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Background We investigated the concurrent validity and test-retest reliability of the Jumpo 2 and MyJump 2 apps for estimating jump height, and the mean values of force, velocity, and power produced during countermovement (CMJ) and squat jumps (SJ). Methods Physically active university aged men (n = 10, 20 ± 3 years, 176 ± 6 cm, 68 ± 9 kg) jumped on a force plate (i.e., criterion) while being recorded by a smartphone slow-motion camera. The videos were analyzed using Jumpo 2 and MyJump 2 using a Samsung Galaxy S7 powered by the Android system. Validity and reliability were determined by regression analysis, typical error of estimates and measurements, and intraclass correlation coefficients. Results Both apps provided a reliable estimate of jump height and the mean values of force, velocity, and power. Furthermore, estimates of jump height for CMJ and SJ and the mean force of the CMJ were valid. However, the apps presented impractical or poor validity correlations for velocity and power. Compared with criterion, the apps underestimated the velocity of the CMJ. Conclusions Therefore, Jumpo 2 and MyJump 2 both provide a valid measure of jump height, but the remaining variables provided by these apps must be viewed with caution since the validity of force depends on jump type, while velocity (and as consequence power) could not be well estimated from the apps.

O futebol feminino está crescendo no Brasil e estudos que avaliem o desempenho físico das atletas permitem criar parâmetros para a modalidade. O objetivo do presente estudo foi descrever as variáveis dos saltos verticais em atletas de futebol feminino e realizar a comparação entre atletas defensivas e ofensivas. A amostra foi constituída de 16 atletas de futebol do sexo feminino. Foram avaliados os dados antropométricos, a posição tática e os saltos verticais. Foram coletados saltos squat jump (SJ) e counter movement jump (CMJ) com o aplicativo MyJump. As atletas de futebol avaliadas apresentaram em média 24,33±3,71 cm de altura e 19,69±3,25 W/kg de potência para o salto SJ. Além disso, apresentaram 24,25±4,09 cm de altura e 19,67±3,59 W/kg de potência para o salto CMJ. Em relação à razão CMJ/SJ, o valor apresentado foi de 1,00±0,08. As variáveis avaliadas nos saltos verticais não apresentaram diferenças entre as atletas de futebol defensivas e ofensivas (p>0,05). Assim, as atletas apresentaram aproximadamente 24 cm de altura e 19 W/kg de potência para os saltos, com baixa contribuição do ciclo alongamento-encurtamento para essas ações. Por fim, as atletas de futebol feminino das posições defensivas apresentaram desempenho semelhante às ofensivas nos saltos verticais.

Purpose: To evaluate whether cell-free DNA (cfDNA) levels increase immediately after an acute light and heavy resistance exercise (RE) bout and whether cfDNA levels are associated with functional muscle capacity up to 48 h after an exercise session. Methods: Twenty healthy volunteers performed 3 sets of leg-press RE with 80% of 1-repetition maximum (1RM) (RE80) or 40% of 1RM (RE40) with similar exercise volume. Blood lactate was measured after completion of the 3 sets. Creatine kinase, cfDNA, and jump performance were evaluated before (pre) exercise, immediately postexercise (post-0h), and every 24 h until 48 h. Results: Lactate concentration increased similarly in both groups (RE40 4.0 [1.3] mmol/L; RE80 4.8 [1.3] mmol/L). No changes were observed in squat-jump and countermovement-jump performance after RE40; however, both jumps remained reduced until 48 h in the RE80 group. Creatine kinase concentration increased post-24h only in the RE80 group (pre 128.8 [73.7] U/L to post-24h 313.8 [116.4] U/L). cfDNA concentration increased post-0h only in the RE80 group (pre 249.8 [82.3] ng/mL to post-0h 406.3 [67.2] ng/mL). There was a negative correlation between post-0h cfDNA concentration and post-24h squat jump (r = −.521; P =.01) and post-0h cfDNA concentration and post-24h countermovement jump (r = −.539; P =.01). Conclusion: cfDNA increases in response to RE intensity even when not performed until exhaustion. cfDNA measured immediately after RE is a promising biomarker for muscle-performance decrement up to 48 h after a RE bout. [ABSTRACT FROM AUTHOR]

Body composition, leg power and aerobic capacity have been shown to be related to performance, although their combined influence in a training task under load carriage in soldiers is still unknown. In this study, the influence of aerobic capacity, body composition and leg strength on performance during an obstacle test with and without combat equipment carriage was analysed. Forty males belonging to the Spanish Army participated in this study. The time needed to complete an obstacle course with and without load, aerobic capacity (20-m shuttle run test), leg power (squat jumps) and body composition variables (body mass index [BMI], fat mass and lean mass) were tested to determine the best predictors of performance. The results indicated that the best predictors of obstacle course performance with and without load carriage are VO2max and BMI. The jump height was not a significant factor in the model. In conclusion, BMI and VO2max are predictors of the obstacle test time with and without load carriage, so it is recommended that both variables are included as criteria for enrolment in the military army to guarantee army members exhibit the highest obstacle course performance possible. Highlight The VO2max and BMI are the best predictors of an obstacle course performance with/without load carriage. The jump height was not a significant performance factor. The VO2max and BMI are recommended as enrolment criteria for military army. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine whether changes in collegiate weightlifters' external training load, biochemical markers, and jumping performance correlate to changes in items of the Short Recovery and Stress Scale (SRSS) throughout four microcycles. Twelve well-trained weightlifters (8 males, 4 females; age 24.30 ± 4.36 yr; height 170.28 ± 7.09 cm; body mass 81.73 ± 17.00 kg) with at least one year of competition experience participated in the study. Measurements included hydration, SRSS, biochemical analysis of blood (cortisol [C], creatine kinase [CK]), and unloaded and loaded squat jumps (SJ), and volume-load displacement. Pearson correlation coefficients were calculated between the changes in SRSS items and all other variables. The alpha criterion for all analyses was set at p = 0.05. Negative relationships were observed between changes in SRSS recovery items and C (r = -0.608 to -0.723), and unloaded and loaded SJ height and peak power (r = -0.587 to -0.636). Positive relationships were observed between changes in several SRSS stress items and C (r = 0.609 to 0.723), CK (r = 0.922), and unloaded and loaded SJ height and peak power (r = 0.583 to 0.839). Relationships between changes in some SRSS items and cortisol agree with previous findings highlighting C as an indicator of training stress. Nonetheless, the non-significant relationships between changes in SRSS items, training volume and biochemical markers disagree with previous findings. This may partly be explained by the smaller undulations in training volume in the current study, which were characteristic of typical training. Further, relationships between changes in some SRSS items and jumping performance were opposite of what was expected indicating athletes' perception of their stress and recovery state does not always correspond with their ability to perform. [ABSTRACT FROM AUTHOR]

Most research concerning the effects of music on physical performance was conducted using endurance parameters. This study investigated the effects of relaxing (RLX) vs. self-selected stimulating music (SM) vs. no music (NM) on jump height (JH), jump power (PWR), and average rest period between jumps (RP) in 13 athletes (age: 25.5 ± 2.6 years). After a warm-up and listening to music (1 min) or NM, participants completed five squat jumps on a force plate. Psychological ratings of mood were assessed using a questionnaire before warm-up and after jumping. A one-way ANOVA was conducted to compare effects of music on JH, PWR, and RP. A Friedman test with Wilcoxon signed-rank test was used to detect changes in mood. There were no significant effects of music on JH (p = 0.162) and PWR (p = 0.162). A trend towards longer RP in RLX when compared to SM was detected (+2.72 s, +22%, p = 0.059, d = 0.35). Participants felt more "relaxed" (+3 ranks) and more "powerful" after listening to SM (+2 ranks). Following NM and RLX, athletes felt more "energetic" (each +3 ranks) but less energetic (-3 ranks) after SM. In conclusion, this study did not find any performance-enhancing effects of self-selected SM on jump performance. The influences of music on psychological ratings were inconclusive. For this reason, no evidence-based guidelines for the practical application of music in elite jumping athletes can be made, and more studies are warranted. [ABSTRACT FROM AUTHOR]

