Relationship Between Single-Leg Vertical Jump and Drop Jump Performance, and Return to Sports After Primary Anterior Cruciate Ligament Reconstruction Using Hamstring Graft.

Background: After anterior cruciate ligament reconstruction (ACLR), asymmetry is likely to persist in single-leg (SL) vertical jump and drop jump performance than in SL hop distance. However, its relationship with the return to sport (RTS) remains unclear. Hypothesis/Purpose: This study aimed to determine the association between vertical jump performance after primary ACLR using hamstring tendon autograft and RTS at a pre-injury competitive level. Study design: Cross-sectional study. Methods: Patients who underwent primary ACLR using hamstring tendon autograft were recruited for this study. Participants who returned to pre-injury competition after ACLR were recruited at least eight months postoperatively. Knee condition was assessed, including joint laxity, range of motion, muscle strength, and knee pain intensity during sports activities. Performance variables were also assessed, including SL hop distance, jump height in SL vertical jump, and reactive strength index (RSI; jump height/contact time) in SL drop jump. Participants were asked to subjectively report whether they had returned to the same level of competition as pre-injury and their perceived sport performance intensity. Those who answered "Yes" to the dichotomous question and had a postoperative subjective athletic performance of > 80% were categorized into the Yes-RTS group. The primary outcome was the ability to achieve RTS at the preinjury level. Results: Sixty-five patients (female, 35; male, 30) at 13.0 (13.0) [median (interquartile)] months after ACLR participated in this study. Thirty-nine (60%) were assigned to the Yes-RTS group. Regarding knee conditions, the No-RTS group had a significantly higher knee pain intensity, as assessed using a numerical rating scale (p<0.001, effect size -0.45). In the performance tests, the No-RTS group exhibited a significantly lower limb symmetry index of RSI during the SL drop jump compared to the Yes-RTS group (p=0.002, effect size 0.81). Conclusion: Patients unable to achieve RTS after primary ACLR using hamstring grafts are more likely to exhibit asymmetric performance during the SL drop jump test, suggesting the significance of assessing jump symmetry when evaluating post-ACLR rehabilitation success. Level of Evidence: 3c.

Heavier loads in flywheel exercise induce greater post-activation performance enhancement in countermovement jumps compared to heavy Smith machine squats in males.

We evaluated the effects of post-activation performance enhancement through flywheel exercise with varying inertial loads compared to traditional resistance exercise on countermovement jump performance and muscle recruitment. In a randomized crossover design, 13 trained men completed four main experimental trials after three familiarization sessions. These conditions included a traditional trial consisting of 5 sets of 1 repetition using the Smith machine (SM) squat at 90% 1RM, and three flywheel ergometer trials. Each flywheel protocol consisted of 3 sets of 8 repetitions with 3-minute rest intervals between sets, utilizing one of three inertial loads (0.0465, 0.0784, and 0.1568 kg · m2 for light, moderate, and heavy, respectively). Participants performed countermovement jumps before (baseline), immediately after (0 minute), and at the fourth (+4 minutes), eighth (+8 minutes), and twelfth (+12 minutes) minute following exercise. Compared to baseline, jump height was higher at +4 minutes for SM squats (p = 0.009). All flywheel conditions exhibited higher jump heights at +4 minutes (p < 0.05), +8 minutes (p < 0.001), and +12 minutes (p < 0.001) compared to baseline. Additionally, moderate and heavy loads resulted in higher jump heights at 0 minute (both p < 0.001). Integrated electromyographic activity values, a proxy for muscle recruitment, were significantly higher for the gluteus maximus muscle at both +8 minutes and +12 minutes for moderate (both p = 0.004) and heavy loads (p ≤ 0.002) compared to SM squats. Overall, flywheel protocols produce greater post-activation performance enhancement, extend the time window for improvement, and recruit more active musculature compared to heavy-load SM squats, particularly with heavier loads acting as a stronger preload stimulus.

Acute Effects of Transcranial Direct Current Stimulation Combined with High-Load Resistance Exercises on Repetitive Vertical Jump Performance and EEG Characteristics in Healthy Men.

