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Objective: The necessity to exclude flat foot when selecting athletes is a controversial issue. This study aimed to investigate whether flat foot affects vertical jump. Methods: The quality of the literature was assessed using the observational study quality assessment tool provided by the Joanna Briggs Institute (JBI) Centre for Evidence-Based Health Care in Australia. Meta-analysis, heterogeneity testing, sensitivity analysis, subgroup analysis, and forest plot were conducted using Review Manager 5.4. Results: In the end, 9 articles met the meta-analysis criteria. Due to the heterogeneity of the studies, only vertical jump height was used as an indicator for meta-analysis. Meta-analysis results showed low heterogeneity among studies (I2 = 6%, P = 0.39), and the combined effect size showed no significant difference in jumping height between flat foot and normal foot (P = 0.73, ES = 0.13, 95%CI [-0.58, 0.83]). Subgroup analyses showed no significant differences in jump heights between flat and normal foot in either the adolescent subgroup (ES = 0.07, 95% CI [-1.04, 1.18]) or the adult subgroup (ES = 0.16, 95% CI [-0.76, 1.08]). Subgroups were divided according to training background, and jump height was unaffected by flat foot in both athletes (ES = -0.08, 95%CI [-1.07, 0.90]) and amateur (ES = 0.34, 95%CI [-0.67, 1.35]). Conclusion: Overall, flat foot do not affect vertical jump height, although flat foot have different vertical jump biomechanics. This study breaks the bias that flat foot have poorer athletic performance. The meta-analysis has been registered with PROSPERO under registration number CRD42023481326. [ABSTRACT FROM AUTHOR]

Abstract Objective The necessity to exclude flat foot when selecting athletes is a controversial issue. This study aimed to investigate whether flat foot affects vertical jump. Methods The quality of the literature was assessed using the observational study quality assessment tool provided by the Joanna Briggs Institute (JBI) Centre for Evidence-Based Health Care in Australia. Meta-analysis, heterogeneity testing, sensitivity analysis, subgroup analysis, and forest plot were conducted using Review Manager 5.4. Results In the end, 9 articles met the meta-analysis criteria. Due to the heterogeneity of the studies, only vertical jump height was used as an indicator for meta-analysis. Meta-analysis results showed low heterogeneity among studies (I2 = 6%, P = 0.39), and the combined effect size showed no significant difference in jumping height between flat foot and normal foot (P = 0.73, ES = 0.13, 95%CI [-0.58, 0.83]). Subgroup analyses showed no significant differences in jump heights between flat and normal foot in either the adolescent subgroup (ES = 0.07, 95% CI [-1.04, 1.18]) or the adult subgroup (ES = 0.16, 95% CI [-0.76, 1.08]). Subgroups were divided according to training background, and jump height was unaffected by flat foot in both athletes (ES = -0.08, 95%CI [-1.07, 0.90]) and amateur (ES = 0.34, 95%CI [-0.67, 1.35]). Conclusion Overall, flat foot do not affect vertical jump height, although flat foot have different vertical jump biomechanics. This study breaks the bias that flat foot have poorer athletic performance. The meta-analysis has been registered with PROSPERO under registration number CRD42023481326.

Background: The extensor apparatus of the knee is of paramount importance in generating the torque needed for a countermovement jump (CMJ), especially in jumping athletes. In anterior cruciate ligament reconstruction (ACLR) procedures, graft harvesting from the extensor apparatus may dramatically affect extensor strength and jumping performance. Hypothesis: The focused jump training of professional jumping athletes would increase the likelihood of restoring jumping performance after ACLR, despite the graft choice (autologous bone-patellar tendon-bone [BPTB] or hamstring [HS] tendon). Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective evaluation of prospectively collected data was carried out. Only professional athletes were included, and all surgical procedures were performed by a single experienced surgeon. Data collection considered the type of surgery, sports activity, and functional evaluation at 3 months after surgery. From the functional evaluation, data on single-leg hop (SLH) test, triple hop (TH) test, and CMJ were extracted. Limb symmetry index (LSI) for maximal voluntary isometric contraction of the quadriceps and for each of the jumping tests was calculated. Multiple analysis of covariance (ANCOVA) models were used to assess mean differences among groups for the LSI in CMJ, SLH, and TH and estimate the effect of confounders. Results: From a subsequent series of 208 athletes, 44 professional athletes were included for data collection. Of these, 26 were male and 18 were female. A jumping sport (basketball, volleyball) was played by 17 athletes, while a running sport (soccer, judo, rugby, tennis, ski) was performed by 27 athletes. The mean time from injury to surgery was 17.8 ± 14.5 days. At 90 days from surgery, the overall mean LSI for CMJ was 85.3% ± 8.9%, for SLH was 92.2% ± 6.4%, and for TH was 90.8% ± 6.1%. When ANCOVA was fitted using the interaction term with BPTB autograft and jumping sport, a nonsignificant effect on LSI for CMJ (P =.56), SLH (P =.72), and TH (P =.98) was observed. Conclusion: The results of the present investigation on professional athletes showed that no difference occurred within the study cohort in overall jumping performance between jumping and running athletes undergoing ACLR either with BPTB or with HS tendon grafts. Although some evidence suggests that quadriceps strength may be dramatically affected by the harvesting of BPTB, the overall performance of the jump was not compromised. [ABSTRACT FROM AUTHOR]

This study assessed the impact of integrated neuromuscular training (INT) on athletes' jumping performance and lower limb injury prevention. A thorough search across multiple databases, including PubMed, Web of Science, Science Direct, and the Cochrane Library, identified a sample of 19,805 athletes aged between 8.5 and 27.7 years. Results showed that INT led to a significant improvement in jumping ability (SMD = 0.45, 95% CI 0.30–0.60, P = 0.000) and a reduction in lower limb injuries (SMD = 0.68, 95% CI 0.62–0.74, P = 0.000). The most effective interventions lasted at least 25 minutes, conducted 2-5 times per week, for a minimum of 9 weeks. This approach was particularly beneficial for children and adolescents, as it enhanced their countermovement jump (CMJ) ability and helped in the prevention of injuries. [ABSTRACT FROM AUTHOR]

