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Purpose: The aim of this study was to analyze the effects of bilateral and unilateral plyometric-training (PT) programs on jumping, sprinting, and change-of-direction (COD) ability in male postpubertal basketball players. Methods: Forty-three young male basketball players (14.2 [1.2] y), from 4 squads belonging to an elite basketball club, were randomly assigned to 1 of 3 groups: (1) bilateral PT group (BG), (2) unilateral PT group (UG), and (3) control group (CG). The experimental groups followed a PT program twice weekly for 6 weeks, with BG and UG performing 2- and 1-legged jumps, respectively. Both groups completed the same number of vertical, horizontal, cyclic, and acyclic jumps. Pretraining and posttraining measurements included (1) countermovement jump (CMJ), (2) unilateral CMJ (CMJL and CMJR), (3) horizontal jump (HJ), (4) unilateral HJ (HJL and HJR), (5) straight-line sprint in 20 m (T20), and (6) V-Cut COD test (V-Cut). Results: CMJ, CMJL, and CMJR were significantly improved by BG and UG (P <.001), while CG did not change. Both the BG and the UG improved their performance significantly (P <.01) in HJL and HJR, but only BG significantly increased (P <.05) HJ and showed significantly greater improvements than CG. Furthermore, only BG improved V-Cut performance (P =.03). Neither group increased T20. CG did not improve in any tests. Conclusions: BG enhances single-leg and double-leg jump performance in vertical and horizontal directions, as well as COD ability. In contrast, an equivalent volume of unilateral PT only improves vertical jumps and unilateral HJs. [ABSTRACT FROM AUTHOR]

Purpose: The aim of the present study was to analyze the effect of different eccentric tempos on eccentric kinetics and kinematics and the subsequent concentric performance when performing countermovement jumps against different loads. Methods: After 1-repetition-maximum assessment and 2 familiarization sessions, 13 well-trained participants performed, in randomized order, 12 sets (4 tempos × 3 loads) of 4 repetitions of the loaded countermovement-jump exercise. The eccentric tempos analyzed were 5 and 2 seconds, as fast as possible, and accelerated (ie, without pause between repetitions), while the loads used were 30%, 50%, and 70% of 1-repetition maximum. Several kinetic and kinematic variables during both phases were recorded by linking a linear position transducer to the barbell. Results: The eccentric work was greater in the accelerated condition despite no changes in the eccentric depth. The peak and mean propulsive velocities were greater in the as-fast-as-possible and accelerated conditions. Correlation analysis showed that, compared with the 5-second condition, the increased concentric performance in the accelerated condition was related to the difference in eccentric work performed in the last 100 milliseconds of the eccentric phase (r >.770). Conclusions: Contrary to current practices, the current study highlights the need for performing the eccentric phase of loaded countermovement jumps, a common exercise performed by athletes for both training and evaluation purposes, as fast as possible. This allows not only a greater eccentric work but also improved concentric performance. [ABSTRACT FROM AUTHOR]

Explosive movements requiring high force and power outputs are integral to many sports, posing distinct challenges for the neuromuscular system. Traditional resistance training can improve muscle strength, power, endurance, and range of motion; however, evidence regarding its effects on athletic performance, such as sprint speed, agility, and jump height, remains conflicting. The specificity of resistance training movements, including velocity, contraction type, and joint angles affects performance outcomes, demonstrates advantages when matching training modalities with targeted sports activities. However, independent of movement speed, the intent to contract explosively (ballistic) has also demonstrated high velocity-specific training adaptations. The purpose of this narrative review was to assess the impact of explosive or ballistic contraction intent on velocity-specific training adaptations. Such movement intent may predominantly elicit motor efferent neural adaptations, including motor unit recruitment and rate coding enhancements. Plyometrics, which utilize rapid stretch-shortening cycle movements, may augment high-speed movement efficiency and muscle activation, possibly leading to improved motor control through adaptations like faster eccentric force absorption, reduced amortization periods, and quicker transitions to explosive concentric contractions. An optimal training paradigm for power and performance enhancement might involve a combination of maximal explosive intent training with heavier loads and plyometric exercises with lighter loads at high velocities. This narrative review synthesizes key literature to answer whether contraction intent or movement speed is more critical for athletic performance enhancement, ultimately advocating for an integrative approach to resistance training tailored for sports-specific explosive action. [ABSTRACT FROM AUTHOR]

Children under the age of 14 years (U14) are particularly susceptible to musculoskeletal disorders because of growth spurts. Plyometric training has been shown to be beneficial for both injury reduction and performance enhancement. The aim of this study was to evaluate the effects of plyometric training on the jumping ability and running biomechanics of U14 track-and-field athletes. A single-blind randomized controlled trial was conducted. Thirty-five (18 female and 17 male) U14 athletes (age: 12.561.2 years; height: 152.367.7 cm; body mass: 47.366.9 kg) were randomized into experimental and control groups. All subjects completed their usual training for 4 weeks, and those in the intervention group added a low-volume plyometric program twice a week. Preintervention and postintervention assessments included a countermovement jump (CMJ) to determine maximum jump height, 10-second repeated jumps to assess reactive strength index (RSI), and a 3-minute run at 12 km·h21 to analyze running kinematics contact time, flight time, step length (SL), step frequency (SF), mean power output, vertical spring stiffness, and leg spring stiffness (LSS). The results revealed no main effect of time for any of the variables. A group-by-time interaction was found for RSI (p 5 0.045) in the intervention group, whereas a significant increase in LSS was also found after the intervention (p50.031). However, no changes in CMJ height or other running parameters were observed. The significance level for the study was set at r # 0.05. Plyometric-jump training may improve the stretch-shortening cycle in U14 athletes by increasing RSI and LSS. Athletes and coaches in running-related sports should be aware of these short-term effects when aiming to optimize the energy storage and release mechanism. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the effects of different plyometric training volumes on jumping, sprinting, and change-of-direction performances in youth basketball players. Thirty-one young male basketball players (age: 15.1 ± 1.8 years) from 4 squads belonging to an elite basketball club were randomly assigned to 1 of 3 groups: (a) low-volume (LV) plyometric training, (b) high-volume (HV) plyometric training, and (c) control group (CG). The subjects followed a plyometric training program twice a week for 6 weeks, differing in the training volume controlled through the number of jumps per session. Both experimental groups performed 8 repetitions in each set of bilateral vertical jumps with free arms, but HV completed twice the training volume of LV (98.7 vs. 49.3 jumps per session). Pretraining and Post-training measurements included the following: (a) squat jump (SJ); (b) countermovement jump (CMJ); (c) horizontal jump (HJ); (d) straight-line sprint in 20 m (Sprint); and (e) V-Cut change-of-direction test (V-Cut). The LV and HV groups showed similar increases in vertical jump performance. The LV group significantly increased its performance in SJ, CMJ, and HJ (p < 0.001-0.05), whereas the HV group showed significant improvements only in SJ and CMJ (p < 0.001). Furthermore, neither group increased their sprint or change of direction performance. Control group did not improve in any performance variable analyzed. Therefore, the LV and HV plyometric training programs produce similar benefits on jump performance variables, but LV is more repetition-efficient than HV in young basketball players. This supports the statement that there is a nonlinear relationship between training volume and performance improvements. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate basketball specific neuromuscular (NM) fatigue effect on countermovement jump (CMJ) force-time (F-T) curve characteristics. Eleven male college-level basketball athletes performed 6 CMJ trials at 3 baseline (pre) and 6 postexercise time points. The fatiguing protocol consisted of high-intensity basketball related exercises commensurate with basketball game or practice. Typical CMJ (CMJ-TYP) and phase-specific CMJ variables were derived from the F-T curve. Meaningful differences in CMJ performance were examined using effect size (ES) compared with baseline and previous postexercise time point. Baseline with 3 separated measurements demonstrated suitable CMJ variables reproducibility (CV, coefficient of variation). Most CMJ-TYP output and performance variables displayed substantial alterations immediately postexercise (0 hour) and returned to baseline at 24 hours postexercise, whereas the time and rate-related CMJ-TYP and CMJ-phase variables tended to display delayed decline peaked at 2 hours and delayed recovery to baseline at 48 hours postexercise. In conjunction with the return of the time and raterelated variables, CMJ performance displayed supercompensation at 72 hours postexercise. The results indicate altered NM functions with desired CMJ performance, such as jump height, which imply an altered movement strategy at early stage of recovery process. Full recovery may take 48-72 hours. Practitioners are, therefore, advised to monitor variables reflecting NM functions for precise manipulation of the intensity and volume of exercise to avoid prolonging the recovery from NM fatigue. [ABSTRACT FROM AUTHOR]

