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This study critically examines the suitability of using a single drop height to assess the reaction strength index in trained and active participants, a key component of athletic performance. Using a cross-sectional design, 377 trained (n = 163) and active (n = 214) participants aged 14–18 years performing drop jumps from 4 different heights (24, 32, 40, and 48 cm) were studied. The primary aim was to explore the individual differences in reaction strength index at these heights and to assess whether a single height can reliably represent stretch-shortening cycle capabilities. While the repeated measures analysis of variance did not reveal any significant differences, the Bland–Altmann analysis revealed significant individual discrepancies between the performance of the drop heights, resulting in a mean absolute error of 32.1 and a mean absolute percentage error of 20.6%. These results strongly suggest that a single drop height is not sufficient to determine performance in the stretch-shortening cycle. This has important practical implications as it can lead to underestimates of performance trends. The study advocates the inclusion of a range of drop heights in routine testing to accurately measure reactive power and thus improve the effectiveness of individualized training programs for young athletes/active youth. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated the test–retest reliability and usefulness of the foot–ankle rebound-jump test (FARJT) for measuring foot–ankle reactive strength metrics in athletes. Methods: Thirty-six highly trained, healthy athletes (5 female; 21.5 [3.9] y; 1.80 [0.10] m; 72.7 [10.4] kg) performed 8 repeated bilateral vertical foot–ankle rebound jumps on 2 testing days. Testing days were 1 week apart, and these sessions were preceded by a familiarization session. Reactive strength metrics were calculated by dividing jump height (in meters) by contact time (in seconds) for the reactive strength index (RSI) and flight time (in seconds) by contact time (in seconds) for the reactive strength ratio (RSR). The mean of 4 jumps (excluding the first and last 2 jumps) on each testing session were considered for RSI and RSR reliability and usefulness analysis. Results: We found a high reliability of the FARJT for RSI (intraclass correlation coefficient [ICC] >.90 and coefficient of variation [CV] = 12%) and RSR (ICC ≥.90 and CV = 8%). Regarding their usefulness, both RSI and RSR were rated as "marginal" in detecting the smallest worthwhile change (typical error > smallest worthwhile change) and "good" in detecting a moderate change in performance. Conclusions: The results showed that a FARJT is a highly reliable test for measuring foot–ankle reactive strength in athletes and useful for quantifying changes, for example, following a training block. However, its usefulness as an accurate daily or weekly monitoring tool in practice is questionable. [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]

The aim of this study was to investigate the effect of maturation on vertical jumping performance, in adolescent boys and girls, concerning plantar flexor activity and Achilles tendon (AT) stiffness. Thirty-nine adolescents were tested in a counter-movement jump (CMJ) at three different time points: 18 and 9 months before peak height velocity (PHV) and at PHV. The EMG activity of the medialis gastrocnemius (MG) and tibialis anterior (TA) muscles was evaluated, in relation to jump height. Boys showed higher jumping ability and AT stiffness than girls. Additionally, boys revealed increased eccentric (ecc) and concentric (con) MG activity, along with decreased ecc and con TA activity, near PHV. On the other hand, girls showed increased ecc and con TA/MG co-contraction compared to boys, mainly near PHV. In conclusion, a different mechanism of vertical jumping performance is adopted between early adolescent boys and girls. Nevertheless, no notable alterations in jumping capability were detected over time, indicating that the maturation process does not influence stretch-shortening cycle (SSC) performance. [ABSTRACT FROM AUTHOR]

The attentional focus strategy (AFS) affects drop jump (DJ) performance; however, its effects on DJ kinetics and kinematics are unclear. This study examines the effects of AFS on DJ performance, kinetics and kinematics. Forty collegiate males were divided into a DJ experienced group and a DJ inexperienced group, and they performed two trials of DJs after listening to instructions designed to elicit internal (INT), external (EXT) or neutral (NEUT) focus of attention. In the experienced group, the reactive strength index (RSI) was larger with the NEUT than with the INT. Hip joint torque and positive hip joint power in the concentric phase was smaller with the NEUT than with the INT, and the hip joint angle at the lowest centre of mass was larger with the NEUT than with the INT (p <.05). In the inexperienced group, RSI was larger with the EXT than with the INT. Further, the hip joint torque in the concentric phase was smaller with the EXT than with the INT; positive ankle joint power was larger with the EXT than with the INT; and the hip joint angles at the lowest centre of mass and take-off were larger with the EXT than with the INT (p <.05). These results showed that the AFS affected the DJ performance, kinetics and kinematics and suggested that effective DJ training may be achieved with the NEUT for DJ experienced and with the EXT for DJ inexperienced. [ABSTRACT FROM AUTHOR]

Purpose: During a soccer match, horizontal acceleration ability during short sprints is determinant for performance. Development of sprint force and velocity qualites have been reported after plyometric training. However, orientation of plyometric training exercises can influence the functional performance. The purpose of this study was to compare the horizontal and vertical orientation of plyometric training on explosiveness performances and sprint force–velocity profile in young soccer players. Methods: Twenty-eight soccer players were recruited and divided in two groups: vertical (VG, n = 14) and horizontal (HG, n = 14) groups. Tests including jumps and sprint performances were conducted before and after the 8 week training period. Sprint force–velocity profile (FVP) was evaluated during a 30 m sprint test. Results: The results demonstrated significant improvements in both VG and HG for jump performances (from + 4.9% to + 9.0%), sprint times (from −5.5% to −8.7%) and FVP parameters. Higher relative changes for the HG than for the VG were observed in 5 m and 15 m sprint times, horizontal jump lengths, and also in FVP parameters, especially improvements in maximal power (VG: + 16.4% vs. HG: + 28.1%) and in the decrease rate of horizontal orientation of force with increasing speed (HG: + 22.9%) during the 30 m sprint. Conclusions: Both horizontal and vertical plyometric training can be either used in young soccer players to improve vertical and horizontal performances in jump and sprint. However, horizontal plyometric training may result in a greater improvement in horizontal ballistic actions while similarly developing vertical jump qualities compared to vertical plyometric training in young soccer players. [ABSTRACT FROM AUTHOR]

