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Introduction. Squat jumps (SJ) and countermovement jumps (CMJ) are commonly used as tests to assess power output of lower extremities. Aim of Study. The aim of this article was to analyze differences between two vertical jumps in order to assess explosive power in elite female volleyball players and identify mechanisms responsible for existence of those differences. Material and Methods. Participants of this study were 14 elite female volleyball players of the Montenegro U19 national team (age: 18.42 ± 1.34 years; height: 178.15 ± 4.9 cm; weight: 68.1 ± 5.83 kg; body mass index: 21.34 ± 1.10 kg/m²; body fat: 18.89 ± 3.70%). Jump height data for a SJ and a CMJ was obtained using OptoJump device (Optojump, Microgate, Bolzano, Italy). Results. The results showed that there is no statistically significant difference (F = 0.093, p < 0.124) between the heights of the SJ (26.64 ± 2.93 cm) and the CMJ (26.65 ± 2.85 cm). Conclusions. The findings suggest that elastic energy has very little effect on improving CMJ performance. On the other hand, CMJ training can reduce an ability to effectively create pre-tension and quickly build stimulation, because athletes are not forced to do so, as the CMJ reduces a degree of muscle relaxation and provides more time to create stimulation. Based on the data, the CMJ may be detrimental to high-intensity sports performance if performed over a longer time frame. [ABSTRACT FROM AUTHOR]

Introduction. Plyometric training (PT) and change of direction (COD) exercises are used to train soccer players because of their well-known positive impact on physical performance indicators. Aim of Study. The aim of this study was to evaluate effects of a low-volume, low-frequency intervention program, that included plyometric exercises in one session and COD exercises in another session, on anaerobic indexes in soccer players under 16 years of age (U16). Material and Methods. The study included 28 players divided into an exercise group (EG) (n = 14) and a control group (CG) (n = 14). The intervention program was conducted for eight weeks. The two-way repeated measures ANOVA was used for data analysis. Results. The results showed that the EG improved its performance in all speed tests (5 m: 0.98-0.95, η² = 0.948; 10 m: 1.75-1.70, η² = 0.966; 20 m: 3.10-3.01, η² = 0.963; 30 m: 4.42-4.29, η² = 0.964; p < 0.001) and in all jumping tests (squat jump, SJ: 28.0-28.9, η² = 0.523; countermovement jump, CMJ: 29.4-30.9, η² = 0.797; CMJ right leg: 15.7-16.5, η² = 0.913; CMJ left leg: 16.8-17.6, η²= 0.926; p < 0.001). Furthermore, EG performance significantly differed from CG performance in postintervention measurements for the 5-m (p < 0.001) sprints, the10-m sprints and the CMJ left leg tests (p < 0.05). No changes in performance were observed in the CG. Conclusions. In conclusion, the application of a weekly program combining the plyometric and COD exercises can positively affect young soccer players' performance. [ABSTRACT FROM AUTHOR]

Problem Statement: Currently, there is a lack of evidence regarding the influence of various breathing conditions on specific strength parameters. Several studies have primarily focused on the health aspects of breathing through the nose versus the mouth. The purpose of this study is to investigate how specific breathing conditions affect explosive power performance. Approach: Fifty male college students performed 5 sets of 3 repetitions of squat jumps (SJ) under three breathing conditions: exhaling through the nose (NE), exhaling through the mouth (ME), and breath hold after inhale (BH). The best performance attained under each breathing condition (SJmax) as well as the average performance of the three best attempts under each condition (referred to as SJave) were recorded. Additionally, the participants' natural breathing pattern (NBP) was identified to assess whether the best results were achieved under it. A repeated measures ANOVA method and parametric paired ttest were used to identify differences in SJmax and SJave among various breathing conditions. The effect size was evaluated using Cohen's d. The Chi-squared test was employed to establish a relationship between SJmax, SJave, and NBP. Results: The ANOVA analysis revealed significant differences between the selected breathing conditions in both SJmax (p = 0.047) and SJave (p = 0.001). In the context of SJmax, both ME and BH led to significantly higher results than NE (NE < ME, p = 0.047, d = 0.29; NE < BH, p = 0.02, d = 0.34). Similarly, ME and BH also achieved significantly higher SJave results (NE < ME, p = 0.003, d = 0.45; NE < BH, p < 0.001, d = 0.53). Chi-squared analysis revealed a significant relationship between NBP and both SJmax (χ² = 6.30, p = 0.043) and SJave (χ² = 6.66, p = 0.036). Conclusion: The NE breathing condition can significantly lower squat jump performance compared to ME or BH in individuals who do not use NE in their training practice. Best squat jump performance is frequently achieved under NBP. However, selected breathing conditions may have a significant, yet likely minor effect on squat jump performance. [ABSTRACT FROM AUTHOR]

