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The objectives of this paper are to explore the correlation of kinetic indices of SJ (squat jump) and CMJ (counter-movement jump) and the differences of lower limb strength mechanics indexes of table tennis, badminton and tennis players under SJ and CMJ. This study included 60 male collegiate athletes, 20 each from table tennis, badminton, and tennis. Subjects performed SJ and CMJ tests on a force platform and the vertical jump data were analyzed. Table tennis, badminton and tennis players demonstrated significant differences in the SJ and CMJ assessments. Badminton players outperformed table tennis players in terms of peak power (PP) (p = 0.005) and peak velocity (PV) (p = 0.017). Badminton players beat table tennis players in PV (p = 0.028), PP (p = 0.022), fast twitch fibers (FTF) (p = 0.033) and pre-stretch effect (EP) (p = 0.0004). Tennis players exhibited lower peak force (PF) (p = 0.006) indicators than badminton players. For athletes in all three sports, the SJ test markers (vertical jump displacement, PF, PP and PV) demonstrated a strong positive correlation. There was a highly significant positive correlation between VJD and PF, PP, PV and FTF among badminton players. Significant positive connections were discovered between PF, PP, PV, FTF and EP, as well as between PP and PV and FTF and EP. PV and FTF had a very strong positive correlation, as did EP, PV and FTF. College badminton players had higher vertical jumps than table tennis and tennis players. In addition to vertical jump height, PP (power production), PV (power velocity) and FTF (force-time factors) are important markers for assessing the success of vertical jumps in athletes’ daily training. These findings can assist coaches and athletes develop better vertical jump training programs.

PurposeThis study investigated the evolution of neuromotor control during a typical short sport-specific rehabilitation program (SSR) in professional soccer players who had incurred a major lower-limb injury (n = 15, chondral and muscle injuries, ACL-reconstruction).MethodsAll injured participants (n = 15) were in the on-field rehabilitation phase of their specific sport rehabilitation process, prior to return to play. An experimental group (EG, chondral and muscle injuries, ACL-reconstruction) followed a 3-week SSR-program composed of muscular and core strengthening (weightlifting, functional stability, explosivity and mobility exercises), running and cycling, neuromotor reprogramming, cognitive development and specific soccer on-field rehabilitation (acceleration, braking, cutting, dual-contact, high-speed-running, sprint, jump, drills with ball). Neuromotor control via analysis of movement kinematics, muscle activation and kinetic parameters was evaluated using a single-leg Countermovement-Jump, pre- and post- rehabilitation program. A control group (n = 22) of healthy soccer players of similar standards performed the same single-leg Countermovement-Jump to provide reference values regarding the level to be attained by the injured players for return to play.ResultsIn the experimental group, almost all kinetic analyses values progressed during the program and significantly for concentric Rate-of-Force-Development (p

Explosive strength is fundamental in the performance of athletes. The objective is to identify the criteria used for the prescription of Explosive Strength Training (EST) and to verify the changes it produces in futsal players. A systematic review of studies analyzing the criteria used for the prescription of explosive strength training was conducted in PubMed/MEDLINE and Scielo, considering the period between 2017 and 2023. The search strategy used the terms: players, Futsal, Futsal training, strength, physical exercise, explosive strength, intervention, experimental study. Data extraction included: year of publication, country, sample, protocol performed (content and activity developed, duration, intensity, frequency, total weeks). A total of six studies were identified. Fifty percent of the studies were developed in Brazil, the others in Italy, Spain and Portugal. Five studies applied a training of 2 sessions per week and one indicated 2-3 sessions. Three studies describe the training sessions (study 1: 15-30 minutes, study 2: 20-25 minutes, study 3: 1 hour). Five studies used 1RM and one study used subjective perception of exertion (PSE). The contents of the interventions were varied, from squats with weights, accelerations and decelerations, leg press, leg extension, plyometrics. The training criteria for explosive strength were: intensity controlled by a 1RM, frequency of 2 to 3 sessions per week, duration of 15 to 30 minutes per session and the training contents were varied. These results suggest positive changes in CMJ, increasing explosive strength from ∼2.0 to 4.6 cm (5.8 to 13.7%). These findings highlight the need to develop a more standardized protocol to optimize the benefits of explosive strength training in this athletic population.

La capacidad del salto es una cualidad importante en el ballet clásico. Se ha demostrado que el entrenamiento pliométrico es efectivo en muchos deportes para mejorar el salto vertical. El objetivo de este estudio fue evaluar el impacto de 8 semanas de entrenamiento pliométrico sobre la capacidad del salto vertical y petit allegros en bailarinas de ballet clásico. 9 bailarinas (22,4 ± 3,05 años; 167 ± 0,06 cm; 56,1 ± 7,66 kg.; 14,2 ± 2,11 años de experiencia) realizaron 8 semanas de entrenamiento pliométrico. Antes (pre) y después (post) del entrenamiento, se evaluó el CMJ, la altura media de 32 petit allegros, la fuerza G y la eficiencia del salto. En el CMJ y en los petit allegros mejoraron después del entrenamiento (p0,05). En conclusión, 8 semanas de entrenamiento pliométrico fueron efectivas para mejorar el CMJ en condiciones de descanso y fatiga y las habilidades específicas de danza en bailarinas de ballet clásico.