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Purpose: To quantify the acute effects of a spectrum of eccentric load reductions on neuromechanical adjustments during the performance of weighted jump squats (WJSs). Methods: On separate days, 16 well-trained participants performed WJS trials with various eccentric load reductions (0% [body mass only], 25%, 50%, 75%, and 100% [standard WJS] of concentric load) with a mechanical braking unit, while concentric load was set at 30% of peak isometric squat force in all trials. A force platform and a motion-capture system were used to assess neuromuscular performance. Results: Peak power output was 6.2% (4.7%) higher when load was reduced by 50% versus 0% (55.4 [7.8] vs 51.9 [7.6] W/kg; P =.001). Compared with no braking (0.326 [0.059] m), jump height was ∼13% to 17% higher for all eccentric load reduction conditions (all P <.001). Vertical ground reaction forces were progressively lower for 25%, 50%, 75%, and 100% loading conditions (–22.1% [14.6%], –32.3% [10.8%], –42.0% [13.2%], and –46.1% [14.7%]; all P ≤.001) in reference to body mass only. Conclusion: Eccentric load reduction is advantageous compared with traditional isoinertial loading for improving both jump height and peak power output during the concentric portion of maximal-effort WJS. This practice also decreases mechanical constraints in the lower extremities, which may become beneficial for load-compromised individuals. [ABSTRACT FROM AUTHOR]

This study examined the effects of three external verbal cues on countermovement rebound jump (CMRJ) performance. Twenty-five recreational athletes completed nine jumps with distinct height, velocity and combined cue focus. A general linear model analysis of variance was used to evaluate systematic bias between conditions (p < 0.05). The height and velocity cues significantly altered jump height and contact times in both jumps during the CMRJ, respectively (p ≤ 0.002). The combined cue significantly reduced contact time while increasing leg stiffness compared to the height cue (p ≤ 0.038). It also increased jump height compared to the velocity cue (p ≤ 0.005) in both jumps, resulting in the highest explosive power and reactive strength values among all conditions. Furthermore, the combined cue enhanced the positive ankle contribution compared to the height cue (p = 0.020) and increased positive hip and negative knee joint work compared to the velocity cue (p ≤ 0.040) in the second jump of the CMRJ. These findings advise practitioners to use the height cue to maximise jump height, the velocity cue to minimise contact times and the combined cue to maximise explosive power and reactive strength. [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]

Purpose: The aim of this study was to analyze the effects of plyometric training direction on jumping, sprinting, and change-of-direction ability in basketball players. Methods: Forty male basketball players (21.8 [3.8] y), from 4 teams that competed in regional and national championships, were randomly assigned to 1 of 4 groups: (1) vertical jump group, (2) horizontal jump group, (3) vertical and horizontal jump group, and (4) control group. The subjects followed a plyometric training program twice a week for 6 weeks, differing in the execution direction of the jumps. All groups performed the same total training volume of acyclic and cyclic jumps controlled through the number of contacts per session. Pretraining and posttraining measurements included (1) rocket jump, (2) Abalakov jump, (3) horizontal jump, (4) 20-m linear sprint, and (5) V-Cut change-of-direction test. Results: The vertical and horizontal jump group showed significant increases in all performance variables examined, except for linear sprint performance, in which no group improved. The vertical jump group showed significant improvements in rocket jump and Abalakov jump (P <.01), but worsened significantly in terms of sprint performance (P <.05). The horizontal jump group showed significant increases in rocket jump and horizontal jump (P <.001–.01). Furthermore, all experimental groups showed improved V-Cut change-of-direction test performance. Conclusions: These results indicate that combining vertical and horizontal jumps induces improvements in more capabilities than does training only vertical or horizontal jumps with the same training volume. Training only vertical or horizontal jumps will improve performance mainly in vertically or horizontally oriented tasks, respectively. [ABSTRACT FROM AUTHOR]

Abstract Plyometric training (PT) is an effective training method for improving physical fitness among trained individuals; however, its impact on health-related physical fitness in untrained participants remains ambiguous. Therefore, this meta-analysis aimed to evaluate the effects of PT on health-related physical fitness among untrained participants. Six electronic databases (PubMed, CINAHL Plus, MEDLINE Complete, Web of Science Core Collection, SCOPUS, and SPORTDiscus) were systematically searched until March 2024. We included controlled trials that examined the effects of PT on health-related physical fitness indices in untrained participants. Twenty-one studies were eligible, including a total of 1263 participants. Our analyses revealed small to moderate effects of PT on body mass index, muscular strength, cardiorespiratory fitness, and flexibility (ES = 0.27–0.61; all p > 0.05). However, no significant effects were detected for body fat percentage and lean mass (ES = 0.21–0.41; all p > 0.05). In conclusion, the findings suggest that PT may be potentially effective in improving health-related physical fitness indices (i.e., body mass index, muscular strength, cardiorespiratory fitness, and flexibility) in untrained participants. However, the results should be interpreted cautiously due to data limitations in some fitness variables.

Plyometric training (PT) is an effective training method for improving physical fitness among trained individuals; however, its impact on health-related physical fitness in untrained participants remains ambiguous. Therefore, this meta-analysis aimed to evaluate the effects of PT on health-related physical fitness among untrained participants. Six electronic databases (PubMed, CINAHL Plus, MEDLINE Complete, Web of Science Core Collection, SCOPUS, and SPORTDiscus) were systematically searched until March 2024. We included controlled trials that examined the effects of PT on health-related physical fitness indices in untrained participants. Twenty-one studies were eligible, including a total of 1263 participants. Our analyses revealed small to moderate effects of PT on body mass index, muscular strength, cardiorespiratory fitness, and flexibility (ES = 0.27–0.61; all p > 0.05). However, no significant effects were detected for body fat percentage and lean mass (ES = 0.21–0.41; all p > 0.05). In conclusion, the findings suggest that PT may be potentially effective in improving health-related physical fitness indices (i.e., body mass index, muscular strength, cardiorespiratory fitness, and flexibility) in untrained participants. However, the results should be interpreted cautiously due to data limitations in some fitness variables. [ABSTRACT FROM AUTHOR]

This study investigates the associations between countermovement rebound jump (CMRJ) performance metrics and various independent measures of athletic performance, including the isometric mid-thigh pull (IMTP), 20 m linear sprint, and 505 change-of-direction (COD) speed tests. Pearson's correlations were used to analyse the relationship between the CMRJ measures with athletic performance, with significance being set at p ≤ 0.006. Results showed large significant positive relationships between IMTP peak force and force at 300 milliseconds with the first jump height of the CMRJ (JH-1, r = 0.54 to 0.55, p ≤ 0.002). Additionally, inverse relationships were observed between reactive strength index modified (RSImod) and reactive strength index (RSI) with 20 m sprint total and split times (r = −0.55 to −0.66, p ≤ 0.001), and the 10 m and total sprint times were significantly correlated with JH-1 (r = −0.54, p = 0.003), indicating that greater vertical explosive power and reactive strength are associated with faster sprint performance. Finally, a significant inverse relationship was identified between CMRJ metrics (two JH values and RSImod) and 505 COD times in both the left and right sides (r = −0.51 to −0.68, p ≤ 0.006). These findings suggest that CMRJ performance metrics are valuable indicators of lower-limb explosive force production, with a strong link to both linear sprint and COD performance. The finding underscores the importance of including CMRJ assessments in athletic performance evaluations due to their dual assessment capacity of slow and fast stretch–shortening cycle mechanics. [ABSTRACT FROM AUTHOR]