Purpose: A variation of the traditional squat (SQ) rebound technique (REBOUND) including a momentary pause ∼2 seconds (PAUSE) between eccentric and concentric phases has been proposed. Although there is a consensus about the lower acute effects on performance of this PAUSE variant compared with traditional REBOUND technique, no information exists about the differences in longitudinal adaptations of these SQ executions. Methods: A total of 26 men were randomly assigned into the PAUSE (n = 13) or REBOUND (n = 13) groups and completed a 10-week velocity-based training using the SQ exercise, only differing in the technique. Neuromuscular adaptations were assessed by the changes in the 1-repetition maximum strength and mean propulsive velocity achieved against the absolute loads (in kilograms) common to pretest and posttest. Functional performance was evaluated by the following tests: countermovement jump, Wingate, and sprint time at 0 to 10, 10 to 20, and 0 to 20 m. Results: Whereas both groups showed significant increases in most of the neuromuscular tests (P <.05), the PAUSE (effect size [ES] = 0.76–1.12) presented greater enhancements than REBOUND (ES = 0.45–0.92). Although not significant, improvements in Wingate and sprint time at 0 to 10 and 0 to 20 m were higher for PAUSE (ES = 0.31–0.46) compared with REBOUND (ES = 0.10–0.29). Conversely, changes on countermovement jump and sprint time at 10 to 20 m were superior for REBOUND (ES = 0.17–0.88) than for PAUSE (ES = 0.09–0.75). Conclusion: Imposing a pause between eccentric and concentric phases in the SQ exercise could be an interesting strategy to increase neuromuscular and functional adaptations in sport actions that mainly depend on concentric contractions. Moreover, sport abilities highly dependent on the stretch-shortening cycle could benefit from the REBOUND or a combination of the 2 techniques. [ABSTRACT FROM AUTHOR]

Purpose: The current study aimed to compare the effects of plyometric (PT) versus optimum power load (OPL) training on physical performance of young high-level soccer players. Methods: Athletes were randomly divided into PT (horizontal and vertical drills) and OPL (squat + hip thrust exercises at the load of maximum power output) interventions, applied over 7 weeks during the in-season period. Squat and countermovement jumps, maximal sprint (10 and 30 m), and change of direction (COD; agility t test) were the pretraining and posttraining measured performance variables. Magnitude-based inference was used for within- and between-group comparisons. Results: OPL training induced moderate improvements in vertical squat jump (effect size [ES]: 0.97; 90% confidence interval [CI], 0.32–1.61) and countermovement jump (ES: 1.02; 90% CI, 0.46–1.57), 30-m sprint speed (ES: 1.02; 90% CI, 0.09–1.95), and COD performance (ES: 0.93; 90% CI, 0.50–1.36). After PT training method, vertical squat jump (ES: 1.08; 90% CI, 0.66–1.51) and countermovement jump (ES: 0.62; 90% CI, 0.18–1.06) were moderately increased, while small enhancements were noticed for 30-m sprint speed (ES: 0.21; 90% CI, −0.02 to 0.45) and COD performance (ES: 0.53; 90% CI, 0.24–0.81). The 10-m sprint speed possibly increased after PT intervention (small ES: 0.25; 90% CI, −0.05 to 0.54), but no substantial change (small ES: 0.36; 90% CI, −0.40 to 1.13) was noticed in OPL. For between-group analyses, the COD ability and 30-m sprint performances were possibly (small ES: 0.30; 90% CI, −0.20 to 0.81; Δ = +1.88%) and likely (moderate ES: 0.81; 90% CI, −0.16 to 1.78; Δ = +2.38%) more improved in the OPL than in the PT intervention, respectively. Conclusions: The 2 different training programs improved physical performance outcomes during the in-season period. However, the combination of vertically and horizontally based training exercises (squat + hip thrust) at optimum power zone led to superior gains in COD and 30-m linear sprint performances. [ABSTRACT FROM AUTHOR]

Purpose: To examine the effects of loaded (LPJT) versus unloaded plyometric jump training (UPJT) programs on measures of muscle power, speed, change of direction (CoD), and kicking-distance performance in prepubertal male soccer players. Methods: Participants (N = 29) were randomly assigned to a LPJT group (n = 13; age = 13.0 [0.7] y) using weighted vests or UPJT group (n = 16; age = 13.0 [0.5] y) using body mass only. Before and after the intervention, tests for the assessment of proxies of muscle power (ie, countermovement jump, standing long jump); speed (ie, 5-, 10-, and 20-m sprint); CoD (ie, Illinois CoD test, modified 505 agility test); and kicking-distance were conducted. Data were analyzed using magnitude-based inferences. Results: Within-group analyses for the LPJT group showed large and very large improvements for 10-m sprint time (effect size [ES] = 2.00) and modified 505 CoD (ES = 2.83) tests, respectively. For the same group, moderate improvements were observed for the Illinois CoD test (ES = 0.61), 5- and 20-m sprint time test (ES = 1.00 for both the tests), countermovement jump test (ES = 1.00), and the maximal kicking-distance test (ES = 0.90). Small enhancements in the standing long jump test (ES = 0.50) were apparent. Regarding the UPJT group, small improvements were observed for all tests (ES = 0.33–0.57), except 5- and 10-m sprint time (ES = 1.00 and 0.63, respectively). Between-group analyses favored the LPJT group for the modified 505 CoD (ES = 0.61), standing long jump (ES = 0.50), and maximal kicking-distance tests (ES = 0.57), but not for the 5-m sprint time test (ES = 1.00). Only trivial between-group differences were shown for the remaining tests (ES = 0.00–0.09). Conclusion: Overall, LPJT appears to be more effective than UPJT in improving measures of muscle power, speed, CoD, and kicking-distance performance in prepubertal male soccer players. [ABSTRACT FROM AUTHOR]

Plyometric exercise is a major tool for improving explosive actions. This study aimed to compare the efficacy of a vertical and horizontal plyometric training program on stretch-shortening performance variables in adolescent soccer players. Thirty-two male soccer players (aged 12.09 ± 0.89 years, with soccer experience 5.37 ± 1.58 years) were divided into horizontal plyometric, vertical plyometric, or control groups. The horizontal and vertical plyometric groups participated in a 6-week training program that was performed twice per week, with a 48-h interval, in conjunction with regular soccer training. The control group participated only in regular soccer training. Vertical jump height, reactive strength index, leg stiffness, ground contact time, standing long jump distance, agility, and 10 and 20 m sprint performances were tested as stretch-shortening performance variables of the participants. Stretch-shortening performance variables were assessed before and after completion of the training program. The results showed that either horizontal or vertical plyometric training had no effect on VJH, RSI, GCT, or Kleg performance (F = 2.14, 1.32, 0.66, 1.03; p > 0.05). Furthermore, there was no effect on SLJ, 10 m sprint, 20 m sprint, or agility performance (F = 2.06, 0.14, 0.06, 0.27; p > 0.05). A 6-week horizontal or vertical plyometric intervention was found to be insufficient to elicit stretch-shortening performance enhancement in adolescent male soccer players. Although there was no performance change in any group, it was observed that the players enjoyed plyometric training. Therefore, coaches could safely use plyometric exercises to design enjoyable training programs. [ABSTRACT FROM AUTHOR]

Pull-ups are usually performed for training in many sports. Different pull-up variations (velocity, hand orientations etc.) can affect the pull-ups performance. While being widely used, athletes can either stop at the bottom of the pull-up (elbow in full extension) or perform non-stop pull-ups. Yet, the physiological and biomechanical impact of such variations are poorly quantified. The objective of this study was to analyze two ways of pull-ups completion: one in which the athletes pause at the bottom of each pull-up (SINGLE) and another in which the athletes perform the pull-ups with no pause between the downward movement and the subsequent upward movement (MULTIPLE). The kinematics and electromyography of the upper limbs and the force generated at the bar were recorded while performing both SINGLE and MULTIPLE pull-ups using two classical hand orientations: the overhand grip and the underhand grip. MULTIPLE pull-ups generated significantly better performance with higher absolute vertical velocities in both the ascent and descent phases (P < 0.05). With MULTIPLE pull-ups, the force applied on the bar was higher at the beginning of the ascent phase and at the end of the descent phase while the force was lower at the top of the pull-ups. These better performances were not accompanied by higher EMG activities during the ascent phase, but a steep increase in muscle activation was observed during the descent phase (P < 0.05). This result showed that, for MULTIPLE pull-ups, muscle and tendon stretch-shortening cycles might be at play in a similar way to that which is observed for the lower limbs during countermovement jumps. Recommendations on pull-ups completion should take into account these new results for better efficiency. [ABSTRACT FROM AUTHOR]