BACKGROUND: Transcranial direct current stimulation (tDCS) is a non-invasive technique known to enhance athletic performance metrics such as vertical jump and lower limb strength. However, it remains unclear whether combining tDCS with the post-activation effects of high-load resistance training can further improve lower limb performance. OBJECTIVE: This study investigated the synergistic effects of tDCS and high-load resistance training, using electroencephalography to explore changes in the motor cortex and vertical jump dynamics. METHODS: Four experiments were conducted involving 29 participants. Each experiment included tDCS, high-load resistance training, tDCS combined with high-load resistance training, and a control condition. During the tDCS session, participants received 20 min of central stimulation using a Halo Sport 2 headset, while the high-load resistance training session comprised five repetitions of a 90% one-repetition maximum weighted half squat. No intervention was administered in the control group. Electroencephalography tests were conducted before and after each intervention, along with the vertical jump test. RESULTS: The combination of tDCS and high-load resistance training significantly increased jump height (p < 0.05) compared to tDCS or high-load resistance training alone. As for electroencephalography power, tDCS combined with high-load resistance training significantly impacted the percentage of α-wave power in the frontal lobe area (F3) of the left hemisphere (F = 6.33, p < 0.05). In the temporal lobe area (T3) of the left hemisphere, tDCS combined with high-load resistance training showed a significant interaction effect (F = 6.33, p < 0.05). For ß-wave power, tDCS showed a significant main effect in the frontal pole area (Fp1) of the left hemisphere (F = 17.65, p < 0.01). In the frontal lobe area (F3) of the left hemisphere, tDCS combined with high-load resistance training showed a significant interaction effect (F = 7.53, p < 0.05). The tDCS combined with high-load resistance training intervention also resulted in higher ß-wave power in the parietal lobe area (P4) and the temporal lobe area (T4) (p < 0.05). CONCLUSIONS: The findings suggest that combining transcranial direct current stimulation (tDCS) and high-load resistance training significantly enhances vertical jump performance compared to either intervention alone. This improvement is associated with changes in the α-wave and ß-wave power in specific brain regions, such as the frontal and temporal lobes. Further research is needed to explore the mechanisms and long-term effects of this combined intervention.

Effects of direction specific exercise training on athletic performance: a systematic review and meta-analysis.

Background: The similarity between movement patterns and force-vector specificity of training exercises and the target movement will likely result in the greatest transfer of the practiced skills and physical abilities to the intended sports skill performance. Therefore, this review aimed to investigate whether specific adaptations in athletic performance would be observed following direction specific exercise training. Methodology: The literature search was performed in PubMed, Web of Science, and MEDLINE. Studies comparing acute (post-activation potentiation enhancement) and short-term (>2 weeks) effects of horizontally vs. vertically oriented resistance and plyometric training on athletic performance of recreationally active participants of either sex were included. The effect sizes were determined using a robust variance estimation random-effects model and were reported as Hedge's g. Results: Twenty-two studies were included. For acute studies (n = 4), a small non-significant effect favoring horizontal training (HT) for sprint performance improvements (g = -0.19, p = 0.17) was evident. For short-term studies (n = 18), the results showed non-significant, small to large differences between HT and vertical training (VT) in pooled vertical and horizontal jump improvements (g = 0.06, p = 0.67), vertical (g = 0.21, p = 0.17) and horizontal jump (g = -0.15, p = 0.40), pooled vertical and horizontal maximal strength (g = 0.27, p = 0.42), horizontal (g = -0.83, p = 0.16) and vertical maximal strength (g = 0.78, p = 0.28), pooled short and medium distance sprint (g = -0.23, p = 0.16), short (g = -0.33 [-0.85, 0.19], p = 0.19) and medium (g = -0.12 [-0.37, 0.13], p = 0.28) distance sprint, and COD speed and maneuverability (g = -0.45, p = 0.26). Conclusions: HT and VT were both equally effective in improving vertically and horizontally athletic performance, potentially refuting the theory of directional specificity of training on athletic performance outcomes.

Influence of an inspiratory muscle fatigue protocol on healthy youths on respiratory muscle strength, vertical jump performance and muscle oxygen saturation: a randomized controlled trial.