Sprint and jump abilities are considered basic skills that are regularly evaluated in training and school contexts. The correlations between these two skills have previously been established in adults and adolescents, but they have not been fully assessed in children. The present study aimed to explore sprinting and jumping ability in prepubertal boys and girls. Thirty-one prepubertal individuals (aged 8–11 years) were assessed during sprinting for different distances (5, 10, and 20 m) and using different vertical and horizontal jump modalities (squat jump, countermovement jump, broad jump, and hop test). Correlations between the different results were tested. Strong correlations were found between vertical jump and sprint performances, especially over short distances. These results suggested that vertical jump tests are more sensitive than horizontal jumps to reveal acceleration capacity in children. [ABSTRACT FROM AUTHOR]

When improving athletic performance in sports with high-speed strength demands such as soccer, basketball, or track and field, the most common training method might be resistance training and plyometrics. Since a link between strength capacity and speed strength exists and recently published literature suggested chronic stretching routines may enhance maximum strength and hypertrophy, this review was performed to explore potential benefits on athletic performance. Based on current literature, a beneficial effect of static stretching on jumping and sprinting performance was hypothesized. A systematic literature search was conducted using PubMed, Web of Science and Google scholar. In general, 14 studies revealed 29 effect sizes (ES) (20 for jumping, nine for sprinting). Subgroup analyses for jump performance were conducted for short- long- and no stretch shortening cycle trials. Qualitative evaluation was supplemented by performing a multilevel meta-analysis via R (Package: metafor). Significant positive results were documented in six out of 20 jump tests and in six out of nine sprint tests, while two studies reported negative adaptations. Quantitative data analyses indicated a positive but trivial magnitude of change on jumping performance (ES:0.16, p = 0.04), while all subgroup analyses did not support a positive effect (p = 0.09–0.44). No significant influence of static stretching on sprint performance was obtained (p = 0.08). Stretching does not seem to induce a sufficient stimulus to meaningfully enhance jumping and sprinting performance, which could possibly attributed to small weekly training volumes or lack of intensity [ABSTRACT FROM AUTHOR]

The aim of this study was to estimate the intra-day and inter-day reliability and usefulness of performance (Jump height (JH), ground contact time (GCT) and reactive strength index (RSI)), kinetic (force, power, eccentric rate of force development [E-RFD] and leg stiffness [LS]) and kinematic (velocity) variables during drop jumping (DJ) in hurling players. Seventeen (n = 17; mean ± SD; age = 23.35 ± 5.78 years, height = 178.35 ± 6.30 cm, body mass = 78.62 ± 8.06 kg) male club-level hurling players completed two maximal DJs from 0.20, 0.30, 0.40, 0.50 and 0.60 m drop heights on three testing days separated by 5–9 days of rest. Reliability was assessed using the coefficient of variation percentage (CV% ≤ 15%) and intraclass correlation coefficient (ICC > 0.70). For intra-day reliability, GCT (0.40 m, 0.50 m and 0.60 m), peak force (absolute and relative) (0.40 m and 0.50 m) and leg stiffness (0.40 m and 0.50 m) were found to be unreliable (ICC = 0.32–0.68 and CV% = 3.67–11.83%) from those specific drop heights. All other variables were found to be reliable (ICC = 0.72–0.98 and CV% = 1.07–14.02%) intra-day. All variables were found to be reliable (ICC = 0.72–0.96 and CV% = 2.57–14.68%) inter-day except for relative peak force and absolute and relative eccentric RFD (0.30 m and 0.40 m) (ICC = 0.68–0.90 and CV% = 7.76–16.47%). Practitioners have multiple reliable DJ performance, kinetic and kinematic variables for performance testing and training purposes. [ABSTRACT FROM AUTHOR]

Reactive Strength Index (RSI) is a neuromuscular assessment used to measure stretch–shortening cycle (SSC) function of the lower limb. Increased RSI scores have been frequently associated with running performance, such as faster sprint times, greater running economy and reduced change of direction times. These locomotor activities are involved in various sports and therefore, RSI is an important indicator of athletic capacity in sport. Whilst RSI has been commonly used in studies to assess SSC performance, no review has been conducted examining the difference in RSI between athletic populations. Thus, the aim of this systematic review was to summarise the literature and determine whether there was any significant difference in RSI between different populations and summarise the underlying factors contributing to these results. The systematic review protocol yielded 865 articles for screening by which 19 were included for final analysis following inclusion/exclusion criteria. Moderate to large differences were predominately found between different athlete populations, and the strength of these relationships varied depending on the populations being compared. The findings indicated that relative strength is an influencing factor that differentiated RSI performance between populations. This should be an area, which practitioners aim to develop if wanting to improve reactive strength. [ABSTRACT FROM AUTHOR]

This study aimed to establish the validity and reliability of a single-beam sensor for assessment of jump performance. Thirty-four male and female university students (age: 21.47 ± 0.98 years; height: 173.97 ± 9.32 cm; weight: 70.03 ± 10.63 kg) executed three trials of countermovement jump (CMJ) and three trials of squat jump (SJ), respectively. CMJ and SJ were simultaneously recorded using a force platform (reference) and single- beam jump sensor (Jump Pro). The flight time (FT) and jump height (JH) for both jumps were utilized for analyses. Results revealed the following for FT in CMJ performance: 1) Pearson's correlation coefficient (r) with lower limit (LL) and upper limit (UL) = 0.90 (0.82, 0.94); 2) Typical error of estimate (TEE) with LL and UL = 0.03 (0.01, 0.02); 3) Bland-Altman estimate = 0.05; and 4) Intraclass correlation coefficient (ICC) = 0.80. On the other hand, JH in CMJ posted: 1) r = 0.96 (0.94, 0.98); 2) TEE = 2.07 (1.73, 2.62); 3) Bland-Altman estimate = 4.00; and 4) ICC = 0.71. In regards to FT in SJ, r = 0.96 (0.94, 0.98), TEE = 0.02 (0.01, 0.02), Bland-Altman estimate = 0.03, and, ICC = 0.88. Further, JH in SJ exhibited r = 0.96 (0.94 - 0.98), TEE = 1.84 (1.53, 2.32), Bland-Altman estimate = 3.55, and ICC = 0.86. These findings support Jump Pro as a valid and reliable tool for measurement of CMJ and SJ performances. [ABSTRACT FROM AUTHOR]

