Search Results (194)

Objectives: Volleyball playing positions are associated with different functional demands. This study compared postural control, jump performance, and upper-limb mobility across playing roles in competitive male volleyball players. Methods: Fifty male volleyball players competing in the Italian Serie C championship were equally distributed across five roles: middle blockers (MB), liberos (LIB), opposite hitters (OH), setters (SET), and outside hitters (HIT). Using a wearable inertial sensor, athletes performed bipodalic balance tasks with eyes open and closed, dominant- and non-dominant-leg single-leg balance, squat jump (SJ), countermovement jump (CMJ), and bilateral upper-limb flexion and extension tests. Results: Significant role-related differences emerged in balance and jump performance. In bipodalic balance, the eyes-open condition showed a mixed pattern, with HIT displaying the largest ellipse area and SET showing the highest path-related values, whereas in the eyes-closed condition, HIT showed the highest values across all stabilometric parameters. In the single-leg stance, OH showed the largest postural excursions on the dominant side, while LIB stood out on the non-dominant side. In jump tests, MB showed the best vertical performance in both SJ and CMJ, whereas LIB and SET generally showed the lowest outputs. Temporal differences also emerged across roles. Upper-limb mobility was similar across roles in flexion, while extension showed a role-specific pattern, with SET displaying greater ROM than LIB, HIT, and OH. Conclusions: Volleyball roles are associated with distinct functional profiles in balance, jump mechanics, and upper-limb mobility. This integrated assessment may support more specific training, monitoring, and injury-prevention strategies. Full article

Background and Objectives: Conditioning activities (CAs) are commonly used to induce post-activation performance enhancement (PAPE); however, it remains unclear whether load-dependent responses established in bilateral, predominantly isotonic models extend to unilateral split squat conditions. In particular, evidence regarding holding isometric muscle action (HIMA) is limited, and it is unknown how external load and holding duration interact to influence both performance outcomes and phase-specific muscle activation. Therefore, this study examined the acute effects of HIMA duration and external load during unilateral split squat CA on jump performance and phase-specific electromyographic (EMG) activity. Materials and Methods: Twenty recreationally active men completed a randomized, counterbalanced crossover design involving four split squat CA conditions, unloaded 3 s, unloaded 5 s, 3 s loaded (60% 1RM), and 5 s loaded (60% 1RM), each performed as three sets of three repetitions. To minimize fatigue effects, standardized rest intervals and familiarization sessions were implemented prior to testing. Single-leg jump (SLJ) and countermovement jump (CMJ) were assessed before and after CA, with post-activation measurements conducted at 3 min (SLJ) and 4 min (CMJ), consistent with established PAPE time windows. Surface EMG was time-normalized across the split squat cycle and analyzed using phase-specific area under the curve. Results: CMJ significantly increased following both loaded conditions (p < 0.05; moderate to large effect sizes), whereas no differences were observed between unloaded durations. External load consistently elevated EMG amplitude across all measured muscles (moderate to large effects). Extending duration under load further increased activation in the hamstrings, stabilizers, vastus medialis, and gastrocnemius medialis (p < 0.05; small to moderate effects), whereas unloaded conditions showed minimal neuromuscular differences. Conclusions: External load, rather than isometric holding duration, appears to be a key factor influencing acute PAPE responses in unilateral split squat HIMA, whereas prolonged holding duration may primarily modulate muscle recruitment patterns without additional performance gains. However, given the acute experimental design and a recreationally active sample, these findings should be interpreted with caution and considered exploratory. Further studies are warranted to confirm these effects across different populations and longer-term training conditions. Full article

