping performance,
plyometric training on the sand surface may be a more effective training surface to improve the agility and
sprint performance of young players.
The revised edition of the Handbook offers the only guide on how to conduct, report and maintain a Cochrane Review.
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This study investigated the effects on neuromuscular performance of a 6-week Optimal Load Training (OLT) and a novel modified Complex Training (MCT) (complex pairs: the same exercise using a moderate and an OL) in basketball players, in-season. Eighteen male athletes were randomly assigned to one of the protocols. Anthropometric measurements were taken to evaluate body composition. Lower- and upper-body maximum dynamic strength, countermovement jump (CMJ), standing long jump (SLJ), 10-m sprint and change of direction (COD) were also assessed. Moderate-to-large strength gains (presented as percentage change ± 90% confidence limits) were obtained for half-squat (OLT: 10.8 ± 5.3%; MCT: 17.2 ± 11.6%) and hip thrust (OLT: 23.5 ± 17.7%; MCT: 28.2 ± 19.0%). OLT athletes achieved likely small improvements in sprint (1.6 ± 1.6%) and COD (3.0 ± 3.2%). Players in the MCT attained likely moderate improvements in COD (3.0 ± 2.0%) and possibly small in SLJ (2.5 ± 4.6%). No protocol relevantly affected CMJ or body composition. An ANCOVA test revealed unclear between-group differences. In conclusion, both protocols increased basketball players’ strength without the use of heavy loads (> 85% 1RM) and without impairing sprint, CMJ and SLJ performance. These findings suggest that basketball strength and conditioning professionals may use either method to counteract strength losses during the season.
Background:
Sprinting is key in the development and final results of competitions in a range of sport disciplines, both individual (e.g., athletics) and team sports. Resisted sled training (RST) might provide an effective training method to improve sprinting, in both the acceleration and the maximum-velocity phases. However, substantial discrepancies exist in the literature regarding the influence of training status and sled load prescription in relation to the specific components of sprint performance to be developed and the phase of sprint.
Objectives:
Our objectives were to review the state of the current literature on intervention studies that have analyzed the effects of RST on sprint performance in both the acceleration and the maximum-velocity phases in healthy athletes and to establish which RST load characteristics produce the largest improvements in sprint performance.
Methods:
We performed a literature search in PubMed, SPORTDiscus, and Web of Science up to and including 9 January 2018. Peer-reviewed studies were included if they met all the following eligibility criteria: (1) published in a scientific journal; (2) original experimental and longitudinal study; (3) participants were at least recreationally active and towed or pulled the sled while running at maximum intensity; (4) RST was one of the main training methods used; (5) studies identified the load of the sled, distance covered, and sprint time and/or sprint velocity for both baseline and post-training results; (6) sprint performance was measured using timing gates, radar gun, or stopwatch; (7) published in the English language; and (8) had a quality assessment score > 6 points.
Results:
A total of 2376 articles were found. After filtering procedures, only 13 studies were included in this meta-analysis. In the included studies, 32 RST groups and 15 control groups were analyzed for sprint time in the different phases and full sprint. Significant improvements were found between baseline and post-training in sprint performance in the acceleration phase (effect size [ES] 0.61; p = 0.0001; standardized mean difference [SMD] 0.57; 95% confidence interval [CI] - 0.85 to - 0.28) and full sprint (ES 0.36; p = 0.009; SMD 0.38; 95% CI - 0.67 to - 0.10). However, non-significant improvements were observed between pre- and post-test in sprint time in the maximum-velocity phase (ES 0.27; p = 0.25; SMD 0.18; 95% CI - 0.49 to 0.13). Furthermore, studies that included a control group found a non-significant improvement in participants in the RST group compared with the control group, independent of the analyzed phase.
Conclusions:
RST is an effective method to improve sprint performance, specifically in the early acceleration phase. However, it cannot be said that this method is more effective than the same training without overload. The effect of RST is greatest in recreationally active or trained men who practice team sports such as football or rugby. Moreover, the intensity (load) is not a determinant of sprint performance improvement, but the recommended volume is > 160 m per session, and approximately 2680 m per week, with a training frequency of two to three times per week, for at least 6 weeks. Finally, rigid surfaces appear to enhance the effect of RST on sprint performance.
The aim of this study was to compare the effects of two different mixed training programs (optimum power load [OPL] + resisted sprints [RS] and OPL + vertical/horizontal plyometrics [PL]) on neuromuscular performance of elite soccer players during a short-term training preseason. Eighteen male professional soccer players took part in this study. The athletes were pair-matched in two training groups: OPL + RS and OPL + PL. Unloaded and resisted sprinting speeds at 5-, 10-, 20-, and 30-m, change of direction (COD) speed, and performance in the squat jump (SJ), countermovement jump (CMJ), and horizontal jump (HJ) were assessed pre- and post- a 5-week training period. Magnitude based inference with the effect sizes were used for data analysis. A possible increase in the SJ and CMJ heights and a likely increase in the HJ distance were observed in the OPL + PL group. Meaningful improvements were observed in the COD speed test for both training groups comparing pre- and post-measures. In both unloaded and resisted sprints, meaningful decreases were observed in the sprinting times for all distances tested. This study shows that a mixed training approach which comprises exercises and workloads able to produce positive adaptations in different phases of sprinting can be a very effective strategy in professional soccer players. Moreover, the possibility of combining optimum power loads with resisted sprints and plyometrics emerges as a novel and suitable option for coaches and sport scientists, due to the applicability and efficiency of this strength-power training approach.
This study aimed to investigate activation characteristics of the biceps femoris long head (BFlh) and semitendinosus (ST) muscles during the acceleration and maximum-speed phases of sprinting. Lower-extremity kinematics and electromyographic (EMG) activities of the BFlh and ST muscles were examined during the acceleration sprint and maximum-speed sprint in 13 male sprinters during an overground sprinting. Differences in hamstring activation during each divided phases and in the hip and knee joint angles and torques at each time point of the sprinting gait cycle were determined between two sprints. During the early stance of the acceleration sprint, the hip extension torque was significantly greater than during the maximum-speed sprint, and the relative EMG activation of the BFlh muscle was significantly higher than that of the ST muscle. During the late stance and terminal mid-swing of maximum-speed sprint, the knee was more extended and a higher knee flexion moment was observed compared to the acceleration sprint, and the ST muscle showed higher activation than that of the BFlh. These results indicate that the functional demands of the medial and lateral hamstring muscles differ between two different sprint performances.