Introduction: Action observation (AO) and motor imagery (MI) are cognitive processes that involve mentally rehearsing and simulating movements without physically performing them. However, the need for the evidence to support influence of imagery on performance is increasing. This study aims to investigate the impact of combining motor imagery with action observation on athletes' performance and performance perception. Method: Using a pre-test post-test design with a factorial setup, participants were randomly assigned to experimental and control groups. A pre-research power analysis determined the sample size, resulting in 21 voluntary participants (10 male). Opto Jump device recorded drop jump performance measurements, while participants predicted their performance post-motor imagery and action observation practices. The experimental group underwent an 8-week AOMI intervention program, involving 24-minute motor imagery sessions during video observation thrice weekly. Post-test measurements were taken after the intervention. Results: Results indicated no significant performance increase in the experimental group post-intervention, yet the group showed enhanced performance estimation following the video observation, but not in motor imagery condition. Conversely, this improvement was absent in the control group. Discussion: Although AOMI intervention didn't enhance physical performance, it has positively affected athletes' perception toward their performance. The findings are discussed in relation to existing literature. [ABSTRACT FROM AUTHOR]

The study aims to compare static and dynamic postural stability, navicular drop, dorsiflexion range of motion, and jumping performance of individuals with neutral, prone, and hyperprone foot postures. Forty-eight participants between the ages of 18 and 40, were categorized into neutral (n=16), prone (n=16), and hyperprone (n=16) according to foot posture index (FPI). Static and dynamic postural control evaluations (with the Biodex Balance System SD), navicular drop test (NDT) weight-bearing lunge test, countermovement jump test without arm swing, and drop vertical jump tests have been completed. In the results, the average age of participants in the NG, PG, and HPG are 22.31 ± 2.75, 23.87± 3.72, and 22.37 ± 1.28 years and BMI are 22.6 ± 3, 23.4 ± 3.8, and 21.4 ± 2.24 (kg/m²), respectively. The demographic data of the participants showed a homogeneous distribution. There were no significant differences in none of the outcomes except the NDT. Navicular drop amount is positively correlated by the subtalar joint pronation. An increase in subtalar joint pronation does not have a significant effect on static and dynamic stability, jump performance, or dorsiflexion range of motion in healthy individuals. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate the effect of weighted vest on-field small-sided games (SSG) soccer training, during the in-season period, on body composition and soccer-specific performances, in young, trained soccer players. A counterbalance study design was adopted, in which the fourteen well-trained players (age: 19.1 ± 0.5 yrs, body mass: 70.3 ± 5.3 kg, body height: 180.3 ± 3.0 cm, body fat: 9.2 ± 4.1%) performed both the Interventional (Vest) and Control (Con) training routines (6 weeks/season; 5 training sessions/week; 1 match/week), in different occasions (winter/spring period). Con group followed a regular weekly training plan. When the Con group performed their intense training sessions, Vest group performed only the on-field SSGs training wearing a vest (12.5% of athletes' body mass). All the evaluations were performed one week before and after each training period. Statistical analyses include repeated ANOVA and T-test (p < 0.05). Significant increases in sprinting, jumping, change of direction (COD), aerobic and anaerobic performances were observed only after Vest intervention (−4.7 ± 2.2% to 11.2 ± 4.2%; p < 0.05). Significant changes were observed only after Vest training, compared to Cont (p < 0.05). These results suggest that using a weighted vest, during the in-season, onfield SSG training two times/week induces greater increases in young soccer players' sprinting, jumping, COD, aerobic and anaerobic performances. [ABSTRACT FROM AUTHOR]

This study's aim is to examine the effect of a combined balance and multidirectional plyometric training intervention on postural balance ability and lower limb explosive performance in U-13 male and female soccer athletes. Twenty pre-adolescent (age: 12.6 ± 1.6 years) soccer athletes followed a 6-week training intervention combining balance exercises, dynamic stabilization tasks and multidirectional plyometric exercises at a frequency of twice/week for 20–25 min, based on a progressive increase in exercise difficulty from phase A (week 1–3) to phase B (week 4–6). Pre- and post-training measurements were carried out to assess the following: (a) static balance performance in single (left, right)-legged and two-legged quiet stance trials with eyes open and eyes closed (two trials per stance and vision condition of 30 s duration) and (b) lower limb explosive performance in countermovement and squat jumps without arm swing (three trials/jump). The vertical GRF was recorded by a customized force plate (Wii, 1.000 Hz, Biovision) and offline, CoP and explosive performance parameters were calculated. The overall results showed that the static balance ability of athletes remained unaffected, while restricting their vision deteriorated their postural control. The lower limb explosive performance showed a trend for improvement; however, inter-individual variations in athletes' responses might have obscured any effect. [ABSTRACT FROM AUTHOR]

The frog-inspired jumping robot is an interesting topic in the field of biomechanics and bionics. However, due to the frog's explosive movement and large range of joint motion, it is very difficult to make their structure completely bionic. To obtain the optimal jumping motion model, the musculoskeletal structure, jumping movement mechanism, and characteristics of frogs are first systematically analyzed, and the corresponding structural and kinematic parameters are obtained. Based on biological characteristics, a model of the articular bone structure is created, which can fully describe the features of frog movement. According to the various factors affecting the frog's jumping movement, mass and constraints are added, and the complex biological joint structure is simplified into four different jumping structure models. The jumping ground reaction force, velocity, and displacement of the center of mass, joint torque, and other motion information of these four models are obtained through ADAMS simulation to reveal the jumping movement mechanism and the influencing factors of frogs. Finally, various motion features are analyzed and compared to determine the optimal structural model of the comprehensive index, which provides a theoretical basis for the design of the frog-inspired jumping robot. [ABSTRACT FROM AUTHOR]

Background: Football is an intermittent effort sport that demands high intensity power performance. To enhance this performance before training and competition, a short and intense warm-up is convenient. However, there is a gap between the performance reached in the warm-up and the performance needed during competition. Thus, the aim of this study was to analyze if adding WB-EMS to the warm-up increases or not football players performance. Methods: Twelve semiprofessional football players randomly performed 2 FIFA11+ protocol warm-up sessions, one wearing a WB-EMS suit and one without it. Player's body temperature, blood lactate, and jumping and sprint abilities were measured. Results: Thermography showed that skin temperature (Tsk) significantly decreased after both protocols, and only left popliteal Tsk was significantly lower after WB-EMS warm-up protocol compared to NO WB-EMS warm-up (p < 0.05). Lactate was greater after No WB-EMS but not after WB-EMS warm-up. Sprint performance in 20 meters was significantly faster after WB-EMS compared to NO WB-EMS. No significant differences were found between trials in the rest of sprint and jumping abilities tests. Conclusions: Adding WB-EMS to the warm-up does not seem to increase body temperature, only left popliteal Tsk, and to improve acute sprint performance in semi-professional football players. [ABSTRACT FROM AUTHOR]