Understanding the physiological changes in players' profiles during the season is crucial to optimize training prescription according to players' needs towards a high-level game performance. The purpose of this study was to assess the variation in body composition and physical fitness of elite female basketball players after 16 weeks of in season training. The sample was composed of 13 elite female basketball players aged 19.7 ± 4.3 years (height: 173.7 ± 9.8 cm, body mass: 70.4 ± 11.3 kg). Body composition, static strength, lower-body explosive strength, speed, agility, and aerobic endurance, were assessed initially (T1) and 16 weeks after the regular season (T2). Significant improvements were found between T1 and T2 for the squat jump (t = -2.433, p ≤ 0.05, d = -0.39), the 20 m linear sprint (t = 2.493, p ≤ 0.05, d = 0.87), and the Yo-Yo Intermittent Endurance Test-Level 2 (t = -3.746, p ≤ 0.01, d = - 0.34). Lower-body explosive strength showed a significant contribution to agility and speed. The visceral fat area presented a greater negative correlation with the aerobic and anaerobic capacity. Sports practitioners and coaches should be aware of the importance of monitoring players' body composition and physical fitness to assess the physiological responses to the training process and to optimize training prescription. Training contents may be adjusted according to the responses recorded to achieve the defined goals. The positive contribution of lower-body explosive strength to speed and agility, emphasizes the need to include in-season strength programs targeted to enhance players' overall physical fitness. [ABSTRACT FROM AUTHOR]

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The aim of this study was to investigation of the relationship between knee and ankle angles and squat/countermovement jump heights at the age group of 15-17 swimmers. 10 girls (mean age 15.30±0.48yrs, mean height 165.00±5.33cm, mean mass 49.60±5.10kg) and 13 boys (mean age 16.00±1.00yrs, mean height 178.00±7.32cm, mean mass 64.31±7.35kg) were participated to this study as voluntarily. 10min dynamic dryland warming time were given and after that reflective markers were placed on the lower extremity joints. The wand calibration method was used for calibrated to the area. Fusion Sport Smart Jump matt was located in the area to calculated swimmers' jump heights. Swimmers performed three squat jump (SJ) and countermovement jump (CMJ) trials which were recorded at a frequency of 120Hz using seven high-speed cameras (Oqus 7+). The results were analyzed by Qualisys Track Manager program. Both knee and ankle angles and jump heights relations were calculated. Pearson Correlation and Mann Whitney-U was used in SPSS 21.0 program for analysed. There were no significant relations between SJ and CMJ performances and angles (p>0.05). There were significant differences between boys and girls in both jump heights (p<0.05). For correct jump performance, it is recommended to position the joints according to the recommended optimal angular values. [ABSTRACT FROM AUTHOR]

We aimed to investigate whether the addition of whole-body vibration (WBV) to resistance training (RT) will be more beneficial in improving lower limbs muscle strength, power and sprinting performance than RT alone in young basketball players. We recruited 30 young basketball players to participate in four weeks of training and assessments. They were randomized into the WBV resistance training group (VRTG, n=15) and a conventional resistance training group (RTG, n=15), performed 3 times per week. At the beginning and end of the four weeks a back squat one-repetition maximum (1RMBS), Countermovement jump (CMJ), Squat jump (SJ), 10 meters (10m) and 20 meters sprint (20m) were performed. We found that: a) VRTG when added to RT can induce greater improvements in 1RMBS (percentage difference [PD], 8.4%, p < 0.001), CMJ (PD = 4.7%, p = 0.001) and SJ (PD = 1.6, p = 0.02) than RT alone. In contrary, significant time*group interactions were found for sprint times at 10m (p=0.08, F=3.2) and 20m (p=0.17, F=1.93). An additional 4-week WBV resistance training program proved effective in improving lower limb power and strength in young basketball players. When performed on a vibration platform (with accurate and constant vibration stimulus parameters), the resistance exercises were superior to their conventional forms and resulted in additional gains on measures of muscle power and strength, while sprint performance remained unchanged. [ABSTRACT FROM AUTHOR]

Background: Ballistic and heavy-resistance exercises may potentially enhance lower body power, which is paramount for the punching performance of amateur boxers. This study aimed to determine the acute effects of ballistic exercise (BE) and heavy-resistance exercise (HRE) on countermovement jump (CMJ) and rear-hand straight punch performance in amateur boxers. Methods: Ten amateur boxers performed two conditioning exercises in a randomized and counterbalanced order as follows: squat jump with 4 sets × 8 repetitions at 30% one-repetition maximum (1RM) for BE and squat with 3 sets × 5 repetitions at 80% 1RM for HRE. The jump height (JH), relative maximal force (RMF), relative maximal power (RMP) of the CMJ, punch force (PF), and punch speed (PS) of a rear-hand straight punch were measured before and 3, 6, 9, and 12 min after either BE or HRE. Results: No significant condition × time interaction was found for JH (p = 0.303), RMF (p = 0.875), RMP (p = 0.480), PF (p = 0.939), and PS (p = 0.939). In addition, no main effect of the condition for JH (p = 0.924), RMF (p = 0.750), RMP (p = 0.631), PF (p = 0.678), and PS (p = 0.712). A significant main effect of time was observed for PF (p = 0.001) and PS (p = 0.001), whereas JH (p = 0.081), RMF (p = 0.141), and RMP (p = 0.430) were not. Pairwise comparison identified that PF (p = 0.031) and PS (p = 0.005) significantly increased at 9 min compared with those at baseline. Conclusions: The findings of this study demonstrated that BE and HRE protocols can potentiate the rear-hand straight punch performance at 9 min but bring less favorable improvements for JH, RMF, or RMP of CMJ. [ABSTRACT FROM AUTHOR]

This network meta-analysis aimed at evaluating the effectiveness of different velocity-based (VBT) and traditional 1RM-based resistance training (TRT) interventions on strength and power indices in healthy participants. The research was conducted until December 2021 using the online electronic databases PubMed, Web of Science, PsycNet, and SPORTDiscus for studies with the following inclusion criteria: 1) controlled VBT trials, 2) strength and/or jump and/or sprint parameters as outcomes (c), participants aged between 18 and 40 years, and 4) peer-reviewed and published in English. Standardized mean differences (SMD) using a random effects models were calculated. Fourteen studies with 311 healthy participants were selected and 3 networks (strength, jump, and sprint) were achieved. VBT, TRT, repetitions in reserve (RIR), low velocity loss (lowVL), and high velocity loss (highVL) were ranked for each network. Based on P-score rankings, lowVL (P-score ≥ 0.59; SMD ≥ 0.33) and highVL (P-score ≥ 0.50; SMD ≥ 0.12) revealed favorable effects on strength, jump, and sprint performance compared to VBT (P-score ≤ 0.47; SMD ≤0.01), TRT (P-score ≤0.46; SMD ≤ 0.00), and RIR (P-score ≤ 0.46; SMD ≤ 0.12). In conclusion, lowVL and highVL showed notable effects on strength, jump, and sprint performance. In particular for jump performance, lowVL induced favorable improvements compared to all other resistance training approaches. [ABSTRACT FROM AUTHOR]

