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Sprinting ability is important for successful performance in sports. The aim of this study was to examine the correlation between force-velocity-power relationship of a whole-body movement and sprint performance. Twelve male participants performed maximal squat jumps with additional loads ranging from 0% to 100% body weight to obtain force-velocity profiles. The mean force and velocity were calculated during the push-off phase for each jump, which resulted in a force-velocity curve. The theoretical maximal force (F0), theoretical maximal velocity (V0) and theoretical maximum power (P0) were computed via extrapolation of the force and velocity data. In the second session, participants performed two 60 m sprints and the time to cover 20 m (t20), time to cover 60 m (t60), and maximum sprint velocity (Vmax) were calculated from the best 60 m trial. Correlation analyses revealed strong and significant correlations between V0 and t20 (r = −0.60), V0 and t60 (r = −0.60), P0 and t20 (r = −0.75) and P0 and t60 (r = −0.78). Multiple linear regression indicated that P0 explained 56%, 61% and 60% of the variability in t20, t60 and Vmax, respectively. Our results emphasise the importance of developing power production capabilities to improve sprint performance. [ABSTRACT FROM AUTHOR]

Copyright of Ido Movement for Culture. Journal of Martial Arts Anthropology is the property of Idokan Poland Association 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 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.)

During vertical jump evaluations in which jump height is estimated from flight time (FT), the jumper must maintain the same body posture between vertical takeoff and landing. As maintaining identical posture is rare during takeoff and landing between different jump attempts and in different individuals, we simulated the effect of changes in ankle position from takeoff to landing in vertical jumping to determine the range of errors that might occur in real-life scenarios. Our simulations account for changes in center of mass position during takeoff and landing, changes in ankle position, different subject statures (1.44–1.98 m), and poor to above-average jump heights. Our results show that using FT to estimate jump height without controlling for ankle position (allowing dorsiflexion) during the landing phase of the vertical jump can overestimate jump height by 18% in individuals of average stature and performing an average 30 cm jump or may overestimate by ≤60% for tall individuals performing a poor 10 cm jump, which is common for individuals jumping with added load. Nevertheless, as assessing jump heights based on FT is common practice, we offer a correction equation that can be used to reduce error, improving jump height measurement validity using the FT method allowing between-subject fair comparisons. [ABSTRACT FROM AUTHOR]

Background and Study Aim. Vertical jump performance is crucial for athletes in many sports. However, the optimal techniques for maximizing jump height and efficiency for both students and professional soccer players require more effective solutions. This study aimed to investigate the influence of various vertical jump techniques, focusing on arm swing and elastic force utilization, and to evaluate the extent of the impact that each modification has on biomechanical characteristics and performance outcomes. Materials and methods. Ten first-grade Sport Science students and ten professional soccer players from F.C. Malisevo participated in the study. The participants performed a series of jumps, including the Countermovement Jump (CMJ), Squat Jump (SJ), and Abalakov jump (ABL), while being recorded on an iPhone 13 Pro at 240 frames per second. Data analysis was conducted using the My Jump 3 app and SPSS 26 software. Descriptive statistics and one-way ANOVA were employed for comparative analysis. The Independent Samples T-test was used to compare differences in jump performance between the groups. Results. Significant differences in jump performance and force production were observed between SP and PES, with professional athletes demonstrating superior neuromuscular capabilities and better utilization of elastic energy. However, within each group, no significant differences were found between the different jump techniques, suggesting that arm swing and elastic force contribute similarly to overall jump height. Arm swing contributed 11.0% to jump performance in PES and 12.0% in SP, while the influence of elastic force stored in tendons during the eccentric phase was 7.0% in PES and 6.0% in SP. Conclusions. Specialized training significantly enhances jump performance, as evidenced by differences in CMJ, SJ, and ABL between SP and PES. Arm swing and elastic force utilization play crucial roles in vertical jumping, with professional athletes potentially leveraging arm mechanics more effectively. The study validates the reliability of the My Jump 3 app for measuring jump performance across diverse athletic backgrounds.

Copyright of Chinese Journal of Applied Mechanics is the property of Chinese Journal of Applied Mechanics Editorial Office 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.)

By looking at previous literature, this study aimed to analyze the construct of plyometric exercise variation. Comprehensive methods are used for these articles, such as searching for articles in database research journals. Semantic, Scopus, Scholar, and Crossref are the data sources for this database. The variety of plyometric exercises and vertical jump skills are the main themes. Fifty-one articles were verified, and then 12 articles were evaluated based on objectives, topics, sample size, research protocols, and results. Plyometric exercises are exercises in which the movements are explosive and, besides being practical, also train muscle strength, muscular endurance, flexibility, and agility. The purpose of volleyball training is so that players can acquire good basic techniques, strengthen physical strength, and develop interests and talents. To improve jumping ability, various exercises are performed from the beginner level. Therefore, the ability to jump and jump is essential for the volleyball game. The novelty in this study is the using a form of plyometric exercise that is varied according to the characteristics of athletes aged 14-17 years that have never previously been applied in volleyball clubs, which is the focus in this study of plyometric exercise variation methods, namely plyometric squat jump, skipping and hurdle hopping. The intensity of the exercise will be adjusted to the characteristics, and physiological development of male athletes aged 14-17 years. [ABSTRACT FROM AUTHOR]