In most sports, mobility of the body's center of mass is as important as muscle strength and posture maintenance. Many dynamic studies have revealed a positive relationship between teeth clenching with a mouthguard (CLMG) and athletic ability. However, the effects of CLMG on mobility remain controversial. Vertical jumping, particularly squat jumping (SJ), can be used to evaluate this ability. During SJ, arm swing and reactionary operation of lower limbs are limited. Therefore, the effects of CLMG can be readily investigated. In the present study, we measured SJ height, biomechanics data and masseter muscle activity under two oral conditions: CLMG, and no mouthguard with no instructions on clenching. The aim of the present study was to clarify whether CLMG improves SJ performance. A total of 10 adult female athletes with an average age of 20.8±1.2 years participated in this study. The study protocol was approved by the Tokyo Dental College Ethics Committee (approval No. 437). The study adhered to the tenets of the Helsinki Declaration on the Ethical Treatment of Human Subjects. A customized EVA MG was used for each subject. Measuring devices included the 3-dimensional motion capture system, ground reaction force meters, and electromyograms. The results indicated that CLMG improved SJ height by enhancing work, work rate of hip joints, steadiness of body balance function during jump preparation, and masseter muscle activity. Within the limitations of this study, the results indicated that CLMG tended to improve SJ performance. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the relationships between vertical jumps (VJ) and various on-ice skating performances of junior ice hockey players (n = 19). The three modes of VJ or off-ice measures were countermovement jump with arm swing (CMJ), squat jump (SJ) and depth drop jump (DDJ). The on-ice skating performance was measured by the skating multistage aerobic test (SMAT), forward and backward acceleration test, top speed test, and repeated sprint ability (RSA) test. The relationships between the variables were quantified using Pearson's product-moment correlation. DDJ showed a significant positive correlation with forward average skating speed (FASS) (r = 0.62) and strong correlations with backward average skating speed (BASS) (r = 0.81), and maximum skating speed (MSS) (r = 0.71). SJ was found to be strongly correlated with BASS (r = 0.82) and MSS (r = 0.76), whereas the only on-ice performance that significantly correlated with CMJ was BASS (r = 0.68). All three modes of VJ were inversely and non-significantly correlated with performance decrement index and fatigue index, as determined by the RSA test. SMAT was not significantly correlated with either VJ or RSA. Correlations between all three modes of VJ tests were significant. Therefore, this study concludes that: (1) DDJ can be used as a predictor of all the ice skating speed tests, whereas SJ can predict BASS and MSS. CMJ, on the other hand, can predict the performance of only BASS. (2) RSA performance cannot be predicted from CMJ, SJ, or DDJ tests, and (3) neither any of the VJ nor RSA can predict skating endurance of junior ice hockey players. [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]

Copyright of Facta Universitatis: Series Physical Education & Sport is the property of Facta Universitatis, Series Physical Education & Sport 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 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]

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]

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]

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]