The level of difficulty of plyometric exercises is currently classified based on a simple system using "low", "moderate" and "high" intensity to describe. However, unclear stress quantification of plyometric drills may lead to a higher injury risk and inappropriate load. Therefore, the current paper presents a novel field base method for strength and conditioning professionals using the Plyometric Stress Index to quantify and estimate the perceived stress for athletes performing various plyometric exercises. A single demonstrator was recruited to illustrate the practical calculation of the Plyometric Stress Index for several common drills including double- and single-leg hurdle jump, countermovement jump, broad jump, 30-cm drop jump, 50-cm depth jump, and box jump. Videos were taken from either front or side view and analyzed with the aid of calibration poles and mobile apps. The stress index for each leg was calculated with the body mass multiplied by the dropping height for the eccentric phase, and also the dropping height for the landing task. The 50-cm depth jump yielded 68.71 units of plyometric stress index and was the most stressful exercise while the second highest was single-leg low hurdle hop yielding 50.68 units. The least stressful drill was a 76-cm box jump with 19.15 units only. Although the ranking of the plyometric stress index for selected drills is somewhat different from the traditional intensity described by the National Strength and Conditioning Association, this novel index may allow practitioners to estimate and monitor the stress or training load for producing periodized plyometric training program. [ABSTRACT FROM AUTHOR]

Providing an external focus of attention through verbal instructions can improve the drop jump (DJ) performance, which differs based on the skill level of athletes. The purpose of this study was to assess the effect of change of focus of attention on the performance of DJs in experienced and inexperienced athletes. Thirty-eight male collegiate athletes divided into the experienced group (E group: age, 21.5 ± 1.4 years; height, 173.4 ± 5.7 cm; and body mass, 65.7 ± 6.2 kg) and the inexperienced group (I group: age, 21.9 ± 1.5 years; height, 172.8 ± 5.1 cm; and body mass, 68.7 ± 5.5 kg) performed 2 trials of DJs after listening to instructions designed to evoke a neutral, internal, or external focus of attention. Contact time (CT), jump height (JH), reactive strength index (RSI), and leg-spring stiffness (kvert) were recorded during DJ and compared between the 2 groups using a repeated-measures analysis of variance. In the E group, the neutral condition was associated with a significantly higher RSI, JH, and kvert than the internal and external conditions (p < 0.05). In the I group, the external condition was associated with significantly higher RSI and kvert and shorter CT than other conditions (p < 0.05). Therefore, this suggests that attentional focus strategies need to be selected depending on DJ experience: A neutral focus may be preferable for athletes experienced in DJs, whereas an external focus may be more suitable for athletes with lesser DJ experience. [ABSTRACT FROM AUTHOR]

Purpose: There are limited data on postactivation potentiation's (PAP) effects after plyometric conditioning contractions (CCs), especially in the upper body. This study compared plyometric CCs with concentric-eccentric and eccentric CCs aiming to improve upper-body power performance due to a PAP effect. Methods: Sixteen resistance-trained males completed 3 experimental trials in a randomized order that comprised either a plyometric (PLY), a concentric-eccentric (CON), or an eccentric-only (ECC) CC. Maximal muscle performance, as determined by a ballistic bench-press throw, was measured before (baseline) and 1, 4, 8, 12, and 16 min after each CC. Results: Compared with baseline, bench-press power was significantly enhanced only in CON (P = .046, ES = 0.21) after 8 min of recovery. However, the results obtained from the comparisons between baseline power performance and the individual best power performance for each subject after each CC stimulus showed significant increases in PLY (P < .001, ES = 0.31) and cOn (P < .001, ES = 0.38). There was no significant improvement in ECC (P = .106, ES = 0.11). Conclusions: The results indicate that only CON CCs generated increases in bench-press power after 8 min of rest. However, considering an individual rest interval, PLY CCs led to an enhanced power performance in the bench-press exercise, and this increase was comparable to that induced by CON CCs. Due to the easy practical application before a competition, PLY CCs might be an interesting part of warm-up strategies aiming to improve upper-body power performance by reason of PAP. [ABSTRACT FROM AUTHOR]

Purpose: To describe the stretch-shortening behavior of ankle plantar-flexing muscle-tendon units (MTUs) during tie push-off in a sprint start. Methods: Fifty-four male (100-m personal best: 9.58-12.07 s) and 34 female (100-m personal best: 11.05-14.00 s) sprinters were analyzed using an instrumented starting block and 2-dimensional high-speed video imaging. Analysis was performed separately for front and rear legs, while accounting for block obliquities and performance levels. Results: The results showed clear signs of a dorsiflexion in the upper ankle joint (front block 15.8° ± 7.4°, 95% Cl 13.2-18.2°; rear block 8.0° ± 5.7°, 95% CI 6.4-9.7°) preceding plantar flexion. When observed in their natural block settings, the athletes' block obliquity did not significantly affect push-off characteristics. It seems that the stretch-shortening-cycle-like motion of the soleus MTU has an enhancing influence on push-off force generation. Conclusion: This study provides the first systematic observation of ankle- joint stretch-shortening behavior for sprinters of a wide range of performance levels. The findings highlight the importance of reactive-type training for the improvement of starting performance. Nonetheless, future studies need to resolve the independent contributions of tendinous and muscle-fascicle structures to overall MTU performance. [ABSTRACT FROM AUTHOR]

Byrne, PJ, Moody, JA, Cooper, S-M, Farrell, E, and Kinsella, S. Short-term effects of "composite training" on strength, jump, and sprint performance in hurling players. J Strength Cond Res 36(8): 2253–2261, 2022—The purpose of this study was to compare the short-term effects of "composite" training to sprint training on strength, jump, and sprint acceleration performance in hurling players. A randomized counterbalanced group design with baseline test, pretest and post-test measures was used. Twenty-five hurling players volunteered to participate and 21 completed the study. Subjects were divided into a "composite" (COMP group, n = 10) or a sprint training (SPRINT group, n = 11) group. Both groups trained twice per week for 7 weeks with the SPRINT group performing 6 repetitions of 20 m sprints and the COMP group completing 6 repetitions (1 repetition = 3 bounce drop jumps [BDJs] with a 20 m sprint after 15 seconds recovery). Significant differences existed pretraining to post-training for the COMP group for BDJ contact time (−7.25%; p = 0.05) and countermovement jump (CMJ) variables (height: 7.43%, p = 0.006; force: 5.24%, p = 0.05; power: 15.11%, p = 0.001). No significant differences were found between groups at baseline and for group by time interactions. Significant improvements were observed pretraining to post-training in both groups for the following: absolute 3 repetition maximum (3RM) back squat strength (12.73–17.62%, p = 0.01), 5 m (5.74–9.49%, p = 0.006–0.04), 10 m (4.27–5.59%, p = 0.007–0.02), and 20 m (3.35–3.98%, p = 0.003–0.01). In conclusion, "composite" training is effective in enhancing fast stretch-shortening cycle efficiency inducing CMJ force and power augmentation. However, "composite" and sprint training are effective training approaches for enhancing maximal strength and sprint performance in a time efficient manner in hurling players. [ABSTRACT FROM AUTHOR]

Purpose: To examine differences between ground-reaction-force (GRF)-based parameters collected from 5 types of plyometric push-ups. Between-trials reliability and the relationships between parameters were also assessed. Methods: Thirty-seven highly active commando soldiers performed 3 trials of 5 variations of the plyometric push-up in a counterbalanced order: standard countermovement push-up (SCPu), standard squat push-up (SSPu), kneeling countermovement push-up (KCPu), kneeling squat push-up (KSPu), and drop-fall push-up (DFPu). Vertical GRF was measured during these exercises using a portable Kistler force plate. The GRF applied by the hands in the starting position (initial force supported), peak GRF and rate of force development during takeoff, flight time, impact force, and rate of force development impact on landing were determined. Results: During standard-position exercises (SCPu and SSPu) the initial force supported and impact force were higher (P < .001) than with kneeling exercises (KCPu, KSPu, and DFPu). The peak GRF and rate of force development during takeoff were higher (P < .001) in the countermovement push-up exercises ([CMP] SCPu, KCPu, and DFPu) than squat push-up exercises ([SP] SSPu and KSPu). Furthermore, the flight time was greater (P < .001) during kneeling exercises than during standard-position exercises. A significant relationship (P < .01) between impact force and the rate of force development impact was observed for CMP and SP exercises (r = .83 and r = .62, respectively). The initial force supported was also negatively related (P < .01) to the flight time for both CMP and SP (r = -.74 and r = -.80, respectively). It was revealed that the initial force supported and the peak GRF during takeoff had excellent reliability; however, other parameters had poor absolute reliability. Conclusions: It is possible to adjust the intensity of plyometric push-up exercises and train athletes' muscle power by correctly interpreting GRF-based parameters. However, caution is required as some parameters had marginal absolute reliability. [ABSTRACT FROM AUTHOR]