Pre-elite female field hockey players have a high incidence of lower extremity injury, highlighting the need for practical and reliable screening approaches. A dual assessment combining Functional Performance Tests (FPTs) with movement quality scoring (QASLS) may provide a more comprehensive evaluation; however, its reliability in this population is unclear. Fifteen pre-elite female field hockey players (16.7 ± 0.7 years) completed an FPT battery (anterior reach (AR), single leg drop vertical jump–land (DVJL), single hop for distance (SHFD), side hop (SH)) on two occasions, 28 days apart. Movement quality was assessed by three raters using QASLS. Reliability was evaluated using ICC with 95% confidence intervals (CI), alongside standard error of measurement (SEM), smallest detectable difference (SDD), and percentage exact agreement (PEA). Test–retest reliability varied across tasks (ICC_2,1 0.33–0.90), with wide confidence intervals indicating uncertainty in several estimates. AR demonstrated the most consistent reliability, supporting its use for monitoring over time. In contrast, the DVJL and SH showed the greatest variability, likely reflecting higher task complexity, while the SHFD required relatively large performance changes to exceed measurement error. Intra-rater reliability for QASLS was consistent across the FPT battery (ICC_2,k 0.79–0.90), whereas inter-rater reliability was more variable (0.38–0.82), indicating rater-dependent differences. PEA demonstrated generally high agreement (60–100%), although lower agreement was observed for pelvic alignment components. These findings support the use of a dual assessment approach as a practicable profiling approach in pre-elite female field hockey, enabling practitioners to identify movement deficits not captured by performance metrics alone. However, variability in complex tasks and between raters highlights the need to consider measurement error and implement standardised rater training when profiling or monitoring performance. Full article

Background and Objectives: The assessment of neuromuscular recovery after ACL reconstruction is crucial for safe return to sport (RTS) in professional soccer players. This retrospective cross-sectional study aimed to compare squat jump (SJ), bilateral countermovement jump (CMJ), and single-leg CMJ performance in three distinct groups: players at 6 months post-ACL reconstruction, players at 9 months post-ACL reconstruction, and healthy controls. Materials and Methods: Seventy-two male players (24 at 6 months post-ACL, 24 at 9 months post-ACL, 24 healthy controls) performed squat jump, bilateral countermovement jump, and single-leg CMJ tests using contact platforms following a controlled warm-up protocol. Results: Significant group differences were observed in all jump tests. At 6 months post-ACL reconstruction, players demonstrated significantly lower squat jump (45.13 ± 6.20 cm) and bilateral countermovement jump (49.67 ± 6.80 cm) heights compared to both 9-month players (SJ: 50.03 ± 5.30 cm; CMJ: 53.79 ± 4.85 cm) and controls (SJ: 51.12 ± 4.97 cm; CMJ: 55.49 ± 5.54 cm) (p ≤ 0.016, η² = 0.187 and η² = 0.156, respectively). No significant differences between 9-month and control groups were observed for the squat jump and the bilateral countermovement jump. Regarding the unilateral countermovement jump, the injured leg showed significant performance deficits compared to controls in both the 6-month and 9-month groups (p = 0.001, η² = 0.378). However, the non-injured leg exhibited deficits only in the 6-month group. Conclusions: Compared to the 6-month post-ACL reconstruction group, the 9-month group showed a marked improvement in bilateral jump performance, indicating substantial neuromuscular recovery over time. However, persistent unilateral deficits in the injured leg remained even at 9 months, underscoring the need for a routine and comprehensive jumping evaluation to identify residual neuromuscular impairments that may require targeted rehabilitation before returning to sport. Full article

This study investigated interlimb asymmetries in lower limb performance using both vertical and horizontal jump tests in elite young basketball players. Specifically, it aimed to determine whether (1) unilateral jump performance and (2) the magnitude of interlimb asymmetry differed across maturity groups, whether (3) limb dominance influences performance, and whether (4) asymmetry direction is consistent across tests. One hundred elite male basketball players (U13 to U19) were categorised into three maturational stages: Pre-PHV (n = 19), Circa-PHV (n = 29), and Post-PHV (n = 52). Each athlete performed the following unilateral tests with both the dominant and non-dominant leg: single-leg hop, triple hop for distance, 6 m timed hop, single-leg countermovement jump (SL-CMJ), and single-leg drop jump (SL-DJ) from a 30 cm box. The Bilateral Strength Asymmetry (BSA) index was computed for each test. All tests showed significant differences between Pre-PHV and Circa-PHV groups (p < 0.001), whereas only the 6 m timed hop differed between Circa-PHV and Post-PHV (p < 0.01). BSA did not differ significantly across maturation stages in any test, except for the single-leg hop. Agreement in asymmetry direction between test pairs was slight to fair (kappa ≤ 0.29). BSA values remained largely stable across maturational stages, suggesting that interlimb asymmetries are established before PHV, likely during childhood. Limb dominance did not affect jump performance, and asymmetry direction varied between tests, confirming they are not interchangeable. Full article