During vertical jump evaluations in which jump height is estimated from flight time (FT), the jumper must maintain the same body posture between vertical takeoff and landing. As maintaining identical posture is rare during takeoff and landing between different jump attempts and in different individuals, we simulated the effect of changes in ankle position from takeoff to landing in vertical jumping to determine the range of errors that might occur in real-life scenarios. Our simulations account for changes in center of mass position during takeoff and landing, changes in ankle position, different subject statures (1.44–1.98 m), and poor to above-average jump heights. Our results show that using FT to estimate jump height without controlling for ankle position (allowing dorsiflexion) during the landing phase of the vertical jump can overestimate jump height by 18% in individuals of average stature and performing an average 30 cm jump or may overestimate by ≤60% for tall individuals performing a poor 10 cm jump, which is common for individuals jumping with added load. Nevertheless, as assessing jump heights based on FT is common practice, we offer a correction equation that can be used to reduce error, improving jump height measurement validity using the FT method allowing between-subject fair comparisons.

Abstract Background This study discusses the effectiveness of a 12-week intervention aimed at improving squat jump and sprint performance among second-year sports students. Methods The students were randomly divided into experimental (n = 89) and control (n = 92) groups. In addition to gym training, students of the experimental group also underwent online PE training. The students’ performance in Squat Jumps, 30 m sprint, and Progressive Aerobic Cardiovascular Endurance Run (PACER), as well as their situational motivation, were assessed before and after the intervention. Furthermore, the students assessed their physical activity weekly using self-reports. Results The implementation of online training has positively impacted intrinsic and identified motivation, as well as external regulation; however, it was less effective in reducing amotivation compared to traditional gym-based training. Conclusions The findings of the study contribute to the data synthesis on the expediency of using modern software in physical education.

Background: This study discusses the effectiveness of a 12-week intervention aimed at improving squat jump and sprint performance among second-year sports students. Methods: The students were randomly divided into experimental (n = 89) and control (n = 92) groups. In addition to gym training, students of the experimental group also underwent online PE training. The students' performance in Squat Jumps, 30 m sprint, and Progressive Aerobic Cardiovascular Endurance Run (PACER), as well as their situational motivation, were assessed before and after the intervention. Furthermore, the students assessed their physical activity weekly using self-reports. Results: The implementation of online training has positively impacted intrinsic and identified motivation, as well as external regulation; however, it was less effective in reducing amotivation compared to traditional gym-based training. Conclusions: The findings of the study contribute to the data synthesis on the expediency of using modern software in physical education. [ABSTRACT FROM AUTHOR]

This research aimed to identify relations of cognitive and power capacities with reactive agility in pubescent boys (n = 55) and girls (n = 46). Cognitive abilities were evaluated by the Stroop test, while the BlazePod system was used to evaluate agility performance conducting 20 yard shuttle and triangle tests of non-reactive (TCODS) and reactive agility (TRAG), respectively. Performance in jumping power was assessed through the squat jump (SJ), countermovement jump (CMJ), and drop jump (DHJ) utilising the Opto Jump system (Microgate, Bolzano, Italy), while sprinting ability over distances of 10 and 20 m was measured using a photocells system. A principal component was extracted from the four Stroop test variables using factor analysis. Forward stepwise multiple regression analysis was conducted separately for boys and girls to evaluate the multivariate relationships among the predictors and the criterion. Among boys, 80% of the TRAG variance was explained (MultipleR = 0.9), with TCODS and SJ as significant predictors (β = 0.53 and −1.01, respectively). For girls, the TCODS was the significant predictor (β = 0.65), explaining 43% of the variance (MultipleR = 0.65). These results show that (i) cognitive abilities measured with the Stroop test were not a reliable tool for predicting TRAG, (ii) jumping power was a significant predictor of TRAG in boys, and (iii) TCODS was a significant predictor of TRAG in girls. The findings indicated that cognitive abilities do not significantly influence reactive agility in pubescent children. It seems that power features have a greater influence on reactive agility, particularly in boys who have more developed motor skills at this age compared to girls. [ABSTRACT FROM AUTHOR]

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]

Copyright of Retos: Nuevas Perspectivas de Educación Física, Deporte y Recreación is the property of Federacion Espanola de Asociaciones de Docentes de Educacion Fisica 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 is widely accepted that athletic performance emerges from a complex interaction between physical and cognitive features. Several studies highlighted self-efficacy (SE) in the cognitive domain of athletic performance, but no studies have correlated SE with sport-specific tasks. According to Bandura, this study explored SE and its relationship with self-prediction (SP), self-perception (PSJ), and actual performance in a squat jump (SJ). Thirty-nine healthy collegiate students were assessed using an SE questionnaire, an SP measurement tool, and a validated optical system for actual SJ performance. An SE score and an SE esteem index (SEE) were determined. The alignment between an individual's SP of their SJ performance and their SE beliefs was also examined. The data revealed a significant correlation between SE score and both SJ (r = 0.432; p = 0.006) and SP (r = 0.441; p = 0.005). Furthermore, disparities among the actual SJ, SP, and SEE were statistically non-significant, implying a congruence between self-belief and performance. With a deeper understanding of the interaction between SE, SP, and sport-specific tasks, sports professionals could develop targeted interventions to enhance athletes' overall athletic achievements and apply SE as a feature linking physical and cognitive athletic performance. [ABSTRACT FROM AUTHOR]