Background: Vertical jump height and body height are almost universally recognised as determinant factors in elite volleyball performance. Objective: The purpose of this study was to assess the correlation between basic anthropometric parameters (body height and body weight) and jumping performance in a group of 16 female volleyball players (age 19.14 ± 5.52 years, height 1.80 ± 0.06 m, weight 69.81 ± 6.85 kg) and in a control group of 15 female university students (age 22.90 ± 0.83 years, height 1.70 ± 0.05 m, weight 61.70 ± 8.23 kg). Methods: The Quattro Jump 9290BA force platform system (Kistler, Winterthur, Switzerland) was used to test jumping performance in single vertical jumps (squat jump, countermovement jump) and 45-s continuous jumps. In single jumps, jump height was analysed and during the 45-s continuous jumps the maximal and mean jump height, the average contact time and the fatigue index were evaluated. The efficiency of the conversion of mechanical work into mechanical energy at the moment of takeoff was calculated. Results: No significant influence of body height and body weight was found in the jumping performance in the squat jump and countermovement jump. In continuous jumps, a significant correlation was found between body height and fatigue index in the volleyball players. In the control group, in most of the tests moderate correlation between body height and jump height was observed. In the volleyball players, rather low values of efficiency of take-off (23.67 ± 2.64%) were calculated. The values in the control group were even lower. Conclusions: Nowadays, many volleyball coaches choose individuals mainly according to body height, but it is important that the talent identification process should also consider jumping abilities in the simple jumps and in continuous jumps. All these parameters should help coaches choose the right players for the appropriate position and role in the team. [ABSTRACT FROM AUTHOR]

Copyright of Facta Universitatis: Series Physical Education & Sport is the property of Facta Universitatis, Series Physical Education & Sport 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.)

Six university soccer players were selected for a correlational and comparative study. The correlation between squat jump height and 10-metre sprints, 30-metre sprints, arrowhead agility test, static balance test and velocity ofball during instep kickwereinvestigated. The comparative study involved comparisons between ball velocityandbetween the muscle activity of vastus lateralis, rectus femoris, biceps femoris and tibialis anterior of kicking limb and supporting limbduring instep soccer kick from 0-degree, 45-degree and 60-degree angle of approach from the target with the dominant limb and non-dominant limb. A significant association was found between squat jump height and 10-metre sprints (r = -0.93, p = 0.007) and 30-metre sprints (r = -0.88, p = 0.021). Also, significantly greater ball velocities were attained from 45-degree angle of approach with the dominant limb(= 7.49, p = 0.010, partial 37.50, p = 0.002, partial = 0.88). Greater muscle activity was found in tibialis anterior of kicking limb(= = 0.60)as well as non-dominant limb(= 6.52, p = 0.015, partial = 0.57) when the dominant limbwas used for instep kick and in rectus femoris of supporting limb(= 5.536, p = 0.024, partial = 0.52) when non-dominant limbwas used from 0-degree approach. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine differences in the neuromechanical properties of knee extensors and vertical jump height between pre-pubertal and pubertal children, as well as to investigate the influence of these properties on the performance of the children's squat jump (SJ). The sample consisted of 13 pre-pubertal and 13 pubertal children of both sexes. The vertical SJ, a maximal isometric voluntary contraction (MVC) of the knee extensors, concomitant with the electromyographic activity (EA) of the vastus lateralis (VL), rectus femoris, vastus medialis (VM), and biceps femoris were collected. We compared the neural-mechanical variables of the CVM as Maximal Force (FMax), EA, Rate of Force Development (RFD), Force Max (FMAX), Rise of Electromyographic Rate (RER), Electromechanical Delay (EMD), and Co-activation. The findings showed that during the MVC of the knee extensors of the pubertal children versus the pre-pubertal children, they presented the following characteristics: (a) higher muscle capacity EA, lower EMD, higher RER, and similar co-activation; and (b) higher RFD at the beginning of MVC. Regarding the performance in the SJ, the pubertal children presented higher performance than the pre-pubertal children. In addition, linear regression identified an influence of the EMD of the VL and VM muscles on the performance of the SJ. [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<0.01), whereas no differences were observed between 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. [ABSTRACT FROM AUTHOR]