Keiner, M, Kadlubowski, B, Sander, A, Hartmann, H, and Wirth, K. Effects of 10 months of speed, functional, and traditional strength training on strength, linear sprint, change of direction, and jump performance in trained adolescent soccer players. J Strength Cond Res 36(8): 2236–2246, 2022—The current study aimed to compare the effects of plyometric and sprint vs. functional vs. strength training on linear sprint (LS 20 m), change of direction (COD; i.e., turning right and left), jump (squat jump [SJ]), and maximum strength (1 repetition maximum [1RM] for a squat) performance in elite adolescent soccer players. A longitudinal design was chosen, and 48 elite male youth were recruited. The athletes were divided into 4 groups (a traditional strength training group [STG], a plyometric and sprint training group [PSTG], a functional training group [FTG], and a control group [CG]). The intervention groups trained for 10 months with additional sessions added to their regular soccer training (4–5 sessions per week); the additional training (2 sessions a week [each about 60 minutes]) consisted of plyometric and sprint training, functional training, and traditional strength training for the PSTG, FTG, and STG, respectively. Data were analyzed using analysis of variance with repeated measurements. The effect sizes were calculated using Hedges g. This study showed significantly superior performance increases with traditional strength training compared with sprint and jump training and functional training for maximum strength (compared with all other groups g = 0.98–1.61), SJ (g = 0.52–0.87 compared with FGT and CG; not significantly different from PSTG), COD (direction of rotation right: compared with all other groups g = 1.58–2.12; direction of rotation left: no significant differences), and 20-m LS (compared with all other groups g = 0.86–1.39) performance over time. Traditional strength training is recommended to increase strength and speed-strength variables and should therefore be given high priority in athletic training programs for elite youth soccer players. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the etiology and extent of neuromuscular fatigue induced by 50 squat jumps performed with and without neuromuscular electrical stimulation (NMES) of the knee extensors. Methods: Nine healthy, recreationally active men (24 ± 2 y) took part in 2 experiments. These consisted of 50 squat jumps performed with stimulation (NMES) or without (CON). Maximal voluntary contraction (MVC) force, maximal voluntary activation level (VAL), and forces evoked by single and double (10 and 100 Hz) stimulations were recorded before and after the 50 jumps. NMES was delivered at the maximal tolerated intensity. Results: Despite average jump height being ~16% lower in the NMES than in the CON session, a reduction over time in jump height was only found in the NMES condition (-6%). After the 50 jumps, MVC force was reduced to a greater extent in NMES than in CON (-25% ± 11% vs -11% ± 12%). Similarly, forces evoked by single stimulations, as well as by 10-Hz and 100-Hz paired stimulations, were reduced to a greater extent in NMES (-33% ± 12%, -42% ± 15%, and -25% ± 13%) than in CON (-21% ± 6%, -30%± 9%, and -14% ± 11%). VAL was not significantly altered by either condition. Conclusion: Performing repeated squat jumps with concomitant NMES induced a greater fatigue than squat jumps performed alone and might potentially represent a stronger training stimulus. [ABSTRACT FROM AUTHOR]

Objectives: The association between single-joint isometric rate of force development (RFDISO) and jumping outcomes remain largely unexplored. Further, the importance of RFD assessed during jumping for jump height and duration (i.e. time from jump onset to take-off) remains ambiguous. We therefore investigated these associations in a large heterogenous sample. Design: Cross-sectional study. Methods: Three-hundred-twenty-six male and female basketball and tennis players, and physical education students performed the bilateral squat jump (SJ) and both bilateral and unilateral countermovement jumps (CMJ). Single-joint RFDISO was assessed for the hip extensors, knee extensors and ankle extensors and associations between relevant outcomes were computed. Results: Knee and hip extensors RFDISO showed small positive correlations with RFDSJ and RFDCMJ. Ankle extensors RFDISO showed a moderate positive correlation with RFDSJ and RFDCMJ. RFDISO showed small to moderate correlations with CMJ and SJ jump height, but trivial correlations with jump duration. Stepwise linear regression showed that a combination of RFDISO from different muscle groups explained a small to moderate variance in jump height (∼23–28%), duration (∼2–3%), and RFD during jumping (∼19–28%). RFDSJ showed small positive and moderate negative correlations with SJ height and duration, respectively while these correlations were small and trivial for the CMJ. Conclusions: The positive correlations between RFD during jumping and jump height, and negative correlation with jump duration imply that improving RFD during jumping could benefit jump performance. However, the mostly small correlations between single-joint RFDISO and jumping RFD suggests that single-joint RFDISO assessments provide only limited information regarding the RFD in sports-related movements.

This network meta-analysis aimed at evaluating the effectiveness of different velocity-based (VBT) and traditional 1RM-based resistance training (TRT) interventions on strength and power indices in healthy participants. The research was conducted until December 2021 using the online electronic databases PubMed, Web of Science, PsycNet, and SPORTDiscus for studies with the following inclusion criteria: 1) controlled VBT trials, 2) strength and/or jump and/or sprint parameters as outcomes (c), participants aged between 18 and 40 years, and 4) peer-reviewed and published in English. Standardized mean differences (SMD) using a random effects models were calculated. Fourteen studies with 311 healthy participants were selected and 3 networks (strength, jump, and sprint) were achieved. VBT, TRT, repetitions in reserve (RIR), low velocity loss (lowVL), and high velocity loss (highVL) were ranked for each network. Based on P-score rankings, lowVL (P-score ≥ 0.59; SMD ≥ 0.33) and highVL (P-score ≥ 0.50; SMD ≥ 0.12) revealed favorable effects on strength, jump, and sprint performance compared to VBT (P-score ≤ 0.47; SMD ≤0.01), TRT (P-score ≤0.46; SMD ≤ 0.00), and RIR (P-score ≤ 0.46; SMD ≤ 0.12). In conclusion, lowVL and highVL showed notable effects on strength, jump, and sprint performance. In particular for jump performance, lowVL induced favorable improvements compared to all other resistance training approaches.

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]

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]

The purpose of this study was to assess the correlation between the body composition, multiple repeated sprint ability (MRSAB) test, and vertical jump performance. Fifteen voluntary elite Turkish badminton players participated in the study. The MRSAB test consisted of 2 repetitions of 4 movements (4x3m) separated by 30 seconds of passive recovery. The best time (BT), meantime (MT), total time (TT), and fatigue index (FI) were measured. Body composition was evaluated through dual-energy X-ray absorptiometry (DEXA). Squat jump (SJ) test for explosive power and countermovement jump (CMJ) test for elastic power were used. The main findings were that there was a significant correlation between MRSAB MT and TT with lean body mass, lean arm mass, and trunk lean mass (kg) of male badminton players. However, no significant correlation was observed among MRSAB MT, BT, and TT with another total/regional body composition of female badminton players (p>0.05). Moreover, the results of male badminton players showed that there was a significant negative correlation between FI and percentage of body fat (%BF), percentage of leg fat (%LF), percentage of trunk fat (%TF), and trunk mass. In addition, there was a significant negative correlation between FI with %BF, body fat mass kg, percentage of arm fat (%AF), arm fat mass, and %LF of female badminton players. It was also found in the study that there was a significant correlation between SJ and %LF; CMJ and %BF, body fat mass kg, %AF, %LF and leg fat mass kg. However, no significant correlation was observed among CMJ and SJ with other total/regional body compositions of male badminton players (p>0,05). Finally, changes in body composition are important issues for the physical performance level of badminton players as regional excess body fat may cause deterioration, especially in repeated-sprint ability and jumping performance. [ABSTRACT FROM AUTHOR]