Purpose: This study examined the test–retest reliability of common assessments for measuring strength and power of the lower body in high-performing athletes. Methods: A total of 100 participants, including both male (n = 83) and female (n = 17) athletes (21 [4] y, 182 [9] cm, and 78 [12] kg), were recruited for this study, using a multicenter approach. The participants underwent physical testing 4 times. The first 2 sessions (1 and 2) were separated by ∼1 week, followed by a period of 2 to 6 months, whereas the last 2 sessions (3 and 4) were again separated by ∼1 week. The test protocol consisted of squat jumps, countermovement jumps, jump and reach, 30-m sprint, 1-repetition-maximum squat, sprint cycling, and a leg-press test. Results: The typical error (%) ranged from 1.3% to 8.5% for all assessments. The change in means ranged from −1.5% to 2.5% for all assessments, whereas the interclass correlation coefficient ranged from.85 to.97. The smallest worthwhile change (0.2 of baseline SD) ranged from 1.2% to 5.0%. The ratio between the typical error (%) and the smallest worthwhile change (%) ranged from 0.5 to 1.2. When observing the reliability across testing centers, considerable differences in reliability were observed (typical error [%] ratio: 0.44–1.44). Conclusions: Most of the included assessments can be used with confidence by researchers and coaches to measure strength and power in athletes. Our results highlight the importance of controlling testing reliability at each testing center and not relying on data from others, despite having applied the same protocol. [ABSTRACT FROM AUTHOR]

Purpose: We tested whether a single session of heavy-load resistance priming conducted in the morning improved double-poling (DP) performance in the afternoon. Methods: Eight national-level male cross-country skiers (mean [SD]: 23 [3] y, 184 [6] cm, 73 [7] kg, maximum oxygen consumption = 69 [6] mL·kg−1·min−1) carried out 2 days of afternoon performance tests. In the morning, 5 hours before tests, subjects were counterbalanced to either a session of 3 × 3 repetitions (approximately 85%–90% 1-repetition maximum) of squat and sitting pullover exercises or no exercise. The performance was evaluated in DP as time to exhaustion (TTE) (approximately 3 min) on a treadmill and 30-m indoor sprints before and after TTE (30-m DP pre/post). Furthermore, submaximal DP oxygen cost, countermovement jump, and isometric knee-extension force during electrical stimulation were conducted. Participants reported perceived readiness on test days. Results: Resistance exercise session versus no exercise did not differ for TTE (approximately 3 min above) (mean ± 95% confidence interval = 3.6% ± 6.0%; P =.29; effect size [ES], Cohen d = 0.27), 30-m DP pre (−0.56% ± 0.80%; P =.21; ES = 0.20), 30-m DP post (−0.18% ± 1.13%; P =.76; ES = 0.03), countermovement jump (−2.0% ± 2.8%; P =.21; ES = 0.12), DP oxygen cost (−0.13% ± 2.04%; P =.91; ES = 0.02), or perceived readiness (P ≥.11). Electrical stimulation force was not different in contraction or relaxation time but revealed low-frequency fatigue in the afternoon for the resistance exercise session only (−12% [7%]; P =.01; ES = 1.3). Conclusion: A single session of heavy-load, low-volume resistance exercise in the morning did not increase afternoon DP performance of short duration in high-level skiers. However, leg low-frequency fatigue after resistance priming, together with the presence of small positive effects in 2 out of 3 DP tests, may indicate that the preconditioning was too strenuous. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to investigate effect of post-activation performance enhancement (PAPE) induced by the eccentric half-squat exercise on vertical jump performance in male jumpers. The jumping height, peak power, and work were measured and evaluated in twenty male jumpers (age: 21.2 ± 1.7 years, height: 191.1 ± 3.3 cm, body mass: 81.56 ± 7.3 kg) who participated in the national championship last year. Participants performed five eccentric half-squats at 85% of their one-repetition maximum (1 RM), with a knee angle below 90°, followed by immediate and 2 min delayed jump assessments using the Squat Jump (SJ) and Countermovement Jump (CMJ) tests. Results showed that this specific PAPE protocol did not significantly improve jump performance for the SJ (Height: ES = 0.613, p = 0.462, Work: ES = 0.124, p = 0.231, Power: ES = 0.382, p = 0.125) or CMJ (Height: ES = 0.523, p = 0.368, Work ecc: ES = 0.133, p = 0.505 (only main effect time p < 0.05), Work con: ES = 0.114, p = 0.101, Power ecc: ES = 0.134, p = 0.177, Power con: ES = 0.182, p = 0.195, Leg stiffness: ES = 0.095, p = 0.358) tests. Factors such as stimulus specificity, rest intervals, muscle length, and the balance between potentiation and fatigue may explain these results. This study highlights the complexity of PAPE responses and suggests that a single set of eccentric squats with a short rest may not improve jump performance in male jumpers. Further research is required to optimize the interplay between conditioning stimuli and rest periods to maximize PAPE effects in athletic performance enhancement. [ABSTRACT FROM AUTHOR]

