The aim of this study was to compare the effects of 3 sets of isometric conditioning activity (ICA), each with an equal total duration (9 s per set) but with different distributions contractions, on force production during ICA and subsequent countermovement jump (CMJ) performance. Fifteen resistance-trained males participated in this study (age: 22.1 ± 2.4 years; body mass: 85.1 ± 9.7 kg; height: 181.3 ± 6.5 cm; relative one-repetition maximum (1RM) in back squat: 1.59 ± 0.32 kg/kg of body mass). Participants completed 3 conditions, each consisting of ICA in the half-back squat with a pushing isometric muscle action (PIMA) position at a 120-degree knee angle against an immovable barbell, differing in repetition distribution: 3 sets of 9 repetitions lasting 1 s each (SUST-1), 3 sets of 3 repetitions lasting 3 s each (SUST-3), 3 sets of single repetitions lasting 9 s (SUST-9), and a control condition (CTRL) without ICA. A 1-minute rest was allowed between sets. Approximately 3 min pre-ICA and at 15 s, 3-, 6-, 9-, and 12-minutes post-ICA, the CMJ performance was assessed. Moreover, peak force (PF) production, and force generated at 100 (Force100) and 200 ms (Force200) during each ICA were evaluated. A two-way repeated measures ANOVA indicated a main effect of time on CMJ height (F = 2.674; p = 0.029; ηp²=0.171) but did not show significant differences between conditions (F = 0.934; p = 0.434; ηp²=0.067) or interactions (F = 0.826; p = 0.648; ηp²=0.060). Post-hoc comparisons indicated a significant decrease in CMJ height at the 9th minute compared to the 3rd minute (35.7 ± 5.6 cm vs. 36.8 ± 5.5 cm post-CA; d = 0.161; p = 0.048). In addition, no significant interactions or main effects were found for CMJ contraction time, PF and Force100 during ICA. However, a main effect of condition was demonstrated on Force200 (F = 19.181; p < 0.001; ηp²= 0.013). Post-hoc comparisons revealed higher Force200 values in SUST-1 (mean difference [MD] = 549 ± 137 N; d = 1.049; p < 0.001) and SUST-3 (MD = 348 ± 112 N; d = 0.665; p = 0.002) compared to the SUST-9 condition. None of the ICAs used in the present study had any effect on the CMJ performance. However, the significantly higher Force200 values noted in the SUST-1, and SUST-3 conditions compared to the SUST-9 condition suggest that the specific distributions of isometric contraction influence the force generated during their execution.

• Klíčová slova
• Force production, Isometric contraction distribution, Isometric squat, Post-activation performance enhancement,
• MeSH
• dospělí MeSH
• isometrická kontrakce * fyziologie   MeSH
• kosterní svaly * fyziologie   MeSH
• lidé MeSH
• mladý dospělý MeSH
• odporový trénink * metody   MeSH
• sportovní výkon * fyziologie   MeSH
• svalová síla fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The post-activation performance enhancement (PAPE) effect has been widely studied; however, its repeatability across training sessions during the competitive season in team sports has not yet been verified. Therefore, this study investigates whether PAPE effect, as measured by the countermovement jump (CMJ) without arm swing, induced by an maximum voluntary isometric squat as a conditioning activity (ICA) three days after the match, could be replicated over a 4-week training period throughout the season. The study also explores whether the magnitude of acute PAPE responses correlates with match running variables, as monitored by global positioning system (GPS) data. METHODS: Fifteen national level soccer players participated in the study (mean age: 26.9 ± 4.2 years, body mass: 79.2 ± 6.5 kg, height: 182.1 ± 6.5 cm, experience in soccer training: 11.2 ± 4.2 years, experience in strength training: 10.5 ± 4.6 years, relative maximal strength in squat: 1.84 kg/body mass). Each participant performed 1 repetition of the CMJ approximately 120 s before (pre-ICA) and approximately 60 s after (as post-ICA) 1 set of maximum voluntary isometric squat using a Smith machine as the ICA lasting 5 s. The measurements were repeated across 4 testing sessions performed week apart and each time 3 days after the soccer match. Moreover, running performance variables during matches including total distance, high-speed running distance, sprint distance, player load, total number of accelerations, total number of decelerations were collected via GPS system. RESULTS: A two-way repeated-measures ANOVA showed a significant main effect of time, indicating an increase in CMJ height (mean difference = 1.05 ± 0.3 cm; Cohen's d = 0.222; p = 0.005) post-ICA compared to pre-ICA. The one-way ANOVA did not reveal significant differences between sessions, which may indicate repeatable acute PAPE responses (F = 0.093, p = 0.963, η2p = 0.006). Additionally, the one-way ANOVAs did not reveal significant differences in all GPS data between particular soccer matches (p > 0.145; for all). The interclass correlation coefficient for the PAPE response was poor to moderate (interclass correlation coefficient = 0.56, 95% confidence interval: 0.06-0.83). The Cochran's Q test indicated that PAPE response distributions varied across sessions (p = 0.018). However, pairwise McNemar tests did not reveal significant differences (p = 0.549-1.000), suggesting that while response distribution fluctuated, no specific session-to-session differences were detected. Moreover, Pearson's product-moment correlation coefficient, did not show significant correlation between the percentage PAPE responses and all of match GPS data variables (p > 0.074; for all). CONCLUSIONS: The findings suggest that ICA can consistently elicit a PAPE response of small magnitude in national-level soccer players with a short 60-s rest interval. However, the variability in individual responsiveness and the lack of a relationship with running variables monitored via GPS during soccer matches indicate that other physiological and neuromuscular factors may influence the magnitude of PAPE responses. Given this variability, individually monitoring PAPE responsiveness may be beneficial for optimizing its application.