BACKGROUND: Inspiratory muscle fatigue has been shown to have effects on limbs blood flow and physical performance. This study aimed to evaluate the influence of an inspiratory muscle fatigue protocol on respiratory muscle strength, vertical jump performance and muscle oxygen saturation in healthy youths. METHODS: A randomized and double-blinded controlled clinical trial, was conducted. Twenty-four participants aged 18-45 years, non-smokers and engaged in sports activity at least three times a week for a minimum of one year were enrolled in this investigation. Participants were randomly assigned to three groups: Inspiratory Muscle Fatigue (IMFG), Activation, and Control. Measurements of vertical jump, diaphragmatic ultrasound, muscle oxygen saturation, and maximum inspiratory pressure were taken at two stages: before the intervention (T1) and immediately after treatment (T2). RESULTS: The IMFG showed lower scores in muscle oxygen saturation and cardiorespiratory variables after undergoing the diaphragmatic fatigue intervention compared to the activation and control groups (p < 0.05). For the vertical jump variables, intragroup differences were found (p < 0.01), but no differences were shown between the three groups (p > 0.05). CONCLUSIONS: Inspiratory muscle fatigue appears to negatively impact vertical jump performance, muscle oxygen saturation and inspiratory muscle strength in healthy youths. TRIAL REGISTRATION: ClinicalTrials.gov ID: NCT06271876. Date of registration 02/21/2024. https://clinicaltrials.gov/study/NCT06271876 .

Fluctuations of Jump Height in Male Basketball Players: Analysis of a Competitive Season.

The present study aimed to determine whether neuromuscular fatigue monitored through countermovement jump height was a reliable and helpful marker for monitoring acute (session) and chronic (between sessions/periods of the season) fatigue throughout an entire basketball season. A longitudinal observational study analyzed the neuromuscular performance (i.e., through countermovement jump) during a basketball season. Fourteen semiprofessional male basketball players participated in the study between September 2021 and May 2022 (34 weeks, 102 practices, and 1574 jumps analyzed). Upon waking up, they completed an online wellness questionnaire. Before practices began, players performed three countermovement jumps on a contact platform after a structured warm-up, repeating the protocol at the end of each practice. Ten minutes after finishing such practice, they also reported perceived exertion's muscular and cardiovascular ratings. The preseason was the period of the season with the lowest absolute countermovement jump height levels (2.06 to 2.50 cm; d = 1.92 to 2.74, very large, p < 0.02). Average pre-session jumps were very largely higher on Wednesdays (0.62 cm, 95% CI = 0.29 - 0.95, p = 0.0095, d = 2.09) and Fridays (0.62 cm, 95% CI = 0.06 - 0.88, p = 0.06, d = 1.43) compared to Mondays. The countermovement jump is a valuable marker for assessing fatigue in semiprofessional basketball players. Games played on weekends mainly and consistently affected Monday's jumping performance, showing the lowest average values. Finally, preseason values were lower than those observed for the rest of the season.

The impact of post-activation potentiation on explosive vertical jump after intermittent time: a meta-analysis and systematic review.

The optimal intermittent time for post-activation potentiation (PAP) training remains uncertain and contentious. This study employed a meta-analysis to systematically evaluate the effect of different intermittent times on PAP in relation to explosive vertical jump height. Relevant literature was sourced from CNKI, Wanfang, VIP, CBM, PubMed, Web of Science, and Google Scholar databases using keywords such as "postactivation potentiation," "activation enhancement effect," "PAP," "explosive vertical jump," "explosive vertical high jump," and "intermittent time." The search covered publications from the inception of each database until June 2024. Studies involving athletes (regardless of sport type) undergoing PAP training were included, with no restrictions on the methods used to induce PAP. Comparative analysis focused on the heights of countermovement jumps (CMJ) and peak ground reaction force (GRF) before and after interventions. The quality of the included studies was assessed using the Cochrane Risk of Bias Tool, and data were analyzed using RevMan5.3. The study included a total of 21 papers with 327 subjects, primarily using the squat as the method of PAP induction. The meta-analysis revealed that intermittent times of 4 min [MD = - 0.03, 95% CI: - 0.04 ~ - 0.01; Z = 2.71, P = 0.007] and 5-8 min [MD = - 0.03, 95% CI: - 0.04 ~ - 0.01; Z = 3.07, P = 0.002] significantly increased the height of explosive vertical CMJs. However, intermittent times of 1-3 min [MD = -0.00, 95% CI: - 0.01 ~ 0.01; Z = 0.38, P = 0.70] and 10-24 min [MD = - 0.01, 95% CI: - 0.02 ~ 0.00; Z = 1.43, P = 0.15] did not show significant effects on CMJ height. These findings indicate that 4-min and 5-8 min intervals significantly enhance CMJ height, while intervals shorter than 4 min or longer than 8 min do not have a significant impact.