Background
Late-stage rehabilitation programs often incorporate ‘sport-specific’ demands, but may not optimally simulate the in-game volume or intensity of such activities as sprinting, cutting, jumping, and lateral movement. Objective
The aim of this review was to characterize, quantify, and compare straight-line running and multi-directional demands during sport competition. Data SourcesA systematic review of PubMed, CINAHL, SPORTDiscus, and Cochrane Central Register of Controlled Trials databases was conducted. Study Eligibility CriteriaStudies that reported time-motion analysis data on straight-line running, accelerations/decelerations, activity changes, jumping, cutting, or lateral movement over the course of an entire competition in a multi-directional sport (soccer, basketball, lacrosse, handball, field hockey, futsal, volleyball) were included. Study Appraisal and Synthesis Methods
Data was organized based on sport, age level, and sex and descriptive statistics of the frequency, intensity, time, and volume of the characteristics of running and multi-directional demands were extracted from each study. ResultsEighty-one studies were included in the review (n = 47 soccer, n = 11 basketball, n = 9 handball, n = 7 field hockey, n = 3 futsal, n = 4 volleyball). Variability of sport demand data was found across sports, sexes, and age levels. Specifically, soccer and field hockey demanded the most volume of running, while basketball required the highest ratio of high-intensity running to sprinting. Athletes change activity between 500 and 3000 times over the course of a competition, or once every 2–4 s. Studies of soccer reported the most frequent cutting (up to 800 per game), while studies of basketball reported the highest frequency of lateral movement (up to 450 per game). Basketball (42–56 per game), handball (up to 90 per game), and volleyball (up to 35 per game) were found to require the most jumping. LimitationsThese data may provide an incomplete view of an athlete’s straight-line running load, considering that only competition and not practice data was provided. Conclusions
Considerable variability exists in the demands of straight-line running and multi-directional demands across sports, competition levels, and sexes, indicating the need for sports medicine clinicians to design future rehabilitation programs with improved specificity (including the type of activity and dosage) to these demands.
The purpose of this study was to investigate the possible arm swing effect on the biomechanical parameters of vertical counter movement jump due to differences of the compliance of the takeoff surface. Fifteen elite male beach-volleyball players (26.2 ± 5.9 years; 1.87 ± 0.05 m; 83.4 ± 6.0 kg; mean ± standard deviation, respectively) performed counter movement jumps on sand and on a rigid surface with and without an arm swing. Results showed significant (p < .05) surface effects on the jump height, the ankle joint angle at the lowest height of the body center of mass and the ankle angular velocity. Also, significant arm swing effects were found on jump height, maximum power output, temporal parameters, range of motion and angular velocity of the hip. These findings could be attributed to the instability of the sand, which resulted in reduced peak power output due to the differences of body configuration at the lowest body position and lower limb joints' range of motion. The combined effect of the backward arm swing and the recoil of the sand that resulted in decreased resistance at ankle plantar flexion should be controlled at the preparation of selected jumping tasks in beach-volleyball.
Numerous national associations and multiple reviews have documented the safety
and efficacy of strength training for children and adolescents. The literature highlights
the significant training-induced increases in strength associated with youth strength
training. However, the effectiveness of youth strength training programs to improve
power measures is not as clear. This discrepancy may be related to training and
testing specificity.Most prior youth strength training programs emphasized lower intensity
resistance with relatively slow movements. Since power activities typically involve higher
intensity, explosive-like contractions with higher angular velocities (e.g., plyometrics),
there is a conflict between the training medium and testing measures. This meta-analysis
compared strength (e.g., training with resistance or body mass) and power training
programs (e.g., plyometric training) on proxies of muscle strength, power, and speed.
A systematic literature search using a Boolean Search Strategy was conducted in the
electronic databases PubMed, SPORT Discus,Web of Science, and Google Scholar and
revealed 652 hits. After perusal of title, abstract, and full text, 107 studies were eligible for
inclusion in this systematic review and meta-analysis. The meta-analysis showed small to
moderate magnitude changes for training specificity with jump measures. In other words,
power training was more effective than strength training for improving youth jump height.
For sprint measures, strength training was more effective than power training with youth.
Furthermore, strength training exhibited consistently large magnitude changes to lower
body strength measures, which contrasted with the generally trivial, small and moderate
magnitude training improvements of power training upon lower body strength, sprint
and jump measures, respectively. Maturity related inadequacies in eccentric strength
and balance might influence the lack of training specificity with the unilateral landings
and propulsions associated with sprinting. Based on this meta-analysis, strength training
should be incorporated prior to power training in order to establish an adequate
foundation of strength for power training activities.
Chronic glaucoma is a multifactorial disease among which oxidative stress may play a major pathophysiological role. We conducted a systematic review and meta-analysis to evaluate the levels of oxidative and antioxidative stress markers in chronic glaucoma compared with a control group. The PubMed, Cochrane Library, Embase and Science Direct databases were searched for studies reporting oxidative and antioxidative stress markers in chronic glaucoma and in healthy controls using the following keywords: “oxidative stress” or “oxidant stress” or “nitrative stress” or “oxidative damage” or “nitrative damage” or “antioxidative stress” or “antioxidant stress” or “antinitrative stress” and “glaucoma”. We stratified our meta-analysis on the type of biomarkers, the type of glaucoma, and the origin of the sample (serum or aqueous humor). We included 22 case-control studies with a total of 2913 patients: 1614 with glaucoma and 1319 healthy controls. We included 12 studies in the meta-analysis on oxidative stress markers and 19 on antioxidative stress markers. We demonstrated an overall increase in oxidative stress markers in glaucoma (effect size = 1.64; 95%CI 1.20–2.09), ranging from an effect size of 1.29 in serum (95%CI 0.84–1.74) to 2.62 in aqueous humor (95%CI 1.60–3.65). Despite a decrease in antioxidative stress marker in serum (effect size = –0.41; 95%CI –0.72 to –0.11), some increased in aqueous humor (superoxide dismutase, effect size = 3.53; 95%CI 1.20–5.85 and glutathione peroxidase, effect size = 6.60; 95%CI 3.88–9.31). The differences in the serum levels of oxidative stress markers between glaucoma patients and controls were significantly higher in primary open angle glaucoma vs primary angle closed glaucoma (effect size = 12.7; 95%CI 8.78–16.6, P < 0.001), and higher in pseudo-exfoliative glaucoma vs primary angle closed glaucoma (effect size = 12.2; 95%CI 8.96–15.5, P < 0.001). In conclusion, oxidative stress increased in glaucoma, both in serum and aqueous humor. Malonyldialdehyde seemed the best biomarkers of oxidative stress in serum. The increase of some antioxidant markers could be a protective response of the eye against oxidative stress.