Aging is associated with impaired strength and power during isometric and shortening contractions, however, during lengthening (i.e., eccentric) contractions, strength is maintained. During daily movements, muscles undergo stretch-shortening cycles (SSCs). It is unclear whether the age-related maintenance of eccentric strength offsets age-related impairments in power generation during SSCs owing to the utilization of elastic energy or other cross-bridge based mechanisms. Here we investigated how aging influences SSC performance at the single muscle fibre level and whether performing active lengthening prior to shortening protects against age-related impairments in power generation. Single muscle fibres from the psoas major of young (∼8 months; n = 31 fibres) and old (∼32 months; n = 41 fibres) male F344BN rats were dissected and chemically permeabilized. Fibres were mounted between a force transducer and length controller and maximally activated (pCa 4.5). For SSCs, fibres were lengthened from average sarcomere lengths of 2.5 to 3.0 μm and immediately shortened back to 2.5 μm at both fast and slow (0.15 and 0.60 Lo/s) lengthening and shortening speeds. The magnitude of the SSC effect was calculated by comparing work and power during shortening to an active shortening contraction not preceded by active lengthening. Absolute isometric force was ∼37 % lower in old compared to young rat single muscle fibres, however, when normalized to cross-sectional area (CSA), there was no longer a significant difference in isometric force between age groups, meanwhile there was an ∼50 % reduction in absolute power in old as compared with young. We demonstrated that SSCs significantly increased power production (75–110 %) in both young and old fibres when shortening occurred at a fast speed and provided protection against power-loss with aging. Therefore, in older adults during everyday movements, power is likely ‘protected’ in part due to the stretch-shortening cycle as compared with isolated shortening contractions.

The aim of this study was to estimate the intra-day and inter-day reliability and usefulness of performance (Jump height (JH), ground contact time (GCT) and reactive strength index (RSI)), kinetic (force, power, eccentric rate of force development [E-RFD] and leg stiffness [LS]) and kinematic (velocity) variables during drop jumping (DJ) in hurling players. Seventeen (n = 17; mean ± SD; age = 23.35 ± 5.78 years, height = 178.35 ± 6.30 cm, body mass = 78.62 ± 8.06 kg) male club-level hurling players completed two maximal DJs from 0.20, 0.30, 0.40, 0.50 and 0.60 m drop heights on three testing days separated by 5–9 days of rest. Reliability was assessed using the coefficient of variation percentage (CV% ≤ 15%) and intraclass correlation coefficient (ICC > 0.70). For intra-day reliability, GCT (0.40 m, 0.50 m and 0.60 m), peak force (absolute and relative) (0.40 m and 0.50 m) and leg stiffness (0.40 m and 0.50 m) were found to be unreliable (ICC = 0.32–0.68 and CV% = 3.67–11.83%) from those specific drop heights. All other variables were found to be reliable (ICC = 0.72–0.98 and CV% = 1.07–14.02%) intra-day. All variables were found to be reliable (ICC = 0.72–0.96 and CV% = 2.57–14.68%) inter-day except for relative peak force and absolute and relative eccentric RFD (0.30 m and 0.40 m) (ICC = 0.68–0.90 and CV% = 7.76–16.47%). Practitioners have multiple reliable DJ performance, kinetic and kinematic variables for performance testing and training purposes.

The aim of this study was to investigate the effect of maturation on vertical jumping performance, in adolescent boys and girls, concerning plantar flexor activity and Achilles tendon (AT) stiffness. Thirty-nine adolescents were tested in a counter-movement jump (CMJ) at three different time points: 18 and 9 months before peak height velocity (PHV) and at PHV. The EMG activity of the medialis gastrocnemius (MG) and tibialis anterior (TA) muscles was evaluated, in relation to jump height. Boys showed higher jumping ability and AT stiffness than girls. Additionally, boys revealed increased eccentric (ecc) and concentric (con) MG activity, along with decreased ecc and con TA activity, near PHV. On the other hand, girls showed increased ecc and con TA/MG co-contraction compared to boys, mainly near PHV. In conclusion, a different mechanism of vertical jumping performance is adopted between early adolescent boys and girls. Nevertheless, no notable alterations in jumping capability were detected over time, indicating that the maturation process does not influence stretch-shortening cycle (SSC) performance.

Objectives: Drop jump (DJ) is a typical exercise of plyometric training in which the state before takeoff (pre-set phase) influences the force exertion of the lower limbs during takeoff, as well as performance variables. This study aimed to examine the effects of watching an instructional movie during the pre-set phase on the performance and lower limb kinematic and kinetic variables during plyometric training. Methods: Fourteen participants (age, 21.9 ± 2.1 years; height, 175.6 ± 2.6 cm; weight, 70.7 ± 4.9 kg) were enrolled in this study. Seven participants with a high rebound jump (RJ) index under normal conditions were classified into the high RJ-index group. Seven participants with a low RJ-index were classified into the low RJ-index group. DJs were performed under normal conditions and under the movie condition (DJ immediately after watching the instructional movie during the pre-set phase). Performance and kinematic and kinetic variables of the lower limb joints were measured. Results: Compared with the normal condition, the movie condition was associated with a significantly high RJ-index, lesser degree of knee flexion (p < 0.011), and significantly larger concentric torque (p < 0.018) of the ankle. An interaction effect was observed for the eccentric torque (p < 0.025) and positive power (p < 0.004) of the ankle, which were significantly greater in the high RJ-index group under the movie condition. Conclusion: Watching an instructional movie during the pre-set phase improves the movement and force production of the ankle and knee joint, which, in turn, improves the DJ performance. However, the effects may be more pronounced in participants with a high RJ-index. [ABSTRACT FROM AUTHOR]

We compared neuromechanical adjustments between traditional and eccentric load reduction weighted jump squats (WJSs). On separate visits, sixteen strength‐trained men performed three sets of six consecutive WJS with 0% (traditional WJS) or 50% eccentric loading reduction with a mechanical braking unit, while concentric load was set at 30% of 1 RM in all trials. A force platform and a motion capture system were used to assess neuromechanical parameters during eccentric and concentric phases of WJS. Peak power output (+4.5 ± 4.1%; p < 0.001), maximal concentric velocity (+3.2 ± 3.6%; p = 0.004), jump height (+19.6 ± 17.4%; p < 0.001), and reactive strength index (+28.2 ± 20.0%; p < 0.001) were higher when eccentric load was reduced by 50% versus 0%. Compared with traditional jump squat, eccentric phase duration (−6.7 ± 9.9%; p = 0.014), contact time (−6.3 ± 7.2%; p = 0.004), and time to reach peak power output (−7.8 ± 7.6%; p < 0.001) were shorter, while peak vertical force (−15.2 ± 17.5%; p = 0.005) and eccentric mechanical work (−23.9 ± 6.6%; p < 0.001) were lower with eccentric load reduction. Eccentric depth (p = 0.613), eccentric velocity (p = 0.070), amortization time (p = 0.060), maximal concentric force (p = 0.727), and concentric mechanical work (p = 0.396) did not differ significantly between conditions. Compared with traditional isoinertial loading, eccentric load reduction promoted more favorable neuromechanical adjustments during landing and propulsion phases in turn maximizing WJS performance. Highlights: Eccentric load reduction weighted jump squat is a form of plyometric exercise during which a rapid, eccentrically braked downward movement is immediately followed by a maximal effort jump.In strength‐trained men, we found this approach advantageous compared with no braking for potentiating weighted jump squat performance due to more favorable eccentric‐ and concentric‐phase metrics.It is possible that smaller training volumes could be completed in each exercise session without compromising on concentric outputs. Under such circumstances, employing eccentric load reduction weighted jump squat might be a more suitable approach when attempting to execute greater workloads while minimizing fatigue. [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]