A detailed review of literature revealed that there is no study of the influence of different types of loads on the performance of a bilateral vertical jump examined on subjects of the same type of F-v profile. Therefore, the aim of this study was to evaluate the influence of two different load types on the squat-jump performance in force-deficient subjects. During the seven-week training program, the 15 participants of force group performed a half back squat with a load of 80-85% 1RM, while the 15 participants of velocity group performed squat jumps with an unloading of 25% of body weight during the same period of time. The force group significantly improved height of the squat jump (+12.43 ± 6.98%; p<.001), with a large effect (ES = 1.92 ± .72), while in the velocity group non-significant changes were recorded (+2.02 ± 5.92%; p=.26), with a small effect (ES = 0.30 ± 0.60). These results in the force group were accompanied by a significant optimization of the F-v profile (+31.53 ± 34.91%; p=.003), with the attribute of large effect (ES = 1.10 ± 0.65), whereas the velocity group again recorded a non-significant change (-2.20 ± 34.34%; p=.70), with a trivial effect (ES = -0.13 ± 0.60). The results of the force group support the hypothesis of the effectiveness of a training program aimed at developing a deficient component of the F-v profile. [ABSTRACT FROM AUTHOR]

Background: In the rehabilitation and sports science fields, comprehensive assessment of the response to exercise is important for accurately prescribing exercise programs. Lactate is an important energy substrate that is frequently measured in clinical practice because it provides information on aerobic capacity. Salivary lactate, which can be measured non-invasively, has recently been focused on as an alternative to blood lactate. This study aimed to determine the combined effects of body fat, body water content, and skeletal muscle mass index on peak salivary lactate levels. Methods: Thirty-seven non-athletic males performed a squat jump exercise. Their salivary lactate levels were measured before, immediately after, and every 5 min after the exercise using a simplified device. We also assessed body composition. A linear multiple regression analysis was performed with peak salivary lactate levels as the dependent variable and body fat ratio, body water content, and the skeletal muscle mass index as independent variables. Results: The participants' body fat ratio (positive effect; p = 0.001) and body water content (negative effect; p = 0.035) significantly affected peak salivary lactate levels. Skeletal muscle mass index tended to positively influence salivary lactate levels (p = 0.099), albeit not significantly. The adjusted R-squared value of the model was 0.312 (p = 0.001). Conclusions: The combined effect of body fat, body water content, and skeletal muscle mass index on peak salivary lactate levels was 31.2%. Better nutritional guidance may be effective in promoting weight loss and increasing body water content to improve aerobic capacity in the rehabilitation setting. [ABSTRACT FROM AUTHOR]

The backward double integration method uses one force plate and could calculate jump height for countermovement jumping, squat jumping and drop jumping by analysing the landing phase instead of the push-off phase. This study compared the accuracy and variability of the forward double integration (FDI), backwards double integration (BDI) and Flight Time + Constant (FT+C) methods, against the marker-based rigid-body modelling method. It was hypothesised that the jump height calculated using the BDI method would be equivalent to the FDI method, while the FT+C method would have reduced accuracy and increased variability during sub-maximal jumping compared to maximal jumping. Twenty-four volunteers performed five maximal and five sub-maximal countermovement jumps, while force plate and motion capture data were collected. The BDI method calculated equivalent mean jump heights compared to the FDI method, with only slightly higher variability (2–3 mm), and therefore can be used in situations where FDI cannot be employed. The FT+C method was able to account for reduced heel-lift distance, despite employing an anthropometrically scaled heel-lift constant. However, across both sub-maximal and maximal jumping, it had increased variability (1.1 cm) compared to FDI and BDI and should not be used when alternate methods are available. [ABSTRACT FROM AUTHOR]

The aim of the study was to test whether ascending to a moderate real altitude affects motoneuron pool excitability at rest, as expressed by a change in the H-reflex amplitude, and also to elucidate whether a possible alteration in the motoneuron pool excitability could be reflected in the execution of lower-body concentric explosive (squat jump; SJ) and fast eccentric-concentric (drop jump; DJ) muscle actions. Fifteen participants performed four experimental sessions that consisted of the combination of two real altitude conditions [low altitude (low altitude, 690 m), high altitude (higher altitude, 2,320 m)] and two testing procedures (H-reflex and vertical jumps). Participants were tested on each testing day at 8, 11, 14 and 17 h. The only significant difference (p < 0.05) detected for the H-reflex was the higher H-reflex response (25.6%) obtained 15 min after arrival at altitude compared to baseline measurement. In terms of motor behavior, DJ height was the only variable that showed a significant interaction between altitude conditions (LA and HA) and time of measurement (8, 11, 14 and 17 h) as DJ height increased more during successive measurements at HA compared to LA. The only significant difference between the LA and HA conditions was observed for DJ height at 17 h which was higher for the HA condition (p = 0.04, ES = 0.41). Although an increased H-reflex response was detected after a brief (15–20 min) exposure to real altitude, the effect on motorneuron pool excitability could not be confirmed since no significant changes in the H-reflex were detected when comparing LA and HA. On the other hand, the positive effect of altitude on DJ performance was accentuated after 6 h of exposure. [ABSTRACT FROM AUTHOR]

The purpose of this study was to establish the validity, reliability, and usefulness of a low-cost contact mat equipment (CM) with a force plate (FP) as the reference. Eleven female (18.6 ± 3.67 yrs.) and male (18.2 ± 2.71 yrs.) basketball athletes performed hands-on-waist countermovement jump (CMJ) and squat jump (SJ) trials. Flight time (FT) and jump height (JH) in CMJ and SJ were subjected for analysis. Relative error expressed as percentage (%RE) was utilized to examine criterion validity between CM and FP. Concurrent validity was also established using Pearson moment correlation (r). Absolute reliability was determined using coefficient of variation (%CV). Relative reliability was identified using intra-class correlation coefficient (ICC). Usefulness was established by comparing typical error (TE) vs. smallest worthwhile change (SWC). Results revealed that CMJ and SJ from a low-cost CM can be used as an alternative tool in assessment of jump performance. [ABSTRACT FROM AUTHOR]

Purpose: A proper warm-up method can be used as a strategy to improve the performance of athletes in various sports fields. The present study aimed to compare the effect of two traditional and post-activation potentiation (PAP) warm-up methods on electromyographic variables of lower limb muscles during squat jumps. Methods: Fourteen trained male athletes randomly performed three different protocols: traditional warm-up method, dynamic Post-activation Potentiation (PD) by implementing two dynamic halfsquat repetitions with 90% 1RM (one rep maximum), and static post-activation potentiation (PS) warm-up by implementing two static half-squat repetitions with 90% 1RM. Vertical jump tests were performed five minutes after implementing each protocol (recovery time). EMG activity of the rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semi-tendinous, medial gastrocnemius, and tibialis anterior was recorded. Also, the co-contraction index and median frequencies were calculated. Repeated measures analysis of variance (ANOVA) was used for data analysis (P<0.05). Results: The results of this study showed that the activity level of all muscles in the concentric and flight phases, the co-contraction index of the ankle and knee joints, and also median frequencies of rectus femoris, vastus lateralis, semi-tendinous, biceps femoris, and medial gastrocnemius significantly changed in the PD and PS warm-up methods compared to the traditional warm-up method (P=0.05). Also, the activity level of rectus femoris, vastus medialis, and biceps femoris muscles had a significant difference between the PD and PS compared to the traditional warm-up method in the eccentric phases (P=0.05). Conclusion: According to the study results, the PAP warm-up method can improve the performance of athletes in training and competition conditions. [ABSTRACT FROM AUTHOR]