The purpose of this study was to examine the strength, velocity and power adaptations in youth rugby league players in response to a variable resistance training (VRT) or traditional free-weight resistance-training (TRAD) intervention.Sixteen elite youth players were assigned to a VRT or TRAD group and completed two weekly upper and lower-body strength and power sessions for 6 weeks. Training programs were identical except that the VRT group trained the bench press exercise with 20% of the prescribed load coming from elastic bands. Bench press 1RM as well as bench press mean velocity and power at 35, 45, 65, 75 and 85% of 1RM were measured before and after the training intervention and the magnitude of the changes was determined using effect sizes (ESs).The VRT group experienced larger increases in both absolute (ES= 0.46 vs. 0.20) and relative (ES= 0.41 vs. 0.19) bench press 1RM. Similar results were observed for mean velocity as well as both absolute and relative mean power at 35, 45, 65, 75 and 85% of 1RM. Furthermore, both groups experienced large gains in both velocity and power in the heavier loads but small improvements in the lighter loads. The improvements in both velocity and power against the heavier loads were larger for the VRT group while smaller differences existed between the two groups at the lighter loads.VRT using elastic bands may offer a greater training stimulus than traditional free-weight resistance training to improve upper-body strength, velocity and power in elite youth rugby league players.
The aim of the present study was to assess the effects of sand volleyball training program on physical
performance in young indoor volleyball players. Twenty adolescent male volleyball athletes (16±1 years)
consented to participate in program and lower-body power and body composition testing. The participants
performed the Attack, Block jump tests and Standing Broad jump test for lower-body power. One cycle of six
weeks was analyzed during off-season (2014). Players were involved in specialized sand volleyball training
program and exercise were selected based on previous experience and according to performance analysis in
beach volleyball studies. There were no significant differences between pre-training and post-training for
Block jump and Standing broad jump. However, there was a significant (p ≤ 0.05) improvement in Spike
jump. Training program did not induced significant changes in body composition. The differences in intensity
of training, training volume and sample size could be a reason of the discrepancy in results compared to
previous studies. However, this kind of study could provide practical application for coaches and sport
researchers.
Systematic reviews should build on a protocol that describes the rationale, hypothesis, and planned methods of the review; few reviews report whether a protocol exists. Detailed, well-described protocols can facilitate the understanding and appraisal of the review methods, as well as the detection of modifications to methods and selective reporting in completed reviews. We describe the development of a reporting guideline, the Preferred Reporting Items for Systematic reviews and Meta-Analyses for Protocols 2015 (PRISMA-P 2015). PRISMA-P consists of a 17-item checklist intended to facilitate the preparation and reporting of a robust protocol for the systematic review. Funders and those commissioning reviews might consider mandating the use of the checklist to facilitate the submission of relevant protocol information in funding applications. Similarly, peer reviewers and editors can use the guidance to gauge the completeness and transparency of a systematic review protocol submitted for publication in a journal or other medium.
Abstract This study compared the use of sand and grass training surfaces throughout an 8-week conditioning programme in well-trained female team sport athletes (n = 24). Performance testing was conducted pre- and post-training and included measures of leg strength and balance, vertical jump, agility, 20 m speed, repeat speed (8 × 20 m every 20 s), as well as running economy and maximal oxygen consumption (VO2max). Heart rate (HR), training load (rating of perceived exertion (RPE) × duration), movement patterns and perceptual measures were monitored throughout each training session. Participants completed 2 × 1 h conditioning sessions per week on sand (SAND) or grass (GRASS) surfaces, incorporating interval training, sprint and agility drills, and small-sided games. Results showed a significantly higher (P < 0.05) HR and training load in the SAND versus GRASS group throughout each week of training, plus some moderate effect sizes to suggest lower perceptual ratings of soreness and fatigue on SAND. Significantly greater (P < 0.05) improvements in VO2max were measured for SAND compared to GRASS. These results suggest that substituting sand for grass training surfaces throughout an 8-week conditioning programme can significantly increase the relative exercise intensity and training load, subsequently leading to superior improvements in aerobic fitness.
The aim of the current investigation was to examine the effects of depth jump and countermovement jump training on neuromuscular adaptations using vertical jump and electromyography activity in the muscles. Twenty-seven healthy males (age 20.4 ± 0.3 years; weight 69.8 ± 6.1 kg; height 177.3 ± 6.2 cm) were recruited to participant in the present study and were randomly divided into three groups: depth jump (DJ), countermovement jump (CMJ) and control group. The experimental groups performed either DJ or CMJ training twice weekly for 6 weeks. The training program included five sets of 20 repetitions DJ (from the height of a 45-cm box) or CMJ exercise onto 20-cm dry sand. The electromyography activities in the vastus medialis (VM), and rectus femoris (RF) muscles, and vertical jump (VJ) were measured a week pre and post 6 weeks of training. The results showed significant increases in the integrated electromyography for the VM and RF following DJ and CMJ training on sand, also the DJ and CMJ training on sand induced significant improvement in VJ performance (P < 0.05). In conclusion, the DJ and CMJ training on sand improved electrical activities in the muscle and jump performance, and it can be recommended that, coaches and athletes design plyometrics on sand, because these types of training on sand can be an effective method for improving neuromuscular adaptations.
Abstract Sand surfaces can offer a higher energy cost (EC) and lower impact training stimulus compared with firmer and more traditional team sport training venues such as grass. This review aims to summarise the existing research on sand training, with a specific focus on its application as a team sports training venue. Compared with grass, significant physiological and biomechanical differences are associated with sand exercise. However, evidence also exists to suggest that training adaptations unique to sand can positively influence firm-ground performance. Furthermore, the lower impact forces experienced on sand can limit muscle damage, muscle soreness, and decrements in performance capacity relative to exercise intensity. Therefore, using a sand training surface in team sports may allow greater training adaptations to be achieved, while reducing performance decrements and injuries that may arise from heavy training. Nevertheless, further research should investigate the effect of sand surfaces over a greater range of training types and performance outcomes, to increase the application of sand training for team sports.
Performing sprints on a sand surface is a common training method for improving sprint-specific strength. For maximum specificity of training the athlete’s movement patterns during the training exercise should closely resemble those used when performing the sport. The aim of this study was to compare the kinematics of sprinting at maximum velocity on a dry sand surface to the kinematics of sprinting on an athletics track. Five men and five women participated in the study, and flying sprints over 30 m were recorded by video and digitized using biomechanical analysis software. We found that sprinting on a sand surface was substantially different to sprinting on an athletics track. When sprinting on sand the athletes tended to ‘sit’ during the ground contact phase of the stride. This action was characterized by a lower centre of mass, a greater forward lean in the trunk, and an incomplete extension of the hip joint at take-off. We conclude that sprinting on a dry sand surface may not be an appropriate method for training the maximum velocity phase in sprinting. Although this training method exerts a substantial overload on the athlete, as indicated by reductions in running velocity and stride length, it also induces detrimental changes to the athlete’s running technique which may transfer to competition sprinting.