The aim of this study was to examine the effects of maturity status on drop jump (DJ) kinetics in young male athletes (categorized as early-pre-peak height velocity [PHV] [<â2.51 years], late-pre-PHV [â'1.99 to â'1.00 years], circa-PHV [â'0.50 to 0.50 years], and post-PHV [>1.00 years]). All athletes performed a DJ from a 30-cm box onto force plates with performance variables (jump height, ground contact time, and reactive strength index) and absolute and relative kinetic variables during the braking and propulsive phases assessed. Subjects were categorized into GOOD (no impact-peak and spring-like), MODERATE (impact-peak and spring-like), or POOR (impact-peak and not spring-like) stretch-shortening cycle (SSC) function. The post-PHV group exhibited significantly greater values for most absolute kinetic variables compared with early-pre-PHV, late-pre-PHV, and circa-PHV (p < 0.05). The differences observed between consecutive maturity groups were similar in magnitude for most absolute variables (Cohen's d = 0.53-1.70). Post-PHV male athletes outperform their less mature counterparts during a DJ, and this may be attributed to the growth and maturity-related structural and motor control strategy changes that occur in children. Stretch-shortening cycle function in boys seems to improve with maturity status reflected by a greater number of post-PHV participants displaying GOOD SSC function (65.8%) and a greater number of early-pre-PHV participants displaying POOR SSC function (54.4%). However, a number of mature boys displayed POOR SSC function (17.8%), suggesting that the development of SSC function is not exclusively related to maturation. [ABSTRACT FROM AUTHOR]

This study aimed to establish a correlation between jumping ability and the isokinetic strength of the trunk and lower limb extensors in female university athletes and to provide recommendations for improving jumping ability. Participants were 26 female university students from the track and field and volleyball teams. They performed a countermovement jump (CMJ) and a 30-cm rebound drop jump (RDJ). The following parameters were measured using high-speed video motion analysis: contact time, jump height, RDJ-index, joint angles, and joint angular velocities of the knee and ankle joints during the CMJ and RDJ. Additionally, the peak torques of the trunk and lower limb extensors and the percentage of total torque of three lower limb joints were measured using an isokinetic dynamometer. Based on the mean RDJ-index, the participants were classified into two groups: those with an RDJ-index of 0.80 m/s or higher (HG; n=12) and those with a lower RDJ-index of less than 0.80 m/s (LG; n=14). Our study yielded the following findings. The HG exhibited significantly greater heights in CMJ and RDJ, along with a higher RDJ-index and a notably shorter contact time compared with the LG. In the RDJ, the HG demonstrated significantly higher maximum knee flexion and ankle dorsiflexion angles compared with the LG. The HG tended to display significantly higher peak ankle plantar flexion and peak hip extension torques compared with the LG. Maximum knee flexion and ankle dorsiflexion angles exhibited significant negative correlations with RDJ contact time and positive correlations with RDJ-index. Significant positive correlations were observed between RDJ jump height and peak trunk extension torque as well as between RDJ-index and peak hip extension torque. These findings suggest that the low RDJ-index group can improve jumping performance by utilizing ankle plantar flexor muscle strength to achieve the jump with less contact time and by enhancing the isokinetic muscle strength of the trunk and hip extensors in order to stabilize the upper body and contribute to the acquisition of jump height. [ABSTRACT FROM AUTHOR]

This study analysed the effects of performing a plyometric training programme on different types of jumping and specific changes of direction, and their respective asymmetries in karatekas. Twenty male karatekas (age 19 ± 4 years) were distributed in two groups, the control group (CG) and the experimental group (EG). The EG group (n = 10) performed a 6-week intervention of unilateral plyometric training, performing countermovement jumps (CMJ), drop jumps (DJ), and long jumps (SH). The tests performed at the beginning and at the end of the intervention were a unilateral and bilateral countermovement jump test (CMJ), single-leg hop test (SH), single-leg side-hop test (SSH), triple hop test (TH), and change of direction in a karate position test (MKUKS). The EG group obtained improvements in the CMJ with the stronger (p = 0.01; ES = 0.39) and weaker leg (p = 0.01; ES = 0.59), in the SH with the weaker leg (p = 0.01; ES = 0.45), in the SSH with the weaker leg (p = 0.03; ES = 0.33), in the MKUKS (p = 0.00; ES = 0.98), and improved the asymmetries obtained in the TH (p = 0.02; ES = −0.85). The GC group obtained significant differences in the CMJ with the stronger (p = 0.03; ES = 0.46) and weaker leg (p = 0.00; ES = 0.69), in the bilateral CMJ (p = 0.02; ES = 0.24), in the SH with the weaker leg (p = 0.00; ES = 0.34), in the TH with the stronger (p = 0.00; ES = −0.15) and weaker leg (p = 0.01; ES = 0.09), and in the MKUKS test (p = 0.04; ES = −0.94). A between-group analysis showed improvements of the EG over the GC in the TH with the stronger leg (p = 0.02; ES = 1.05). Performing plyometric training provides improvements in jumping, mainly in horizontal jumps, reducing inter-limb asymmetries in repetitive jumps. [ABSTRACT FROM AUTHOR]