La utilización de técnicas de elongación muscular se ha puesto en práctica durante mucho tiempo antes de iniciar actividades físicas para incrementar la activación, aumentar la amplitud articular o como parte de técnicas de calentamiento. En los últimos años, ha habido discrepancia a la hora de utilizar elongaciones estáticas (STA), dinámicas o intermitentes (DYN), o no hacerlas (CON) antes de iniciar la sesión de Educación Física. El objetivo de este estudio fue averiguar qué tipo de trabajo de flexibilidad obtendría mejores resultados en el salto con contramovimiento (CMJ) con las variables: índice de fuerza relativa (RSI), altura del salto (HGT) y tiempo de contacto (CT) con una plataforma de contacto. Formaron parte de esta investigación 86 participantes de 16.74 ± 0.19 años, 65.17 ± 30.03 kg y 1.71 ± 0.09 m. Todos los participantes se sometieron de forma aleatorizada a los 3 protocolos, 2 de elongación (STA y DYN) durante 30 segundos y 1 de control sin ninguna elongación (CON). Los resultados mostraron incrementos significativos en el RSI y HGT (p < .001) en la condición de DYN vs. CON y STA. Por otra parte, el CT mostró aumentos significativos en STA con respecto a CON (p < .01) y DYN. A partir de los resultados obtenidos, se podría afirmar que un programa agudo de estiramientos dinámicos podría producir mejoras sobre el salto con contramovimiento (CMJ) en comparación con la ausencia de estiramiento o un mantenimiento de elongación muscular de 30 s.

Countermovement jump (CMJ) performance analysis is vital in sports science for assessing lower-body strength and neuromuscular efficiency. This study evaluated the validity of the Enode Sensor and My Jump 3 App for measuring vertical jump heights, comparing them to those measured using the established Force Plate. Twenty-nine participants performed CMJs measured using each device. Descriptive statistics indicated mean jump heights of 48.4 ± 4.18 cm (for the Enode Sensor), 47.3 ± 4.05 cm (for My Jump 3), and 46.1 ± 4.03 cm (for the Force Plate). Reliability was confirmed via Intraclass Correlation Coefficients (ICCs), with the Enode Sensor at 0.914 and My Jump 3 at 0.968, demonstrating excellent reliability. Bland–Altman analysis showed mean biases of 2.281 cm (for the Enode Sensor) and 1.297 cm (for My Jump 3) against the Force Plate, with limits of agreement suggesting close alignment. Strong positive correlations were observed (for the Enode Sensor, r = 0.972 and for My Jump 3, r = 0.987; p < 0.001), and linear regression analysis produced R2 values of 0.945 and 0.973, respectively, confirming both tools’ accuracy for vertical jump measurement. These findings indicate that although both tools are suitable for CMJ assessment, My Jump 3 demonstrated slightly superior accuracy, underscoring the potential for accessible, reliable performance monitoring in sports contexts.

The objective of this study was to assess the concurrent validity of the Kunwei force plate system in relation to variables during a counter-movement jump (CMJ) task, in comparison to the Kistler in-ground force plate system, which is considered the “gold standard”. Methods: In a single testing session, the Kunwei force plates were placed directly on top of the in-ground Kistler force plate. This allowed for the simultaneous collection of vertical ground reaction forces from 30 participants (male, age = 22.8 ± 2.8 years, body mass = 74.3 ± 12.3 kg, height 178.2 ± 4.6 cm) during CMJ tests. The consistency between force plate systems was assessed using ordinary least products regression (OLPR) with bootstrapped 95% confidence intervals and the Interclass Correlation Coefficient (ICC). Results: There was no fixed or proportional bias in the CMJ variables measured between the force plate systems. The variables exhibited a strong correlation across the force plates during the CMJ task (ICC > 0.950, p < 0.01). Conclusion: The findings of this study indicate that there was no statistical difference between the Kunwei and Kistler force plate systems when evaluating common CMJ strategy and outcome variables, which are considered the gold standard. Hence, the Kunwei force plate can be regarded as a reliable substitute for the established industry benchmark in evaluating the force–time characteristics of the CMJ. Researchers, athletes, and coaches have the option to utilize this affordable and portable choice as a substitute for the more expensive laboratory-based force plate system. This alternative allows for the precise measurement of CMJ performance and force–time variables.