Ankle dorsiflexion range of motion (ADF-ROM) deficits has been linked to impaired function, altered gait, and injury risk. This study’s objective was to examine the acute effects of static self-stretching (SSS), foam rolling (FR), and instrument-assisted soft tissue mobilization (IASTM) of the posterior lower-leg on ADF-ROM and functional ankle outcomes in individuals with ADF-ROM deficits. Thirteen healthy, physically active college students with active ADF-ROM ≤ 13°, assessed in a non-weight-bearing position, completed all three interventions in a randomized, within-subject repeated-measures design. Pre- and post-intervention assessments included ADF-ROM, ankle plantar flexor isometric strength (APF-IS), single-leg countermovement vertical jump (SLCVJ), anterior reach distance in the Y-Balance Test (A-YBT), and gait parameters (contact time and plantar pressure). A two-way repeated-measures ANOVA with Bonferroni post hoc tests was used. Effect sizes reported as partial eta squared (${\eta }_p^2$) and Cohen $d_{\mathrm{z}}$. All interventions significantly improved ADF-ROM (p < 0.001; ${\eta }_p^2$ = 0.885), with IASTM showing the largest increase (50.7%, $d_{\mathrm{z}}$= 2.15), followed by FR (35.4%, $d_{\mathrm{z}}$ = 2.20) and SSS (21.5%, $d_{\mathrm{z}}$ = 1.82). Differences between IASTM and FR (p > 0.05, $d_{\mathrm{z}}$ = 0.40) and between FR and SSS (p > 0.05, $d_{\mathrm{z}}$ = 0.69) were nonsignificant, while IASTM was significantly greater than SSS (p < 0.05, $d_{\mathrm{z}}$ = 0.92). Significant gains were also seen in A-YBT (p < 0.05; ${\eta }_p^2$ = 0.302) and rearfoot plantar pressure (p < 0.01; ${\eta }_p^2$ = 0.482), although pairwise comparisons were nonsignificant and demonstrated small-to-moderate effect sizes ($d_{\mathrm{z}}$ = 0.35–0.52). No significant changes occurred in APF-IS, SLCVJ, or contact time and mid- and forefoot plantar pressures during roll-off. In conclusion, all interventions improved ADF-ROM, with IASTM and FR being comparably effective. However, only slight improvements in dynamic balance and certain gait parameters were noted, with no effect on strength or power. Full article

Background: Conditioning activity (CA) is used to elicit post-activation performance enhancement (PAPE), but it is unclear whether load response principles from back squat models generalize to unilateral split squat conditioning when external load and surface instability are manipulated together. Thus, the current study examined acute effects of stable vs. unstable split squat CA with or without external load on jump performance and phase-specific electromyography (EMG). Methods: Twenty men completed a randomized crossover of three CAs (2 × 3 reps): unloaded stable split squat (SS), unloaded BOSU SS, and BOSU loaded at 50% split squat one-repetition maximum. Single leg jump (SLJ) and countermovement jump (CMJ) were assessed pre-CA and at 3 min (SLJ) and 4 min (CMJ) post-CA. EMG was recorded from the biceps femoris (BF), semitendinosus (ST), vastus lateralis (VL), vastus medialis (VM) gluteus medius (Gmed), peroneus longus (PL), gastrocnemius lateralis (GL) and gastrocnemius medialis (GM). Signals were time-normalized across the split squat cycle and quantified using phase-specific area under the curve (AUC) (descending/ascending). Results: SLJ and CMJ increased after all conditions compared with the pre-test (p < 0.05). SS and unloaded BOSU SS produced comparable jump outcomes, whereas BOSU loaded yielded the greatest CMJ increase (p < 0.04). Unloaded BOSU SS selectively increased hamstring activation (BF, ST) without changes in Gmed or PL. BOSU loaded increased EMG amplitude across all measured muscles. Conclusions: External load primarily drives acute CMJ potentiation, whereas instability mainly redistributes recruitment toward the hamstrings without improving jump performance beyond the stable condition. These findings indicated that when the goal is acute jump enhancement, external load should be prioritized, whereas unstable surfaces may be used to selectively target posterior chain activation. Full article