Background: By directly recording electromyographic activity profiles and muscle-tendon interaction, this study aimed to elucidate the mechanisms why well-trained track and field athletes (experts) are able to outperform untrained individuals without former systematic experience in reactive jump training (novices). In particular, reactive power output and the elastic recoil properties of the muscle-tendon unit (MTU) were of special interest. For this purpose, stiffness regulation on muscle and joint level, energy management in terms of storing or dissipating elastic energy were compared between experts and novices during various stretch loads. Methods: Experts were compared with novices during reactive drop jumps (DJs) from drop heights ranging between 25 and 61 cm. Delta kinetic energy (Ekin) was calculated as the difference between the Ekin at take-off and ground contact (GC) to determine energy management. By recording electromyography of the lower limb muscles, in vivo fascicle dynamics (gastrocnemius medialis) and by combining kinematics and kinetics in a 3D inverse dynamics approach to compute ankle and knee joint kinetics, this study aimed to compare reactive jump performance, the neuromuscular activity and muscle-tendon interaction between experts and novices among the tested stretch loads. Results: Experts demonstrated significantly higher power output during DJs. Among all drop heights experts realized higher delta Ekin compared to novices. Consequently, higher reactive jump performance shown for experts was characterized by shorter GC time (GCT), higher jump heights and higher neuromuscular activity before and during the GC phase compared to novices. Concomitantly, experts were able to realize highest leg stiffness and delta Ekin in the lowest stretch load; however, both groups compensated the highest stretch load by prolonged GCT and greater joint flexion. On muscle level, experts work quasi-isometrically in the highest stretch load, while in novices GM fascicles were forcefully stretched. Conclusion: Group-specific stiffness regulation and elastic recoil properties are primarily influenced by the neuromuscular system. Due to their higher neuromuscular activity prior and during the GC phase, experts demonstrate higher force generating capacity. A functionally stiffer myotendinous system through enhanced neuromuscular input enables the experts loading their elastic recoil system more efficiently, thus realizing higher reactive power output and allowing a higher amount of energy storage and return. This mechanism is regulated in a stretch load dependent manner. [ABSTRACT FROM AUTHOR]

When improving athletic performance in sports with high-speed strength demands such as soccer, basketball, or track and field, the most common training method might be resistance training and plyometrics. Since a link between strength capacity and speed strength exists and recently published literature suggested chronic stretching routines may enhance maximum strength and hypertrophy, this review was performed to explore potential benefits on athletic performance. Based on current literature, a beneficial effect of static stretching on jumping and sprinting performance was hypothesized. A systematic literature search was conducted using PubMed, Web of Science and Google scholar. In general, 14 studies revealed 29 effect sizes (ES) (20 for jumping, nine for sprinting). Subgroup analyses for jump performance were conducted for short- long- and no stretch shortening cycle trials. Qualitative evaluation was supplemented by performing a multilevel meta-analysis via R (Package: metafor). Significant positive results were documented in six out of 20 jump tests and in six out of nine sprint tests, while two studies reported negative adaptations. Quantitative data analyses indicated a positive but trivial magnitude of change on jumping performance (ES:0.16, p = 0.04), while all subgroup analyses did not support a positive effect (p = 0.09–0.44). No significant influence of static stretching on sprint performance was obtained (p = 0.08). Stretching does not seem to induce a sufficient stimulus to meaningfully enhance jumping and sprinting performance, which could possibly attributed to small weekly training volumes or lack of intensity.

Skill-related physical fitness significantly correlates with sports performance. Plyometric training (PT) is an effective method for improving physical fitness in athletes. However, its impact on skill-related physical fitness in badminton players remains uncertain. Therefore, this systematic review and meta-analysis aimed to evaluate the effectiveness of PT on skill-related physical fitness in badminton players. Five electronic databases (Web of Science, PubMed, SCOPUS, MEDLINE, and SPORTSDiscus) were searched until February 2024. A PICOS approach was used to identify inclusion criteria, (1) healthy badminton players, (2) a PT program, (3) an active control group, (4) a measure of skill-related physical fitness before and after PT, and (5) randomized controlled studies. The PEDro scale was used to assess the methodological quality of PT studies, while the level of evidence certainty was determined through the GRADE framework. The calculation of effect sizes (ESs) was based on mean values and standard deviations, and heterogeneity was measured with the I2 statistic. The extended Egger's test was employed to check for publication bias. Eleven studies comprising 445 badminton players were eligible for inclusion. The analysis revealed significant small-to-moderate effects of PT on power (ES = 0.60, p

Purpose: To evaluate the metabolic relevance of type of locomotion in anaerobic testing by analyzing and comparing the metabolic profile of the Bosco Continuous Jumping Test (CJ30) with the corresponding profile of the Wingate Anaerobic Test (WAnT). Methods: A total of 11 well-trained, male team-sport athletes (age = 23.7 [2.2] y, height = 184.1 [2.8] cm, weight = 82.4 [6.4] kg) completed a CJ30 and WAnT each. During the WAnT, power data and revolutions per minute were recorded, and during the CJ30, jump height and jumping frequency were recorded. In addition, oxygen uptake and blood lactate concentration were assessed, and metabolic profiles were determined via the PCr-LA-O2 method. Results: In the CJ30, metabolic energy was lower (109.3 [18.0] vs 143.0 [13.1] kJ, P <.001, d = −2.302), while peak power (24.8 [4.4] vs 11.8 [0.5] W·kg−1, P <.001, d = 3.59) and mean power (20.8 [3.6] vs 9.1 [0.5] W·kg−1, P <.001, d = 4.14) were higher than in the WAnT. The metabolic profiles of the CJ30 (aerobic energy = 20.00% [4.7%], anaerobic alactic energy [WPCr] = 45.6% [4.5%], anaerobic lactic energy = 34.4% [5.2%]) and the WAnT (aerobic energy = 16.0% [3.0%], anaerobic alactic WPCr = 34.5% [5.0%], anaerobic lactic energy = 49.5% [3.3%]) are highly anaerobic. Absolute energy contribution for the CJ30 and WAnT was equal in WPCr (49.9 [11.1] vs 50.2 [11.2] kJ), but anaerobic lactic energy (37.7 [7.7] vs 69.9 [5.3] kJ) and aerobic energy (20.6 [5.7] vs 23.0 [4.0] kJ) were higher in the WAnT. Mechanical efficiency was substantially higher in the CJ30 (37.9% [4.5%] vs 15.6% [1.0%], P <.001, d = 6.86), while the fatigue index was lower (18.5% [3.8%] vs 23.2% [3.1%], P <.001, d = −1.38) than in the WAnT. Conclusions: Although the anaerobic share in both tests is similar and predominant, the CJ30 primarily taxes the WPCr system, while the WAnT more strongly relies on the glycolytic pathway. Thus, the 2 tests should not be used interchangeably, and the type of locomotion seems crucial when choosing an anaerobic test for a specific sport. [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]