• Klíčová slova
• Isometric conditioning activity, Post-activation performance enhancement, Vertical jump,
• Publikační typ
• časopisecké články MeSH

BACKGROUND: The study aimed to assess the acute effects of overcoming isometric split squats on subsequent single-leg drop jump (DJ) performance and the contralateral effect in volleyball players, considering training status differences. METHODS: Ten male elite (ELI) and ten amateur (AMA) volleyball players took part in two experimental sessions in which they performed conditioning activity (CA) consisted of 3 sets of overcoming isometric 3-second split squats, differing in the limb used: dominant (DL) or non-dominant (ND-L). Single-leg DJ was performed before and at the 4th and 8th minute post-CA for both limbs. The best post-CA attempt in terms of jump height (JH) was analyzed. RESULTS: Results revealed a significant increase in jump height (JH) in the non-dominant limb (ND-L) from 13.7 ± 2.6 cm to 15.5 ± 2.7 cm after CA performed by the ND-L (p = 0.001; Hedge's g = 0.65). Similarly, the reactive strength index (RSI) of the ND-L improved from 0.40 ± 0.06 to 0.45 ± 0.08 (p = 0.008; g = 0.58). Additionally, contact time in the ND-L increased significantly from 342 ± 36 ms to 375 ± 42 ms after CA performed by the dominant limb (p = 0.001; g = 0.66). In the elite (ELI) group, JH significantly increased from 16.4 ± 2.4 cm to 18.3 ± 3.3 cm (p < 0.001; g = 0.79), while RSI in the dominant limb (DL) improved from 0.47 ± 0.06 to 0.53 ± 0.07 (p = 0.011; g = 0.68). CONCLUSIONS: Results suggest that the examined CA effectively induces the post-activation performance enhancement in DJ among elite volleyball players, with a predominantly local impact on the limb executing the CA. TRIAL REGISTRATION: NCT06459050 (Retrospectively registered).

• Klíčová slova
• Explosive strength, Isometric exercise, Neuromuscular performance, Plyometric training, Post-activation potentiation, Unilateral movement,
• Publikační typ
• časopisecké články MeSH

This study aimed to investigate the effects of performing either eccentric-only (ECC) or eccentric-concentric (ECC-CON) back squats (BS) with a supramaximal load on countermovement jump (CMJ) performance. Changes in front thigh skin surface temperature and mechanical properties (oscillation frequency and stiffness) of the vastus lateralis were also examined. Fourteen male powerlifters participated in this study (age: 22.5 ± 2.3 years, body weight: 84.2 ± 11.1 kg, height: 178 ± 7 cm, training experience: 5.4 ± 1.6 years, BS one-repetition maximum [1RM]: 177 ± 22.8 kg). The experimental sessions included 2 sets of 2 BS at 110% 1RM of either ECC-CON (load distributed by half on the barbell [55%] and on weight releasers [55%]) or ECC (only eccentric phase of BS) and CTRL with no CA applied. CMJ performance, mechanical properties, and skin surface temperature were measured before and at the third, sixth, ninth, and 12th min. After each protocol, only the ECC-CON condition led to a significant increase in CMJ height after individual optimal rest time compared to pre-CA (38.1 ± 5.2 vs. 39.8 ± 5.0 cm; p = 0.003; effect size [ES] = 0.32; Δ = 4.9 ± 5.0%) with a significant rise in skin surface temperature (32.98 ± 1.24 vs. 33.69 ± 0.96°C; p = 0.006; ES = 0.62; Δ = 2.2 ± 2.6%) and no significant changes in mechanical properties of the vastus lateralis. The ECC-CON condition led to a significant acute improvement in CMJ height and an increase in front thigh skin surface temperature among powerlifters. The ECC-CON supramaximal lower limb PAPE protocol should be effectively used among males representing high levels of lower limb muscle strength (>2 × body mass).