Study aim(s): The study aims to determine the effect of arm swing technique and the elastic force stored in tendon during the eccentric phase of jumping on the vertical jump performance of Volleyball Players (U15). Methods: Ten U15 women volleyball players from KV Theranda, averaging 157.0 cm in height and 48.8 kg in weight, participated. Participants performed Countermovement Jumps (CMJ) and Squat Jumps (SJ), recorded at 240 fps on an iPhone 13 Pro using My Jump 3 application. Jump heights were calculated from selected take-off and landing frames. Data analysis using SPSS 26 included normality tests and T-tests to compare CMJ and SJ performance, focusing on arm technique and elastic force. Results: Based on the results, except for strength and power, which showed significant differences (p < 0.05), the analysis revealed a significant advantage for CMJ over SJ in all parameters (p < 0.05). This 70% difference is due to the elastic force in the tendons during the eccentric phase and arm momentum. Conclusions: Countermovement jumps (CMJ) significantly outperform squat jumps (SJ) due to the elastic force stored in tendons and arm momentum during the eccentric phase, resulting in a 70% performance difference. Cheraghi et al. (2017) emphasized peak power's role in higher jumps. Future research should separately analyze CMJ with and without arm movement to understand their impacts. [ABSTRACT FROM AUTHOR]

Background: The countermovement jump (CMJ) and the squat jump (SJ) are two vertical jump (VJ) tests widely used to evaluate lower limb muscle strength and power, respectively. Biomechanical analysis of SJ and CMJ could help to predict the strength associated musculoskeletal clinical disorder which is most commonly seen among females such as patellofemoral pain syndrome, osteoarthritis etc. Therefore, the purpose of the study was to conduct and compare the biomechanical analysis of squat and countermovement jump using advanced motion analysis system and compare the changes among sedentary and active young females of the United Arab Emirates. Methodology: The experimental study was conducted at the Thumbay Physical Therapy and Rehabilitation Hospital, Gulf Medical University, Ajman, UAE. A total of 60 sedentary females, and 60 active females within age group 18-30 years were recruited under the convenience sampling method. The participants were randomly divided into two subgroups of 30 each for SJ and CMJ jump analysis respectively for sedentary and active group. Results: There was a statistically significant difference between the CMJ and SJ among the young females in UAE population (p < 0.05). The outcome variables such as jump height, and lower limb joint force were significantly reduced for SJ and CMJ in the sedentary group compared to active group. Majority of the variables showed moderate to severe effect size. Conclusion: Based on the study findings, it could be suggested that the "Sedentary Group" in the present study had poor muscle strength and ability to sustain the stress on the lower limb joints as also shown with lower mean total work. Since we have conducted the study on healthy non-athletes' young females, the data could be used for further clinical correlation and comparison for lower limb muscle strength and power. [ABSTRACT FROM AUTHOR]

Background: The countermovement jump (CMJ) and the squat jump (SJ) are two vertical jump (VJ) tests widely used to evaluate lower limb muscle strength and power, respectively. Biomechanical analysis of SJ and CMJ could help to predict the strength associated musculoskeletal clinical disorder which is most commonly seen among females such as patellofemoral pain syndrome, osteoarthritis etc. Therefore, the purpose of the study was to conduct and compare the biomechanical analysis of squat and countermovement jump using advanced motion analysis system and compare the changes among sedentary and active young females of the United Arab Emirates. Methodology: The experimental study was conducted at the Thumbay Physical Therapy and Rehabilitation Hospital, Gulf Medical University, Ajman, UAE. A total of 60 sedentary females, and 60 active females within age group 18-30 years were recruited under the convenience sampling method. The participants were randomly divided into two subgroups of 30 each for SJ and CMJ jump analysis respectively for sedentary and active group. Results: There was a statistically significant difference between the CMJ and SJ among the young females in UAE population (p < 0.05). The outcome variables such as jump height, and lower limb joint force were significantly reduced for SJ and CMJ in the sedentary group compared to active group. Majority of the variables showed moderate to severe effect size. Conclusion: Based on the study findings, it could be suggested that the “Sedentary Group” in the present study had poor muscle strength and ability to sustain the stress on the lower limb joints as also shown with lower mean total work. Since we have conducted the study on healthy non-athletes’ young females, the data could be used for further clinical correlation and comparison for lower limb muscle strength and power.