NEUROMUSCULAR TRAINING OF THE SPINAL STABILIZING MUSCULATURE IS RELEVANT FOR LOWER BACK PAIN PREVENTION AND TREATMENT. INSTABILITY RESISTANCE EXERCISES PROMOTE COCONTRACTIONS, INCREASING JOINT STABILITY. OF GREATEST IMPORTANCE TO JOINT STABILITY IS NOT NECESSARILY STRENGTH OR ENDURANCE BUT MOTOR CONTROL. DYNAMIC PROVOCATIVE CALISTHENIC EXERCISES MAY IMPROVE CORE STABILIZING FUNCTIONS. HIGHER CORE MUSCLE ACTIVATION IS POSSIBLE WITH STABLE GROUND-BASED EXERCISES. PERFORMING RESISTANCE EXERCISES ON UNSTABLE SURFACES MAY HAVE BENEFITS IN JOINT INJURY PREVENTION AND IMPROVING BALANCE; HOWEVER, STRENGTH GAINS COULD BE COMPROMISED. HIGHER LEVELS OF DYNAMIC STABILIZATION MAY BE RECOMMENDED WITH REHABILITATION BUT SHOULD ONLY BE ONE COMPONENT OF A PERIODIZED PLAN.
QUALITY MOVEMENT IS A FUNDAMENTAL ASPECT OF PERFORMANCE IN THE MAJORITY OF FIELD SPORTS. AS A BASIC MOTOR SKILL, SPORT MOVEMENT SHOULD BE SUBJECT TO A SYSTEMATIC DEVELOPMENT PROGRAM IN WHICH QUALITY PRACTICE AND QUALITY COACHING PLAY A LEAD ROLE.
This study compared the effect of sand and grass training surfaces during a common pre-season interval training session in well-trained team sport athletes (n=10). Participants initially completed a preliminary testing session to gather baseline (BASE) performance data for vertical jump (VJ), repeated sprint ability (RSA) and a 3 km running time trial (RTT). Three days subsequent to BASE, all athletes completed the first interval training session, which was followed by a repeat of the BASE performance tests the following day (24 h post-exercise). Seven days later, the same interval training session was completed on the opposing surface, and was again followed 24 h later by the BASE performance tests. During each session, blood lactate (BLa), ratings of perceived exertion (RPE) and heart rate (HR) were recorded. Additionally, venous blood was collected pre-, post-, and 24 h post-exercise, and analysed for serum concentrations of Myoglobin (Mb), Creatine Kinase (CK), Haptoglobin (HP) and C-Reactive Protein (CRP). Results showed significantly higher BLa and HR responses experienced during the SAND session (p<0.05), with no differences observed between surfaces for the blood markers of muscle damage, inflammation and hemolysis (p>0.05). Twenty-four hours later, the RTT was performed significantly faster following the SAND session compared to GRASS (p=0.001). These results suggest that performing interval training on a sand (versus grass) surface can result in a greater physiological response, without any additional detriment to next day endurance performance.
This series of reviews focuses on the most important neuromuscular function in many sport performances: the ability to generate maximal muscular power. Part 1, published in an earlier issue of Sports Medicine, focused on the factors that affect maximal power production while part 2 explores the practical application of these findings by reviewing the scientific literature relevant to the development of training programmes that most effectively enhance maximal power production. The ability to generate maximal power during complex motor skills is of paramount importance to successful athletic performance across many sports. A crucial issue faced by scientists and coaches is the development of effective and efficient training programmes that improve maximal power production in dynamic, multi-joint movements. Such training is referred to as 'power training' for the purposes of this review. Although further research is required in order to gain a deeper understanding of the optimal training techniques for maximizing power in complex, sports-specific movements and the precise mechanisms underlying adaptation, several key conclusions can be drawn from this review. First, a fundamental relationship exists between strength and power, which dictates that an individual cannot possess a high level of power without first being relatively strong. Thus, enhancing and maintaining maximal strength is essential when considering the long-term development of power. Second, consideration of movement pattern, load and velocity specificity is essential when designing power training programmes. Ballistic, plyometric and weightlifting exercises can be used effectively as primary exercises within a power training programme that enhances maximal power. The loads applied to these exercises will depend on the specific requirements of each particular sport and the type of movement being trained. The use of ballistic exercises with loads ranging from 0% to 50% of one-repetition maximum (1RM) and/or weightlifting exercises performed with loads ranging from 50% to 90% of 1RM appears to be the most potent loading stimulus for improving maximal power in complex movements. Furthermore, plyometric exercises should involve stretch rates as well as stretch loads that are similar to those encountered in each specific sport and involve little to no external resistance. These loading conditions allow for superior transfer to performance because they require similar movement velocities to those typically encountered in sport. Third, it is vital to consider the individual athlete's window of adaptation (i.e. the magnitude of potential for improvement) for each neuromuscular factor contributing to maximal power production when developing an effective and efficient power training programme. A training programme that focuses on the least developed factor contributing to maximal power will prompt the greatest neuromuscular adaptations and therefore result in superior performance improvements for that individual. Finally, a key consideration for the long-term development of an athlete's maximal power production capacity is the need for an integration of numerous power training techniques. This integration allows for variation within power meso-/micro-cycles while still maintaining specificity, which is theorized to lead to the greatest long-term improvement in maximal power.
Objective: Funnel plots (plots of effect estimates against sample size) may be useful to detect bias in meta-analyses that were later contradicted by large trials. We examined whether a simple test of asymmetry of funnel plots predicts discordance of results when meta-analyses are compared to large trials, and we assessed the prevalence of bias in published meta-analyses. Design: Medline search to identify pairs consisting of a meta-analysis and a single large trial (concordance of results was assumed if effects were in the same direction and the meta-analytic estimate was within 30
The aim of the present study was to investigate the effects of voluntary maximal leg strength training on peak power output (Wpeak), vertical jump performance, and field performances in junior soccer players. Twenty-two male soccer players participated in this investigation and were divided into 2 groups: A resistance training group (RTG; age 17 +/- 0.3 years) and a control group (CG; age 17 +/- 0.5 years). Before and after the training sessions (twice a week for 2 months), Wpeak was determined by means of a cycling force-velocity test. Squat jump (SJ), countermovement jump (CMJ), and 5-jump test (5-JT) performances were assessed. Kinematics analyses were made using a video camera during a 40-m sprint running test and the following running velocities were calculated: The first step after the start (V(first step)), the first 5 m (V(first 5 meters)), and between the 35 m and 40 m (V(max)). Back half squat exercises were performed to determine 1-repetition maximum (1-RM). Leg and thigh muscle volume and mean thigh cross-sectional area (CSA) were assessed by anthropometry. The resistance training group showed improvement in Wpeak (p < 0.05), jump performances (SJ, p < 0.05 and 5-JT, p < 0.001), 1-RM (p < 0.001) and all sprint running calculated velocities (p < 0.05 for both V(first step) and V(first 5 meters), p < 0.01 for V(max)). Both typical force-velocity relationships and mechanical parabolic curves between power and velocity increased after the strength training program. Leg and thigh muscle volume and CSA of RTG remained unchanged after strength training. Back half squat exercises, including adapted heavy loads and only 2 training sessions per week, improved athletic performance in junior soccer players. These specific dynamic constant external resistance exercises are highly recommended as part of an annual training program for junior soccer players.