The aim of the study was to test whether ascending to a moderate real altitude affects motoneuron pool excitability at rest, as expressed by a change in the H-reflex amplitude, and also to elucidate whether a possible alteration in the motoneuron pool excitability could be reflected in the execution of lower-body concentric explosive (squat jump; SJ) and fast eccentric-concentric (drop jump; DJ) muscle actions. Fifteen participants performed four experimental sessions that consisted of the combination of two real altitude conditions [low altitude (low altitude, 690 m), high altitude (higher altitude, 2,320 m)] and two testing procedures (H-reflex and vertical jumps). Participants were tested on each testing day at 8, 11, 14 and 17 h. The only significant difference (p < 0.05) detected for the H-reflex was the higher H-reflex response (25.6%) obtained 15 min after arrival at altitude compared to baseline measurement. In terms of motor behavior, DJ height was the only variable that showed a significant interaction between altitude conditions (LA and HA) and time of measurement (8, 11, 14 and 17 h) as DJ height increased more during successive measurements at HA compared to LA. The only significant difference between the LA and HA conditions was observed for DJ height at 17 h which was higher for the HA condition (p = 0.04, ES = 0.41). Although an increased H-reflex response was detected after a brief (15–20 min) exposure to real altitude, the effect on motorneuron pool excitability could not be confirmed since no significant changes in the H-reflex were detected when comparing LA and HA. On the other hand, the positive effect of altitude on DJ performance was accentuated after 6 h of exposure.

Foam rolling (FR) durations totaling ≤60 s per muscle are reported to acutely increase flexibility and vertical jump performance. However, limited research has investigated whether these benefits can outlast the inactive post-warmup preparatory period that typically separates warmups from the start of sporting competition. Eleven male athletes (height 1.77 0.09 m, body mass 78.0 17.0 kg, age 22 2 years) completed familiarization, followed by three experimental trials in a randomized and counterbalanced repeated measures crossover design. Trials commenced with 5 min jogging, before ankle dorsiflexion range of motion (ADF-ROM), sit and reach (S&R), countermovement jump (CMJ) and squat jump (SJ) baseline testing. Participants then sat inactively for 10 min (control) or performed lower extremity FR totaling either 30 (30FR) or 60 s (60FR) that targeted four agonist-antagonist leg muscles. Testing was then repeated before and after a simulated inactive 15 min post-warmup preparatory period to establish the acute and delayed effects of FR on performance. A two-way repeated measures analysis of variance was used to identify any significant interaction effects between conditions (30FR, 60FR, control) and timepoint (baseline, acute, delayed). No significant condition x timepoint interaction effect was detected for the ADF-ROM (f = 1.63, p = 0.19), S&R (f = 0.80, p = 0.54), CMJ ((f = 0.83, p = 0.99) or SJ (f = 0.66, p = 0.99). Therefore, FR totaling ≤60 s appears insufficient to enhance flexibility or vertical jump performance in male athletes.

The aim of the present study was to determine if an inertial measurement unit placed on the metatarsal part of the foot can provide valid and reliable data for an accurate estimate of vertical jump height. Thirteen female volleyball players participated in the study. All players were members of the Republic of Serbia national team. Measurement of the vertical jump height was performed for the two exemplary jumping tasks, squat jump and counter-movement jump. Vertical jump height estimation was performed using the flight time method for both devices. The presented results support a high level of concurrent validity of an inertial measurement unit in relation to a force plate for estimating vertical jump height (CMJ t = 0.897, p = 379; ICC = 0.975; SQJ t = −0.564, p = 0.578; ICC = 0.921) as well as a high level of reliability (ICC > 0.872) for inertial measurement unit results. The proposed inertial measurement unit positioning may provide an accurate vertical jump height estimate for in-field measurement of jump height as an alternative to other devices. The principal advantages include the small size of the sensor unit and possible simultaneous monitoring of multiple athletes. [ABSTRACT FROM AUTHOR]

Problem statement: The assessment of players' physical attributes such as explosive power has been relevant for players' selection and talent identification in youth football. Among individual features, the literature describes a high positive correlation between explosive leg power (countermovement -- CMJ, and squat jump -- SJ) and superior levels of sports performance. Purpose: The aims of this study were twofold: 1) to investigate the effects of chronological age, body composition, and functional capacities on the CMJ and SJ performance; and (2) to develop a regression equation using easy-field tests to estimate CMJ and SJ performance. Approach: The sample was composed of 161 male football players (age = 15.8 ± 1.7 years, height = 170.7 ± 8.5 cm, body mass = 63.6 ± 10.1 kg). The calf skinfold thickness was measured as a specific body composition indicator. Strength tests included sit-ups, handgrip, CMJ and SJ heights. Linear speed and agility (T-test) were also measured. Results: Calf skinfold, handgrip, linear speed (35 m) and change of direction speeds in CMJ and SJ performance, and situps only in SJ, were all statistically significant predictors after controlling for the effect of chronological age. Specific regression equation using calf skinfold (X¹), handgrip (X²), sit-ups(X³), linear speed (35 m) (X4), and T-test (X5) to estimate the CMJ [Y = 64.69 + (-.17) (X¹) + .10 (X²) + .04 (X³) + (-3.03) (X4) + (-2.32) (X5)] and SJ [Y = 64.82 + (-.32) (X¹) + .09 (X²) + .05 (X³) + (-2.97) (X4) + (-2.28) (X5)] are presented. Conclusions: After controlling chronological age, calf skinfold, strength, linear speed, and agility are important predictors of explosive leg power. All these predictors should be considered in the monitoring training process to improve leg explosive power performance. [ABSTRACT FROM AUTHOR]

Copyright of SPORMETRE: The Journal of Physical Education & Sport Sciences / Beden Eğitimi ve Spor Bilimleri Dergisi is the property of SPORMETRE: The Journal of Physical Education & Sport Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Spor Hekimligi Dergisi/Turkish Journal of Sports Medicine is the property of Turkish Journal of Sports Medicine / Spor Hekimleri Dernegi and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The vertical jump test is one of the simplest and most prevalent physical tests used in practice and research. This study investigated the validity and reliability of a new mobile application (Jumpo) for measuring jump performance on Android devices. Universityaged students (n = 10; 20 ± 3 years; 176 ± 6 cm; 68 ± 9 kg) reported to the laboratory on three occasions (2-7 days apart): to be familiarized with the jump performance measurements and then for test-retest reliability assessments. Participants performed countermovement jumps (CMJ), squat jumps (SJ), and right and left single-legged jumps in random order on a force platform while being recorded by a smartphone's slow-motion camera. Flight time was selected as the criterion variable. Strong positive correlations between the Jumpo and force platform were observed for each jump type tested (r = 0.93), although the flight times obtained with the Jumpo App were systematically shorter than those provided by the force platform by 3-6% (p < 0.001). The Jumpo App demonstrated a high testretest reliability (ICC = 0.94, CV = 3.7%) with no differences between the coefficients of variation obtained from the Jumpo App and force platform (p = 0.25). With respect to jump type, data from double-legged jumps (CMJ and SJ) were more accurately measured than data from single-legged jumps. The Jumpo App provides a valid and reliable measurement of jump performance, but the following equation should be used to calibrate its flight time results, allowing comparisons to be made to force platform data: Force platformflight time = 0.948 × Jumpoflight time + 41.515. Future studies should cross-validate the calibration equation in a different sample of individuals. [ABSTRACT FROM AUTHOR]