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]

Masalah: Kemampuan shooting yang dimiliki oleh atlet sepakbola masih rendah. Tujuan: Penelitian ini bertujuan untuk mengetahui seberapa besar efektivitas latihan squat jump terhadap kemampuan shooting pada permainan sepakbola. Metode: Populasi yang masuk dalam kategori penelitian ini yaitu seluruh siswa yang aktif mengikuti kegiatan latihan sepak bola pada kegiatan ekstrakurikuler SMP Negeri 10 Kendari berjumlah 25 orang. Sedangkan teknik penarikan sampel penelitian menggunakan teknik total sampling, artinya seluruh jumlah populasi, maka itu juga yang akan dijadikan sampel penelitian, sehingga sampel terdiri dari 25 orang siswa. Instrumen tes yang digunakan untuk pengukuran awal (pretest), kemudian dilakukan latihan kekuatan menggunakan latihan squat jump selama 16 kali latihan, setelah itu dilakukan pengukuran akhir (posttest) yaitu tes kemampuan shooting. Teknik analisis data dilakukan dengan uji-t, terlebih dahulu dilakukan uji prasyarat yaitu normalitas data, reliabilitas data dengan uji statistika pada taraf signifikan atau taraf kepercayaan 0,05. Hasil: Berdasarkan hasil analisis menggunakan uji-t pada taraf signifikan α 0,05 maka penelitian ini dapat disimpulkan bahwa terdapat pengaruh latihan kekuatan terhadap kemampuan shooting pada permainan sepak bola, dimana thitung = 5,46 dan ttabel pada saat distribusi nilai yaitu pada taraf kepercayaan 0,05 = 2,060 Kesimpulan: Latihan kekuatan sangat dianjurkan karena akan menunjang kemampuan menendang bola bagi atlet.

This research aimed to identify relations of cognitive and power capacities with reactive agility in pubescent boys (n = 55) and girls (n = 46). Cognitive abilities were evaluated by the Stroop test, while the BlazePod system was used to evaluate agility performance conducting 20 yard shuttle and triangle tests of non-reactive (TCODS) and reactive agility (TRAG), respectively. Performance in jumping power was assessed through the squat jump (SJ), countermovement jump (CMJ), and drop jump (DHJ) utilising the Opto Jump system (Microgate, Bolzano, Italy), while sprinting ability over distances of 10 and 20 m was measured using a photocells system. A principal component was extracted from the four Stroop test variables using factor analysis. Forward stepwise multiple regression analysis was conducted separately for boys and girls to evaluate the multivariate relationships among the predictors and the criterion. Among boys, 80% of the TRAG variance was explained (MultipleR = 0.9), with TCODS and SJ as significant predictors (β = 0.53 and −1.01, respectively). For girls, the TCODS was the significant predictor (β = 0.65), explaining 43% of the variance (MultipleR = 0.65). These results show that (i) cognitive abilities measured with the Stroop test were not a reliable tool for predicting TRAG, (ii) jumping power was a significant predictor of TRAG in boys, and (iii) TCODS was a significant predictor of TRAG in girls. The findings indicated that cognitive abilities do not significantly influence reactive agility in pubescent children. It seems that power features have a greater influence on reactive agility, particularly in boys who have more developed motor skills at this age compared to girls.

This study aimed to determine whether the provision of jump height feedback (knowledge of result; KR) can increase the performance and the consistency of output variables. In a randomised order, sixteen participants performed six squat or countermovement jumps (three from a 90º knee angle and three from a self-preferred knee angle) with or without KR over four sessions. The provision of KR significantly increased peak force (p = 0.046, 1.83%), mean force (p = 0.037, 1.45%), peak velocity (p < 0.001, 3.71%), mean velocity (p = 0.004, 3.44%), peak power (p < 0.001, 4.22%) and mean power (p = 0.001, 4.69%). A high within-session reliability was observed for all variables (coefficient of variation [CV] ≤ 5.62%, intraclass correlation coefficient [ICC] ≥ 0.95). No systematic differences in reliability were detected between the jumps performed without KR (CV = 3.00 ± 1.38%, ICC = 0.97 ± 0.03) and with KR (CV = 3.04 ± 1.49%, ICC = 0.97 ± 0.04). These results suggest that the provision of jump height feedback during vertical jump testing is effective to enhance vertical jump performance but it does not reduce the variability between jumps. [ABSTRACT FROM AUTHOR]

Clarifying the muscular factors that contribute to performance improvement can be beneficial for athletes and coaches. The present study examined the relationships between the resting muscle shear modulus and dynamic performance during the stretch-shortening cycle (SSC) and explosive exercises. To this end, we measured the jump height during three types of vertical jumps (squat jump [SJ], countermovement jump [CMJ], and rebound jump [RJ]) and the multi-joint leg extension power at three velocities (low, moderate, and high) of 30 healthy women. Using ultrasound elastography, the resting shear modulus of the vastus lateralis was assessed in the sitting position as an index of passive muscle mechanical properties. The results showed that the shear modulus was positively correlated with RJ height and multi-joint leg extension power at moderate and high velocities (r = 0.435–0.563, P < 0.05). There was no significant correlation between the shear modulus and SJ height, CMJ height, and multi-joint leg extension power at low velocity. Contact time (i.e. the time under force exertion against the ground) during RJ (161 ± 19 ms) was 19% of that during CMJ (869 ± 171 ms). The results suggest that passive muscle mechanical properties play an important role in high-speed SSCs and dynamic explosive performance. Highlights The resting shear modulus was related to performance in stretch-shortening cycle (SSC) exercise involving a series of rapidly performed SSCs. The resting shear modulus was associated with muscular power in high-velocity conditions but not in low-velocity conditions. This study suggests that the passive mechanical properties of an agonist muscle play an important role in high-speed dynamic performance. [ABSTRACT FROM AUTHOR]

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Abstract 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.