The aims of this study were to (1) determine the activity profiles of a large sample of English FA Premier League soccer players and (2) examine high-intensity running during elite-standard soccer matches for players in various playing positions. Twenty-eight English FA Premier League games were analysed during the 2005-2006 competitive season (n=370), using a multi-camera computerised tracking system. During a typical match, wide midfielders (3138 m, s=565) covered a greater distance in high-intensity running than central midfielders (2825 m, s= 73, P=0.04), full-backs (2605 m, s=387, P < 0.01), attackers (2341 m, s=575, P < 0.01), and central defenders (1834 m, s=256, P < 0.01). In the last 15 min of a game, high-intensity running distance was approximately 20% less than in the first 15-min period for wide midfielders (467 m, s=104 vs. 589 m, s=134, P < 0.01), central midfielders (429 m, s=106 vs. 534 m, s=99, P < 0.01), full-backs (389 m, s=95 vs. 481 m, s=114, P < 0.01), attackers (348 m, s=105 vs. 438 m, s=129, P < 0.01), and central defenders (276 m, s=93 vs. 344 m, s=80, P < 0.01). There was a similar distance deficit for high-intensity running with (148 m, s=78 vs. 193 m, s=96, P < 0.01) and without ball possession (229 m, s=85 vs. 278 m, s=97, P < 0.01) between the last 15-min and first 15-min period of the game. Mean recovery time between very high-intensity running bouts was 72 s (s=28), with a 28% longer recovery time during the last 15 min than the first 15 min of the game (83 s, s=26 vs. 65 s, s=20, P < 0.01). The decline in high-intensity running immediately after the most intense 5-min period was more evident in attackers (216 m, s=50 vs. 113 m, s=47, P < 0.01) and central defenders (182 m, s=26 vs. 96 m, s=39, P < 0.01). The results suggest that high-intensity running with and without ball possession is reduced during various phases of elite-standard soccer matches and the activity profiles and fatigue patterns vary among playing positions. The current findings provide valuable information about the high-intensity running patterns of a large sample of elite-standard soccer players, which could be useful in the development and prescription of specific training regimes.
Oxygen uptake (VO2) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3-7 km.h-1) or running (7-14 km.h-1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of VO2 to speed and expressed in J.kg-1.m-1 assuming an energy equivalent of 20.9 J.ml O2-1. At the highest speeds C was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand, C increased linearly with speed from 3.1 J.kg-1.m-1 at 3 km.h-1 to 5.5 J.kg-1.m-1 at 7 km.h-1, whereas on a firm surface C attained a minimum of 2.3 J.kg-1.m-1 at 4.5 km.h-1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km.h-1, C was about 1.8 times greater on sand than on compact terrain. When running on sand C was approximately independent of the speed, amounting to 5.3 J.kg-1.m-1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.
Velocity specificity of resistance training has demonstrated that the greatest strength gains occur at or near the training velocity. There is also evidence that the intent to make a high speed contraction may be the most crucial factor in velocity specificity.
The mechanisms underlying the velocity-specific training effect may reside in both neural and muscular components. Muscular adaptations such as hypertrophy may inhibit high velocity strength adaptations due to changes in muscle architecture. However, some studies have reported velocity-specific contractile property adaptations suggesting changes in muscle kinetics. There is evidence to suggest velocity-specific electromyographic (EMG) adaptations with explosive jump training. Other researchers have hypothesised neural adaptations because of a lack of electrically evoked changes in relation to significant voluntary improvements. These neural adaptations may include the selective activation of motor units and/or muscles, especially with high velocity alternating contractions. Although the incidence of motor unit synchronisation increases with training, its contribution to velocity-specific strength gains is unclear. However, increased synchronisation may occur more frequently with the premovement silent period before ballistic contractions. The preprogrammed neural circuitry of ballistic contractions suggests that high velocity training adaptations may involve significant neural adaptations. The unique firing frequency associated with ballistic contractions would suggest possible adaptations in the frequency of motor unit discharge. Although co-contraction of antagonists increases with training and high velocity movement, its contribution is probably related more to joint protection than the velocity-specific training effect.
Eight men and eight women trained 3 days/wk for 16 wk by doing attempted ballistic unilateral ankle dorsiflexions against resistance that either rendered the resultant contractions isometric (one limb) or allowed a relatively high-velocity (5.23 rad/s on an isokinetic dynamometer) movement (other limb). Training sessions consisted of five sets of 10 contractions of each type. Training produced the same high-velocity-specific training response in both limbs (P < 0.001). Peak torque increased most at 5.23 rad/s (38%) in comparison to lower velocities (0, 0.26, 0.52, 1.04, 1.55, 3.02, and 4.19 rad/s). Both limbs also showed similar increases in voluntary isometric rate of torque development (26%) and relaxation (47%) and in evoked tetanus rate of torque development (14%). A similar decrease in evoked twitch time to peak torque (6%) and half-relaxation time (11%) was also observed. Thus, all of these training responses, previously associated specifically with high-velocity resistance training, were produced by a training regimen that prevented an actual rapid movement through a range of movement. The results suggest that the principal stimuli for the high-velocity training response are the repeated attempts to perform ballistic contractions and the high rate of force development of the ensuing contraction. The type of muscle action (isometric or concentric) appears to be of lesser importance.
Moving about in nature often involves walking or running on a soft yielding substratum such as sand, which has a profound effect on the mechanics and energetics of locomotion. Force platform and cinematographic analyses were used to determine the mechanical work performed by human subjects during walking and running on sand and on a hard surface. Oxygen consumption was used to determine the energetic cost of walking and running under the same conditions. Walking on sand requires 1.6-2.5 times more mechanical work than does walking on a hard surface at the same speed. In contrast, running on sand requires only 1.15 times more mechanical work than does running on a hard surface at the same speed. Walking on sand requires 2.1-2.7 times more energy expenditure than does walking on a hard surface at the same speed; while running on sand requires 1.6 times more energy expenditure than does running on a hard surface. The increase in energy cost is due primarily to two effects: the mechanical work done on the sand, and a decrease in the efficiency of positive work done by the muscles and tendons.
Maximizing the neuromuscular capacities of players is a critical challenge during short soccer preseasons. This study compared the effects of two strength-power training regimes, on the strength, speed, and power performance of elite young soccer players during a 4-week preseason. Twenty-five under-20 players from the same club were pair-matched in two training groups as follows: traditional training group (TTG) (n=13), athletes performed half-squat (HS) and jump-squat (JS) exercises as traditionally prescribed; and EB group (EBG) (n=12), athletes performed HS and JS with EB attached to the barbell. Vertical jump height, 20-m sprint velocity, change-of-direction (COD) speed, HS and JS power, and one-repetition maximum (1RM) in the HS were assessed pre, post 2-week, and post 4-week of training. An ANOVA two-way with repeated measures was used to assess the effects of both training protocols over the experimental period. Both strategies were effective for significantly improving HS and JS power (effect sizes [ES] 1.00 - 1.77), HS 1RM (ES = 1.68 and 1.51 for TTG and EBG, respectively), vertical jumping ability (ES 0.37 - 0.65), and COD speed (ES = 0.81 and 0.39 for TTG and EBG, respectively), when comparing pre- and post-measures. In contrast, both TTG and EBG failed to increase 20-m sprint velocity (ES ranging between -0.54 and 0.23). In conclusion, both training schemes were able to improve the strength and power performance, but not the sprint capacity of young soccer players. To accelerate strength gains over very-short time periods (i.e., 2-week), variable resistance training may be advantageous. Conversely, to optimize power adaptations in ballistic exercises across a similar time period, traditional FW training may be preferred.