• Klíčová slova
• accentuated eccentric loading, muscle strength, post‐activation performance enhancement, post‐activation potentiation, power output, weight releasers,
• MeSH
• biomechanika MeSH
• čtyřhlavý sval stehenní fyziologie   MeSH
• dospělí MeSH
• kosterní svaly fyziologie   MeSH
• lidé MeSH
• mladý dospělý MeSH
• odporový trénink MeSH
• sportovní výkon * fyziologie   MeSH
• stehno fyziologie   MeSH
• svalová síla fyziologie   MeSH
• teplota kůže * fyziologie   MeSH
• vzpírání * fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

Knowledge about the acute effects of supramaximal-loaded resistance exercises on muscle mechanical properties is scarce. Therefore, this study aimed to examine changes in dominant limb biceps femoris and vastus lateralis oscillation frequency and stiffness before and after high- and supramaximal-loaded front squats. Nineteen male handball players participated in the experimental session with a barbell front squat 1RM. The first set was performed at 70% of the 1RM for four repetitions, and the second and third sets were performed at 90%1RM in an eccentric-concentric or an eccentric-only manner at 120% of the 1RM for three repetitions. The handheld myometer was used for the measurement of the biceps femoris and vastus lateralis stiffness and the oscillation frequency of the dominant limb 5 min before and at the 5th and 10th min after front squats. A two-way ANOVA neither indicated a statistically significant interaction (p = 0.335; η2 = 0.059 and p = 0.103; η2 = 0.118), the main effect of a condition (p = 0.124; η2 = 0.126 and p = 0.197; η2 = 0.091), nor the main effect of the time point (p = 0.314; η2 = 0.06 and p = 0.196; η2 = 0.089) for vastus lateralis and biceps femoris stiffness. However, there was a statistically significant interaction (F = 3.516; p = 0.04; η2 = 0.163) for vastus lateralis oscillation frequency. The post hoc analysis showed a significantly higher vastus lateralis oscillation frequency at POST (p = 0.037; d = 0.29) and POST_10 (p = 0.02; d = 0.29) compared to PRE during the SUPRA condition. Moreover, Friedman's test indicated statistically significant differences in biceps femoris oscillation frequency (test = 15.482; p = 0.008; Kendall's W = 0.163). Pairwise comparison showed a significantly lower biceps femoris oscillation frequency in POST (p = 0.042; d = 0.31) and POST_10 (p = 0.015; d = 0.2) during the HIGH condition compared to that in the corresponding time points during the SUPRA condition. The results of this study indicate that the SUPRA front squats, compared to the high-loaded ones, cause a significant increase in biceps femoris and vastus lateralis oscillation frequency.

• Klíčová slova
• eccentric, fatigue, muscle tone, myotonometry, resistance training, stiffness,
• Publikační typ
• časopisecké články MeSH

The goal of this study was to compare the effects of a bilateral conditioning activity consisting of back squats and drop jumps with a unilateral one consisting of split squats and depth jumps to lateral hop over sequentially performed countermovement jump (CMJ), modified t-agility test (MAT), and Achilles tendon stiffness. Twenty-six basketball players participated in this study and were randomly and equally assigned to one of two different test groups: bilateral (B - CA) or unilateral (U - CA) conditioning activity group. The B - CA group completed 2 sets of 4 repetitions of back squats at 80% of one-repetition maximum (1RM), then 10 drop jumps, while the U - CA group performed 2 sets of 2 repetitions of split squats on each leg at 80%1RM, followed by 5 depth jumps to lateral hop on each leg as conditioning activity (CA) complexes. After a warm-up and 5 min before the CA the baseline Achilles tendon stiffness, CMJ, and MAT time measurement were performed. In the 6th min after the CA, all tests were re-tested in the same order. The two-way repeated measures mixed ANOVAs revealed that both B - CA and U - CA failed to produce significant improvements in CMJ and MAT performance. In addition, a significant increase in Achilles stiffness was demonstrated with both protocols (a main effect of time: p = 0.017; effect size = 0.47; medium). This study revealed that combining back squats and drop jumps, as well as split squats and depth jumps to a lateral hop, had no effect on subsequent CMJ and MAT performance in basketball players. Based on these results, it can be assumed that combinations of exercises, even if they have similar movement patterns, may cause excessive fatigue, resulting in no PAPE effect.

• Klíčová slova
• PAPE, Post-activation performance enhancement, change of direction, countermovement jump,
• MeSH
• Achillova šlacha * MeSH
• basketbal * MeSH
• cvičení MeSH
• lidé MeSH
• postura těla MeSH
• sportovní výkon * MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• randomizované kontrolované studie MeSH