BACKGROUND: Repetitive stretch-shortening cycle exercises generate high rates of mechanical work and consequently induce substantial muscular fatigue related to delayed neuromuscular functions. OBJECTIVE: To investigate the neuromuscular impairment after high-intensity exercise protocols involving different gravity loads in stretch-shortening cycle – running (RUN) and vertical jumps (VJ). METHODS: Twenty-two healthy men, divided into two groups, VJ and RUN participated in this study. The individuals performed a training session involving six bouts of 30 s of VJ or RUN. The isokinetic PM (PM) of the knee extensors and flexor muscles, rate of perceived exertion and delayed onset muscle soreness (DOMS) were evaluated at pre, post, 24 h and 48 h post-training. RESULTS: The concentric and eccentric PM of the extensor in the RUN group was reduced until 24 h, while in the VJ a decrement was observed until 48 h. Following running, the PM of the flexors decreased until 48 h, while for VJ there was an eccentric PM decrement at 48 h. The DOMS increased at the anterior thigh and only after VJ training for 48 h. CONCLUSION: Acute and delayed neuromuscular impairment may be observed after both exercise regimens, but high-intensity training using vertical jumps seems to induce a more pronounced impairment than running. [ABSTRACT FROM AUTHOR]

The aim of this study was to compare the effects of maturation on physical fitness adaptations to plyometric jump training (PJT) in youth females. Jumping, sprinting, change of direction speed, endurance, and maximal strength were measured pre-post 6 weeks of PJT in 7th- and 10th-grade subjects. In the seventh grade, subjects formed a PJT group (Plyo-7, n = 10; age, 12.7 ± 0.6 years; breast maturation stages IV [n = 2], III [n = 7], and II [n=1]) and an active control group (Con-7, n = 9; age, 12.8 ± 0.6 years; breast maturation stages IV [n =2], III [n = 6], and II [n = 1]). In the 10th grade, subjects conformed a PJT group (Plyo-10, n = 9; age, 16.3 ± 0.5 years; breast maturation stages V [n =5] and IV [n = 4]) and an active control group (Con-10, n = 9; age, 16.2 ± 0.5 years; breast maturation stages V [n = 5] and IV [n = 4]). Magnitude-based inferences were used for data analysis, with effect sizes (ESs) interpreted as < 0.2 5trivial; 0.2–0.6 = small; 0.6–1.2 = moderate; 1.2–2.0 = large; and 2.0–4.0 = very large. The Plyo-7 and Plyo- 10 showed meaningful improvements in all physical fitness measures (ES =0.21–2.22), while Con-7 and Con-10 showed only trivial changes. The Plyo-7 and Plyo-10 showed meaningful (ES = 0.16–2.22) greater improvements in all physical fitness measures when compared with their control counterparts. The Plyo-10 showed meaningful greater improvements in 20-m sprint, 2-km running time trial, maximal strength, squat jump, and drop jump from 20 cm (ES =0.21–0.42) when compared with Plyo-7. In conclusion, PJT is effective in improving physical fitness in younger and older female youths. However, greater adaptations were observed in more mature subjects [ABSTRACT FROM AUTHOR]

This study examined the effects of an 8-week plyometric training (PT) program on components of physical fitness in young female handball players. Twenty-one female adolescent handball players were assigned to an experimental group (EG, n = 12; age = 15.9 ± 0.2 years) or an active control group (CG, n = 9, age = 15.9 ± 0.3 years). While EG performed plyometric exercises in replacement of some handball-specific drills, CG maintained the regular training schedule. Baseline and follow-up tests were performed for the assessment of linear speed (i.e., 5-, 10-, and 20-m time), change-of-direction (CoD) speed (i.e., T-test time), muscle power (i.e., countermovement jump [CMJ] height and reactive strength index [RSI]), and repeated sprint ability (RSA) (RSA total time [RSAtotal], RSA best time [RSAbest], and RSA fatigue index [RSAFI]). Data were analyzed using magnitude-based inferences. Within-group analyses for the EG revealed moderate-to-large improvements for the 5-m (effect size [ES] = 0.81 [0.1-1.5]), 10-m sprint time (ES = 0.84 [0.1-1.5]), RSI (ES = 0.75 [0.1-1.4]), RSAFI (ES = 0.65 [0.0-1.3]), and T-test time (ES = 1.46 [0.7-2.2]). Trivial-to-small ES was observed for RSAbest (ES = 0.18 [-0.5 to 0.9]), RSAtotal (ES = 0.45 [-0.2 to 1.1]), 20-m sprint time (ES = 0.56 [-0.1 to 1.2]), and CMJ height (ES = 0.57 [-0.1 to 1.3]). For the CG, within-group analyses showed a moderate performance decline for T-test time (ES = -0.71 [-1.5 to 0.1]), small decreases for 5-m sprint time (ES = -0.46 [-1.2 to 0.3]), and a trivial decline for 10-m (ES = -0.10 [-0.9 to 0.7]) and 20-m sprint times (ES = -0.16 [-0.9 to 0.6]), RSAtotal (ES = 0.0 [-0.8 to 0.8]), and RSAbest (ES = -0.20 [-0.9 to 0.6]). The control group achieved trivial-to-small improvements for CMJ height (ES = 0.10 [-0.68 to 0.87]) and RSI (ES = 0.30 [-0.5 to 1.1]). In conclusion, a short-term in-season PT program, in replacement of handball-specific drills, is effective in improving measures of physical fitness (i.e., linear/CoD speed, jumping, and RSA) in young female handball players. [ABSTRACT FROM AUTHOR]

Ramirez-Campillo, R, Garcia-Pinillos, F, Chaabene, H, Moran, J, Behm, DG, and Granacher, U. Effects of plyometric jump training on electromyographic activity and its relationship to strength and jump performance in healthy trained and untrained populations: a systematic review of randomized controlled trials. J Strength Cond Res 35(7): 2053–2065, 2021—This systematic review analyzed the effects of plyometric jump training (PJT) on muscle activation assessed with surface electromyography during the performance of strength and jumping tasks in healthy populations across the lifespan. A systematic literature search was conducted in the electronic databases PubMed/MEDLINE, Web of Science, and SCOPUS. Only randomized controlled studies were eligible to be included in this study. Our search identified 17 studies comprising 23 experimental groups and 266 subjects aged 13–73 years, which were eligible for inclusion. The included studies achieved a median Physiotherapy Evidence Database score of 6. No injuries were reported among the included studies. Significant PJT-related improvements were reported in 7 of 10 studies and in 6 of 10 studies for measures of muscle activation during the performance of strength and jumping tasks, respectively. Moreover, a secondary correlational analysis showed significant positive relationships (r = 0.86; p = 0.012; r² = 0.74) between changes in muscle activation and changes in jump performance. However, from the total number (n = 287) of muscle activation response variables analyzed for strength and jumping tasks, ;80% (n= 226) were reported as nonsignificant when compared with a control condition. In conclusion, PJT may improve muscle activation during the performance of strength and jumping tasks. However, conflicting results were observed probably arising from (a) studies that incorporated a large number of outcomes with reduced sensitivity to PJT, (b) methodological limitations associated to muscle activation measurement during strength and jumping tasks, and (c) limitations associated with PJT prescription. Future studies in this field should strive to solve these methodological shortcomings. [ABSTRACT FROM AUTHOR]