Objective: This randomized controlled trial aimed to investigate how volume-matched unilateral and bilateral jump training affects physical performance in prepubertal and pubertal male youth soccer players and to examine whether maturational status influences these training adaptations. Methods: Sixty-five male soccer players (age 10.5 ± 2.9 years; height 136.7 ± 17.8 cm; body mass 32.8 ± 8.6 kg; maturity offset −1.6 ± 1.0 years) completed an 8-week training program (two sessions/week). Participants were randomly assigned to a bilateral jump group (n = 22), unilateral jump group (n = 22), or control group (n = 21). Performance was evaluated in a single testing session, which included horizontal jump tests (bilateral standing long jump and single-leg hop distance), linear sprint tests over 10 m (acceleration) and 30 m (maximal sprint performance) using timed trials, and change-of-direction (COD) ability assessed via a standardized timed COD test. Results: Significant main effects of time, maturation, and time × group interactions were observed for all outcomes (p ≤ 0.013). A maturation × group interaction was found for bilateral jump performance (p = 0.045), a group effect for 10 m sprint time (p = 0.015), and a time × maturation × group interaction for COD performance (p < 0.001). Both training groups had improved jump performance (jump distance) and 10 m sprint time across maturity levels, while no changes were observed in the control group. For 30 m sprint time, improvements were observed in both training groups in prepubertal players, whereas only the unilateral group showed improvements in pubertal players. COD performance (completion time) improved in the unilateral group at both maturity levels and in the bilateral group at the pubertal level. Conclusions: Structured jump training enhances horizontal jump distance, sprint performance, and COD ability in youth soccer players. Adaptations appear to be influenced by training modality and maturation, although these effects may vary depending on the specific performance task. Full article

This study compared collegiate sprinters from two common admission routes in China to identify pathway-associated differences that may inform subsequent training for athletes entering via the Physical Education College Entrance Examination pathway. Twenty male collegiate sprinters were allocated to a Sports Independent Enrollment group and a Physical Education College Entrance Examination group, with ten participants in each. Participants completed isokinetic knee testing, drop jump tests, static balance tests, and drop jump electromyography assessment. Isokinetic outcomes were largely comparable between groups, although the Sports Independent Enrollment group showed faster time to reach peak torque in the nondominant-side knee extensors. In drop jumps, the Sports Independent Enrollment group demonstrated higher reactive strength, shorter ground contact time, greater leg stiffness normalized to body weight, and shorter propulsion duration. Electromyography patterns differed between groups across movement phases. Balance differences were mainly observed under the single-leg eyes-closed condition in unadjusted comparisons, but none remained significant after false discovery rate adjustment. Overall, between-group differences were more evident in rapid force production and neuromuscular control than in the magnitude of isokinetic strength. These findings provide practical targets for designing subsequent training priorities for athletes entering through the Physical Education College Entrance Examination pathway. Full article

Background and Objectives: Throughout the return-to-play process after anterior cruciate ligament reconstruction (ACLR), clearance criteria and limb symmetry indices (LSI) play an important role in clinical decision-making by helping evaluate patient readiness and informing safe activity progressions, with the goal of reducing re-injury risk. How clearance criteria are implemented in research studies to evaluate patient readiness, specifically in force plate jumping studies, is currently unknown. This scoping review was a focused examination of clearance criteria and limb symmetry indices in studies performing force plate-based jumping assessments with ACLR patients. The research questions guiding this scoping review were as follows: (1) What clearance criteria are reported in studies involving primary ACLR patients who participate in jumping assessments on force plates? (2) What LSI are reported in force plate studies, and what level of symmetry is deemed acceptable to allow for safe participation of ACLR patients who participate in jumping assessments of force plates? Materials and Methods: Nine databases were searched on 7 or 8 September 2024 for three concepts: ACLR, force plates, and movement properties. Inclusion criteria were as follows: (a) primary ACLR patients at least 6 months post-surgery; (b) performing a countermovement or drop jump; (c) collecting at least one kinetic parameter using a force plate. Clearance criteria was operationally defined as a time from surgery boundary, functional or performance-based testing criteria, medical evaluation, or completion/participation in a rehabilitation program. Results: Thirty-five studies were included. Time from surgery was the most frequently reported clearance criteria (26/35; 74.3%), followed by medical evaluation (18/35; 51.4%), and completion of rehabilitation (10/35; 28.6%). Use of LSI as clearance criteria was limited (5/35; 14.3%). Minimum required LSI ranged from 85 to 90% in quadriceps strength and hop testing. Conclusions: Clearance criteria varied by jump type and post-surgical time frame when the participant was tested. Standardized rehabilitation was common prior to 2 years post-surgery, whereas medical clearance was common after 2 years post-surgery. Single leg jumps typically required 2–3 clearance criteria, whereas double leg jumps required 1–2 clearance criteria. Limb symmetry indices were used in combination with two other clearance criteria in studies with single-leg countermovement or drop jumps. Improvements in clearance criteria and adverse event reporting may help improve patient safety and interpretation of findings across studies. Full article