IntroductionAction observation (AO) and motor imagery (MI) are cognitive processes that involve mentally rehearsing and simulating movements without physically performing them. However, the need for the evidence to support influence of imagery on performance is increasing. This study aims to investigate the impact of combining motor imagery with action observation on athletes’ performance and performance perception.MethodUsing a pre-test post-test design with a factorial setup, participants were randomly assigned to experimental and control groups. A pre-research power analysis determined the sample size, resulting in 21 voluntary participants (10 male). Opto Jump device recorded drop jump performance measurements, while participants predicted their performance post-motor imagery and action observation practices. The experimental group underwent an 8-week AOMI intervention program, involving 24-minute motor imagery sessions during video observation thrice weekly. Post-test measurements were taken after the intervention.ResultsResults indicated no significant performance increase in the experimental group post-intervention, yet the group showed enhanced performance estimation following the video observation, but not in motor imagery condition. Conversely, this improvement was absent in the control group.DiscussionAlthough AOMI intervention didn’t enhance physical performance, it has positively affected athletes’ perception toward their performance. The findings are discussed in relation to existing literature.

This study’s aim is to examine the effect of a combined balance and multidirectional plyometric training intervention on postural balance ability and lower limb explosive performance in U-13 male and female soccer athletes. Twenty pre-adolescent (age: 12.6 ± 1.6 years) soccer athletes followed a 6-week training intervention combining balance exercises, dynamic stabilization tasks and multidirectional plyometric exercises at a frequency of twice/week for 20–25 min, based on a progressive increase in exercise difficulty from phase A (week 1–3) to phase B (week 4–6). Pre- and post-training measurements were carried out to assess the following: (a) static balance performance in single (left, right)-legged and two-legged quiet stance trials with eyes open and eyes closed (two trials per stance and vision condition of 30 s duration) and (b) lower limb explosive performance in countermovement and squat jumps without arm swing (three trials/jump). The vertical GRF was recorded by a customized force plate (Wii, 1.000 Hz, Biovision) and offline, CoP and explosive performance parameters were calculated. The overall results showed that the static balance ability of athletes remained unaffected, while restricting their vision deteriorated their postural control. The lower limb explosive performance showed a trend for improvement; however, inter-individual variations in athletes’ responses might have obscured any effect.

This study explored the relationships between passive muscle stiffness (shear modulus) and vertical jumping performance, countermovement utilization ratio (CUR) and rate of force development (RFD) in an attempt to unravel the mechanism that may explain the association between shear modulus and performance. 32 recreationally active participants (16 males, 16 females; age: 22.4 ± 5.1 years) participated. Shear modulus was assessed for the lateral and medial gastrocnemius (GL and GM), and vastus medialis (VM) and lateralis (VL) muscles using shear wave elastography. Squat jump (SJ) and countermovement (CMJ) jump were determined, with CUR being expressed as the ratio between the two. RFD in ankle and knee extension tasks was measured using isometric dynamometers. Our results suggest that within a heterogeneous group of recreational athletes, passive muscle stiffness is not related to RFD and jump performance, but positively related to CUR. In males, shear modulus of the GL was positively related to SJ height (r = 0.55). We also found inverse moderate correlations between VL and VM shear modulus and RFD in females only (r = –0.50 to –0.51), but this relationship was possibly affected by age and body fat content. Different mechanisms may underpin the association between shear modulus and performance depending on the muscle, task and population investigated. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the hamstring onset time and recruitment level during jumping tasks in athletes with chronic hamstring strain injuries. Thirteen hamstring injured athletes and thirteen matched healthy athletes were recruited. Activation onset time and muscle recruitment (median frequency of the EMG) of the lateral hamstring (LH) and medial hamstring (MH) was measured during double leg jumps in vertical and horizontal directions on the force platforms. The peak vertical ground reaction force and loading rate were obtained for all jumps. The injured group showed a delayed onset time (p = 0.029) and a lower recruitment of the LH during the landing (p = 0.018) than the control group. Activation deficits in the injured group led to a higher landing force and loading rate. Additionally, the LH and MH were lesser recruited in the vertical direction than the horizontal directions in the landing. In conclusion, athletes with hamstring injuries show hamstring activation deficits of the injured leg during jumping leading to degrading jump-landing performance. Also, jumping in different directions play a role to modify the recruitment of the hamstrings in the injured athletes. Therefore, movement plane is suggested to be considered in clinical rehabilitation for the hamstring injury. [ABSTRACT FROM AUTHOR]

Background: There is no clear agreement regarding the ideal rest interval and training intensity to optimize post-activation performance enhancement (PAPE) after barbell squat (BS). Therefore, the aim of this study was to investigate the effects of rest interval and training intensity on jumping performance due to PAPE. Methods: Searches were performed in PubMed, Web of Science, and EBSCO databases. We included studies that satisfied the following criteria: (1) eligible studies should be randomized controlled trials; (2) eligible studies should investigate the acute effect of barbell squat-induced PAPE on jump performance; (3) eligible studies should use countermovement jump, squat jump, or vertical jump as the outcome measure. Results: From 2518 search records initially identified, 19 studies were eligible for meta-analysis. Our meta-analysis results showed that BS had no significant effect on improving jumping performance due to PAPE (Cohen’s d = 0.09, p = 0.08). Subgroup analysis showed that rest interval between 0–1 min was detrimental to jumping performance (Cohen’s d = −0.33, p < 0.01), while rest intervals between 4–7 min (Cohen’s d = 0.31, p < 0.01) and 8-9 min (Cohen’s d = 0.26, p = 0.02) provided favorable jumping performance outcomes. In addition, low-intensity and moderate-intensity BS had no significant effect on jump performance, while high-intensity BS showed results consistent with rest interval. Conclusion: Our study indicated that both low-intensity and moderate-intensity BS failed to induce PAPE, and it is recommended that future studies use high-intensity BS to induce PAPE. A rest interval of 4–9 min had a beneficial impact on jump height, and an interval range of 4–7 min seems to be the best rest interval between conditioning activity and jumping performance. [ABSTRACT FROM AUTHOR]