This study examined the effect of 6 weeks of progressed and nonprog-ressed volume-based overload plyometric training (PT) on components of physical fitness and body composition measures in young male basketball players, compared with an active control group. Subjects were randomly assigned to a progressed PT (PPT, n =7; age = 14.6 ± 1.1 years), a non-PPT (NPPT, n = 8, age =13.8 ± 2.0 years), or a control group (CG, n =7, age = 14.0 ± 2.0 years). Before and after training, body composition measures (muscle mass and fat mass), countermovement jump with arms (CMJA) and countermovement jump without arms (CMJ), horizontal bilateral (HCMJ) and unilateral jump with right leg (RJ) and left leg (LJ), 20-cm drop jump (DJ20), sprint speed (10 m sprint), and change of direction speed (CODS [i.e., T-test]) were tested. Significant effects of time were observed for muscle and fat mass, all jump measures, and CODS (all p < 0.01; d = 0.37-0.83). Significant training group X time interactions were observed for all jump measures (all p < 0.05; d = 0.24-0.41). Post hoc analyses revealed significant pre-post performance improvements for the PPT (RJ and LJ: Δ18.6%, d = 0.8 and Δ22.7%, d = 0.9, respectively; HCMJ: Δ16.4%, d = 0.8; CMJ: Δ22.4%, d = 0.7; CMJA: Δ23.3%, d = 0.7; and DJ20: Δ39.7%, d = 1.1) and for the NPPT group (LJ: Δ14.1%, d = 0.4; DJ20: Δ32.9%, d = 0.8) with greater changes after PPT compared with NPPT for all jump measures (all p < 0.05; d = 0.21-0.81). The training efficiency was greater (p < 0.05; d = 0.22) after PPT (0.015% per jump) compared with NPPT (0.0053% per-jump). The PPT induced larger performance improvements on measures of physical fitness as compared to NPPT. Therefore, in-season progressive volume-based overload PT in young male basketball players is recommended. [ABSTRACT FROM AUTHOR]

BACKGROUND: Postactivation potentiation (PAP) is an acute and temporary enhancement of muscular performance resulting from previous muscular contraction. Extensive research exists examining the PAP effect after a heavy resistance exercise but there is limited research examining the PAP effect after a plyometric stimulus to the pre-competition practices (e.g., warm-up) of well-trained athletes. OBJECTIVE: The purpose of this study was to investigate the acute effects of plyometric warm-up with different box heights on sprint and agility performance in national-level field hockey athletes at recovery time of immediately, 5 minutes and 10 minutes. METHODS: In a randomized crossover design, ten male national-level field hockey athletes performed 30-m sprint (with 10-m split) and agility test at baseline, immediately (∼ 15 sec), 5 minutes and 10 minutes after a high-intensity plyometric warm-up (HIPW), a low-intensity plyometric warm-up (LIPW) and a control trial (CT). RESULTS: Mean 10-m sprint times, 30-m sprint times and agility times were similar between trials at baseline (p > 0.05). Significant trial x time interactions (p ⩽ 0.05) were observed for 10-m sprint time, 30-m sprint time and agility time. 10-m sprint times were significantly decreased after HIPW at all time-points and LIPW at immediately time-point, relative to baseline (p ⩽ 0.05). HIPW 10-m sprint times were faster at all time-points and LIPW sprint time was faster at 10 minutes when compared with CT (p ⩽ 0.05). Thirty-meter sprint times were significantly decreased after HIPW and LIPW at all time-points, relative to baseline (p ⩽ 0.05). HIPW 30-m sprint times at all time-points and LIPW at both the 5 and 10 minute time-points were faster than CT (p ⩽ 0.05). Agility times were significantly decreased after HIPW at all time-points and LIPW at both the immediately and 5 minutes time-points, relative to baseline (p ⩽ 0.05). HIPW and LIPW agility times were faster than CT, at all time-points (p ⩽ 0.05). CONCLUSIONS: Both HIPW and LIPW may be effective in enhancing the pre-training or pre-competition practices in off-season for national-level field hockey athletes. However, the individualization of HIPW is highly recommended in order to maintain PAP effects for 10-m sprint times, 30-m sprint times and agility times throughout the 10 minutes when compared to LIPW. [ABSTRACT FROM AUTHOR]

To compare the effects of short-term (i.e., 7 weeks) plyometric jump training applied before (PJT-B) or after (PJT-A) soccer practice on components of physical fitness in young soccer players, a single-blind randomized controlled trial was conducted. Postpubertal boys aged 17.0 ± 0.5 years were allocated to 3 groups: PJT-B (n = 12), PJT-A (n = 14), and control (CON; n = 12). The outcome measures included tests to evaluate 20-m speed, standing long jump (SLJ), squat jump (SJ), countermovement jump (CMJ), and drop jump (DJ), 20-m multistage shuttle run endurance (MSSRT), and Illinois change-of-direction speed (ICODT). Although the CON performed soccer-specific training, the PJT-A and PJT-B groups conducted the same soccerspecific sessions but replaced ;11% of their time with plyometric training. The PJT-B group performed plyometric exercises after a warm-up program, and the PJT-A group conducted plyometric exercises ;10 minutes after the completion of soccer training. Analyses of variance were used to detect differences between groups in all variables for pretraining and posttraining tests. Main effects of time (all p, 0.01; d = 0.19-0.79) and group 3 time interactions (all p# 0.05; d = 0.17-0.76) were observed for all examined variables. Post hoc analyses revealed significant increases in the PJT-B group (SLJ: 9.4%, d = 1.7; CMJ: 11.2%, d = 0.75; 20-m MSSRT: 9.0%, d = 0.77) and the PJT-A group (SLJ: 3.1%, d = 0.7; CMJ: 4.9%, d = 0.27; 20-m MSSRT: 9.0%, d = 0.76). Post hoc analyses also revealed significant increases in the PJT-B group (20-m speed: 27.4%, d = 0.75; 20-cm DJ reactive strength index: 19.1%, d = 1.4; SJ: 6.3%, d = 0.44; ICODT results: 24.2%, d = 1.1). In general, our study revealed that plyometric training is effective in improving measures of physical fitness in young male soccer players when combined with regular soccer training. More specifically, larger traininginduced effects on physical fitness were registered if plyometric training was conducted before soccer-specific training. [ABSTRACT FROM AUTHOR]

This study aimed to compare the effects of 1 vs. 2 sessions of equal-weekly volume plyometric training (PT) across 8 weeks on measures of athletic performance (i.e., sprint time, change of direction [CoD], jumping ability, and muscle strength) in prepuberal male soccer players. Thirty participants were randomly assigned either to 1 session PT group (1SPT [n = 15]) or 2 sessions PT group (2SPT [n = 15]). Plyometric training was integrated into their regular soccer training routine. Pretraining and posttraining tests for the assessment of sprint time (e.g., 5, 10, 20, and 30-m), CoD (e.g., T-test and modified Illinois change of direction test [MICODT]), jumping ability (e.g., standing long jump [SLJ], countermovement jump [CMJ], and squat jump [SJ]), muscle strength (reactive strength index [RSI]), and kicking distance were conducted. Results showed a main effect of time for 5-m sprint-time performance (F(1,56) = 4.00, effect size [ES] = 0.53 [medium], p = 0.05), T-test (F(1,56) = 23.19, ES = 1.28 [large], p < 0.001), MICODT (F(1,56) = 5.72, ES = 0.94 [large], p = 0.02), SLJ (F(1,56) = 16.63, ES = 1.09 [large], p < 0.001), CMJ (F(1,56) = 15.43, ES = 1.04 [large], p < 0.001), SJ (F(1,56) = 20.27, ES = 1.20 [large], p < 0.001), RSI (F(1,56) = 26.26, ES = 1.36 [large], p < 0.001), and kicking distance (F(1,56) = 47.19, ES = 1.83 [large], p < 0.001). There were no training group × time interactions in all the measured outcomes. In conclusion, when an equated moderate volume of jumps is performed, higher PT frequency across 8 weeks has no extra effects on prepuberal male soccer players' measures of athletic performance. The present findings may help optimizing PT interventions dedicated to prepuberal male soccer players. [ABSTRACT FROM AUTHOR]

This study compared the influence of 10 weeks of plyometric training with 2 different jumping techniques on Achilles tendon properties and the height achieved in drop jumps (from 20, 40, and 60 cm) and countermovement jumps (CMJ). Subjects were allocated to 2 training groups (n = 11 in each group) and 1 control group (CON, n = 10). One training group kept the knees extended (KE) during ground contact, whereas the other training group flexed the knees to ∼80–90° (KF). Achilles tendon stiffness was assessed with ultrasonography, and jump performance was derived from force platform recording. Training increased jump height (p < 0.01) in both groups. The increase for the 20-cm drop jump was greater (p < 0.05) for the KE group (11.3%) thanfor the KF group (6.3%), with no statistical difference between groups for the 40- and 60-cm drop jumps. Contact time during the 20-cm drop jump decreased (∼8%; p < 0.01) after training, with no difference between the training groups. The increase in CMJ height was greater (p = 0.05) for the KF group (17.5%) than for the KE group (11.8%). Achilles tendon stiffness increased (32%; p < 0.001) for the KE group but not for the KF group (11%; p = 0.28). There was a positive association (p < 0.001) between the changes in tendon stiffness and jump height for 20-cm drop jump in both KE group (r² = 0.49) and KF group (r² = 0.62). None of these parameters changed in CON group. In conclusion, the extent of increase in jump height (20-cm drop jump and CMJ) and in Achilles tendon stiffness after training differed between the 2 jumping techniques. [ABSTRACT FROM AUTHOR]