Background: Caffeine is an ergogenic aid shown to delay fatigue, increase arousal, and improve performance. Recommended doses are 3–6 mg/kg BM, although evidence supports lower doses (<3 mg/kg). Some conflicting results have highlighted that lower doses may still be ergogenic, and with new pouch and gum products, further research is warranted. Method: This study investigated the effects of novel low-dose caffeine products on muscular endurance, strength, and power. A repeated-measure, crossover design (pouch 80 mg, gum 80 mg, control gum 0 mg) was employed, recruiting nineteen participants (age 22.4 + 4.8 yrs; weight 72.8 + 16.9 kg; relative caffeine dose 1.1 mg/kg). Participants completed a battery of tests, including 60% 1 RM single leg press (LP) and shoulder press (SP) to exhaustion, counter-movement jump, and isometric mid-thigh pull, in addition to providing ratings of perceived exertion (RPE) during endurance tests. One-way repeated measures ANOVA was conducted on all measures associated with physical tasks, with a two-way repeated measures ANOVA conducted for RPE. Results: No significance was observed among conditions for physical tests. However, effect sizes, employing Cohen’s D classification, identified a moderate (d = 0.55) and small (d = 0.45) effect for the caffeine pouch compared to the placebo and caffeine gum for the LP respectively. Further, small effects for the pouch compared to the placebo were observed (d = 0.33) for the SP. Significant differences were produced for RPE during the LP (p = 0.022), with post hoc analysis identifying significant differences between the placebo vs. caffeine pouch (p = 0.032). Conclusion: Low-dose caffeine has the potential to produce meaningful effects on strength endurance, likely linked to caffeine mechanisms reducing RPE. Full article

Background: This systematic review examined the relationship between horizontal multi-step jumps and sprint performance, and whether training interventions including these exercises improve sprinting. Methods: A systematic literature search was conducted in SPORTDiscus and PubMed (MEDLINE) and included English-language studies of athletes aged ≥14–15 years that assessed at least one horizontal multi-step jump and reported sprint outcomes over distances up to 100 m. Methodological quality and risk of bias were assessed using design-appropriate critical appraisal tools. Of 316 records identified, 19 studies met the inclusion criteria (10 intervention studies and 9 correlational studies). Results: Across correlational studies, horizontal multi-step jump performance showed associations ranging from weak to very large with sprint performance, with the strongest relationships typically observed during acceleration (≤20–30 m). In trained sprinters, correlations were often large to very large (r ≈ −0.65 to −0.88), whereas team-sport athletes showed more moderate associations, and younger or less specialized populations showed weak or non-significant relationships. Across intervention studies, horizontal multi-step jump training generally improved short-distance sprint performance, with the largest improvements reported for acceleration (up to ~7–12% in some studies), while effects at longer sprint distances and maximal-speed performance were smaller, inconsistent, or not different from comparison training. Conclusions: Overall, the evidence suggests that the association between horizontal multi-step jumps and sprint performance is strongest during the acceleration phase and is influenced by athlete population and training status. Horizontal multi-step jumps appear to be useful for assessing and potentially developing sprint acceleration. However, the findings should be interpreted with caution due to heterogeneity in study design and variable methodological quality, and associations with maximal sprint speed are less consistent across studies. Full article