Background and Study Aim. The purpose of this study was to investigate of the relationships between total/segmental body composition and anaerobic performance parameters in female handball players. Material and Methods. Voluntary 16 women handball players (age= 19.6±2.6years, body height= 168.0±5.5cm, body weight= 64.7±10.7kg), trained last 3 years, were participated to the study. Twelve of them were students from Faculty of Sports Sciences. All measurement and tests were completed in the week right after Turkish Women Handball 1th League. Total and segmental body composition parameters (body fat percentage, body fat mass, lean body mass, leg fat percentage, leg fat mass, lean leg mass, torso fat percentage, torso fat mass, and lean torso mass) of each player were evaluated with dual-energy X-ray absorptiometry method. Squat jump test for explosive power, countermovement jump test for elastic (reactive) power, and Wingate test for anaerobic power (WAnT AP) and anaerobic capacity (WAnT AC) were used. Relationships of total/segmental body composition parameters with jump and anaerobic power-capacity parameters were analysed with Pearson correlation and the probability level was set to p£0.05. Results. As a result of statistical analyses, there were negative relationships (p

Comprehensive information regarding neuromuscular function, as assessed through force-velocity-power (FVP) profiling, is of importance for training optimization in athletes. However, neuromuscular function is highly task-specific, potentially governed by dissimilarity of the overall orientation of forceapplication. The hip thrust (HT) exercise is thought to be of relevance for sprinting considering its antero-posterior force orientation and considerable hip-extensor recruitment, however, the association between their respective FVP profiles remains unexplored. Therefore, to address the concept of force orientation specificity within FVP profiling, the maximal theoretical neuromuscular capabilities of 41 professional male footballers (22.1 ± 4.1 years, 181.8 ± 6.4 cm, 76.4 ± 5.5 kg) were assessed during sprint acceleration, squat jumping (SJ) and the HT exercise. No significant associations were observed for maximal theoretical force or velocity between the three FVP profiling modalities, however, maximal theoretical power (Pmax) was correlated between sprinting and SJ (r = 0.73, P < 0.001) and HT and SJ (r = 0.44, P = 0.01), but not between sprinting and HT (r = 0.18, P = 0.36). In conclusion, although Pmax may be considered a somewhat universal lower-extremity capability, neuromuscular function is associated with substantial task-specificity not solely governed by the overall direction of force orientation. [ABSTRACT FROM AUTHOR]

Copyright of Turkiye Klinikleri Journal of Sports Sciences is the property of Turkiye Klinikleri and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Purpose: To determine the reliability of the Dynamic Strength Index (DSI) in college athletes. Method: Nineteen male college athletes performed the squat jump (SJ) and isometric midthigh pull (IMTP) to determine peak force, on 2 separate days. Reliability was assessed by intraclass correlation coefficient (ICC), typical error (TE), percentage change in the mean, smallest worthwhile change (SWC), and coefficient of variation (%CV). Results: Peak force for the SJ was 2137 ± 499 N and 2781 ± 435 N for the IMTP, resulting in a mean DSI of 0.78 ± 0.19. Peak forces in the SJ (ICC = .99, TE = 57.22 N, change in mean = 0.2%, SWC = 4.7%, CV = 2.6%) and IMTP (ICC = .95, TE = 104.22 N, change in mean = 0.5%, SWC = 3.1%, CV = 3.8%) were considered highly reliable between sessions. However, IMTP peak force was the only variable with an overall TE 4.67%, 3.13%, and 5.13%, respectively, identifying meaningful changes in response to training or competition. [ABSTRACT FROM AUTHOR]

Body composition and power are impactful variables of athletic performance. However, few studies have assessed power and body composition changes from pre-, to mid-, to end-of-season in American Football linebackers. The purpose of this study was to determine how power and body composition respond to a competitive season in Division I Football Championship Series (FCS) American football linebackers. Participants (n=9; Age=19.7 ± 1.5 years; Weight=101.5±11.6 kg; Height=183.3±5.2 cm; [Body Fat percent (BF %) =21.31 ± 6.02%)] performed a Dual-Energy X-ray Absorptiometry (DXA) scan, and power was assessed via three vertical jumps and squat jumps at 40, 60, 80, and 100 kg at three time points: a) 1 week prior to their regular season, b) 2 days after the bye week in the middle of the season, and c) 1 week prior to the completion of the season. An Analysis of Variance (ANOVA) revealed no significant differences (p ≤ 0.05) in power or body composition. These results support past research, indicating power and body composition can be maintained throughout a competitive season. However, more research is needed to determine the optimal programming methods to maintain or improve athletic performance via optimization of body composition and power during a competitive season.

The primary purpose of this study is to examine the effect of two different deadlift barbell height positions on maximal isometric force and subsequent maximal squat jump performance in recreationally-trained men. Fifteen young, healthy, recreationally-trained men (age: 24.7 ± 3.5years, height: 177.1 ± 7.9cm, and total body mass: 81.2 ± 9.8kg) volunteered to participate. All participants performed maximal squat jumps (MSJ) at 90° of knee flexion before (pre-test) and after 4-min (post-test) performing the deadlift exercise using maximal isometric force (MIF) and MIF normalized by body mass (ratioMIF) in two barbell height positions (25% and 75% of the lower limb height, LLH) in a randomized and counterbalanced order. A paired-sample t-test was used to test differences in MIF and ratioMIF between 25% LLH and 75% LLH. Two-way ANOVAs were used for positions (25% LLH and 75% LLH) and time (pre- and post-test) for all dependent variables with an alpha of 5%. Differences were found for MIF and ratioMIF during the deadlift between 25% LLH and 75% LLH (p < 0.001). There was observed an increase in impulse between pre- and post-test only at 75% LLH (p < 0.001), decrease in time to peak force between pre- and post-test only at 75% LLH (p < 0.001), and increase in peak force between pre- and post-test at 75% LLH (p = 0.029). The present results showed that the maximal isometric deadlift exercise at 75% LLH (midthigh) improves subsequent jump performance of the squat jump recreationally-trained men. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to investigate the relationship between knee extensors maximum voluntary contraction (MVC) torque and rate of torque development (RTD) with jump performance and with echography intensity (EI) from the vastus lateralis muscle (VL). Methods: We assessed the MVC torque and RTD from knee extensors by a standard isokinetic device from 16 male professional soccer players (25.5 ± 3.9 years). Counter-movement jump (CMJ) and squat jump (SJ) height were calculated from their flight times. EI was determined from VL ultrasound images' grayscale histogram acquired in the middle of the tight. Correlation between variables was investigated by the Pearson correlation coefficient. Results: We observed a VL EI of 26.4 ± 7.8 a.u., and the SJ and CMJ heights were 36.0 ± 3.0 and 36.2 ± 4.1 cm, respectively. There was a significant correlation between the MVC torque and absolute late-phase RTD (r = 0.67 and 0.76—RTD200 and RTD250, respectively), between the CMJ height and absolute RTD50 (r = 0.50), and between the normalized early-phase RTD and SJ height (r = 0.53–0.60—RTD50 and RTD150). Additionally, normalized RTD200 (r = − 0.51) and RTD250 (r = − 0.56) were negatively correlated with EI. Conclusions: Such results suggest that athletes with the ability to produce torque explosively in the very beginning (between 50 and 150 ms) of knee extension can jump higher. Also, the muscle quality assessed by the VL IE seems to be more important to maximum strength and later periods of torque rise (> 200 ms). [ABSTRACT FROM AUTHOR]