Inspired by the instantaneous power of the hindlimbs of frogs and the dexterous posture adjustment of their forelimbs, a frog-like jumping robot based on a soft body detonation drive was designed. By combining the flexibility of silicone material and the detonation characteristics of mixed hydrogen–oxygen gas, a soft body detonation driver was constructed to cause the robot to jump from the hindlimbs to achieve a high energy instantaneous explosive force. Moreover, a spring-based forelimb mechanism is designed. This mechanism not only adjusts the robot with different starting jump posture angles but also maintains a smooth landing by providing cushioning. The kinematics and efficiency models of jumping are also established by the D-H parameter method and geometric method, and they are verified and analysed. Finally, combined with the control system, an experimental prototype (weight 495 g) with a height of 135 mm, a trunk length of 120 mm, front and hindlimbs of 195 mm, and a width of 90 mm is developed. The experiment proved that the robot can not only achieve 6 consecutive jumps, a single jump height of 0.6 m and a spanning distance of 1.2 m but also easily cross rectangular obstacles.

The frog-inspired jumping robot is an interesting topic in the field of biomechanics and bionics. However, due to the frog’s explosive movement and large range of joint motion, it is very difficult to make their structure completely bionic. To obtain the optimal jumping motion model, the musculoskeletal structure, jumping movement mechanism, and characteristics of frogs are first systematically analyzed, and the corresponding structural and kinematic parameters are obtained. Based on biological characteristics, a model of the articular bone structure is created, which can fully describe the features of frog movement. According to the various factors affecting the frog’s jumping movement, mass and constraints are added, and the complex biological joint structure is simplified into four different jumping structure models. The jumping ground reaction force, velocity, and displacement of the center of mass, joint torque, and other motion information of these four models are obtained through ADAMS simulation to reveal the jumping movement mechanism and the influencing factors of frogs. Finally, various motion features are analyzed and compared to determine the optimal structural model of the comprehensive index, which provides a theoretical basis for the design of the frog-inspired jumping robot.

Abstract Background Over the last years there have been a wide body of research exploring the best strategies to promote acute enhancements in players’ performance. Despite that, most studies have been focused on adult and elite players, and different results may be identified when considering players from lower levels of performance and belonging to youth categories. In addition, most studies conducted in this domain focused in repetitive movement patterns, and while adding variability has been considered as a useful approach to enhance players’ performance at short and long-term perspectives, less is known regarding it applicability to acute enhance players physical performance. Therefore, this study aimed to compare the acute enhancement effects of performing the half-squat in a flywheel ergometer between a more-repetitive approach (low noise) and a more variable approach (differential learning, high noise) in youth soccer players. Methods A total of sixteen players (age = 16.2 ± 0.6 years) was exposed to four conditions in a randomized order: (1) repetitive intervention for 30 s; (2) repetitive intervention for 10-min; (3) differential learning intervention for 30 s; (4) differential learning intervention for 10-min. Each condition consisted in 3 sets of 6 repetitions of eccentric half squats performed in a flywheel ergometer. Countermovement jump, 10 m and 30 m linear sprint, and change-of-direction ability were measured every session at baseline (pre-test) and after each protocol (post-test). Results No potentiation effect was observed overall with any of the interventions. In addition, no differences between protocols were found for sprinting. However, the repetitive intervention impaired jumping performance for both 30 s (small effects, p ≤ .05) and 10-min intervals (small effects, p ≤ .05), as well as in the change-of-direction task for 30 s (p ≤ .05). Conclusions These results may be due to the players’ low experience in eccentric flywheel training. Despite these findings, individual potentiation responses emerged from both protocols when considering the individual responses, reinforcing the need to establish more personalized approaches.

During the COVID-19 lockdown, professional soccer players ceased their regular team training sessions and were provided with exercise programs to follow independently. This investigation assessed the impact of a 7-week COVID-19 lockdown and home-based individual physical training on professional soccer players’ body composition and physical fitness. The study consisted of nineteen division 1 elite soccer players (age 27.68 ± 5.99 years, height 178.47 ± 5.44 cm) and compared the anthropometric and physical fitness parameters obtained post-transition period to those obtained post-COVID-19 lockdown. The statistical analysis indicated that body fat percentage was significantly higher after the lockdown period [t(18) = -5.59, p < 0.01, d = 0.56]. Furthermore, VO2max [t(17) = -11.54, p < 0.01, d = 0.57] and running time [t(17) = 3.94, p < 0.01, d = 0.76] values were significantly higher after the COVID-19 lockdown than those obtained after the transition period. In addition, significantly higher level of performance was demonstrated on squat jump [t(18) = -4.10, p < 0.01, d = 0.30], countermovement jump [t(18) = -7.43, p < 0.01, d = 1.11] and sit and reach tests [t(19) = -5.33, p < 0.01, d = 0.32]. Concurrently, lower body strength was indicated to be significantly greater (p < 0.01) following the COVID-19 lockdown. The training protocol provided during the confinement, due to the COVID-19 outbreak, was effective in keeping physical fitness at a significantly higher level compared to the transition period. Coaches and trainers are encouraged to examine the effectiveness of this protocol, as it may help them develop effective periodization programs during the transition period. This protocol may aid in the development of effective periodization programs that require minimal equipment and can be followed in similar situations.