EMD as a factor influencing the speed of muscle force production, measured during squat jump, can be used as a relevant substitution for isometric or isokinetic assessment. The purpose of this study was to examine the reliability of measurement of EMD in knee muscles (biceps femoris, semitendinosus, rectus femoris) during a vertical jump. Thirteen volunteers unfamiliar with the squat jump participated in this study and were measured 2 times, with rest periods of 7 days between measurements. EMD was calculated using a force platform and electromyography. Intraclass correlation coefficients ranged (ICC) from 0.69 to 0.78, indicating high reliability for the rectus femoris (RF) and semitendinosus (ST) and moderate reliability for the biceps femoris (BF). Absolute reliability expressed by standard error of the measure (SEM) ranged for RF 28.11, BF 23.18 and ST 21.20, better used as a coefficient of variation (CV of SEM) for RF 22.81%, BF 25.19% and ST 19.72%. These findings provide researchers and clinicians with another method for relatively fast measurement of EMD using portable devices. [ABSTRACT FROM AUTHOR]

Background: Loss of power has been demonstrated to have severe functional consequences to perform physical daily living tasks in old age. Purpose: This study aimed to assess how moment and velocity were affected for each joint of the lower limbs during squat jumping for older men in comparison with young adults. Methods: Twenty-one healthy older men (74.5 ± 4.6 years) and 22 young men (21.8 ± 2.8 years) performed maximal squat jumps. Inverse dynamics procedure was used to compute the net joint power, moment and velocity produced at the hip, knee and ankle joints. Results and discussion: Vertical jump height of the elderly was 64 % lower than the young adults. The maximal power of the body mass center ( P ) was 57 % lower in the older population. For the instant at P , the vertical ground reaction force and the vertical velocity of the body mass center were 26 % and 35 % less in the older adults than in the young adults, respectively ( p < 0.05; ES = −1.64 for vertical ground reaction force; p < 0.05; ES = −1.10). A lower value of the hip (−60 %), knee (−72 %) and ankle (−68 %) joint powers was observed in older adults. This was explained by both lower values of joint moments (−64, −57 and −61 % for the hip, knee and ankle, respectively) and angular velocities (−59, −49 and −52 % for the hip, knee and ankle, respectively). Conclusion: This study showed a lower joint power when performing vertical jump. This smaller power resulted from both a lower moment and angular velocity produced at each joint. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Capital Institute of Physical Education is the property of Shoudu Tiyu Xueyuan 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.)

This study compared vertical displacement of rock climbers performing a dyno maneuver using a squat jump (SJ) and a counter-movement (CM) technique. These techniques were tested at three different starting positions, varying in distance between hand and foot holds. Thirteen recreational rock climbers performed two SJ and two CM dynos at each starting position. Vertical displacement was measured through video analysis. Results showed that there were no significant differences in vertical displacement of the hand (VDH) between jump techniques (p > 0.05). There was, however, a significant improvement in VDH as the subjects moved from the low-to-medium and medium-to-high starting positions (p < 0.05). Therefore, a climber should base their technique on preference or experience while leaving a sufficient amount of space between the hands and feet if possible. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the relationship between anaerobic power and vertical jump performance in adolescent athletes. Twenty four track and field athletes participated in this study (mean age: 15.79±0.83 years; height: 166.78±9.77 cm; weight: 57.44±13.42 kg; BM: 20.45±3.01 kg/m2; body fat percentage (%): 18.80±5.55). The 12 minute Cooper test was performed to estimate VO2max (41.73±6.92 ml/kg.min). After 3-7 days the subjects applied counter movement jump (CMJ) and squat jump (SJ) for the following parameters: (1) the maximum jumping height [SJh and CMJh], (2) the total work produced by the body in each jumping condition [SJw and CMJw: weight (kg) × jump height (m)] and (3) the anaerobic performance [CMJpower and SJpower (kg.m/s): P= √4.9 × weight (kg) × √jump height (m)]. The Wingate anaerobic test was applied to determine peak power, average power and fatigue index. The jumping performance variables (height, total work and anaerobic power) and VO2max did not relate significantly to the fatigue index (p>0.05). All jump performance variables had a significant relationship with peak power and mean power (p<0.05 and p<0.01). Although both the absolute and relative Wingate test variables were significantly correlated with all jump performance variables, the r values for the relative variables were lower than their absolute counterparts. The results of the present study indicated that in field conditions the trainers may predict anaerobic performance using the jumping properties and when the subjects' body weight was incorporated, this led to a more representative indicator of the subjects jumping abilities. [ABSTRACT FROM AUTHOR]