Traditional, assisted and resisted plyometrics are considered to be effective training methods for improving vertical jump performance. The purpose of this systematic review and meta-analysis was to compare effectiveness of traditional, assisted and resisted plyometric methods on vertical jumping ability in adults. Available literature was searched using MEDLINE (via EBSCO), SPORTDiscus (via EBSCO), Scopus and Web of Science databases. The methodological quality of studies was assessed using the PEDro scale. Peer-reviewed studies were accepted only if they met all eligibility criteria: (a) healthy adults mean age > 18 years (b) training program based on plyometric exercises (c) the study reported on vertical jump height for the countermovement jump or drop jump performance. Of the 5092 articles identified, 17 studies were included in the qualitative and quantitative analyses. Both funnel plot analysis and Egger's test (p = 0.04) indicated publication bias for the comparison of resisted plyometrics and control condition. No publication bias was found for the other meta-analyses (p > 0.05). The effects of the traditional and assisted plyometric methods, when compared with the control condition (a non-plyometric condition), on jump height were moderate (SMD = 0.68, 95% CI 0.37 to 0.99, p < 0.0001; SMD = 0.70, 95% CI 0.20 to 1.20, p = 0.006, respectively). The effects of the resisted plyometric methods, when compared with the control condition, on a jump height was small (SMD = 0.48, 95% CI 0.17 to 0.79, p = 0.002). There were no significant differences between the training effects of the assisted and traditional plyometric interventions on jump height (SMD = 0.62, 95% CI -1.66 to 2.91, p = 0.59), nor between the resisted and traditional plyometric training programs (SMD = 0.2, 95% CI -0.19 to 0.23, p = 0.86). Traditional, assisted and resisted plyometric methods are effective training modalities for augmenting vertical jump performance in healthy adults. Resisted and assisted plyometric methods are equally effective as the traditional plyometric method in improving vertical jumping ability in healthy adults. [ABSTRACT FROM AUTHOR]

Purpose: The mechanical responses to two non-ballistic squat and two ballistic jump squat protocols performed over multiple sets were investigated. One protocol from each of the two non-ballistic and ballistic conditions incorporated a pause between the eccentric and concentric phases of the movements in order to determine the influence of the coupling time on the mechanical variables and post-activation potentiation (PAP). Methods: Eleven men (age: 21.9 ± 1.8 years; height: 1.79 ± 0.05 m; mass: 87.0 ± 7.4 kg) attended four sessions where they performed multiple sets of squats and jump squats with a load equivalent to 30% 1-repeititon maximum under one of the following conditions: 1) 3 x 4 repetitions of non-ballistic squats (30N-B); 2) 3 x 4 repetitions of non-ballistic squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PN-B); 3) 3 x 4 repetitions of ballistic jump squats (30B); 4) 3 x 4 repetitions of ballistic jump squats with a 3-second pause between the eccentric and concentric phases of each repetition (30PB). Force plates were used to calculate variables including average vertical velocity, average vertical force (GRF), and average power output (PO). Results: Vertical velocities during the ballistic conditions were significantly greater than those attained during the non-ballistic conditions (mean differences: 0.21 - 0.25 m/s, p<0.001, effect sizes [ES]: 1.70 - 1.89) as were GRFs (mean differences: 478 - 526 N, p<0.001, ES: 1.61 - 1.63), and PO (mean differences: 711 - 869 W, p<0.001, ES: 1.66 - 1.73). Moreover, the increase in PO across the three sets in 30B was significantly greater than the changes observed during 30N-B, 30PN-B, and 30PB (p≤0.015). The pause reduced the mechanical variables during both the non-ballistic and ballistic conditions, although the differences were not statistically significant (p>0.05). Conclusion: Ballistic jump squats may be an effective exercise for developing PO given the high velocities and forces generated in these exercises. Furthermore, the completion of multiple sets of jump squats may induce PAP to enhance PO. The coupling times between the eccentric and concentric phases of the jump squats should be short in order to maximize the GRF and PO across the sets. [ABSTRACT FROM AUTHOR]

Purpose: To identify the effect of additional elastic force on the kinetic and kinematic characteristics, as well as the magnitude of leg stiffness, during the performance of accentuated countermovement jumps (CMJs). Methods: Fifteen trained male subjects performed 3 types of CMJ including free CMJ (FCMJ; ie, body weight), ACMJ-20, and ACMJ-30 (ie, accentuated eccentric CMJ with downward tensile force equivalent to 20% and 30% body mass, respectively). A force platform synchronized with 6 high-speed infrared cameras was used to measure vertical ground-reaction force (VGRF) and displacement. Results: Using downward tensile force during the lowering phase of a CMJ and releasing the bands at the start of the concentric phase increased maximal concentric VGRF (6.34%), power output (23.21 %), net impulse ( 16.65%), and jump height (9.52%) in ACMJ-30 compared with FCMJ (all P < .05). However, no significant difference was observed in the magnitude of leg stiffness between the 3 modes of jump. The results indicate that using downward recoil force of the elastic material during the eccentric phase of a CMJ could be an effective method to enhance jump performance by applying a greater eccentric loading on the parallel and series elastic components coupled with the release of stored elastic energy. Conclusions: The importance of this finding is related to the proposition that power output, net impulse, takeoff velocity, and jump height are the key parameters for successful athletic performance, and any training method that improves impulse and power production may improve sports performance, particularly in jumping aspects of sport. [ABSTRACT FROM AUTHOR]

Swimming performance can be improved not only by in-water sport-specific training but also by means of dry land-training (e.g., plyometric jump training [PJT]). This study examined the effects of an 8-week PJT on proxies of muscle power and swimming performance in prepubertal male swimmers. Participants were randomly allocated to a PJT group (PJT; n = 14; age: 10.3 ± 0.4 years, maturity-offset = -3±0.3) or a control group (CG; n = 12; age: 10.5 ± 0.4 years, maturity-offset = -2.8 ± 0.3). Swimmers in PJT and CG performed 6 training sessions per week. Each training session lasted between 80 and 90 minutes. Over the 8 weeks in-season training period, PJT performed two PJT sessions per week, each lasting between 25 to 30 minutes (~1 hour per week) in replacement of sport-specific swimming drills. During that time, CG followed their regular sport-specific swimming training (e.g., coordination, breathing, improving swimming strokes). Overall training volume was similar between groups. Pre- and post-training, tests were conducted to assess proxies of muscle power (countermovement-jump [CMJ]), standing-longjump [SLJ]) and sport-specific swimming performances (15-, 25-, and 50-m front-crawl, 25-m kick without push [25-m kick WP], and 25-m front-crawl WP). No training or test-related injuries were detected over the course of the study. Between-group analyses derived from magnitude-based inferences showed trivial-tolarge effects in favour of PJT for all tests (ES = 0.28 to 1.43). Within-group analyses for the PJT showed small performance improvements for CMJ (effect-size [ES] = 0.53), 25-m kick WP (ES = 0.25), and 50-m front crawl (ES = 0.56) tests. Moderate performance improvements were observed for the SLJ, 25-m frontcrawl WP, 15-m and 25-m front-crawl tests (ES = 0.95, 0.60, 0.99, and 0.85, respectively). For CG, the within-group results showed trivial performance declines for the CMJ (ES=-0.13) and the 50-m front-crawl test (ES = -0.04). In addition, trivial-tosmall performance improvements were observed for the SLJ (ES = 0.09), 25-m kick WP (ES = 0.02), 25-m front-crawl WP (ES = 0.19), 25-m front-crawl (ES = 0.2), (SLJ [ES = 0.09, and 15-m front crawl (ES = 0.36). Short-term in-season PJT, integrated into the regular swimming training, was more effective than regular swimming training alone in improving jump and sport-specific swimming performances in prepubertal male swimmers. [ABSTRACT FROM AUTHOR]