Objective: This study aimed to evaluate the effects of an experimental shorttime warm-up consisting of a small number of intermittent high-intensity sprints on explosive muscle strength performance in soccer players and to identify recovery times after performing the sprints. Furthermore, we evaluated the reliability of a smartphone app in jumping performance. Methods: Twenty male soccer players were given the following tests: 1) the counter-movement jump (CMJ) test with the Microgate system, 2) the countermovement jump (CMJ) test with the MyJump smartphone app, and 3) the handgrip strength test. The experimental short-time high-intensity warm-up was carried out 1 week after test administration. The warm-up consisted of three maximum sprints over 60mwith 120 s of recovery between sprints. Then, the tests were administered again: the vertical jump height (VJH) performances (five trials) were measured 90 s after the last sprint; the handgrip strength performances (three trials) were measured 120 s after the last vertical jump test. Results: The maximum VJH was found in the third trial of the CMJ test, 330 s after the last sprint (p < 0.01), the result closest to the baseline. The lowest VJH was found in the first trial of the CMJ test, 90 s after the last sprint (p < 0.05). Pearson's analysis between the CMJ test with the Microgate system and the CMJ test with MyJump showed a strong correlation (R = 0.96). Lin's concordance correlation coefficient showed a substantial concordance (c = 0.959) between measures. Conclusion: This experimental short-time warm-up of high-intensity intermittent sprints appears to be a simple, quick, and efficient activity to accelerate soccer players' optimal performance. [ABSTRACT FROM AUTHOR]

Objective: This study aimed to evaluate the effects of an experimental short-time warm-up consisting of a small number of intermittent high-intensity sprints on explosive muscle strength performance in soccer players and to identify recovery times after performing the sprints. Furthermore, we evaluated the reliability of a smartphone app in jumping performance.Methods: Twenty male soccer players were given the following tests: 1) the counter-movement jump (CMJ) test with the Microgate system, 2) the counter-movement jump (CMJ) test with the MyJump smartphone app, and 3) the handgrip strength test. The experimental short-time high-intensity warm-up was carried out 1 week after test administration. The warm-up consisted of three maximum sprints over 60 m with 120 s of recovery between sprints. Then, the tests were administered again: the vertical jump height (VJH) performances (five trials) were measured 90 s after the last sprint; the handgrip strength performances (three trials) were measured 120 s after the last vertical jump test.Results: The maximum VJH was found in the third trial of the CMJ test, 330 s after the last sprint (p < 0.01), the result closest to the baseline. The lowest VJH was found in the first trial of the CMJ test, 90 s after the last sprint (p < 0.05). Pearson’s analysis between the CMJ test with the Microgate system and the CMJ test with MyJump showed a strong correlation (R = 0.96). Lin’s concordance correlation coefficient showed a substantial concordance (ρc = 0.959) between measures.Conclusion: This experimental short-time warm-up of high-intensity intermittent sprints appears to be a simple, quick, and efficient activity to accelerate soccer players’ optimal performance.

The aim of this study was to conduct a comprehensive examination of caffeine’s effects on countermovement jump (CMJ) performance. In this randomized, double-blind, crossover study, twenty-two resistance-trained men (age: 28 ± 5 years; height: 183 ± 5 cm; weight: 79 ± 10 kg; habitual caffeine intake: 127 ± 102 mg/day) performed the CMJ test on two occasions, following the ingestion of capsule containing 3 mg/kg of caffeine or placebo (3 mg/kg of dextrose). Fifteen outcomes derived from the force plate during the CMJ test were analyzed. As compared to placebo, there was a significant ergogenic effect of caffeine for peak force, force at eccentric to concentric action transition, time to peak force, peak power, maximum rate of power development, peak velocity, power at peak force, velocity at peak power, velocity at peak force, and vertical jump height. Effect sizes ranged from 0.11 to 0.38, p-values ranged from 0.048 to 0.002. There were no significant differences between caffeine and placebo for mean force, mean power, time to peak power, impulse at 300 ms, and force at peak power. This study shows that caffeine ingestion impacts a wide array of outcomes derived from the force plate during the CMJ test, not only jump height. From a practical perspective, the findings suggest that: (1) individuals interested in acute increases in CMJ performance may consider caffeine supplementation; and, (2) caffeine intake should be standardized before CMJ testing.

Traditionally, a larger difference between countermovement (CMJ) and squat jump (SJ) was seen as beneficial, as it reflects the ability to utilize the stretch-shortening cycle. However, strong arguments have been made that this might not always be the case, as larger differences between the jumps could also suggest higher muscle-tendon slack, or poor capability to take this slack up quickly. The purpose of this study was to explore SJ and CMJ, as well as the CMJ to SJ difference (CMJSJDiff) in 9 groups of young athletes. In total, 712 athletes from various disciplines (mean age range: 15.7–36.3 years) and 58 physical education students (mean age: 19.6 years) participated in the study. The major finding of this study was that the groups that showed better SJ and CMJ performance did not show the larger CMJSJDiff. For instance, SJ and CMJ heights were highest in short-distance runners and lowest in long-distance runners, while the largest and smallest CMJSJDiff was shown in physical education students and speed skaters, respectively. Male athletes had a higher CMJSJDiff than female athletes, but the difference was very small. While a larger CMJSJDiff has been traditionally associated viewed as positive, our results could indicate both superior ability to utilize the stretch-shortening cycle, as well as poor ability of rapid force development and excessive muscle slack. Further studies are needed to directly investigate the associations between CMJSJDiff and indicators of athletic performance. [ABSTRACT FROM AUTHOR]

The aim of this study was to conduct a comprehensive examination of caffeine's effects on countermovement jump (CMJ) performance. In this randomized, double-blind, crossover study, twenty-two resistance-trained men (age: 28 ± 5 years; height: 183 ± 5 cm; weight: 79 ± 10 kg; habitual caffeine intake: 127 ± 102 mg/day) performed the CMJ test on two occasions, following the ingestion of capsule containing 3 mg/kg of caffeine or placebo (3 mg/kg of dextrose). Fifteen outcomes derived from the force plate during the CMJ test were analyzed. As compared to placebo, there was a significant ergogenic effect of caffeine for peak force, force at eccentric to concentric action transition, time to peak force, peak power, maximum rate of power development, peak velocity, power at peak force, velocity at peak power, velocity at peak force, and vertical jump height. Effect sizes ranged from 0.11 to 0.38, p-values ranged from 0.048 to 0.002. There were no significant differences between caffeine and placebo for mean force, mean power, time to peak power, impulse at 300 ms, and force at peak power. This study shows that caffeine ingestion impacts a wide array of outcomes derived from the force plate during the CMJ test, not only jump height. From a practical perspective, the findings suggest that: (1) individuals interested in acute increases in CMJ performance may consider caffeine supplementation; and, (2) caffeine intake should be standardized before CMJ testing. [ABSTRACT FROM AUTHOR]