Several field-test devices exist to assess vertical jump, but they either lack proper validation or have been validated for the countermovement jump (CMJ) only. This study aimed to quantify the validity and reliability of metrics, including jump height and the calculated reactive strength index (RSI), obtained using the flight-time method from 4 different assessment devices with 3 different vertical jump modalities in comparison to a force platform (criterion assessment). The Optojump, Push-Band 2.0, MyJump2 mobile application, and What'sMyVert mobile application were used synchronously and together with the force platforms. Thirty subjects (17 males and 13 females; age ± SD: 23.37 ± 1.87 years) performed 5 repetitions of CMJ, squat jump (SQJ), and drop jump (DJ) with a standardized 90° knee flexion for all jumps. Relative reliability was determined by intraclass correlation (ICC) and absolute reliability by coefficient of variation (CV) analyses. Excellent reliability was considered as ICC.0.9 and CV,10%. Validity was obtained through an ordinary least products regression, ICC, and CV. Significance was set at p, 0.05. Reliability was excellent on jump height for the CMJ (ICC ≥ 0.98; CV ≤ 8.14%) for all instruments. With the exception of the Optojump, all instruments also had excellent reliability for the SQJ (ICC$0.98; CV ≤ 6.62) and DJ (ICC ≥ 0.94; CV ≤ 8.19). For the RSI metric, all instruments had excellent relative reliability (ICC ≥ 0.92), but none had excellent absolute reliability (CV ≤ 12.5%). The MyJump2 and What'sMyVert apps showed excellent validity on all jump modalities and RSI. The Optojump and Push-Band 2.0 devices both showed system and proportional bias for several jump modalities and RSI. Overall, both mobile applications may provide coaches with a cost-effective and reliable measurement of various vertical jumps. [ABSTRACT FROM AUTHOR]

Vertical jumping ability (VJ) is an important component for successful performance in various team sports such as volleyball, basketball, and soccer. There is evidence that the sport-specific training in these sports may affect the development of VJ throughout the developmental years. Thus, the main objective of this study was to investigate the sport-related effect (volleyball, basketball, soccer) on vertical jumping ability (VJ) and on the stretch-shortening cycle (SSC) during puberty. 320 boys (12–15 years old) – 80 basketball players (BP), 80 soccer players (SP), 80 volleyball players (VP) and 80 non-athletes (NA) – participated in the present study. VJ was evaluated by the squat jump (SJ) and countermovement jump (CMJ) tests, and the contribution of SSC was calculated. The SJ and CMJ were significantly higher in VP vs. NA at the age of 12 years old and significantly greater in all sports vs. NA at the age of 13, 14 and 15 years. Furthermore, 15-year-old VP demonstrated significantly higher SJ and CMJ compared with BP and SP (p 0.05). Finally, pairwise comparisons revealed non-significant sport- and agerelated differences (p > .05) in SSC. The pattern of age-related increase in VJ is different between athletes and non-athletes during puberty. Furthermore, sport-specific training adaptations are evident at the age of 15 years old where VP demonstrate greater VJ than BP and SP, while in younger age groups, there are no significant differences in VJ between athletes of different sports.

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.

Background: The purpose of this study is threefold: (1) compare differences in countermovement jump (CMJ) variables and squat jump (SJ) variables in male track and field athletes; (2) explore the correlation of Fast Twitch Fibers (FT), Effect of Pre-stretch (EP) and other variables during the CMJ in male track and field athletes; (3) explore the correlation of SJ variables in male track and field athletes. Methods: 96 male university athletes (21.25 ± 1.04 years; 71.96 ± 8.58 kg; 180.05 ± 5.66 cm) in track and field volunteered to participate in this study. They are from Capital University of Physical Education and Sports, and all athletes are above the national standard at the second level. Subjects sequentially completed 3 CMJs and 3 SJs on the force plate. Throughout the entire range of motion, the CMJ and SJ were performed with both hands on the hips. In a laboratory, all of the individuals were assessed at the same time. SPSS 25.0 (Chicago, IL, USA) was used to run independent samples t-test and Pearson correlation analysis. Results: The vertical jump displacement (VJD) (p < 0.01), squat displacement (SD) (p < 0.01), peak velocity (PV) (p < 0.01), peak power (PP) (p < 0.05), average power (AP) (p < 0.01) were significantly higher during the CMJ than during the SJ. The peak force (PF) (p < 0.01) was significantly smaller during the CMJ than during the SJ. The FT and EP during the CMJ were associated with low test-retest reliability (coefficient of variation (CV): 9.73–8.86%). VJD, SD, PF, PP, and AP produced high test-retest reliability (CV: 2.29–4.48%) during both the CMJ and SJ movements. The correlation results were as follows, the VJD during the CMJ was significantly related to SD, PF, PP, AP (r = 0.21, r = 0.42, r = 0.8, r = 0.69, respectively). The PF during the CMJ was significantly related to PP and AP (r = 0.87, r = 0.72, respectively). The PV during the CMJ was significantly related to PP and AP (r = 0.63, r = 0.79, respectively). During the CMJ, there were significant connections between PP and AP (r = 0.94). Except for SD showed no significant relationships and the results for the correlation of other variables were the same as CMJ during the SJ. Furthermore, the Fast Twitch Fibers (FT) during the CMJ was significantly related to PP and AP (r = 0.49, r = 0.46, respectively). The Effect of Pre-stretch (EP) during the CMJ was significantly related to PV, PP, AP and FT (r = 0.36, r = 0.24, r = 0.27, r = 0.22, respectively). Conclusions: Our results indicate that both FT and EP were highly significantly correlated with PP in CMJ, and both FT and EP were significantly correlated with AP in CMJ. In addition, FT and EP data have good reliability. It means that FT and EP may be important indicators of lower limb strength in male track and field athletes under certain conditions. This will inform the training of male track and field athletes.

Specific force capacities might be a limiting factor for alpine skiing performance, yet there is little consensus on the capabilities in question, and whether they differ between disciplines. We aimed to test discipline (speed and technical) and performance (event‐specific world standing) effects on lower limb force‐production qualities. National‐level skiers (N = 31) performed loaded squat jumps and isometric mid‐thigh pulls to detect dynamic force output at extremely low and high velocities and maximum isometric force and rate of force development, respectively. Discipline differences were assessed via a general linear model including performance and allowing for interaction effects, with performance associations further characterized via distinct Pearson's correlations. Jump height did not differentiate disciplines, with absolute power slightly higher in speed athletes (F(1,27) = 4.42, P =.045, ω2 = 0.10), and neither variables were related to performance. Speed athletes possessed greater dynamic force at low velocities (F0; F(1,27) = 13.8, P <.001, ω2 = 0.17), and greater relative and absolute maximum isometric force (F(1,25) = 11.19‐20.70, ω2 = 0.16‐0.22, P <.003). Overall, higher ranked athletes possessed more force‐dominant profiles (F(1,27) = 16.28, ω2 = 0.34; r = 0.60 to 0.67, P <.001) and increased rate of force development characteristics (average and maximum, r = −0.50 to −0.82, P <.048). Very robust associations existed between maximum isometric force and speed performance (r = −0.88, P <.001), but only a trend for higher absolute isometric force in technical athletes (r = −0.49, P =.052). Alpine skiers display a preponderance for dynamic force output at low velocities, and isometric force for speed athletes, which highlights the interest in specific assessment and conditioning practices for ski athletes. [ABSTRACT FROM AUTHOR]

This study aimed to compare the reliability and validity of the force-velocity (F-V) relationship parameters obtained from two-point methods differing in the distance between experimental points, and to evaluate the acute change in unloaded jump height after a vertical jump testing procedure based on multiple loads. Totally, 18 men randomly performed two sessions of the squat jump (SJ) and two sessions of the countermovement jump (CMJ) exercises against five external loads (17, 30, 45, 60 and 75 kg). The unloaded jump height was evaluated before and after each testing procedure. Five two-point methods (0–17, 0–30, 0–45, 0–60 and 0–75 kg) and the multiple-point method (0–17–30–45–60–75 kg) were used to model the F-V relationship. The most distant two-point method (0–75 kg) revealed a comparable reliability (CV< 12.1%; ICC> 0.72) and high concurrent validity (r > 0.91) with respect to the multiple-point method (CV< 10.9%; ICC> 0.72). The reliability and validity of the two-point methods decreased with the proximity of the applied loads. Unloaded jump height was significantly reduced after both testing procedures (p < 0.05). These results support the two-point method based on distant loads as a quick and less prone to fatigue procedure for testing the F-V relationship through vertical jumps. [ABSTRACT FROM AUTHOR]