Copyright of Facta Universitatis: Series Physical Education & Sport is the property of Facta Universitatis, Series Physical Education & Sport 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.)

It was previously reported that the performance of the ballistic movements is positively affected when a maximal stimulus is preceded and this phenomenon was caused from Post Activation Potentiation (PAP). The effect of PAP on ballistic movements has not been extensively investigated between the intervals of the resistance trials during a training session. Aim of the present research was to evaluate the effect of 10 highresistance half-squats (90% of 1 RM) on squat jump (SJ) which was performed after two different intervals between resistance trials. Fifteen recreationally active adults (aged: 20.73 ± 2.12y) participated in the study. Resistance Maximal (RM) and maximal SJ of each participant were evaluated the same day with the test. The 10 Half-Squats trials were performed within a 5 minute rest interval between one another. On the 1st and on the 4th minute of the rest interval, the participants performed a SJ. This procedure was repeated 10 times. Afterwards, 7 minutes after the last set, participants performed a squat jump every 3 minutes for 22 minutes. For the statistical analysis, an AnoVa with repeated measurements (2x10) was used for jump scores between sets and an one- way AnoVa with repeated measurements for the jump scores after the sets. The level of significance was defined in p <0.05. The statistical analysis revealed no statistically significant effect of the interval on jump height as no difference was observed between maximum SJ and the SJs performed in the first and the fourth minute of the interval. Thus, in the present research no PAP effect was found in recreationally active men on SJs performed between high-intensity resistance sets, independently of the applied interval, and also after the end of the training session. The obtained results indicate that the enhancement of performance due to PAP in ballistic movements does not always occur and fatigue does not play any role. It could be possibly attributed to the fact that subjects were not systematically active in resistance training. So this issue needs further investigation. However, from practical point of view, it seems that ballistic movements can be performed between resistance sets without interval limitation during power training. [ABSTRACT FROM AUTHOR]

Abstract: During the past five years, systems with small accelerometers have been increasingly used to measure human sport motion. Few studies have defined the measurement error and limit of agreement of those systems in the particular case of squat jump when the sensor is directly fixed to the athlete. The aim of this study is to define the measurement accuracy of the centre of mass of the subject with the use of the Myotest Pro system (Myotest SA, Swiss). The reliability of the Myotest Pro system measurement is compared to those of a force platform. Nine male subjects performed squat jumps on a force platform. The data of both the tools (force platform and the Myotest Pro system) are synchronized at the instant of maximal velocity (Vmax). For each jump, data of the force platform and Myotest Pro were converted to define maximal velocity (Vmax), take off velocity (Vtoff) and the flight time (t), using the same method. Paired t-test, r correlation coefficient and Bland & Altman test were used to compare the validity and the limit of agreement between the two tools. Results showed no significant difference between the measurements of Vmax and Vtoff. Significant difference was observed between the measurements of t (p<0.005). The correlation between the tool''s measurements for Vmax, Vtoff and t is respectively r>0.92, r>0.58 and r>0.77. Bland & Altman test shows very low bias and high reliability (± 0.125 m.s-1) between tools for Vmax data. Bland & Altman test shows a significant under estimation of the bias for t data of the Myotest Pro system and low reliability for Vtoff data (± 0.35 m.s-1). In conclusion, the Myotest Pro system can only be used to evaluate Vmax of subject''s centre of mass during a squat jump with acceptable accuracy and reliability. Myotest Pro cannot be used to estimate other kinetic''s parameters of the centre of mass of the subject during a squat jump. These results can be explained by the hypothesis of measurements between both tools (centre of mass versus side of the hip). [Copyright &y& Elsevier]