Reliability and validity of "My Jump 2" application for countermovement jump free arm and interlimb jump symmetry in different sports of professional athletes.

Background: Vertical jumping is an important evaluation tool to measure muscle strength and power as well as lower limb symmetry. It is of practical importance and value to develop and utilize a portable and low-cost mobile application (APP) to evaluate jumping. The "My Jump 2" app is an iPhone camera-based application for measuring jumping movements, which is applied to the countermovement jump (CMJ) vertical jumps of the lower limbs of athletes in different sports. The validity of this application and previous versions applied to different forms of vertical jump tests has been preliminarily demonstrated in different population, which has an obvious progress in research. Therefore, the reliability and validity of the jump height, time of flight parameters and symmetry of the CMJ vertical jump of athletes in different sports are needed to be verified by more experiments. Purpose: The purpose of this study is to verify whether "My Jump 2" can effectively and reliably assess jump height, flight practice and lower limb symmetry in CMJAM (countermovement jump free arm) tests in fencing, swimming and diving athletes. Methods: Seventy-nine fencers, swimmers and divers with training experience participated in this study. They completed a total of three CMJAM vertical jump and lower limb symmetry tests in 1 day, while being assessed by using the "My Jump 2" application and a force platform. The intra-group correlation coefficient (ICC) was used to verify reliability, while the Cronbach's alpha and coefficient of variation (CV%) was used to analyze the stability of the CMJAM vertical jump test over three jumps. The Pearson correlation coefficient was used to verify the strength of the relationship between methods (i.e., concurrent validity), and the Bland-Altman plot was used to represent consistency, meanwhile, the t-test was used to determine the systematic bias between methods. Results: Compared with the force platform, the cumulative height values of the total number of jumps (r = 0.999; p = 0.000), the cumulative time to vacate (r = 0.999; p = 0.000) for the CMJAM test obtained by the "My Jump 2" application, the height (ICC = 0.999-1, p = 0.000), the time to vacate flight (ICC = 0.999-1, p = 0.000), contact time symmetry (ICC = 0.976-0.994, p = 0.000), and flight time symmetry (ICC = 0.921-0.982, p = 0.000), respectively. Showed high correlation between the results of "my jump 2" app and the force platform. Conclusion: The "My Jump 2" application is a valid tool to assess CMJAM vertical jump and lower limb symmetry in fencing, swimming and diving athletes with training experience.

The dynamic strength index is a reliable and feasible tool to assess neuromuscular performance in male and female handball players.

The aim of this study was to explore the reliability and feasibility of the isometric mid-thigh pull (IMTP) and dynamic strength index (DSI) in semi-professional handball players (seventeen male and eighteen female). A cross-sectional design was used to determine the test-retest reliability of several kinetic metrics registered with a force plates. The peak force, peak relative force, rate of force development (RFD 0-250 ms), and impulse 0-250 ms were selected from the IMTP test, whereas the peak propulsive force was chosen from the countermovement jump test to obtain the DSI. The intraclass correlation coefficient (ICC), coefficient of variation (CV), standard error of the measurement (SEM) and smallest detectable difference (SDD) were calculated. A paired sample t-test was also performed. No significant differences were found between the testing sessions for all variables, except for peak propulsive force for all players (p = 0.036) and DSI for female players (p = 0.037). Reliability for all kinetic metrics was good to excellent (ICC = 0.78-0.97), with low variability (CV ≤ 8.64%), being the SEM scores lower than SDD. In conclusion, the IMTP test and DSI are highly reliable and feasible tools for assessing neuromuscular performance in semi-professional handball players.