Copyright of Italian Journal of Health Education, Sport & Inclusive Didactics is the property of Edizioni Universitarie Romane 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. This study aimed to investigate the associations between muscular strength tests and vertical jumping performance (countermovement jump [CMJ] and squat jump [SJ]) in adolescent male football players, while controlling for important predictors such as chronological age and body composition. Methods. The sample involved 161 male footballers (mean age: 15.8 ± 1.7 years) from the under-19, under-17, and under-15 age groups. Body fat percentage (BF%) was calculated with Slaughter equations. Muscular strength assessment included handgrip strength and push-up and sit-up tests. Vertical jumping was examined through CMJ and SJ. Pearson correlations and hierarchical regression analyses were run to analyse the data. Results. All muscular strength tests showed significant correlations with CMJ and SJ. Handgrip strength was the most substantial predictor for CMJ (r = 0.43, p < 0.01) and SJ (r = 0.44, p < 0.01). However, regression models identified sit-ups (CMJ: = 0.15, p < 0.01, R2 = 0.23; SJ: = 0.16, p < 0.01, R2 = 0.27) and push-ups (CMJ: = 0.13, p < 0.01; SJ: = 0.15, p < 0.01) as significant predictors after controlling for chronological age, body mass, and BF%. In contrast, BF% remained a significant predictor of jumping performance (CMJ: = -0.43, p < 0.01, R2 = -0.39; SJ: = -0.52, p < 0.01, R2 = -0.52) in the whole hierarchical regression model. Conclusions. This study reinforces the importance of players' overall physical development, including healthy diet habits, to enhance jumping performance. [ABSTRACT FROM AUTHOR]

It is widely accepted that athletic performance emerges from a complex interaction between physical and cognitive features. Several studies highlighted self-efficacy (SE) in the cognitive domain of athletic performance, but no studies have correlated SE with sport-specific tasks. According to Bandura, this study explored SE and its relationship with self-prediction (SP), self-perception (PSJ), and actual performance in a squat jump (SJ). Thirty-nine healthy collegiate students were assessed using an SE questionnaire, an SP measurement tool, and a validated optical system for actual SJ performance. An SE score and an SE esteem index (SEE) were determined. The alignment between an individual’s SP of their SJ performance and their SE beliefs was also examined. The data revealed a significant correlation between SE score and both SJ (r = 0.432; p = 0.006) and SP (r = 0.441; p = 0.005). Furthermore, disparities among the actual SJ, SP, and SEE were statistically non-significant, implying a congruence between self-belief and performance. With a deeper understanding of the interaction between SE, SP, and sport-specific tasks, sports professionals could develop targeted interventions to enhance athletes’ overall athletic achievements and apply SE as a feature linking physical and cognitive athletic performance.

The purpose of the present study was to investigate effect of post-activation performance enhancement (PAPE) induced by the eccentric half-squat exercise on vertical jump performance in male jumpers. The jumping height, peak power, and work were measured and evaluated in twenty male jumpers (age: 21.2 ± 1.7 years, height: 191.1 ± 3.3 cm, body mass: 81.56 ± 7.3 kg) who participated in the national championship last year. Participants performed five eccentric half-squats at 85% of their one-repetition maximum (1 RM), with a knee angle below 90°, followed by immediate and 2 min delayed jump assessments using the Squat Jump (SJ) and Countermovement Jump (CMJ) tests. Results showed that this specific PAPE protocol did not significantly improve jump performance for the SJ (Height: ES = 0.613, p = 0.462, Work: ES = 0.124, p = 0.231, Power: ES = 0.382, p = 0.125) or CMJ (Height: ES = 0.523, p = 0.368, Work ecc: ES = 0.133, p = 0.505 (only main effect time p < 0.05), Work con: ES = 0.114, p = 0.101, Power ecc: ES = 0.134, p = 0.177, Power con: ES = 0.182, p = 0.195, Leg stiffness: ES = 0.095, p = 0.358) tests. Factors such as stimulus specificity, rest intervals, muscle length, and the balance between potentiation and fatigue may explain these results. This study highlights the complexity of PAPE responses and suggests that a single set of eccentric squats with a short rest may not improve jump performance in male jumpers. Further research is required to optimize the interplay between conditioning stimuli and rest periods to maximize PAPE effects in athletic performance enhancement.