Abstract: During the past five years, systems with small accelerometers have been increasingly used to measure human sport motion. Few studies have defined the measurement error and limit of agreement of those systems in the particular case of squat jump when the sensor is directly fixed to the athlete. The aim of this study is to define the measurement accuracy of the centre of mass of the subject with the use of the Myotest Pro system (Myotest SA, Swiss). The reliability of the Myotest Pro system measurement is compared to those of a force platform. Nine male subjects performed squat jumps on a force platform. The data of both the tools (force platform and the Myotest Pro system) are synchronized at the instant of maximal velocity (Vmax). For each jump, data of the force platform and Myotest Pro were converted to define maximal velocity (Vmax), take off velocity (Vtoff) and the flight time (t), using the same method. Paired t-test, r correlation coefficient and Bland & Altman test were used to compare the validity and the limit of agreement between the two tools. Results showed no significant difference between the measurements of Vmax and Vtoff. Significant difference was observed between the measurements of t (p<0.005). The correlation between the tool''s measurements for Vmax, Vtoff and t is respectively r>0.92, r>0.58 and r>0.77. Bland & Altman test shows very low bias and high reliability (± 0.125 m.s-1) between tools for Vmax data. Bland & Altman test shows a significant under estimation of the bias for t data of the Myotest Pro system and low reliability for Vtoff data (± 0.35 m.s-1). In conclusion, the Myotest Pro system can only be used to evaluate Vmax of subject''s centre of mass during a squat jump with acceptable accuracy and reliability. Myotest Pro cannot be used to estimate other kinetic''s parameters of the centre of mass of the subject during a squat jump. These results can be explained by the hypothesis of measurements between both tools (centre of mass versus side of the hip). [Copyright &y& Elsevier]

Summary: Further match analysis and observations were performed in soccer in recent years. During soccer matches female and male players cover a total running distance about ±10km, which is unchanged for many years. The amount of high-intensity activities during soccer matches shows significant differences between the levels of competition in both sexes. The comparison of conditional abilities between female and male teams from the first German soccer league show significant differences in linear running speed (30m -14.7%, p≤.05), nonlinear running speed (FLT-Z-Run-Sprint 22m -9.4%, p≤.05), jump performance (squat jump -32.1%, p≤.05, counter movement jump -33.8%, p≤.05) and endurance performance (lactate threshold test, running velocity at 4 mmol/l [km/h] blood lactate concentration -8.9%, p≤.05; ISRT -37.0%, p≤.05). With the exception of the dorsal trunk muscles in favor of women (dorsal trunk muscles +27.3%, p≤.05), no significant differences in trunk strength were found between women and men. Significant correlations were found between the total running distance at the Interval-Shuttle-Run-Test and the running velocity at 4 mmol/l blood lactate concentration in women from the first German league (r=0.87, p≤.05) but not in men from the fourth German league (r=0.47, p=n.s.). The current findings show that the general development in soccer matches has to be reflected by the methodology of performance assessment. Success in playing soccer requires resources, which are beyond the conditional abilities and are displayed in a new model. [ABSTRACT FROM AUTHOR]