Futsal is a sport that originates from soccer and is increasingly practiced all over the world. Since training and warm-up protocols should be sport-specific in order to reduce injuries and maximize performance, this study aimed to evaluate the effects of 5 weeks of the FIFA 11+ warm-up program on explosive strength, speed, and perception of physical exertion in elite female futsal athletes. Twenty-nine elite female futsal athletes participating in the Italian national championships were divided into two groups: the experimental group (EG) underwent 5 weeks of the FIFA 11+ warm-up program, and the control group (CG) underwent 5 weeks of a dynamic warm-up. We evaluated any effect on explosive strength (by Squat Jump test), speed (by Agility T-test), and perception of physical exertion (by Borg CR-10 scale). All measurements were carried out by a technician of the Italian Football Federation before (T0), at the middle (T1), and at the end (T2) of the protocol. The EG showed significant improvements on performances between T0 vs. T1 and T0 vs. T2 both in the Squat Jump test (p = 0.0057 and p = 0.0030, respectively) and in the Agility T-test (p = 0.0075 and p = 0.0122). No significant differences were found in the Squat Jump test performances in the CG, while significant improvements were detected in the Agility T-test performances (p = 0.0004 and p = 0.0053, T0 vs. T1 and T0 vs. T2, respectively). As for the Borg CR-10 scale, we found a significant difference between T0 and T2 in the EG (p = 0.017) and no differences in the CG. This study showed that 5 weeks of the FIFA 11+ warm-up program improves the jumping performance of female futsal athletes without adversely affecting speed. These findings can be useful for coaches and athletic trainers in order to consider FIFA 11+ warm-up program also in female futsal athletes. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of the external load of elastic bands attached to the waist and heels to enhance the pre-activation of leg extensor muscles on drop jumps (DJs). Twelve male college athletes volunteered for this study. Eight cameras and two force platforms were used to collect data. Each subject performed DJs with elastic band loads of 0% and 20% body weight (BW) attached to the waist and heels during the airborne and landing phases from 40- and 50-cm drop heights. Repeated measures of two-way analysis of variance were performed with two loads of the elastic bands and two heights of the platform for each dependent biomechanical variable. Jump height, reactive strength index, leg stiffness, hip, knee flexion, and ankle plantarflexion angles at the initial foot contact and ankle dorsiflexion range of motion (ROM) significantly increased with 20% BW loads. The peak ground reaction force of impact, eccentric work, and hip flexion range of motion significantly decreased with 20% BW loads. The use of the elastic bands as accentuated loading during the airborne and landing phases of DJs can induce pre-activation of the joint extensors of the lower extremity to achieve stretch-shortening cycle benefits and performance and reduce the ground impact for the lower extremity. Attaching elastic bands to the waist and heels enables the following during drop jumps. The joint extensors of the lower extremities act as a counterbalance to the pull from the elastic bands. The performance of the drop jump was improved. The ground impact was reduced. [ABSTRACT FROM AUTHOR]

In basketball high intensity jumping and sprinting performance is of high importance. There seems to be a relationship between maximal strength (MSt) and jumping performance in general, but influence of MSt in the plantar flexors and jumping performance seems not to be investigated very well. Thus, the aim of this study was to investigate the influence of MSt in the plantar flexors on jumping performance. 37 young elite basketball players were included (age: 13.9±1.8 years; weight: 66.4±16.8 kg; height: 179.21±13.24 cm) and countermovement jump (CMJ) and squat jump (SJ) height as well as unilateral and bilateral maximal isometric contraction in the plantar flexors with bended knee joint were assessed. Pearson correlations were calculated for MSt and jumping performance and Bland-Altman Analysis was performed to determine the level of variance between bilateral MSt assessment and cumulated MSt value of unilateral measurements. This study shows a moderate influence of isometric MSt in the calf muscle on jumping performance, so it seems beneficial to include the training of the plantar flexors in the training routine of basketball players. When determining MSt, the bilateral force deficit must be considered, even though there was no influence on determined correlations. [ABSTRACT FROM AUTHOR]

The relationship between asymmetry and performance is still undetermined in the literature. Methods of assessing asymmetry have been inconsistent and focused on the analysis of jumping asymmetry. Dual ground reaction forces are prevalent in athlete monitoring, though underutilized in asymmetry research. The purpose of this study was to assess the relationship of countermovement jump (CMJ) impulse asymmetry to performance in collegiate soccer athletes. Male and female athletes were selected from an ongoing athlete research repository database of NCAA D-I soccer athletes. All athletes contributed two maximal effort unweighted (CMJ0) and weighted countermovement jumps (CMJ20) using the mean for calculations. Propulsive phase asymmetry scores (PrPAS) and positive impulse asymmetry scores (PIAS) were calculated to determine the magnitude of asymmetry for each prospective phase. Statistically significant correlations were found between CMJ0 jump height and unweighted PIAS (r = −0.43) in females. Males had statistically significant correlations between CMJ20 jump height and weighted PIAS (r = −0.49). Neither unweighted PrPAS nor weighted PrPAS produced statistically significant correlations (r < 0.26) to their prospective jump heights. When assessing CMJ asymmetry, it is recommended to conduct both weighted and unweighted CMJ testing, utilizing PIAS as the metric to be assessed. [ABSTRACT FROM AUTHOR]

Background: Over the last years there have been a wide body of research exploring the best strategies to promote acute enhancements in players' performance. Despite that, most studies have been focused on adult and elite players, and different results may be identified when considering players from lower levels of performance and belonging to youth categories. In addition, most studies conducted in this domain focused in repetitive movement patterns, and while adding variability has been considered as a useful approach to enhance players' performance at short and long-term perspectives, less is known regarding it applicability to acute enhance players physical performance. Therefore, this study aimed to compare the acute enhancement effects of performing the half-squat in a flywheel ergometer between a more-repetitive approach (low noise) and a more variable approach (differential learning, high noise) in youth soccer players. Methods: A total of sixteen players (age = 16.2 ± 0.6 years) was exposed to four conditions in a randomized order: (1) repetitive intervention for 30 s; (2) repetitive intervention for 10-min; (3) differential learning intervention for 30 s; (4) differential learning intervention for 10-min. Each condition consisted in 3 sets of 6 repetitions of eccentric half squats performed in a flywheel ergometer. Countermovement jump, 10 m and 30 m linear sprint, and change-of-direction ability were measured every session at baseline (pre-test) and after each protocol (post-test). Results: No potentiation effect was observed overall with any of the interventions. In addition, no differences between protocols were found for sprinting. However, the repetitive intervention impaired jumping performance for both 30 s (small effects, p ≤.05) and 10-min intervals (small effects, p ≤.05), as well as in the change-of-direction task for 30 s (p ≤.05). Conclusions: These results may be due to the players' low experience in eccentric flywheel training. Despite these findings, individual potentiation responses emerged from both protocols when considering the individual responses, reinforcing the need to establish more personalized approaches. [ABSTRACT FROM AUTHOR]