Velocity-Load Jump Testing Predicts Acceleration Performance in Elite Speed Skaters: But Does Movement Specificity Matter?

PURPOSE: In this study, we compared the influence of movement specificity during velocity-load jump testing to predict on-ice acceleration performance in elite speed skaters. METHODS: Elite long-track speed skaters (N = 27) performed velocity-load testing with 3 external loads during unilateral horizontal jumping, lateral jumping, and bilateral vertical countermovement jumping. For the unilateral tests, external load conditions were set to 10 N, 7.5% and 15% of external load relative to body weight. For the countermovement jumping, load conditions were body weight and 30% and 60% of external load relative to body weight. On-ice performance measures were obtained during maximal 50-m accelerations from a standing start, including maximal skating speed, maximal acceleration capacity, and maximum horizontal power. The 100-m split time from a 500-m race was also obtained. Regularized regression models were used to identify the most important predictors of on-ice acceleration performance. In addition to regularized regression coefficients, Pearson correlation coefficients (r) were calculated for all variables retained by the model to assess interrelationships between single predictors and on-ice performance measures. RESULTS: The countermovement jump with 30% of body mass demonstrated the strongest association with maximal skating speed, maximum horizontal power, and 100-m time (regularized regression coefficient = .16-.49, r = .84-.97, P < .001). Horizontal jump with 15% of body mass was the strongest predictor of maximal acceleration capacity performance (regularized regression coefficient = .08, r = .83, P < .001). CONCLUSIONS: The findings of this study suggest that mechanical specificity rather than movement specificity was more relevant for predicting on-ice acceleration performance.

Pedagogical control scales of vertical jumping performance in untrained adolescents (13-16 years): research by strata.

Background: A scale is used to establish performance ranges in different sciences, it being necessary to design specialized biological and pedagogical indicators in physical activity, sport and health. Objective: To design a scale for the pedagogical control of the vertical jumping ability in untrained adolescents (13-16 years), stratifying the sample by age range, ethnicity, urban and rural area, socioeconomic level, and gender. Methods: A representative sample of the Ecuadorian population (n = 3,705) is studied, classifying it into the aforementioned strata, controlling the vertical jump by ISAK I and II level experts, applying the Sargent Test to measure vertical jumps on a multi-force wall, establishing scales with seven percentile levels, and making comparisons related to chronological age, gender, socioeconomic, and genetic indicators. Results: Significant differences in the vertical jumping performance were determined according to the category or age range (13-14 ≠ 15-16 years) and by gender (w = 0.000). Various levels of performance were determined, classifying the maximum level as talented in the female gender (≥40 cm; and ≥42 cm) and male gender (≥47 cm; and ≥57 cm) in the 13‒14 and 15‒16 years categories, respectively. Sampling comparisons by geographical area only determined significant differences in the male gender, with the jumping ability being higher in urban areas (13‒14 years: w = 0.046; 15‒16 years: w = 0.013). The comparison by ethnic groups showed significant differences (k = 0.030), favoring the Afro-Ecuadorian ethnic group in both genders, while there are significant differences by socioeconomic level, especially between the middle and lower classes. Conclusions: The present research solves the lack of a tool for making correct didactic decisions related to the vertical jumping ability, taking into account various important stratified indicators. The complementary conclusions show significant differences according to the category stratum or age range, the gender stratum, and the ethnic stratum in females and males, where the best average rank favored the Afro-Ecuadorian ethnic group in both genders. There are significant differences in the geographical area stratum in the male gender, and differences in the socioeconomic stratum in favor of the upper and middle classes.

Residual Effects of Same Day Lower Extremity Strength Training on Countermovement Jump Performance in Collegiate Women Athletes.