Abstract: Frequency and amplitude determine the training load of whole-body vibration (WBV) exercise and thereby possible neuromuscular adaptations. We investigated the effects of amplitude and frequency of a single bout of WBV on flexibility and squat jump performance (SJ) and the time-course of these effects. In the amplitude study, twenty-five females performed three vibration protocols (VPs) for 6min at frequency of 25Hz and amplitudes of 4mm, 6mm, and 8mm and one control protocol (CP). In the frequency study, eighteen females performed three VPs at 6mm amplitude and frequencies of 15Hz, 20Hz, and 30Hz and one CP. Flexibility and SJ were measured before, immediately-post and 15min recovery. All protocols were performed on a side-to-side alternating vibration plate. In the amplitude study, flexibility was improved (p <0.01) immediately-post in VP4, VP6, VP8 (31.8±8.2, 31.9±7.6, 31.5±7.9, respectively) and at 15min recovery (31.6±8.1, 31.5±7.9, 31.0±8.2, respectively) vs. pre-vibration (30.2±8.6, 30.3±8.1, 30.2±8.3, respectively), but remained unchanged in CP (30.6±8.3 immediately-post, 30.7±8.2 at 15min vs. 30.4±8.2 pre-vibration). In the frequency study, flexibility was improved (p <0.01) immediately-post in VP15, VP20, VP30 (31.5±5.2, 31.3±5, 31.7±5.3, respectively) and at 15min recovery (31.3±5.4, 31.3±5.0, 31.3±5.3, respectively) vs. pre-vibration (30.6±5.4, 30.2±5.7, 30.3±5.9, respectively), but not in CP (30.7±5.1 immediately-post, 30.6±5 at 15min vs. pre-vibration 30.5±5.7). There were no significant effects of amplitude or frequency on SJ. In conclusion, a single WBV bout using a side-to-side alternating vibration plate may increase flexibility which persists for at least 15min, without altering jumping performance. These effects were observed irrespective of frequency and amplitude. [Copyright &y& Elsevier]

The authors present the findings of their research comparing the functional outcome of open surgical reconstruction without reinforcement versus a mini-invasive procedure to treat Achilles tendon injuries. Functional assessment was based on the standing vertical jump using an accelerometer. The jumping evaluation produced similar results between the two surgical repairs.

The purpose of the present study was to examine the maximum isometric force, force produced in initial 100 ms, and vertical jump performance in swimmers with different force-time curve characteristics, such as the index of rate of force development (IRFD), the index of relative force (IRelF), and the index of reactive force (IReaF). Our results showed that swimmers with high IRFD, IRelF and IReaF values presented higher maximum isometric force, force produced in initial 100 ms, and drop jump height. Thus, the ability to develop high levels of maximum isometric force and vertical jump performance depends on force-time curve characteristics. [ABSTRACT FROM AUTHOR]

Whole-Body Vibration (WBV) is a new form of neuromuscular training that seems to improve muscular performance. The aim of this study was to examine the acute effects of WBV on vertical jumping ability. Sixteen physically active young women volunteered to participate in the research (20.59±1.9 years old) performing two different protocols (vibration protocol and control protocol). During both interventions, participants were standing at an upright position, maintaining their knees semi-flexed on a vibrating platform (Galileo Fitness) for 6min, at a fixed frequency of 25Hz and an amplitude of 8mm, while in the control protocol no vibration was performed. For the evaluation of the vertical jumping ability, the squat jump (SJ) and the counter-movement jump (CMJ) tests were used and were performed on a force platform (Bertec). The measurements were set before, post and 15 min after the completion of the protocol. The subjects executed each vertical jump three times and the best performance was recorded. A two-way (protocol x measurement, 2x3) analysis of variance (ANOVA), with repeated measures on both factors, was used to examine the effects of WBV on vertical jumping ability. Tukey's post-hoc pairwise analyses were used when appropriate. The results revealed no statistical interaction between the factors "protocol" and "measurement" for both jumps (SJ and CMJ). The performance on the SJ during the three measurements, before, post, after 15min, was 20.47±2.9, 20.46±2.7 and 19.75±2.9cm for the vibration protocol and 20.06±2.5, 19.4±3.0 and 19.15±2.8cm for the control protocol. Similarly, for the CMJ the performance during the three measurements was 21.73±2.7, 21.23±3.0 and 21.4±3.0cm for the vibration protocol and 21.5±2.6, 20.72±3.0 and 20.53±3.0 cm for the control protocol. Conclusively, it appears that WBV does not affect the vertical jumping ability of young women. [ABSTRACT FROM AUTHOR]

Copyright of Revista Kronos is the property of Revista Kronos 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.)