Spiliopoulou, P, Zaras, N, Methenitis, S, Papadimas, G, Papadopoulos, C, Bogdanis, GC, and Terzis, G. Effect of concurrent power training and high-intensity interval cycling on muscle morphology and performance. J Strength Cond Res 35(9): 2464-2471, 2021--The aim of the study was to examine the effect of performing high-intensity interval cycling on muscle morphology and performance immediately after power training (PT). Twenty healthy female physical education students were assigned into 2 training groups. One group performed PT, and the other group performed the same PT followed by high-intensity interval aerobic training on a cycle ergometer (PTC). Training was performed 3 days per week for 6 weeks. Countermovement jump (CMJ) height and CMJ power, half-squat maximal strength (1 repetition maximum), maximum aerobic power, vastus lateralis muscle fiber composition, and cross-sectional area (CSA) were evaluated before and after the intervention. Countermovement jump height increased after PT (10.1 6 6.6%, p 5 0.002) but not after PTC (25.1 6 10.5%, p 5 0.099), with significant difference between groups (p 5 0.001). Countermovement jump power increased after PT (4.5 6 4.9%, p 5 0.021) but not after PTC (22.4 6 6.4, p 5 0.278), with significant difference between groups (p 5 0.017). One repetition maximum increased similarly in both groups. Muscle fiber composition was not altered after either PT or PTC. Vastus lateralis muscle fiber CSA increased significantly and similarly after both PT (I: 16.9 6 16.2%, p 5 0.035, IIA: 12.7 6 10.9%, p 5 0.008, IIX: 15.5 6 17.1%, p 5 0.021) and PTC (I: 18.0 6 23.7%, p 5 0.033, IIA: 18.2611.4%, p50.001, IIX: 25.5619.6%, p50.003). These results suggest that the addition of high-intensity interval cycling to PT inhibits the anticipated increase in jumping performance induced by PT per se. This inhibition is not explained by changes in muscle fiber type composition or vastus lateralis muscle fiber CSA adaptations. [ABSTRACT FROM AUTHOR]

Knee pads have become increasingly popular among volleyball players. Given the fact high-intensity activities that are crucial to successfully playing this sport lead to an increased risk of a knee injury, the primary use of knee pads is to prevent potential injury. However, no research has been carried out to explain the effects of knee pads on the most important physical abilities in volleyball players, thus directly affecting performance. This study was undertaken to determine the effects of knee pads on the explosive power of the lower extremities, linear speed, and agility in young female volleyball players. In two separated sessions, 84 female volleyball players (age: 14.83 ± 0.72 years; height: 163.19 ± 8.38 cm; body mass: 53.64 ± 10.42 kg; VE: 5.30 ± 3.39 years) completed squat jumps (SJ), countermovement jumps (CMJ) with and without arm swing, linear sprints at 5-m and 10-m, modified t-test, and 5-10-5 shuttle test. Data analyses included descriptive statistics, paired sample T-tests and use of effect size (ES). There was no statistical difference between the two conditions for SJ (p = 0.156; ES = 0.18), CMJ (p = 0.817; ES = 0.03), CMJ with arm swing (p = 0.194; ES = 0.14), linear sprint at 5 m (p = 0.789; ES = 0.03) and 10 m (p = 0.907; ES = −0.01), modified t-test (p = 0.284; ES = 0.13), and 5-10-5 shuttle test (p = 0.144; ES = 0.19). Wearing knee pads has neither an inhibitory nor positive effects on explosive power of the lower extremities, linear speed, and agility in young female volleyball players. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of rectus abdominis (RA) fatigue on the jumping performance and landing loads of volleyball players during countermovement jumps (CMJs) and spike jumps (SPJs). Twelve healthy university volleyball players were evaluated using a three-dimensional motion analysis system, force plates, and surface electromyography (EMG). The lowest center of mass (Min-CoM), maximum jumping height (Max-JH), angles of joints at take-off and landing, joint moment of the lower limbs, and EMG parameters of the RA, erector spinae, and lower limb muscles, when performing the CMJs and SPJs, were recorded before and after a 10 min RA muscle fatigue intervention. After RA fatigue, the Max-JH was significantly reduced, and the lowest Min-CoM was significantly increased. The take-off angles changed significantly at the ankle (SPJ), knee (CMJ), and hip (SPJ), and the plantar flexion torque changed significantly at the SPJ touchdown. The contribution ratio of the feet during SPJs and CMJs changed after fatigue. Temporary RA fatigue decreases the jump height of athletes and causes a change in the landing strategy. [ABSTRACT FROM AUTHOR]

Locusts generally live and move in complex environments including different kind of substrates, ranging from compliant leaves to stiff branches. Since the contact force generates deformation of the substrate, a certain amount of energy is dissipated each time when locust jumps from a compliant substrate. In published researches, it is proven that only tree frogs are capable of recovering part of the energy that had been accumulated in the substrate as deformation energy in the initial pushing phase, just before leaving the ground. The jumping performances of adult Locusta migratoria on substrates of three different compliances demonstrate that locusts are able to adapt their jumping mode to the mechanical characteristics of the substrate. Recorded high speed videos illustrate the existence of deformed substrate's recoil before the end of the takeoff phase when locusts jump from compliant substrates, which indicates their ability of recovering part of energy from the substrate deformation. This adaptability is supposed to be related to the catapult mechanism adopted in locusts' jump thanks to their long hind legs and sticky tarsus. These findings improve the understanding of the jumping mechanism of locusts, as well as can be used to develop artifact outperforming current jumping robots in unstructured scenarios.