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]

Purpose This study aimed to investigate the associations between muscular strength tests and vertical jumping performance (countermovement jump [CMJ] and squat jump [SJ]) in adolescent male football players, while controlling for important predictors such as chronological age and body composition. Methods The sample involved 161 male footballers (mean age: 15.8 ± 1.7 years) from the under-19, under-17, and under-15 age groups. Body fat percentage (BF%) was calculated with Slaughter equations. Muscular strength assessment included handgrip strength and push-up and sit-up tests. Vertical jumping was examined through CMJ and SJ. Pearson correlations and hierarchical regression analyses were run to analyse the data. Results All muscular strength tests showed significant correlations with CMJ and SJ. Handgrip strength was the most substantial predictor for CMJ ( r = 0.43, p < 0.01) and SJ ( r = 0.44, p < 0.01). However, regression models identified sit-ups (CMJ: β = 0.15, p < 0.01, R 2 = 0.23; SJ: β = 0.16, p < 0.01, R 2 = 0.27) and push-ups (CMJ: β = 0.13, p < 0.01; SJ: β = 0.15, p < 0.01) as significant predictors after controlling for chronological age, body mass, and BF%. In contrast, BF% remained a significant predictor of jumping performance (CMJ: β = –0.43, p < 0.01, R 2 = –0.39; SJ: β = –0.52, p < 0.01, R 2 = –0.52) in the whole hierarchical regression model. Conclusions This study reinforces the importance of players’ overall physical development, including healthy diet habits, to enhance jumping performance.

Abstract 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.

Arm swing improves vertical jump height but the underlying mechanism is not well understood. We assume that the negative acceleration of arm swing can increase the load and tension of the lower limb’s extensor muscles enhancing force output and resulting in higher jump. The purpose of this study was to examine how arm swing affects the EMG activity of the lower limb muscles during vertical jumping in relation to the arm swing kinematics. Sixteen physically active male college students were asked to perform squat (SJ) and countermovement jumps (CMJ) with arms akimbo and with arm swing. Jumps were carried out on a force platform while kinematic data and EMG activity of the right lower limb were measured. Jumping height increased by 33% in SJ and by 18.9% in CMJ when performed with arm swing. In SJ with arm swing the vertical ground reaction force (GRF) was larger during the negative acceleration of the arm (71–91% of the jump, p < 0.001) with significantly slower relative joint extension. Similarly, in CMJAS during the negative acceleration of the arm vertical GRF was larger (89–97% of the jump, p < 0.001) compared to CMJ. Arm swing increased the jump time, net impulse and take off velocity in both jumps. No differences were detected in EMG between jumps carried out with and without arm swing. When jumps carried out with arm swing, we can observe higher vertical GRF during the negative acceleration of the arm swing that indicate higher load on the lower limb, but we cannot confirm our initial idea with the results of the EMG comparison. Increase in jump height can be explained by the extended jump time resulting in greater mechanical variables in jumps with arm swing.

Introduction: The force–velocity profile has been analysed previously in different sports modalities; nevertheless, it has not been analysed in CrossFit. Objective: The aim of this study was to report neuromuscular characteristics of CrossFit athletes using their individual force-velocity profile, investigating differences according to sex, age, and training frequency. Materials and Methods: 72 males (33.17 ± 6.86 years; BMI: 25.93 ± 3.64 kg/m2) and 18 females (30.11 ± 6.92 years; BMI: 23.53 ± 3.98 kg/m2) participated in this study. The force-velocity profile was calculated using Samozino’s method. Furthermore, neuromuscular characterization was completed with a squat jump and three drop jumps (20, 30, and 40 cm). Results: Regarding sex, significant differences in all analysed mechanical variables (p < 0.001) were found except for the theoretical maximal force (p = 0.944). No significant differences were found between age groups. Considering training frequency, athletes who train more than 5 days per week showed higher performance in all analysed mechanical variables (p < 0.05). Conclusion: CrossFit athletes have a force-velocity profile more oriented towards velocity than force. Males and females have different neuromuscular characteristics, also neuromuscular improvements can be achieved at any age. Moreover, higher neuromuscular performance is developed with a training frequency of 5 days or more per week.

Introduction: Speed-strength performance is important during human movements such as jumping, sprinting, and change of direction (COD) tasks, which are a substantial part of sports practice. Sex and age seem to influence performance output in young persons; however, few studies have focused on the influence of sex and age measured via standard protocols of performance diagnostics.Method: Therefore, the aim of this study was to investigate the influence of age and sex on linear sprint (LS), COD sprint, countermovement jump (CMJ) height, squat-jump (SJ) height, and drop-jump (DJ) height performance in untrained children and adolescents via a cross-sectional analysis. This study comprised 141 untrained male and female participants 10–14 years of age.Results: The results showed the influence of age in male participants on speed-strength performance, while in female participants, age did not significantly influence performance parameters. Moderate to high correlations between sprint and jump performance (r = 0.69–0.72), sprint and COD sprint performance (r = 0.58–0.72), and jump and COD sprint performance (r = 0.56–0.58) were found.Discussion: Based on the data from this study, it appears that the growth phase of age 10–14 does not necessarily lead to improvements in athletic performance. To ensure holistic motor development, female subjects in particular should be provided with specific training interventions with a focus on strength and power.