Background: Explosive and reactive strength of the lower extremities are essential performance determinants in artistic gymnastics. This study analyzed ten years of performance diagnostic data from Swiss junior and elite gymnasts to describe age- and sex-specific development patterns of lower-limb strength and to examine whether early strength levels predict later selection to the Swiss national elite team. Methods: Longitudinal performance data from 234 Swiss gymnasts (125 females, 109 males; 7–30 years) were analyzed. Explosive and reactive strength were assessed using countermovement, squat, single-leg, and drop jumps. Age- and sex-related differences, as well as associations with later national team selection, were examined. Results: Explosive and reactive strength increased significantly across age categories in both sexes (p < 0.001). In females, the greatest improvements occurred between U14 and U16 (explosive strength: +8.7–12.9%; reactive strength: +15.6–21.2%), followed by stagnation in explosive strength at older ages. In males, both strength qualities increased continuously from U14 to U18 (+9.3–15.7% per category; p < 0.001), with smaller gains at the elite level. Sex differences in explosive strength emerged from U16 and became pronounced from U18 onwards, favoring males (+11.3–19.2%). Reactive strength showed smaller and partly reversed sex differences, with females demonstrating higher values in U16 and elite athletes (up to +16.5%). Differences between athletes later selected for the national team and non-selected athletes were small and mostly non-significant. Conclusions: Lower-limb strength development in gymnastics follows distinct age- and sex-specific patterns. Systematic training appears to moderate sex-related differences, particularly in reactive strength. While physical capacities form an important foundation, technical proficiency seems to play a more decisive role in elite selection and long-term athlete development. Full article

Non-contact anterior cruciate ligament (ACL) injuries cause substantial time loss in female football. Although altered lower-limb muscle excitation is a modifiable risk factor, the reliability of surface electromyography (sEMG) during dynamic tasks in female players remains uncertain. This repeated-measures reliability study examined sEMG during a single-leg jump landing (LAND) and 90° sidestep cut (CUT) in 16 second-tier English female footballers. We evaluated reliability across: (1) within- versus between-session measures; (2) mean versus peak amplitudes; (3) pre-initial contact (PRE-IC) versus post-initial contact (POST-IC) phases; and (4) 10 ms versus 50 ms smoothing windows. Reliability was quantified using intraclass correlation coefficient (ICC[2,k]) and absolute measurement error. Within-session ICCs were moderate to excellent (LAND 0.61 to 0.95; CUT 0.68 to 0.96), whereas between-session ICCs varied from poor to excellent (LAND −0.48 to 0.94; CUT −0.08 to 0.93). Mean amplitudes showed marginally higher ICCs and lower absolute error than peaks. Phase-specific patterns were task-dependent: PRE-IC was more reliable in LAND, whereas POST-IC was more reliable in CUT. Practitioners should prioritize within-session comparisons using mean amplitudes, and the most reliable task-specific phase is recommended. Between-day application warrants caution, as the consistently lower reliability demonstrated may reflect task variability and/or physiological fluctuations rather than the sEMG method alone. Full article

Introduction: Anterior cruciate ligament (ACL) injuries are among the most severe and frequent injuries in alpine skiing, often occurring in non-contact situations during high-demand turns. Various instrumental techniques were used to assess susceptibility to anterior cruciate ligament (ACL) injuries in alpine ski racers and recreational skiers. This cross-sectional exploratory study aimed to identify key factors contributing to ACL injury susceptibility, comparing lab-based and on-snow tests. Materials and Methods: We examined nine elite ski racers and nine recreational skiers with strong athletic backgrounds. Skiing technique was analyzed using an instrumented insole system (CARV) to measure body position, pressure symmetry, and edge angle. Dynamic Q-angle symmetry during single-leg squats were assessed with an optical system (DynaKnee), while balance, strength, and agility were evaluated through ACL-specific lab tests (CoRehab). Group comparisons were performed using the nonparametric Mann–Whitney U test. Results: No significant differences were found between groups in ACL-specific lab tests, including balance, agility, and jump performance. However, ski racers exhibited 34.9% higher asymmetry in the Q-angle symmetry index during the one-leg squat. In contrast, ski technique differences were significant: ski racers achieved 16.3% higher Edge Similarity, 48% better Pressure Symmetry, and 5.8% better Fore-Aft Balance compared to recreational skiers. Conclusions: Despite similar general athletic abilities, elite skiers showed higher Q-angle asymmetry, which has been previously associated with ACL injury risk. However, their advanced skiing technique may partially mitigate the functional consequences of this asymmetry during on-snow tests. This suggests that refined skiing skills may influence functional performance in racing conditions, while pronounced one-sided dominance could indicate potential injury risk. Full article