We examined the effects of five loading conditions (0%, 20%, 40%, 60%, and 80% of body-mass [BM]), on resisted sprint performance and kinematics in male rugby players over different distances. Ten players from the Brazilian National Team (20.1±3.3 years; 88.7±18.8 kg; 178.3±6.2 cm) performed 20-m sprints under the five loading conditions. Sprint times in 5-, 10- and 20-m were recorded. Stride length (SL), and hip, knee and ankle angles were measured using an eight-sensor motion analysis system. The kinematic parameters were calculated over the different distances. Heavier loads led to significantly greater velocity loss (P < 0.001-0.05). Significant reductions in SL were also observed when comparing 0% BM and all resisted sprints in all assessed distances (P < 0.001-0.05, Effect Size, [ES]: 1.35-4.99). Very-heavy (80% BM) sled load provoked significantly greater decreases in SL than the rest of loading conditions (P < 0.01-0.05). Important kinematic alterations were observed for all loading conditions and sprint distances when compared to 0%BM (ES: 0.76-1.79, for hip-angle; 0.20-1.40, for knee-angle; and 0.73-1.88, for ankle-angle). Moreover, 80% BM induced significantly higher hip flexion, lower knee flexion and higher ankle dorsiflexion than 20% BM condition at 5-10- and 10-20-m distances (P < 0.05). Lighter sled loads (< 40% BM) seem to be more adequate to improve speed ability without provoking drastic changes in unloaded sprinting technique, whereas heavier loads might be more suitable for optimizing horizontal force production and thus, acceleration performance.
Vertical force production (VFP) is widely recognized as a critical determinant of performance in a series of soccer-specific activities, such as sprinting, jumping, and changing direction. Therefore, practitioners are constantly seeking better and more effective strategies to improve VFP in professional soccer players. This article analyzes the mechanical aspects associated with the actual role played by VFP in elite soccer, and also examines and highlights the training considerations related to its appropriate and effective development during modern soccer seasons.
Abstract Ramirez-Campillo, R, Álvarez, C, García-Pinillos, F, García-Ramos, A, Loturco, I, Chaabene, H, and Granacher, U. Effects of combined surfaces vs. single-surface plyometric training on soccer players' physical fitness. J Strength Cond Res XX(X): 000–000, 2018—The aim of this study was to compare the effects of a 8-week plyometric jump training (PJT) performed on different surfaces (grass, land-dirt, sand, wood, gym mat, and tartan-track) vs. a single-surface PJT (grass) on components of physical fitness (muscle power, speed, and change-of-direction speed [CODS] tasks) and sport-specific performance (i.e., maximal kicking velocity [MKV]) in male soccer players aged 11–14 years. Athletes were randomly assigned to a combined surfaces PJT (PJTc, n = 8), a single-surface PJT (PJTs, n = 8), or an active control (CON, n = 7). Although the PJT group trained on grass, the PJTc trained on 6 different surfaces and equally distributed the total jump volume according to the surface. Pre-post tests were conducted on grass. Significant main effects of time were observed for the countermovement jump, the standing-long-jump, the 20-cm drop jump, 30-m sprint time, CODS, and MKV (all p < 0.001; d = 0.53–0.87). Group × time interactions were identified for all jump tests, MKV, 30-m sprint time, and CODS (all p < 0.001; d = 0.58–0.71) in favor of PJTc. No significant pre-post changes were observed in the CON (all p > 0.05; d = 0.07–0.1). In conclusion, PJT is effective in improving physical fitness in young soccer players when conducted in combination with regular soccer training. Although general fitness testing and PJTs were performed on grass, larger physical fitness improvements were found after PJTc. Thus, PJTc is recommended, as it provides a better overload stimulus compared with more conventional training overload (e.g., increase in training volume or intensity). Future studies still have to address the underlying physiological adaptations after PJTc.
This study aimed at testing whether there are mean propulsive velocities (MPV) capable of maximizing the mean propulsive power (MPP) during the execution of bench-press (BP), bench-throw (BT), half-squat (HS) and jump-squat (JS). Additionally, we assessed the differences in MPP/MPV between ballistic and traditional exercises. Seventeen male rugby sevens players performed MPP tests in BP, BT, HS and JS and maximum isometric force (MIF) tests in HS and BP. The JS presented higher MPP (977.4 ± 156.2 W) than the HS (897.9 ± 157.7 W) (P< 0.05); the BP (743.4 ± 100.1 W) presented higher MPP than the BT (697.8 ± 70.4 W) (P< 0.05). Ballistic exercises presented higher MPV (JS = 1.02 ± 0.07 m.s-1; BT = 1.67 ± 0.15 m.s-1) than traditional exercises (HS = 0.93 ± 0.08 m.s-1; BP = 1.40 ± 0.13 m.s-1) (P< 0.05). The MPP in the JS, BT, HS and BP occurred at 28.2 ± 5.79, 23.3 ± 4.24, 32.4 ± 9.46 and 27.7 ± 5.33% of the MIF, respectively. The coefficient of variation (CV) of MPV at MPP ranged from 7.4 to 9.7%, while the CV of %MIF ranged from 18.2 to 29.2%. The MPV is a more precise indicator of the optimum loads than the percentages of MIF due to its low inter-subject variability as expressed by CV. Therefore, MPV can be used to determine the optimum power load in the four investigated exercises.
Objective:
The lower impact on the musculoskeletal system induced by plyometric exercise on sand compared to a firm surface might be useful to reduce the stress of intensified training periods or during rehabilitation from injury. The aim of this study was to compare the effects of plyometric training on sand versus a grass surface on muscle soreness, vertical jump height and sprinting ability.
Design:
Parallel two-group, randomised, longitudinal (pretest-post-test) study.
Methods:
After random allocation, 18 soccer players completed 4 weeks of plyometric training on grass (grass group) and 19 players on sand (sand group). Before and after plyometric training, 10 m and 20 m sprint time, squat jump (SJ), countermovement jump (CMJ), and eccentric utilization ratio (CMJ/SJ) were determined. Muscle soreness was measured using a Likert scale.