Objectives: Drop jump (DJ) is a typical exercise of plyometric training in which the state before takeoff (pre-set phase) influences the force exertion of the lower limbs during takeoff, as well as performance variables. This study aimed to examine the effects of watching an instructional movie during the pre-set phase on the performance and lower limb kinematic and kinetic variables during plyometric training.Methods: Fourteen participants (age, 21.9 ± 2.1 years; height, 175.6 ± 2.6 cm; weight, 70.7 ± 4.9 kg) were enrolled in this study. Seven participants with a high rebound jump (RJ) index under normal conditions were classified into the high RJ-index group. Seven participants with a low RJ-index were classified into the low RJ-index group. DJs were performed under normal conditions and under the movie condition (DJ immediately after watching the instructional movie during the pre-set phase). Performance and kinematic and kinetic variables of the lower limb joints were measured.Results: Compared with the normal condition, the movie condition was associated with a significantly high RJ-index, lesser degree of knee flexion (p < 0.011), and significantly larger concentric torque (p < 0.018) of the ankle. An interaction effect was observed for the eccentric torque (p < 0.025) and positive power (p < 0.004) of the ankle, which were significantly greater in the high RJ-index group under the movie condition.Conclusion: Watching an instructional movie during the pre-set phase improves the movement and force production of the ankle and knee joint, which, in turn, improves the DJ performance. However, the effects may be more pronounced in participants with a high RJ-index.

Rapid force production and its transmission to the skeleton are important factors in movements that involve the stretch-shortening cycle. Plyometric exercises are known to augment this cycle and thereby improve the neuromechanical function of the muscle. However, the training exercises that maximize translation of these gains to sports performance are not well defined. We discuss ways to improve this transfer. [ABSTRACT FROM AUTHOR]

Attentional focus strategies eliciting external focus of attention effectively enhance drop jump (DJ) performance, however, their effects vary depending on the words used for the instructions. We aimed to examine the effects of different words on DJ performance using instructions eliciting external focus to minimize contact time (CT) or maximize jump height (JH). Twenty collegiate athletes performed DJs from a 30-cm platform after receiving one of the four instructions: two instructions (COND 1 and 2) about minimizing CT, and two instructions (COND 3 and 4) about maximizing JH. The reactive strength index (RSI), CT, JH, relative peak vertical ground reaction force (vGRF), and leg stiffness (kvert) were compared between conditions using repeated-measures analysis of variance. There was no significant main effect of conditions on the RSI, relative peak vGRF, and kvert (p > 0.05). CT was significantly shorter under CONDs 1 and 2 than COND 3 (p < 0.05); JH was significantly higher under COND 3 than CONDs 1 and 2 (p < 0.05), and under COND 4 than COND 1 (p < 0.05). When using attentional focus strategies in DJ, it is necessary to use different words and purposes according to the players' tasks. [ABSTRACT FROM AUTHOR]

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The aim of the study was to examine the inter-limb asymmetry in force application in a 1-s maximum isometric leg press test (ISOM) and vertical jump tests without an arm swing (VJ)of male long jumpers. Nine experienced jumpers (age: 18–30 y, LJ personal best: 6.50–8.05 m) were examined. Participants performed: (a) bilateral VJs from the squatting position (SQJ) and with a countermovement (CMJ), (b) unilateral CMJ from the take-off (TOL) and swing (SWL) leg used in the LJ take-off, and c) bilateral 1-s ISOM tests. Data were collected for each lower limb with separate force dynamometers (sampling frequency: VJs = 1 kHz, ISOM = 500 Hz). The inter-limb asymmetry of the peak applied force was evaluated using the symmetry angle. The paired samples T-test revealed non-significant (p > 0.05) inter-limb differences for the force output in the bilateral jump tests, in the unilateral jump tests, and in the ISOM. In conclusion, despite the fact that a powerful unilateral take-off is required for the optimization of long jump performance, no asymmetry was found in the examined tests, suggesting that the dominant/take-off leg was not stronger than the contra-lateral leg. This is possibly due to the intensive execution of other bilateral tasks involved, like the approach run. [ABSTRACT FROM AUTHOR]

This study explored the capabilities of sport climbers to pull up with arms. The methodology aimed at assessing (i) concentric capabilities of arm muscles, (ii) body coordination skills (iii) characteristics of energy storage and (iv) capabilities to resist fatigue. Twenty-eight climbers were tested and the force exerted was recorded during three pull-up exercises: jump tests (with or without coordination, or preceded by an eccentric phase), incrementally weighted pull-ups and maximum number of pull-ups. Force, velocity, muscle power and muscle work were analysed using ANOVA with post-hoc tests and principal component analysis. Correlations with climbing level were also studied. Overall, jump test results showed that body coordination and stretchshortening cycle phenomena contributed significantly to performance but only the body coordination was related to the climber's grade level. Muscle work and maximum number of pull-ups are correlated with climbing level which showed that the capacity to resist fatigue is another crucial capability of climbers arms. The development of force capacities appeared crucial for performing whereas the velocity capabilities seemed to originate from the climber's own characteristics/style without correlating with climbing performance. Our study provides the basis for evaluating these parameters in order to help trainers in the diagnosis process and training follow-up. [ABSTRACT FROM AUTHOR]

Little is known about the differences in vertical jump biomechanics executed on rigid (RJS) and sand (SJS) surfaces in female indoor and beach volleyball players. Eleven young female beach volleyball players with a combined indoor and beach volleyball sport background performed squat jumps, countermovement jumps with and without an arm swing, and drop jumps from 40 cm on a RJS (force plate) and SJS (sand pit attached to the force plate). The results of the 2 (surface) × 4 (vertical jump test) repeated-measure ANOVA revealed a significant (p < 0.05) main effect of the surface and the vertical jump test on the jump height and time to achieve peak vertical body center of mass velocity. A significant (p < 0.05) main effect of the test, but not of the surface (p > 0.05), was observed for the other examined biomechanical parameters. The only significant (p < 0.05) jump height gain difference between RJS and SJS was observed for the utilization of the stretch-shortening cycle, which was higher in SJS (15.4%) compared to RJS (7.5%). In conclusion, as the testing was conducted during the beach volleyball competitive season, the examined female players showed adaptations relating the effective utilization of the pre-stretch and enhanced stability during the execution of the vertical jump tests on a SJS compared to RJS. [ABSTRACT FROM AUTHOR]

This study examined the relationship between Achilles tendon (AT) length and 100-m sprint time in sprinters. The AT lengths at 3 different portions of the triceps surae muscle in 48 well-trained sprinters were measured using magnetic resonance imaging. The 3 AT lengths were calculated as the distance from the calcaneal tuberosity to the muscle–tendon junction of the soleus, gastrocnemius medialis, and gastrocnemius lateralis, respectively. The absolute 3 AT lengths did not correlate significantly with personal best 100-m sprint time (r = −.023 to.064, all Ps >.05). Furthermore, to minimize the differences in the leg length among participants, the 3 AT lengths were normalized to the shank length, and the relative 3 AT lengths did not correlate significantly with personal best 100-m sprint time (r =.023 to.102, all Ps >.05). Additionally, no significant correlations were observed between the absolute and relative (normalized to body mass) cross-sectional areas of the AT and personal best 100-m sprint time (r =.012 and.084, respectively, both Ps >.05). These findings suggest that the AT morphological variables, including the length, may not be related to superior 100-m sprint time in sprinters. [ABSTRACT FROM AUTHOR]