We sought to examine the relationship between upper-leg compartmental lean mass, muscle-specific strength, and explosive strength following anterior cruciate ligament reconstruction. Twleve adolescent female athletes with prior anterior cruciate ligament reconstruction were individually-matched by age (16.4±0.9 vs. 16.4±1.0 yrs.), body mass index (23.2±2.1 vs. 23.2±2.7 kg/m2), and sport to 12 female athlete controls. One total-body and 2 lateral-leg dual X-ray absorptiometry scans measured total/segmental body composition. Isokinetic dynamometry measured knee extensor/flexor peak torque. Squat jumps on force platforms measured bilateral peak vertical ground reaction force. Paired t-tests assessed lean mass, peak torque, and force between previously-injured athletes' legs and between previously-injured and control athletes' legs. Previously-injured athletes' involved vs. non-involved leg demonstrated lower total (7.13±0.75 vs. 7.43±0.99 kg; p<0.01) and anterior (1.49±0.27 vs. 1.61±0.23 kg; p<0.01) and posterior (1.90±0.19 vs. 2.02±0.21 kg; p=0.04) upper-leg lean mass. Involved leg peak torque (1.36±0.31; 1.06±0.27; 0.97±0.19 Nm/kg) was lower vs. non-involved leg (1.71±0.36; 1.24±0.33; 1.04±0.15 Nm/kg; p<0.01−0.02) for extension at 60 and 120°/sec and flexion at 60°/sec and vs. controls' 'matched' leg (1.77±0.40 Nm/kg; p=0.01) for extension at 60°/sec. Involved leg force (296±45N) was lower vs. non-involved leg (375±55N; p<0.01) and vs. controls' 'matched' leg (372±88N; p=0.02). One-year post-anterior cruciate ligament reconstruction, adolescent female athletes' involved leg demonstrated relative muscle dysfunction. [ABSTRACT FROM AUTHOR]

This study aimed to assess the reliability and validity of the Polar V800 to measure vertical jump height. Twenty-two physically active healthy men (age: 22.89 ± 4.23 years; body mass: 70.74 ± 8.04 kg; height: 1.74 ± 0.76 m) were recruited for the study. The reliability was evaluated by comparing measurements acquired by the Polar V800 in two identical testing sessions one week apart. Validity was assessed by comparing measurements simultaneously obtained using a force platform (gold standard), high-speed camera and the Polar V800 during squat jump (SJ) and countermovement jump (CMJ) tests. In the test-retest reliability, high intraclass correlation coefficients (ICCs) were observed (mean: 0.90, SJ and CMJ) in the Polar V800. There was no significant systematic bias ± random errors (p > 0.05) between test-retest. Low coefficients of variation (<5%) were detected in both jumps in the Polar V800. In the validity assessment, similar jump height was detected among devices (p > 0.05). There was almost perfect agreement between the Polar V800 compared to a force platform for the SJ and CMJ tests (Mean ICCs = 0.95; no systematic bias ± random errors in SJ mean: -0.38 ± 2.10 cm, p > 0.05). Mean ICC between the Polar V800 versus high-speed camera was 0.91 for the SJ and CMJ tests, however, a significant systematic bias ± random error (0.97 ± 2.60 cm; p = 0.01) was detected in CMJ test. The Polar V800 offers valid, compared to force platform, and reliable information about vertical jump height performance in physically active healthy young men. [ABSTRACT FROM AUTHOR]

Change of direction (COD) performance has an essential role in soccer. In the literature, there is a wide range of explained variance in correlation analyses between linear-sprint performance, concentric power and maximum strength and COD performance. Therefore this study has (1) analyzed the influence of linear-sprint performance, concentric power and maximum strength on COD performance in elite youth soccer players and (2) compared the calculated influence on the different COD tests. To answer the research questions, 67 elite youth soccer players were tested. The linear-sprint (10 m, [LS]) performance, concentric power (squat jump [SJ]) and maximum strength (1 repetition maximum [1 RM]) and COD (measured via the Illinois agility test [IAT], the 505 agility test [505], the agility test of the German Soccer Association [GewT], and the triangle test [TriT]) were assessed. The Pearson correlation analysis was used to assess the relationship. Benjamini and Hochberg's method, which was used to control the study-wise false discovery rate, was 0.05. The LS performance had the greatest impact on COD performance with a wide range of explained variance between the different COD tests (r2 = 0.18 to 0.39). However, SJ compared to LS performance had lower influence, but also a wide range of explained variance (r2 = −0.02 to −0.29). Correlations for 1 RM and COD test were calculated with r2 = −0.01 to −0.09. Thus, (1) the greater the similarity between the performance tests (i.e., LS, SJ, 1 RM) and the COD tests, the higher the explained variance between the variables in question. Furthermore, (2) as the different COD tests are affected to different degrees by linear-sprint, concentric power and maximum strength performance, it might be concluded that the tests have a different physiological requirement profile. Therefore, coaches and sport scientists must review and select different tests with logical validity, based on the requirement profiles of soccer. [ABSTRACT FROM AUTHOR]

Featured Application: This investigation attempts to ascertain the value of testing general jump types for the assessment of specific jump performance and provides improved models including the most frequently used jump types with additional variables to more precisely predict sport-specific jump performance. In performance testing, it is well-established that general jump types like squat and countermovement jumps have great reliability, but the relationship with volleyball spike jumps is unclear. The objectives of this study were to analyze the relationship between general and spike jumps and to provide improved models for predicting spike jump height by general jump performance. Thirty female and male elite volleyball players performed general and spike jumps in a randomized order. Two AMTI force plates (2000 Hz) and 13 Vicon MX cameras (250 Hz) captured kinematic and kinetic data. Correlation and stepwise-forward regression analyses were conducted at p < 0.05. Simple regression models with general jump height as the only predictor for spike jumps revealed 0.52 ≤ R2 ≤ 0.76 for all general jumps in both sexes (p < 0.05). Alternative models including rate of force development and impulse improved predictions during squat jumps from R2 = 0.76 to R2 = 0.92 (p < 0.05) in females and from R2 = 0.61 to R2 = 0.71 (p < 0.05) in males, and during countermovement jumps with arm swing from R2 = 0.52 to R2 = 0.78 (p < 0.01) in males. The findings include improved prediction models for spike jump height based on general jump performance. The derived formulas can be applied in general jump testing to improve the assessment of sport-specific spike jump performance. [ABSTRACT FROM AUTHOR]

This case study examines the longitudinal jump data of 1 male and 1 female world-class mogul skier over the course of a quadrennial leading to the 2010 Winter Olympics. Between-subjects standard deviation, smallest worthwhile enhancement, % coefficient of variance, and effect size (ES) were calculated from team jump testing taking place immediately preceding the 2010 Winter Olympics, as this was deemed the point in the quadrennial that the athlete group would be most likely near their best performance. These data were then used to characterize the progression of explosive power of elite mogul skiers over an Olympic quadrennial. Jump data for both the male and the female athlete showed trivial to large improvements in jump performance from Ql (quadrennial year 1) to Q2, variable changes in performance from Q2 to Q4, and an overall improvement (small to large ES) from Ql to Q4. Explosive power is a critical component of performance for moguls, and an analysis of the group data (Canadian athletes 2006-2010) shows that of all performance markers, jump testing is the variable that clearly delineates between World Cup and developmental athletes. [ABSTRACT FROM AUTHOR]