Background: The squat jump (SJ) and isometric midthigh pull (IMTP) are often implemented to assess an athlete's ability to produce maximum ballistic and isometric force, respectively. More recently, practitioners have calculated a dynamic strength index (DSI) in an attempt to better inform and individualise strength and ballistic training. Aim: To determine the relationship between SJ performance and maximum IMTP force production; as well as evaluate the usefulness of the DSI to guide strength and ballistic training. Methods: Twenty professional rugby union players volunteered as participants for the study and performed 3 acyclic static SJ's and three 5 sec maximum IMTPs using two portable dual-axis force plates sampled at a frequency of 200 Hz. Pearson product moment correlations (r) were used to determine the relationship between SJ and IMTP absolute (N) and relative (N/kg) peak force. The DSI (PFSJ/PFIMTP) was also calculated to better categorise individual ballistic and isometric force qualities. Results: Mean group peak force outputs of 4034 ± 345 N (38.5 ± 4.1 N/kg) and 2635 ± 285 N (25.1 ± 2.5 N/kg) were produced during the IMTP and SJ, respectively. A DSI of 0.65 ± 0.06 U was also calculated as the ratio between SJ and IMTP peak force. Large correlations were observed between SJ and IMTP absolute (r = 0.57) and relative (r = 0.64) peak force, respectively. Conclusions: The findings suggest that peak force production of elite rugby union players during ballistic and maximum isometric strength tasks are largely related. The DSI results also indicate that rugby union players produce much larger peak forces during the IMTP in comparison to the SJ; possibly suggesting a need to focus on improving ballistic force qualities in these athletes. [ABSTRACT FROM AUTHOR]

Copyright of Revista Portuguesa de Ciências do Desporto is the property of Universidade do Porto, Faculdade de Desporto 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.)

Abstract: During these last five years, devices with small accelerometer have been increasingly used to measure human sport motion. Few studies have defined the measurement errors and limits of agreement of those sensors in the particular case of squat jumps when the accelerometer was attached on the athlete. The aim of this study is to define the accuracy and reliability of measurement with the use of a nIMU Memsens sensor. Measurements of Memsens device is compared to those of a force plate. Nine male subjects (mean ± standard deviation), with 179.8±5.12 cm height and 76.02±6.9 kg body mass performed squat jumps on a force plate (Kisler, 500 Hz). For each jump, the nIMU sensor (Memsens, USA) was attached at the hip of the athlete. The Memsens device includes the nIMU (120 Hz) sensor and software developed at INSEP laboratory. The device finds the motion start, defines the vertical acceleration of the subject, provides a 500 Hz interpolation, and then estimates the maximal velocity , the take off velocity and the flight time . The data of both devices of measurement (force plate and Mensens system) are synchronized. For each jump, data of the force plate were converted to define , and . Paired t-test, R correlation coefficient and Bland & Altman test were used to compare the validity and the limits of agreement between the two devices. Results show no significant difference between the measurement of , and . The correlation between the tool’s measurements is for each parameter. Bland & Altman test shows very low bias and good reliability between measurements. In conclusion, the Memsens system can be used to evaluate the squat jump with acceptable accuracy and reliability. This study shows that a sensor attached on the hip permits to estimate kinetic’s variables of a squat jump in agreement with measurement of the centre of mass maximal velocity time flight as well as using a force plate. The underestimation of the take off velocity using the sensor could be explained by the difference of the point of measurement between the devices. In the case of training and testing, this study shows that a sensor using tri-axial accelerometers can help to estimate human motion accurately. This new device could help the athletic subject to test his physical abilities without laboratory restriction. [Copyright &y& Elsevier]