Balancing of strength programming intensity with sport demands is necessary to avoid excessive workloads that could inhibit performance. To expand previous jump height focused literature, this study evaluated whether countermovement jump (CMJ) movement strategies, including eccentric characteristics, might reveal CMJ execution strategy shifts to achieve similar afternoon CMJ height following a morning resistance training session (RTS). Fifteen collegiate women's soccer and volleyball athletes (18-24 years, 73.6 ± 8.4 kg, 1.74 ± 0.19 m) participating in an offseason RTS completed five CMJs during two afternoon sessions (48 h apart), one 4-6 h post morning RTS, and one on a rest day. The RTS consisted of 2 sets of 10 repetitions at 70-80% 1RM for the back squat, the front squat, and the forward lunge. Vertical ground reaction forces were recorded from which 13 outcome measures describing elements of the eccentric and concentric CMJ phases were computed. No significant differences in jump height (p = 0.427, d = 0.17) or outcome measures (p = 0.091-0.777, d = -0.07-0.21) between sessions with exception of a significant concentric phase time decrease (p = 0.026, d = 0.23) following the RTS were identified. Given the magnitude of the mean concentric phase time change (0.01 s), the result likely has limited practical meaning. As these results confirm previous CMJ height literature, practitioners have further evidence that a morning RTS does not interfere or enhance afternoon CMJ performance in athletic women.

Test-retest reliability and longitudinal validity of drop vertical jump biomechanics during rehabilitation after ACL reconstruction.

Hip and knee biomechanics measured during a drop vertical jump (DVJ) can be used to assess patients undergoing rehabilitation after anterior cruciate ligament (ACL) reconstruction. To confidently interpret such data for use as outcome measures, additional information about reliability and validity is required. Therefore, the objective of this study was to estimate the test-retest reliability and longitudinal validity of selected lower limb biomechanics assessed during a DVJ in patients undergoing rehabilitation after ACL reconstruction. Biomechanical analysis of the DVJ in primary unilateral ACL reconstruction patients (22.3 ± 5.5y) were tested twice within 1 week at 6 months post-surgery (n = 46), and again at 12 months post-surgery (n = 36). Peak and initial contact knee angles and moments, hip impulse, vertical ground reaction forces (VGRF), isokinetic knee extension and flexion strength, and global ratings of change (GRC) were assessed. Reliability was evaluated based on the 6-month post-surgery data using intraclass correlation coefficients (ICC2,1), standard errors of measurement and minimum detectable change. Longitudinal validity was evaluated by assessing change from 6 to 12 months, using standardized response means (SRM), and by assessing the correlation (Pearson's r) of change in landing biomechanics with change in strength, and GRC. ICCs ranged from 0.58 to 0.90 for peak knee abduction and flexion moments, 0.44-0.85 for knee flexion and abduction angles, 0.82-0.93 for VGRFs, and 0.42-0.65 for hip impulse. SRMs and correlations of change ranged from 0.00 to 0.50. Reliability and longitudinal validity of DVJ measures varied, ranging from poor-to-excellent; the present results assist in their interpretation when assessed during rehabilitation after ACL reconstruction.

Does anaerobic speed reserve influence post-activation performance enhancement in endurance runners?

We investigated the influence of anaerobic speed reserve (ASR) on post-activation performance enhancement (PAPE). Twenty-two endurance runners and triathletes were evaluated for maximum sprinting speed (MSS) and countermovement jump (CMJ) before (non-fatigued) and after (fatigued) an incremental running test. They were allocated in LASR (low-ASR) and HASR (high-ASR) groups for comparisons between conditions. HASR showed greater CMJ and MSS (both p ≤ 0.005) performances, with enhanced CMJ in fatigued condition (p ≤ 0.008). Significant correlations were found between ASR, CMJ, and MSS in both conditions (p ≤ 0.01) for the entire sample, and between ∆CMJ and ∆MSS (p ≤ 0.001) in LASR. Our results show that ASR profile influences PAPE.

Large inter-individual variability in force-velocity profile changes in response to acute high-load resistance training.