Objective: To determine the effect of lower body plyometric training (PLY) on jumping, sprint performance, and lower body muscle strength in healthy adults. Methods: A systematic literature search (PubMed, Embase) was performed. Studies were included if they (a) described a lower body PLY intervention lasting ≥4 weeks; (b) included measures of jumping, sprint, and/or lower body muscle strength; (c) included healthy individuals ≥18 years; (d) included a training or non‐training control group; and (e) were written in English. Meta‐analyses identifying the effects of PLY on jumping, sprint, and lower body muscle strength were conducted providing the standardized mean difference (SMD). Results: A total of 826 records were identified of which 25 fulfilled the inclusion criteria, yielding 19, 11, and seven data points for the meta‐analyses of jumping, sprint performance, and lower body muscle strength, respectively. The data showed improvements for all three performance variables after 4‐12 weeks of PLY. The SMD (CI95%) across studies for jump height, sprint time, and muscle strength were 0.45 (0.16: 0.75), −0.59 (−1.01: −0.17), and 0.33 (0.03: 0.63), respectively, where the latter two showed within‐sample heterogeneity. Conclusion: The systematic review and meta‐analyses showed that PLY elicits a small‐to‐moderate positive effect on jumping, sprint performance, and lower body muscle strength in healthy adults being recreationally active or athletes. [ABSTRACT FROM AUTHOR]

The aim of this single-blind randomized controlled trial was to compare the effects of plyometric jump training (PJT), with (RG) and without (NRG) between-session drill randomization, on performance measures (i.e., jumping and sprinting abilities, change of direction speed, and technical performance) in youth male basketball players (age, 10.2 ± 1.7 years), assigned to either the NRG (n = 7), RG (n = 6), or control group (n = 6). Before and after the intervention, countermovement jump, 20-cm drop jump, 30-m sprint (with or without ball dribbling), and change-of-direction speed tests were completed. The PJT was applied twice per week for seven weeks. The only difference between PJT groups was the order of drill execution. An ANOVA was used to detect differences between study groups. The analyses revealed significant main effects of time (all p<.01; d = 0.64-0.89) and group x time interaction (all p<.05; d=0.31-51) for all examined variables. Post hoc analyses revealed moderate-large significant improvements for the RG (countermovement jump: 18.8%, d = 0.6; 20-cm drop jump: 23.9%, d = 0.80; 30-m sprint: 11.6%, d = 1.13; 30-m sprint with ball dribbling: 9.3%, d = 0.54; change of direction speed test: 14.6%, d = 1.82). In contrast, post hoc analyses revealed only small improvements for the NRG (20-cm drop jump: 14.1%, d = 0.36; 30-m sprint: 6.8%, d = 0.45; 30-m sprint with ball dribbling: 8.8%, d = 0.35; change of direction speed test: 10.5%, d = 0.49). Application of PJT without randomization is effective for improving physical and technical qualities. However, PJT could be more beneficial when executed with between-session randomization of drills. [ABSTRACT FROM AUTHOR]

This study aimed to compare the effects of drop-jump training using a fixed drop-box height (i.e., 30-cm [FIXED]) vs. an optimal (OPT) drop-box height (i.e., 10-cm to 40-cm: generating an OPT reactive strength index [RSI]) in youth soccer players' physical fitness. Athletes were randomly allocated to a control group (n = 24; age = 13.7 years), a fixed drop-box height group (FIXED, n = 25; age = 13.9 years), or an OPT drop-box height group (OPT, n = 24; age = 13.1 years). Before and after 7 weeks of training, tests for the assessment of jumping (countermovement jump [CMJ], 5 multiple bounds), speed (20-m sprint time), change of direction ability (CODA [Illinois test]), strength {RSI and 5 maximal squat repetition test (5 repetition maximum [RM])}, endurance (2.4-km time trial), and kicking ability (maximal kicking distance) were undertaken. Analyses revealed main effects of time for all dependent variables (p < 0.001, d = 0.24-0.72), except for 20-m sprint time. Analyses also revealed group x time interactions for CMJ (p < 0.001, d = 0.51), depth jump (DJ) (p < 0.001, d = 0.30), 20-m sprint time (p < 0.001, d = 0.25), CODA (p < 0.001, d = 0.22), and 5RM (p < 0.01, d = 0.16). Post hoc analyses revealed increases for the FIXED group (CMJ: 7.4%, d = 0.36; DJ: 19.2%, d = 0.49; CODA: -3.1%, d = -0.21; 5RM: 10.5%, d = 0.32) and the OPT group (CMJ: 16.7%, d = 0.76; DJ: 36.1%, d = 0.79; CODA: -4.4%, d = -0.34; 5RM: 18.1%, d = 0.47). Post hoc analyses also revealed increases for the OPT group in 20-m sprint time (-3.7%, d = 0.27). Therefore, to maximize the effects of plyometric training, an OPT approach is recommended. However, using adequate fixed drop-box heights may provide a rational and practical alternative. [ABSTRACT FROM AUTHOR]

Previous studies contrasted the effects of plyometric training (PT) conducted on stable vs. unstable surfaces on components of physical fitness in child and adolescent soccer players. Depending on the training modality (stable vs. unstable), specific performance improvements were found for jump (stable PT) and balance performances (unstable PT). In an attempt to combine the effects of both training modalities, this study examined the effects of PT on stable surfaces compared with combined PT on stable and unstable surfaces on components of physical fitness in prepuberal male soccer athletes. Thirty-three boys were randomly assigned to either a PT on stable surfaces (PTS; n = 17; age = 12.1 ± 0.5 years; height = 151.6 ± 5.7 cm; body mass = 39.2 ± 6.5 kg; and maturity offset = -2.3 ± 0.5 years) or a combined PT on stable and unstable surfaces (PTC; n = 16; age = 12.2 ± 0.6 years; height = 154.6 ± 8.1 cm; body mass = 38.7 ± 5.0 kg; and maturity offset = -2.2 ± 0.6 years). Both intervention groups conducted 4 soccer-specific training sessions per week combined with either 2 PTS or PTC sessions. Before and after 8 weeks of training, proxies of muscle power (e.g., countermovement jump [CMJ], standing long jump [SLJ]), muscle strength (e.g., reactive strength index [RSI]), speed (e.g., 20-m sprint test), agility (e.g., modified Illinois change of direction test [MICODT]), static balance (e.g., stable stork balance test [SSBT]), and dynamic balance (unstable stork balance test [USBT]) were tested. An analysis of covariance model was used to test between-group differences (PTS vs. PTC) at posttest using baseline outcomes as covariates. No significant between-group differences at posttest were observed for CMJ (p > 0.05, d = 0.41), SLJ (p > 0.05, d = 0.36), RSI (p > 0.05, d = 0.57), 20-m sprint test (p > 0.05, d = 0.06), MICODT (p > 0.05, d = 0.23), and SSBT (p > 0.05, d = 0.20). However, statistically significant between-group differences at posttest were noted for the USBT (p < 0.01, d = 1.49) in favor of the PTC group. For most physical fitness tests (except RSI), significant pre-to-post improvements were observed for both groups (p < 0.01, d = 0.55-3.96). Eight weeks of PTS or PTC resulted in similar performance improvements in components of physical fitness except for dynamic balance. From a performance-enhancing perspective, PTC is recommended for pediatric strength and conditioning coaches because it produced comparable training effects as PTS on proxies of muscle power, muscle strength, speed, agility, static balance, and additional effects on dynamic balance. [ABSTRACT FROM AUTHOR]

The aim of this study was to ascertain the differences in kinetic and kinematic profiles between better and poorer performers of the vertical jump within a homogeneous group of trained adults. Fifty rugby players were divided into low scoring (LOW) and high scoring (HIGH) groups based on their performance in the vertical jump. The force, velocity, displacement, and rate of force development (RFD)-time curves were analyzed to determine the differences between groups. The analysis of the data showed differences in all the patterns of the ensemble mean curves of the HIGH and LOW groups. During the eccentric phase, the differences in the HIGH group with respect to the LOW group were lower crouch position, higher downward velocity, and higher force and RFD during the braking of the downward movement. During the concentric phase, the HIGH group achieved higher upward velocity, higher force at the end of phase, and a higher position at takeoff. The higher jump performances seem to be related to a more effective stretch-shortening cycle function that is characterized by a deeper and faster countermovement with higher eccentric forces being applied to decelerate the downward movement leading to enhanced force generation during the concentric phase. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the effects of 6-week plyometric training on vertical jump performance and electromyography (EMG) activities of vastus lateralis (VL), vastus medialis (VM), and gastrocnemius (GAS) muscles during countermovement jump (CMJ). Twenty-four highly physically active physical education students were randomly assigned either to a plyometric (PLY) group or a control group. The experimental group performed plyometric exercises 2 times a week for 6 weeks, whereas the control group participated only in their lectures. The results revealed that there were no significant changes in either vertical jump height or EMG activities of selected muscles for the control group (p greater than 0.05). However, after 6 weeks of plyometric training, significant improvements (p less than 0.05) were observed in EMG activities of VL (13.25%), VM (9.60%), and GAS (13.93%) muscles, and no significant increase (p greater than 0.05) was found in CMJ (2.77%) in the PLY group. In conclusion, the findings of the this study suggest that 6 weeks of PLY training, in addition to the regular academic program, induced significant improvements in EMG activities of lower extremity muscles but no significant increases in vertical jump height. Accordingly, PLY exercises are recommended as part of a regular academic program in order to increase important components of athletic performance for physical education students. [ABSTRACT FROM AUTHOR]