The ability to automatically quantify jump performance and lower limb muscle function in athletes would be beneficial for both training and rehabilitation purposes. Countermovement jumps (CMJs) and non-CMJs (NCMJs) are simple, quick, and require relatively inexpensive equipment to effectively and reliably monitor lower limb function. In a previous study, CMJ characteristics were assessed across different varsity sports. This study is a follow-up study to incorporate NCMJs into assessing jump characteristics of the same sports and investigate the additional information provided by the complementary jump type. The main objective of this study was to look at a means of quantifying the lower limb mechanical muscle function automatically to provide information for rehabilitation and performance purposes in athletes of specific sports. Male and female varsity athletes from 4 different sports completed 5 trials of an NCMJ on dual force plates. An analysis program was developed using Wolfram Mathematica to analyze force-time jump data. Various parameters of interest were generated, including peak force, force-time curve shape classification, jump phase lengths, phase-specific kinetic impulse, asymmetry index, takeoff velocity, jump height, phase-specific center of mass displacements, and reactive strength index modified. Results obtained indicate that similar jump characteristics to the CMJ study can be quantified, which can be used for performance enhancement or injury rehabilitation. Additional data found, such as the ability of an athlete to hold a steady squat during an NCMJ, could also be meaningful in aiding trainers to design programs tailored for athletes. [ABSTRACT FROM AUTHOR]

Background: Vertical jump is a critical activity for performance in different sports. Different types of interventions showed effects on vertical jumps. Still there is lack of comparative evidence between Post - isometric relaxation of Quadriceps and core stability exercises in vertical jump performance. Objective: To determine the role of post isometric relaxation of quadriceps and core stability exercises in vertical jump performance. Methods: A Randomized Clinical Trial, conducted in Islamic International University after having the ethical permission from Institutional review Board of Riphah International University Islamabad. Sampling technique was Non-probability convenience sampling with the sample size of 30 athletes, that were divided by sealed and envelop method into core stability exercise treated group (n=17) and Post isometric relaxation treated group (n= 13). Male Athletes within age range of 20-35 years and playing at the domestic level were included and athletes with history of sprain or strain in lower limbs within last 6 month, having neuromusculoskeletal and cardiovascular pathology were excluded from the study. Force plate was used to measure the different parameters of jump. Data were entered and analyzed through SPSS version 22. Results: The mean age of group A and B was 20.35 + 2.01 and 20.03 + 2.42 in years respectively. BMI of core stability exercise treated group and Post isometric relaxation treated group was 22.35 + 2.32, 22.58 + 1.95 respectively in kg/m2. Comparison between core stability exercise treated group and Post isometric relaxation treated group showed that there was no significant immediate effects (F= 1.235; p= 0.852) of treatment on three style of jumps. Conclusion: No significant immediate effects of treatment on three styles of jumps was found. [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]

Introduction: The force-velocity profile has been analysed previously in different sports modalities; nevertheless, it has not been analysed in CrossFit. Objective: The aim of this study was to report neuromuscular characteristics of CrossFit athletes using their individual force-velocity profile, investigating differences according to sex, age, and training frequency. Materials and Methods: 72 males (33.17 ± 6.86 years; BMI: 25.93 ± 3.64 kg/m2) and 18 females (30.11 ± 6.92 years; BMI: 23.53 ± 3.98 kg/m2) participated in this study. The force-velocity profile was calculated using Samozino's method. Furthermore, neuromuscular characterization was completed with a squat jump and three drop jumps (20, 30, and 40 cm). Results: Regarding sex, significant differences in all analysed mechanical variables (p < 0.001) were found except for the theoretical maximal force (p = 0.944). No significant differences were found between age groups. Considering training frequency, athletes who train more than 5 days per week showed higher performance in all analysed mechanical variables (p < 0.05). Conclusion: CrossFit athletes have a force-velocity profile more oriented towards velocity than force. Males and females have different neuromuscular characteristics, also neuromuscular improvements can be achieved at any age. Moreover, higher neuromuscular performance is developed with a training frequency of 5 days or more per week. [ABSTRACT FROM AUTHOR]

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 D 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. [ABSTRACT FROM AUTHOR]

Arm swing improves vertical jump height but the underlying mechanism is not well understood. We assume that the negative acceleration of arm swing can increase the load and tension of the lower limb's extensor muscles enhancing force output and resulting in higher jump. The purpose of this study was to examine how arm swing affects the EMG activity of the lower limb muscles during vertical jumping in relation to the arm swing kinematics. Sixteen physically active male college students were asked to perform squat (SJ) and countermovement jumps (CMJ) with arms akimbo and with arm swing. Jumps were carried out on a force platform while kinematic data and EMG activity of the right lower limb were measured. Jumping height increased by 33% in SJ and by 18.9% in CMJ when performed with arm swing. In SJ with arm swing the vertical ground reaction force (GRF) was larger during the negative acceleration of the arm (71-91% of the jump, p < 0.001) with significantly slower relative joint extension. Similarly, in CMJAS during the negative acceleration of the arm vertical GRF was larger (89-97% of the jump, p < 0.001) compared to CMJ. Arm swing increased the jump time, net impulse and take off velocity in both jumps. No differences were detected in EMG between jumps carried out with and without arm swing. When jumps carried out with arm swing, we can observe higher vertical GRF during the negative acceleration of the arm swing that indicate higher load on the lower limb, but we cannot confirm our initial idea with the results of the EMG comparison. Increase in jump height can be explained by the extended jump time resulting in greater mechanical variables in jumps with arm swing. [ABSTRACT FROM AUTHOR]

Copyright of Revija Šport is the property of Sport: Revija Za Teoreticna in Praticna Vprasanja Sporta 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.

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.