Background: While the acute effects of high-load resistance training on the force generating capacity of muscles have been widely examined, limited data exist on the relationship with the force-velocity profile (FV). Evidence suggests high sensitivity of the vertical FV profile to monitor changes in the muscle's mechanical properties according to the type of the exercise protocol. However, the interpretation of the findings seems not as straightforward. Therefore, the purpose of this study was to examine the effects of a high-load resistance training protocol on the muscle's mechanical properties during loaded jumps and on the vertical force-velocity profile (FV) in relation to maximal strength. Methods: 29 resistance-trained male (mean age±SD: 35.4 ± 7.8 years) and 29 female athletes (mean age±SD: 32.5 ± 7.0 years) participated in the study. Five-repetition maximum (5RM) in back squat, unloaded countermovement jump (CMJ) and FV profile were assessed. Loaded jumps were performed against 25, 50, 75, and 100 percent of body mass. Participants performed exercise protocols corresponding to their 5RM. Immediately after, unloaded CMJ and FV profile measurements were repeated. Results: A significant decrease in CMJ height (∼5-6%) and in average power (∼4%) was recorded for both men and women. The FV profile did not change after the exercise protocol; however, there was a significant decrease in theoretical maximal power (from 4 to 5%) and in theoretical maximal velocity (∼3%). Maximal strength was not associated with the changes in FV profile. Conclusions: Findings suggest that an acute high-load exercise decreased vertical jump performance and maximal power output, but without a concomitant change in FV profile. The large interindividual variability in FV measures indicates a less straightforward connection of the applied exercise with the acute response in the FV profile, highlighting the complexity of the FV profile to monitor changes in response to an acute training load.

Single Sequential Trajectory Optimization with Centroidal Dynamics and Whole-Body Kinematics for Vertical Jump of Humanoid Robot.

High vertical jumping motion, which enables a humanoid robot to leap over obstacles, is a direct reflection of its extreme motion capabilities. This article proposes a single sequential kino-dynamic trajectory optimization method to solve the whole-body motion trajectory for high vertical jumping motion. The trajectory optimization process is decomposed into two sequential optimization parts: optimization computation of centroidal dynamics and coherent whole-body kinematics. Both optimization problems converge on the common variables (the center of mass, momentum, and foot position) using cost functions while allowing for some tolerance in the consistency of the foot position. Additionally, complementarity conditions and a pre-defined contact sequence are implemented to constrain the contact force and foot position during the launching and flight phases. The whole-body trajectory, including the launching and flight phases, can be efficiently solved by a single sequential optimization, which is an efficient solution for the vertical jumping motion. Finally, the whole-body trajectory generated by the proposed optimized method is demonstrated on a real humanoid robot platform, and a vertical jumping motion of 0.5 m in height (foot lifting distance) is achieved.

Phase angle as an indicator of body composition and physical performance in handball players.

BACKGROUND: Phase angle (PhA), obtained from the bioimpedance analysis, is widely used in clinical situations and in sports. This study evaluated the association between PhA with body composition and physical performance of handball athletes. METHODS: 43 national-level players (22.19 ± 3.86 years) of both sexes were evaluated regarding anthropometry, body composition, squat (SJ) and countermovement (CMJ) jumps, handgrip strength, and cardiorespiratory fitness. RESULTS: We verified a correlation between PhA of the whole body and fat-free mass (r = 0.511), body mass index (r = 0.307), and body fat % (r = -0.303). There was a positive correlation between PhA of the whole body and SJ (r = 0.376), CMJ (r = 0.419), and handgrip for the dominant hand (r = 0.448). Moreover, PhA of the upper limbs was more strongly correlated with handgrip for the dominant (r = 0.630) and non-dominant hand (r = 0.575) compared to PhA of the whole body considering both sexes. Similarly, segmental PhA had a stronger significant correlation with SJ (r = 0.402) and handgrip for the dominant hand (r = 0.482) in males, as well as CMJ (r = 0.602) in females, compared to PhA of the whole body. CONCLUSION: PhA of the whole body was positively related to fat-free mass, body mass index, body fat %, and lower- and upper-limbs strength in handball athletes. Segmental PhA might be used as a tool for estimating lower and upper limbs performance considering the sex, in preference to the PhA of the whole body.

Test-retest reliability of lower limb muscle strength, jump and sprint performance tests in elite female team handball players.