The inability to control the body center of mass (BCM) initial conditions, when executing plyometric exercises, comprises a restrictive factor to accurately compare jumps executed vertically and horizontally. The purpose of the study was to present a methodological approach for the examination of BCM initial conditions during vertical drop jumps (VDJ) and plyometric rebound jumps performed with a pendulum swing (HPRJ). A system consisting of two force plates was used for the evaluation of VDJ. A bifilar pendulum, equipped with a goniometer and accelerometer, was constructed for the evaluation of the HPRJ. Kinematic parameters from both jump modalities were obtained by means of videography (100 Hz). Thirty-eight physically active young males executed VDJ and HPRJ with identical BCM kinetic energy at the instant of impact (KEI). Results revealed that participants produced higher power and lower force outputs at HPRJ (p < 0.01). The rate of force development was larger in VDJ, while hip movement was less in HPRJ. The use of the presented methodology provided the means to reliably determine the exact BCM release height during the execution of the examined jumps. This provided an accurate determination of the amount of KEI, being the main parameter of calculating load during plyometric exercise.

This study investigates the associations between countermovement rebound jump (CMRJ) performance metrics and various independent measures of athletic performance, including the isometric mid-thigh pull (IMTP), 20 m linear sprint, and 505 change-of-direction (COD) speed tests. Pearson’s correlations were used to analyse the relationship between the CMRJ measures with athletic performance, with significance being set at p ≤ 0.006. Results showed large significant positive relationships between IMTP peak force and force at 300 milliseconds with the first jump height of the CMRJ (JH-1, r = 0.54 to 0.55, p ≤ 0.002). Additionally, inverse relationships were observed between reactive strength index modified (RSImod) and reactive strength index (RSI) with 20 m sprint total and split times (r = −0.55 to −0.66, p ≤ 0.001), and the 10 m and total sprint times were significantly correlated with JH-1 (r = −0.54, p = 0.003), indicating that greater vertical explosive power and reactive strength are associated with faster sprint performance. Finally, a significant inverse relationship was identified between CMRJ metrics (two JH values and RSImod) and 505 COD times in both the left and right sides (r = −0.51 to −0.68, p ≤ 0.006). These findings suggest that CMRJ performance metrics are valuable indicators of lower-limb explosive force production, with a strong link to both linear sprint and COD performance. The finding underscores the importance of including CMRJ assessments in athletic performance evaluations due to their dual assessment capacity of slow and fast stretch–shortening cycle mechanics.

Sprint and jump abilities are considered basic skills that are regularly evaluated in training and school contexts. The correlations between these two skills have previously been established in adults and adolescents, but they have not been fully assessed in children. The present study aimed to explore sprinting and jumping ability in prepubertal boys and girls. Thirty-one prepubertal individuals (aged 8–11 years) were assessed during sprinting for different distances (5, 10, and 20 m) and using different vertical and horizontal jump modalities (squat jump, countermovement jump, broad jump, and hop test). Correlations between the different results were tested. Strong correlations were found between vertical jump and sprint performances, especially over short distances. These results suggested that vertical jump tests are more sensitive than horizontal jumps to reveal acceleration capacity in children.

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]

Background: By directly recording electromyographic activity profiles and muscle-tendon interaction, this study aimed to elucidate the mechanisms why well-trained track and field athletes (experts) are able to outperform untrained individuals without former systematic experience in reactive jump training (novices). In particular, reactive power output and the elastic recoil properties of the muscle-tendon unit (MTU) were of special interest. For this purpose, stiffness regulation on muscle and joint level, energy management in terms of storing or dissipating elastic energy were compared between experts and novices during various stretch loads.Methods: Experts were compared with novices during reactive drop jumps (DJs) from drop heights ranging between 25 and 61 cm. Delta kinetic energy (Ekin) was calculated as the difference between the Ekin at take-off and ground contact (GC) to determine energy management. By recording electromyography of the lower limb muscles, in vivo fascicle dynamics (gastrocnemius medialis) and by combining kinematics and kinetics in a 3D inverse dynamics approach to compute ankle and knee joint kinetics, this study aimed to compare reactive jump performance, the neuromuscular activity and muscle-tendon interaction between experts and novices among the tested stretch loads.Results: Experts demonstrated significantly higher power output during DJs. Among all drop heights experts realized higher delta Ekin compared to novices. Consequently, higher reactive jump performance shown for experts was characterized by shorter GC time (GCT), higher jump heights and higher neuromuscular activity before and during the GC phase compared to novices. Concomitantly, experts were able to realize highest leg stiffness and delta Ekin in the lowest stretch load; however, both groups compensated the highest stretch load by prolonged GCT and greater joint flexion. On muscle level, experts work quasi-isometrically in the highest stretch load, while in novices GM fascicles were forcefully stretched.Conclusion: Group-specific stiffness regulation and elastic recoil properties are primarily influenced by the neuromuscular system. Due to their higher neuromuscular activity prior and during the GC phase, experts demonstrate higher force generating capacity. A functionally stiffer myotendinous system through enhanced neuromuscular input enables the experts loading their elastic recoil system more efficiently, thus realizing higher reactive power output and allowing a higher amount of energy storage and return. This mechanism is regulated in a stretch load dependent manner.

This study explored the capabilities of sport climbers to pull up with arms. The methodology aimed at assessing (i) concentric capabilities of arm muscles, (ii) body coordination skills (iii) characteristics of energy storage and (iv) capabilities to resist fatigue. Twenty-eight climbers were tested and the force exerted was recorded during three pull-up exercises: jump tests (with or without coordination, or preceded by an eccentric phase), incrementally weighted pull-ups and maximum number of pull-ups. Force, velocity, muscle power and muscle work were analysed using ANOVA with post-hoc tests and principal component analysis. Correlations with climbing level were also studied. Overall, jump test results showed that body coordination and stretch-shortening cycle phenomena contributed significantly to performance but only the body coordination was related to the climber’s grade level. Muscle work and maximum number of pull-ups are correlated with climbing level which showed that the capacity to resist fatigue is another crucial capability of climbers arms. The development of force capacities appeared crucial for performing whereas the velocity capabilities seemed to originate from the climber’s own characteristics/style without correlating with climbing performance. Our study provides the basis for evaluating these parameters in order to help trainers in the diagnosis process and training follow-up.