Results:
No training surface x time interactions were found for sprint time (p>0.87), whereas a trend was found for SJ (p = 0.08), with both groups showing similar improvements (p<0.001). On the other hand, the grass group improved their CMJ (p = 0.033) and CMJ/SJ (p = 0.005) significantly (p<0.001) more than players in the sand group. In contrast, players in the sand group experienced less muscle soreness than those in the grass group (p<0.001).
Conclusions:
Plyometric training on sand improved both jumping and sprinting ability and induced less muscle soreness. A grass surface seems to be superior in enhancing CMJ performance while the sand surface showed a greater improvement in SJ. Therefore, plyometric training on different surfaces may be associated with different training-induced effects on some neuromuscular factors related to the efficiency of the stretch-shortening cycle.
Fourteen male elite sprinters performed short-distance sprints and jump tests up to 18 days prior to 100-m dash competitions in track & field to determine if these tests are associated with 100-m sprint times. Testing comprised squat jumps (SJ), countermovement jumps (CMJ), horizontal jumps (HJ), maximum mean propulsive power relative to body mass in loaded jump squats (MPPR) and a flying start 50-m sprint. Moderate associations were found between speed tests and competitive 100-m times (r = 0.54, r = 0.61 and r = 0.66 for 10-, 30- and 50-m, respectively, P < 0.05). In addition, the MPPR was very largely correlated with 100-m sprinting performance (r = 0.75, P < 0.01). The correlations of SJ, CMJ and HJ with actual 100-m sprinting times amounted to -0.82, -0.85 and -0.81, respectively. Due to their practicality, safeness and relationship with the actual times obtained by top-level athletes in 100-m dash events, it is highly recommended that SJ, CMJ, and HJ be regularly incorporated into elite sprint testing routines.
This study compared the effect of an 8-week pre-season conditioning program conducted on a sand (SAND) or grass (GRASS) surface on 20 m sprint performance. Twelve team sport athletes were required to attend three 1 h training sessions per week, including two surface-specific sessions (SAND, n=6 or GRASS, n=6), and one group session (conducted on grass). Throughout the training period, 20 m sprint times of all athletes were recorded on both sand and grass surfaces at the end of week 1, 4 and 8. Results showed a significant improvement in 20 m sand time in the SAND group only (p<0.05), whereas 20 m grass time improved equally in both training sub-groups (p<0.05). These results suggest that surface-specificity is essential for 20 m speed improvements on sand, and also that there is no detriment to grass speed gains when incorporating sand surfaces into a pre-season program.
We quantified the acceleration and high-velocity running of elite Australian soccer players. We hypothesised that high-intensity activity would be underestimated when excluding acceleration during match analysis given its high metabolic demand and occurrence at low velocities. Player movements were observed from 29 players (forwards and central and wide defenders and midfielders) during domestic Australian competition using 5-Hz global positioning system. Effort occurrence were determined for high-velocity running, sprinting and maximal accelerations. The commencement and final velocity of maximal accelerations were also identified. Players undertook an 8~fold greater number of maximal accelerations than sprints per game (65±21 vs. 8±5). Of maximal accelerations ~98% commenced from a starting velocity lower than what would be considered high-velocity running while ~85% did not cross the high-velocity running threshold. The number of efforts performed in all categories were position dependent (P<0.001). Wide defenders performed more maximal accelerations (P<0.006) and central defenders and midfielders performed less sprints compared to all other positions (P<0.02). Maximal accelerations are frequently undertaken during a match often occurring at low velocities. Excluding maximal accelerations in match analysis research may underestimate the amount of high-intensity movements undertaken. Additionally positional differences in high-intensity movements should be accounted for when developing specific conditioning drills.
This study compared the effect of sand and grass training surfaces during a sport-specific conditioning session in well-trained team sport athletes (n=10). Participants initially completed a preliminary testing session to gather baseline (BASE) performance data for vertical jump (VJ), repeated sprint ability (RSA) and 3 km running time trial (RTT). Three days subsequent to BASE, all athletes completed the first sport-specific conditioning session, which was followed by a repeat of the BASE performance tests the following day (24 h post-exercise). Seven days later, the same training session was completed on the opposing surface, and was again followed 24 h later by the BASE performance tests. During each session, blood lactate (BLa), ratings of perceived exertion (RPE) and heart rate (HR) were recorded, with player movement patterns also monitored via global positioning system (GPS) units. Additionally, venous blood was collected pre-, post-, and 24 h post-exercise, and analysed for serum concentrations of Myoglobin (Mb), Haptoglobin (Hp) and C-Reactive Protein (CRP). Results showed significantly higher HR and RPE responses on SAND (p>0.05), despite significantly lower distance and velocity outputs for the training session (p>0.05). There were no differences in 24 h post-exercise performance (p>0.05), and blood markers of muscle damage, inflammation and hemolysis were also similar between the surfaces (p>0.05). These results suggest that performing a sport-specific conditioning session on a sand (versus grass) surface can result in a greater physiological response, without any additional decrement to next day performance.
This study investigated the neural and peripheral adaptations to short-term training for explosive force production. Ten men trained the knee extensors with unilateral explosive isometric contractions (1 s 'fast and hard') for 4 weeks. Before and after training, force was recorded at 50-ms intervals from force onset (F(50), F(100) and F(150)) during both voluntary and involuntary (supramaximal evoked octet; eight pulses at 300 Hz) explosive isometric contractions. Neural drive during the explosive voluntary contractions was measured with the ratio of voluntary/octet force, and average EMG normalized to the peak-to-peak M-wave of the three superficial quadriceps. Maximal voluntary force (MVF) was also measured, and ultrasonic images of the vastus lateralis were recorded during ramped contractions to assess muscle-tendon unit stiffness between 50 and 90% MVF. There was an increase in voluntary F(50) (+54%), F(100) (+15%) and F(150) (+14%) and in octet F(50) (+7%) and F(100) (+10%). Voluntary F(100) and F(150), and octet F(50) and F(100) increased proportionally with MVF (+11%). However, the increase in voluntary F(50) was +37% even after normalization to MVF, and coincided with a 42% increase in both voluntary/octet force and agonist-normalized EMG over the first 50 ms. Muscle-tendon unit stiffness between 50 and 90% MVF also increased. In conclusion, enhanced agonist neural drive and MVF accounted for improved explosive voluntary force production in the early and late phases of the contraction, respectively. The increases in explosive octet force and muscle-tendon unit stiffness provide novel evidence of peripheral adaptations within merely 4 weeks of training for explosive force production.