PURPOSE: This study aimed to assess the reliability of lower limb muscle function (knee extensor/flexor peak torque, rate of torque development (RTD), impulse, and countermovement jump (CMJ) performance) and sprint performance (acceleration capacity). METHODS: CMJ performance was evaluated on a force plate. MVIC, RTD and impulse variables were investigated using a portable isometric dynamometer and sprint performance was assessed with dual-beam photocells in elite female athletes. RESULTS: CMJ test variables maximal vertical jump height, peak and mean power, concentric work, and body center of mass displacement demonstrated good-to-excellent test-retest correlations between Test 1 and Test 2 (ICC ≥ 0.70, CWw-s = 3.4-11.0%). Peak MVIC torque for the knee extensors and flexors demonstrated excellent test-retest correlations (both ICC = 0.84) along with CVw-s values of 6.8 and 6.0%, respectively. Late-phase (0-100 ms, 0-200 ms) RTD for the knee flexors demonstrated excellent test-retest correlations (ICC = 0.89-0.91, CVw-s = 4.8-8.5%). Sprint times at 10- and 20-m demonstrated excellent test-retest reproducibility (ICC = 0.83 and ICC = 0.90, respectively) with CVw-s values of 1.9 and 1.5%. For 5-m sprint times, test-retest reproducibility was good (ICC = 0.71) with CVw-s of 2.8%. Sprint testing performed while dribbling a handball improved (p < 0.05) from test to retest at 5-, 10- and 20-m. CONCLUSION: In conclusion, the force plate, the mobile isometric dynamometer, and dual-beam photocells provide reproducible tools for field-based testing of countermovement jump performance, knee extensor and flexor strength and sprint performance.

Effects of focal vibration on changes in sports performance in amateur athletes: A randomized clinical trial.

The aim of this study was to evaluate the effectiveness of a focal vibration protocol added to an activation protocol with active muscle contractions and to see what repercussions it has on sprint, countermovement jump (CMJ), and lower limb isometric strength. A double-blind randomized clinical trial was conducted in the Functional Anatomy Laboratory and the sample consisted of 70 athletes. The main outcome measures were knee extension force, CMJ, sprint, and surface electromyography. Repeated-measures analysis of variance revealed significant improvements. They were found in the within-group analysis for the Experimental Group in the isometric extension force (p < 0.001; η2 = 0.368), CMJ (p < 0.001; η2 = 0.301) and 30 m sprint (p < 0.001; η2 = 0.376). In the electromyography, there are changes in the Sham Group in all muscles, in CMJ and Sprint tests, and no differences in the Experimental Group, except for the RF muscle. In the between-group analysis, statistically significant differences were found only in favor of the Experimental Group in CMJ (p = 0.017; η2 = 0.81) and 30 m sprint (p < 0.001; η2 = 0.152). These results confirm a significant improvement in the sprint, CMJ performance, and quadriceps strength, after a focal vibration protocol, added to a muscle active contraction, compared to a focal vibration sham protocol. Therefore, our results suggest that the focal vibration can be a very useful tool in sports involving high-powered actions.

Validity and reliability of the My Jump 2 app for detecting interlimb asymmetry in young female basketball players.

Introduction: The aim of this study was to examine the validity and reliability of the My Jump 2 app for the assessment of interlimb jump asymmetry in young female basketball players. Methods: Nine athletes (age 15 ± 0.9 years; weight 62.9 ± 5.8 kg; height 173.6 ± 6.1 cm) performed single-leg drop jumps (DJs) and both-leg drop jumps on a force plate (Kistler Quattro jump) and were simultaneously recorded on two smartphones using the My Jump 2 app. Jump height from flight time and contact time data were statistically analyzed to evaluate the validity of two different camera settings, drop jump performance, and interlimb jump asymmetry in basketball players. The testing was repeated after 1 week for test retest reliability. Results: High test-retest reliability [intraclass correlation coefficient (ICC) > 0.88] was observed in DJ height. High correlation between the force plate and the My Jump 2 app was observed in DJ height (r = 0.99) and DJ contact time (r = 0.98). For the interlimb jump height asymmetries, mean differences were 0.6 percentages for the My Jump 2 app and the force plate, respectively (p = 0.77). Inter-device reliability revealed almost perfect correlation for the DJ height (ICC = 0.99, r = 0.98). Conclusion: The My Jump 2 app is a valid and reliable tool to assess drop jump performance and interlimb asymmetry in young female basketball players.