The relationship between asymmetry and performance is still undetermined in the literature. Methods of assessing asymmetry have been inconsistent and focused on the analysis of jumping asymmetry. Dual ground reaction forces are prevalent in athlete monitoring, though underutilized in asymmetry research. The purpose of this study was to assess the relationship of countermovement jump (CMJ) impulse asymmetry to performance in collegiate soccer athletes. Male and female athletes were selected from an ongoing athlete research repository database of NCAA D-I soccer athletes. All athletes contributed two maximal effort unweighted (CMJ0) and weighted countermovement jumps (CMJ20) using the mean for calculations. Propulsive phase asymmetry scores (PrPAS) and positive impulse asymmetry scores (PIAS) were calculated to determine the magnitude of asymmetry for each prospective phase. Statistically significant correlations were found between CMJ0 jump height and unweighted PIAS (r = −0.43) in females. Males had statistically significant correlations between CMJ20 jump height and weighted PIAS (r = −0.49). Neither unweighted PrPAS nor weighted PrPAS produced statistically significant correlations (r < 0.26) to their prospective jump heights. When assessing CMJ asymmetry, it is recommended to conduct both weighted and unweighted CMJ testing, utilizing PIAS as the metric to be assessed.

Self-myofascial release (SMR) is a popular method to potentially increase the compliance and extensibility of the fascia and reduce muscle stiffness. The purpose of this study was to examine the acute effects of posterior muscle chain SMR on flexibility, vertical jump performance and balance ability. Eighteen young participants volunteered to take part in this crossover design study. They performed two self-massage sessions in randomized order separated by at least one week. One session consisted of posterior muscle chain SMR whereas the other one was performed on the upper limbs as a control intervention (CON). Flexibility was measured with the Toe Touch Test (TTT), Weight-Bearing Lunge Test (WBLT), and Straight Leg Raise Test (SLR). Jump performance was evaluated during a squat jump, a counter movement jump and a stiffness jump. Dynamic balance ability was assessed through the Star Excursion Balance Test. All these variables were measured before and after each intervention. A significant increase in flexibility (+3.5 ± 1.8 cm, +1.6 ± 1.0°, and +7.7 ± 4.0° for the TTT, WLBT, and SLR, respectively, p < 0.003) and balance performance (4.8 ± 3.9 cm, p < 0.003) was observed following SMR intervention compared to CON. Conversely, jumping performance was unchanged in both groups. SMR improves joint flexibility and dynamic balance ability. [ABSTRACT FROM AUTHOR]

In this study, we investigated the prevalence of inter-limb asymmetries in young volleyball players and assessed the differences in the outcomes of different strength and power tests. The study sample comprised of 54 young volleyball players (25 males). Both limbs were tested for single-leg jumping for distance (forward and lateral single jump and triple jump forward for distance), single-leg vertical counter-movement jump (CMJ), change-of-direction (CoD) ability with 90 and 180° turn tests, unilateral maximal isometric knee extension torque, rate of torque development (RTD), and rate of torque development scaling factor (RTD-SF). For all tests, inter-limb asymmetry indexes were calculated. The average magnitude of the inter-limb asymmetries varied substantially (2.0-31.2 %) among different outcome measures. The agreement in the categorization of participants into ''symmetrical'' or ''asymmetrical'', based on the >10% threshold, was very poor in general, with the exception of the outcomes within the same task (e.g. CMJ power and CMJ force). Similar findings were found for the agreement on the direction of the asymmetries. Inter-limb asymmetry in RTD-SF was weakly associated with the CoD performance (r = 0.30; p = 0.031). Multiple strength and power testing protocols are needed to obtain a comprehensive overview of athlete's imbalances. The commonly accepted 10 % threshold for classification of individuals as asymmetrical should be reconsidered and reinvestigated. RFD-SF is suggested as a novel outcome measure that can provide additional information to researchers and coaches. [ABSTRACT FROM AUTHOR]

Knee pads have become increasingly popular among volleyball players. Given the fact high-intensity activities that are crucial to successfully playing this sport lead to an increased risk of a knee injury, the primary use of knee pads is to prevent potential injury. However, no research has been carried out to explain the effects of knee pads on the most important physical abilities in volleyball players, thus directly affecting performance. This study was undertaken to determine the effects of knee pads on the explosive power of the lower extremities, linear speed, and agility in young female volleyball players. In two separated sessions, 84 female volleyball players (age: 14.83 ± 0.72 years; height: 163.19 ± 8.38 cm; body mass: 53.64 ± 10.42 kg; VE: 5.30 ± 3.39 years) completed squat jumps (SJ), countermovement jumps (CMJ) with and without arm swing, linear sprints at 5-m and 10-m, modified t-test, and 5-10-5 shuttle test. Data analyses included descriptive statistics, paired sample T-tests and use of effect size (ES). There was no statistical difference between the two conditions for SJ (p = 0.156; ES = 0.18), CMJ (p = 0.817; ES = 0.03), CMJ with arm swing (p = 0.194; ES = 0.14), linear sprint at 5 m (p = 0.789; ES = 0.03) and 10 m (p = 0.907; ES = −0.01), modified t-test (p = 0.284; ES = 0.13), and 5-10-5 shuttle test (p = 0.144; ES = 0.19). Wearing knee pads has neither an inhibitory nor positive effects on explosive power of the lower extremities, linear speed, and agility in young female volleyball players.

Background: Research on gender differences of elite long jumpers in competition, although limited, provides useful information concerning the execution of the technique elements of the event. Objective: The purpose of the study was to explore possible gender differences of the spatiotemporal parameters and their development during the final steps of the approach executed by elite jumpers during a major international competition. Methods: The jumpers competed in the 2009 International Amateur Athletics Federation World Athletics Final (7 males and 7 females; official distance: 7.83 ± 0.22 m and 6.58 ± 0.20 m, respectively) were recorded with a panning digital video-camera (sampling frequency: 210 fps, resolution: 480 × 366 pixels). The APAS v13.2.5 software was used for the kinematical analysis. Differences between groups concerning performance, the touchdown on the board and the take-off parameters were examined using the Mann-Whitney U test. Possible gender differences concerning the modulation of the examined parameters during the final three steps of the approach were compared by 2 × 3 (gender × step) ANOVA. Results: Male long jumpers executed the final steps of the approach and the take-off with greater velocity (p = .001) compared to the female athletes. Gender differences (p = .04) were also revealed for the flight to contact time ratio of the penultimate step. Additionally, no gender differences were observed for the majority of the temporal parameters. Nevertheless, female jumpers seemed to significantly differentiate in step length, step frequency and step velocity only at the last step of their approach compared to the previous two steps. Conclusion: When examining gender differences in long jump biomechanics the defining parameter is the penultimate step, where it is suggested for female jumpers to improve the transition from the sprinting gait to the preparation for the take-off.