The purpose of this study was to examine the time course of adaptation through 20 days of eccentric training and 5 days of detraining. A total of 22 untrained subjects trained one arm every 2nd day for 20 days. Subjects performed maximal isokinetic eccentric biceps brachii training at 90 degrees /s (six sets of eight reps). Muscle thickness (reported in cm) via ultrasound, strength (reported in Nm) and muscle activation (electromyography) were measured before, during, and after training (nine time points). Strength in the trained arm decreased after 8 days of training (65.6 +/- 4.1 to 57.5 +/- 3.5; p < 0.05) and remained decreased throughout the study. Agonist muscle activation amplitude of the trained arm increased after 14 days of training (p < 0.05) and remained elevated throughout the study. Antagonist muscle activation decreased after 20 days of training (p < 0.05). Muscle thickness increased after 8 days of training (3.66 +/- 0.11 to 3.90 +/- 0.12; p < 0.05) and remained above baseline until the end of training (3.97 +/- 0.12). After 5 days of detraining, muscle thickness decreased (3.97 +/- 0.12 vs. 3.85 +/- 0.11; p < 0.05), but remained higher than baseline (p < 0.05). Muscle thickness did not change significantly in the untrained arm at any time point. In conclusion, the early increase in biceps brachii muscle thickness coupled with a significant decrease in strength is an indicator of muscle damage leading to swelling and impaired muscle function. The persistent decrease in strength, despite an increase in muscle activation, suggests that the recovery interval was inadequate to allow complete repair of muscle damage. Intense eccentric training performed every 2nd day leads to a prolonged impairment of muscle strength in previously untrained individuals.
Does the PEDro scale measure only one construct ie, the methodological quality of clinical trials? What is the hierarchy of items of the PEDro scale from least to most adhered to? Is there any effect of year of publication of trials on item adherence? Are PEDro scale ordinal scores equivalent to interval data?
Rasch analysis of two independent samples of 100 clinical trials from the PEDro database scored using the PEDro scale.
Both samples of PEDro data showed fit to the Rasch model with no item misfit. The PEDro scale item hierarchy was the same in both samples, ranging from the most adhered to item random allocation, to the least adhered to item therapist blinding. There was no differential item functioning by year of publication. Original PEDro ordinal scores were highly correlated with transformed PEDro interval scores (r = 0.99).
The PEDro scale is a valid measure of the methodological quality of clinical trials. It is valid to sum PEDro scale item scores to obtain a total score that can be treated as interval level measurement and subjected to parametric statistical analysis.
Plyometric training improves vertical jump height (VJH). However, the effectiveness of plyometric training depends on various factors. A meta-analysis of 56 studies with a total of 225 effect sizes (ESs) was carried out to analyze the role of various factors on the effects of plyometrics on VJH performance. The inclusion criteria for the analysis were a) studies using plyometric programs for lower-limb muscles, b) studies employing true experimental designs and valid and reliable measurements, and c) studies including enough data to calculate ESs. Subjects with more experience in sport obtained greater enhancements in VJH performance (p < 0.01). Subjects in either good or bad physical condition benefit equally from plyometric work (p < 0.05), although men tend to obtain better power results than women after plyometric training (p < 0.05). With relation to the variables of performance, training volumes of more than 10 weeks and more than 20 sessions, using high-intensity programs (with more than 50 jumps per session), were the strategies that seemed to maximize the probability of obtaining significantly greater improvements in performance (p < 0.05). To optimize jumping enhancement, the combination of different types of plyometrics (squat jump + countermovement jump + drop jump) is recommended rather than using only 1 form (p < 0.05). However, no extra benefits were found to be gained from doing plyometrics with added weight. The responses identified in this analysis are essential and should be considered by strength and conditioning professionals with regard to the most appropriate dose-response trends for optimizing plyometric-induced gains.
To investigate the influence of explosive type strength training on isometric force- and relaxation-time and on electromyographic and muscle fibre characteristics of human skeletal muscle, 10 male subjects went through progressive training which included primarily jumping exercises without extra load and with light extra weights three times a week for 24 weeks. Specific training-induced changes in force-time curve were observed and demonstrated by great (P less than 0.05-0.01) improvements in in parameters of fast force production and by a minor (P less than 0.05) increase in maximal force. The continuous increases in fast force production during the entire training were accompanied by and correlated with the increases (P less than 0.05) in average IEMG-time curve and with the increase (P less than 0.05) in the FT:ST muscle fibre area ratio. The percentage of FT fibres of the muscle correlated (P less than 0.05) with the improvement of average force-time curve during the training. The increase in maximal force was accompanied by significant (P less than 0.05) increases in maximum IEMGs of the trained muscles. However, the hypertrophic changes, as judged from the anthropometric and muscle fibre area data, were only slight during the training. It can be concluded that in training for fast force production considerable neural and selective muscular adaptations may occur to explain the improvement in performance, but that genetic factors may determine the ultimate potential of the trainability of this aspect of the neuromuscular performance.
A biomechanical study of 13 runners which consisted of 2 male sprinters, 5 experienced joggers, and 6 elite long-distance runners were studied. We obtained hip, knee, and ankle joints motions in the sagittal plane and electromyographic data from specific muscle groups.
As the speed of gait increased, the length of stance phase progressively decreased from 62% for walking to 31% for running and to 22% for sprinting. The sagittal plane motion increased as the speed of gait increased. Generally speaking, the body lowers its center of gravity with the increased speed by increasing flexion of the hips and knees and magnifying dorsiflexion at the ankle joint. Electromyographic activity about the knee demonstrated increased activity in the quadricep muscle group and hamstring group with increased speed. Mus cle function about the ankle joint demonstrated that the pos terior calf musculature which normally functions during the midstance phase in walking became a late swing phase muscle and was active through the first 80% of stance phase, as compared to 15% in walking.
Beside the changes in the electromyographic activity of the muscles, the anterior compartment muscles of the calf undergo a concentric contracture at the time of initial floor contact during running and sprinting but undergo an eccentric contrac tion during walking.
Stretch-shortening cycle (SSC) in human skeletal muscle gives unique possibilities to study normal and fatigued muscle function. The in vivo force measurement systems, buckle transducer technique and optic fiber technique, have revealed that, as compared to a pure concentric action, a non-fatiguing SSC exercise demonstrates considerable performance enhancement with increased force at a given shortening velocity. Characteristic to this phenomenon is very low EMG-activity in the concentric phase of the cycle, but a very pronounced contribution of the short-latency stretch-reflex component. This reflex contributes significantly to force generation during the transition (stretch-shortening) phase in SSC action such as hopping and running. The amplitude of the stretch reflex component - and the subsequent force enhancement - may vary according to the increased stretch-load but also to the level of fatigue. While moderate SSC fatigue may result in slight potentiation, the exhaustive SSC fatigue can dramatically reduce the same reflex contribution. SSC fatigue is a useful model to study the processes of reversible muscle damage and how they interact with muscle mechanics, joint and muscle stiffness. All these parameters and their reduction during SSC fatigue changes stiffness regulation through direct influences on muscle spindle (disfacilitation), and by activating III and IV afferent nerve endings (proprioseptic inhibition). The resulting reduced stretch reflex sensitivity and muscle stiffness deteriorate the force potentiation mechanisms. Recovery of these processes is long lasting and follows the bimodal trend of recovery. Direct mechanical disturbances in the sarcomere structural proteins, such as titin, may also occur as a result of an exhaustive SSC exercise bout.