The growth promoting effects of eccentric (ECC) contractions are well documented but it is unknown if the rate of stretch per se plays a role in such muscular responses in healthy aging human skeletal muscle. We tested the hypothesis that exercise training of the quadriceps muscle with low rate ECC and high rate ECC contractions in the form of stretch-shortening cycles (SSCs) but at equal total mechanical work would produce rate-specific adaptations in healthy old males age 60–70. Both training programs produced similar improvements in maximal voluntary isometric (6%) and ECC torque (23%) and stretch-shortening cycle function (reduced contraction duration [24%] and enhanced elastic energy storage [12%]) ( p < 0.05). The rate of torque development increased 30% only after SSC exercise ( p < 0.05). Resting testosterone and cortisol levels were unchanged but after each program the acute exercise-induced cortisol levels were 12–15% lower ( p < 0.05). Both programs increased quadriceps size 2.5% ( p < 0.05). It is concluded that both ECC and SSC exercise training produces favorable adaptations in healthy old males' quadriceps muscle. Although the rate of muscle tension during the SSC vs. ECC contractions was about 4-fold greater, the total mechanical work seems to regulate the hypetrophic, hormonal, and most of the mechanical adaptations. However, SSC exercise was uniquely effective in improving a key deficiency of aging muscle, i.e., its ability to produce force rapidly. [ABSTRACT FROM AUTHOR]

The article discusses research which was conducted to investigate whether a different number of repetitions could be performed on the individual muscle actions of the bench press and squat in men and women. Researchers evaluated 10 resistance trained men and 10 trained women who performed the squat and bench press. They found that there were significant diferences betwen three muscle actions that they investigated across both exercises and sexes, that women performed more eccentric and concentric actions on the bench press and men performed more combined repetitions.

The article presents a study examining the effect of increased eccentric phase loading on drop jumps performed from different heights. It states that changes in the electromyographic activity of leg muscles and the kinetics, eccentric and concentric impulse, rate of force development, and concentration velocity were of special interest. It comments that observed greater eccentric loading didn't immediately change concentric kinetics and jump height or alter muscle activation levels.

This study explored the age-related deterioration in stretch-shortening cycle ( SSC) muscle power and concurrent force-velocity properties in women and men across the adult life span. A total of 315 participants (women: n = 188; men: n = 127) aged 18-81 years performed maximal countermovement jumps on an instrumented force plate. Maximal SSC leg extension power expressed per kg body mass ( Ppeak) was greater in men than in women across the adult age span ( P < 0.001); however, this gender difference was progressively reduced with increasing age, because men showed an ∼50% faster rate of decline in SSC power than women ( P < 0.001). Velocity at peak power ( VPpeak) was greater in men than in women ( P < 0.001) but declined at a greater rate in men than in women ( P = 0.002). Vertical ground reaction force at peak power ( FPpeak) was higher in men than in women in younger adults only ( P < 0.001) and the age-related decline was steeper in men than in women ( P < 0.001). Men demonstrated a steeper rate of decline in Ppeak than women with progressive aging. This novel finding emerged as a result of greater age-related losses in men for both force and velocity. Consequently, maximal SSC power production was observed to converge between genders when approaching old age. [ABSTRACT FROM AUTHOR]

The article reports on research which was conducted to investigate the effect an eight week in season plyometric training regimen had on upper and lower limb performance in elite adolescent handball players. Researchers evaluated the regimen with 23 young men. They found that the regimen improved components of handball performance, including sprinting, jumping and ball throwing.

The article reports on research which was conducted to investigate the effects an in season, low volume, high intensity plyometric training regimen had on the explosive actions and endurance of young soccer players. Researchers evaluated 76 players who either received the training regimen or did not.They found that the regimen improved explosive actions and endurance.

Research is presented which compared the effectiveness of plyometric only (PLYO) training with balance and plyometric (COMBINED) training on balance and power measures in children, noting the variables include static and dynamic balance, sprint running speed, shuttle run ability, and leg stiffness. The study found that COMBINED training can be a consideration in reducing high velocity impacts and stretch-shortening cycle stress on the neuromuscular system.

The article presents information on neuromuscular features of drop and hurdle jumps with various types of landings. Topics discussed include effect of landing on jump performance, lower limb plyometric exercises for gaining explosive-reactive movement, and use of elastic energy accumulated in body during plyometric exercises.

The article presents a study of the evaluation of various vertical jump (VJ) performance variables of male and female elite Italian soccer players. Countermovement and squatting jump heights were analyzed to determine stretch-shortening cycle efficiency (SSCE), as well as differences based on competitive levels and sex. The results indicate that vertical jump testing does not differentiate competitive levels, but can be used to assess lower limb muscle strength in soccer players.

The article discusses research investigating the acute effect of drop jump (DJ) protocols with different volumes and recovery time on countermovement jump (CMJ) performance. 10 male collegiate volleyball players performed a series of CMJs and one of two randomly-assigned DJ protocols. Results from a repeated-measures analysis of variance, used to examine the differences between training volumes and recovery times in CMJ (HCMJ) height and ground reaction force, are discussed.

The article reports on research which was conducted to investigate the effect four weeks of plyometric training had on reactive strength index and leg stiffness in male youths. Researchers evaluated 129 boys who were either nine, 12 or 15 years of age. They found that improvements in reactive strength index and leg stiffness after a plyometric training program were age dependent during childhood.

The article reports on research which was conducted to investigate the relationship between reactive strength variables in horizontal and vertical drop jumps. Researchers evaluated 28 subjects with previous jumping experience who performed six vertical and six horizontal drop jumps. They found that there was a large relationship between reactive ability in both jumps and that contact times were lower in vertical drop jumps.

The present study investigated the effect of movement frequencies on the behavior of fascicles and tendons of synergistic muscles. Seven male subjects performed ankle bending (calf-raise) exercises at four movement frequencies (1.33, 1.67, 1.84, and 2.00 Hz), performed with an identical range of ankle joint motion. The fascicle and tendon behavior of medial gastrocnemius (MG) and soleus (SOL) was measured by ultrasonography while kinematic and kinetic parameters of the ankle were recorded. The torque of ankle joint was larger at higher exercise frequencies. The length change of muscle decreased and that of tendon increased at higher frequencies both for MG and for SOL, with no significant inter-muscle differences in the relative changes of muscle or tendon lengths to that of MTU. Changes of pennation angles and electromyographic activities as a function of movement frequency were also comparable for MG and SOL. These results suggest that under a stretch-shortening cycle action, the muscle-tendon interaction is altered by the movement frequency toward greater use of tendon elastic energy to provide greater MTU power at a higher frequency. Results also suggest that the movement frequency dependence of fascicle and tendon behavior is comparable between MG and SOL. [ABSTRACT FROM AUTHOR]

Many sport and exercise activities require powerful movements of the upper body. Despite their importance, there is a paucity of research examining stretch-shortening cycle (SSC) activities occurring in the upper limbs. The purpose of this study was to examine the effect of fatigue on throwing performance (height of throw) and biomechanical factors of the upper limbs (reactive strength index; hand contact time) using a specially constructed sledge apparatus for the upper body. Ten male subjects aged between 19 and 21 years performed a series of rebound throws (RBT) in a non-fatigued state to obtain a maximal baseline throw score. Subjects then performed a RBT fatiguing protocol on the upper body sledge followed by further RBT, at 15, 45, 120 and 300-seconds post fatigue. Markers on the subjects' limb and the sledge were analysed using Motion Analysis Corporation 3-D kinematic analysis system (200 Hz). Throwing height, contact time and reactive strength index were determined. Mean throwing height and reactive strength index showed significant decreases following fatigue and increases during recovery (p < 0.05). The results confirm the presence of post-activation potentiation (PAP) in RBT performance. This finding could be useful when optimising recovery periods in training or implementing complex training methods. [ABSTRACT FROM AUTHOR]