This study aimed to compare lower limb strength disparities between male college volleyball and basketball players in four distinct vertical jump types. We recruited 100 second-level (above the national standard) male college athletes (50 basketball and 50 volleyball players) from Capital University of Physical Education and Sports who volunteered to participate. We assessed the performance of each athlete with regards to the squat jump (SJ), countermovement jump (CMJ), continuous jump with straight legs (CJs), and continuous jump with bent legs (CJb). Data analysis was performed by independent samples t-tests in SPSS version 25.0. software. In the CMJ test, volleyball players had a significantly higher vertical jump displacement (VJD; p = 0.047, t = −2.018), squat displacement (SD; p = 0.005, t = −2.883), peak force (p = 0.023, t = −1.964), and peak velocity (p = 0.011, t = −1.687) than basketball players. In the SJ test, volleyball players had a significantly higher VJD (p = 0.041, t = −1.21) and SD (p = 0.008, t = −1.46) than basketball players. In the CJs test, volleyball players had a significantly higher average vertical jump displacement (AVJD; p = 0.042, t = −2.067) than basketball players. In the CJb test, volleyball players had a significantly higher AVJD (p = 0.001, t = −3.448), average squat displacement (p = 0.017, t = −2.44), and average contact time (p = 0.045, t = −2.038) than basketball players. The overall vertical jump ability of college volleyball players was better than that of college basketball players. CMJ, SJ, CJs and CJb training should be included in daily training sessions and considered in the selection of basketball and volleyball players. In addition, coaches can use fast twitch Fibers, the effect of pre-stretch and k as the main evaluation indicators to assess daily training progress.

En el fútbol juvenil, el entrenamiento sistemático de fuerza puede mejorar significativamente el rendimiento. Con frecuencia, este tipo de entrenamiento se lleva a cabo durante el período preparatorio y se interrumpe o reduce su énfasis en el período competitivo. El objetivo del presente estudio fue evaluar la eficacia de tres mesociclos consecutivos de entrenamiento combinado de fuerza (levantamiento de pesas y pliometría en los dos primeros, pliometría y cambios de dirección en el tercero) para lograr mejoras continuas en el rendimiento de sprint, salto vertical y cambios de dirección en jugadores de fútbol juvenil masculino. Dieciocho jugadores de fútbol, con una edad de 14,1 ± 0,3 años y sin experiencia previa en entrenamiento estructurado de fuerza, fueron los sujetos del estudio. Antes y después de cada mesociclo, se evaluó a los deportistas en salto con contramovimiento (CMJ), sprint de 5m, sprint de 10m, sprint de 15m, sprint de 20m y cambio de dirección (test 505). Además, se evaluó el rendimiento en ejercicios específicos utilizados en cada mesociclo, que incluyeron sentadilla, sentadilla búlgara, empuje de cadera unilateral y bilateral, y saltos horizontales unilaterales y bilaterales (simples y múltiples). Se observaron mejoras en el rendimiento en los tres mesociclos para todas las variables analizadas (p ≤ 0,05), excepto para el CMJ (p > 0,05) en el último mesociclo. Dado que las mejoras de rendimiento se lograron con magnitudes de carga relativamente bajas, en comparación con las reportadas en intervenciones similares en esta población, se infiere que esta estrategia tiene el potencial de generar mejoras sostenidas a lo largo de todo el año de entrenamiento en futbolistas jóvenes sin experiencia previa en entrenamiento de fuerza.

This study aimed to investigate the longitudinal evolution of vertical jump height in soccer players and its association with their genotypic profiles. The genotypes of 37 soccer players were characterized and the countermovement jump (CMJ) height, concentric mean power, force, and jump strategy were assessed at two time points: at the onset of the regular season (Pre) and at the conclusion of the first half (Mid). AMPD1 (rs17602729), ACE (rs4646994), ACTN3 (rs1815739), CKM (rs8111989), and MLCK (rs2849757 and rs2700352) polymorphisms were genotyped. No significant differences were found between Pre and Mid in concentric power (p = 0.068; d = 0.08) or force (p = 0.258; d = 0.04), while jump height displayed trivial increases (p = 0.046; d = 0.15). Individual analysis revealed that 38% of participants increased the vertical jump height and mean concentric power over the smallest worthwhile change (SWC), while 27% experienced an increased mean concentric force. The positive responders were characterized by a decreased frequency of the AA genotype and an increased frequency of the CA genotype for the c.37885C>A polymorphism of MLCK (p = 0.035), as well as a decreased frequency of the TT genotype of ACTN3 (p = 0.042) and the CC genotype of AMPD1 (p = 0.022). Our findings suggest that genetic analysis could explain some variability in neuromuscular adaptations during the in-season.

The purpose of this study was to determine the variables of acute neuromuscular fatigue (NMF) and its correlation with the serum concentration of creatine kinase (CK) pre- and post-training through performance analysis counter movement jump (CMJ). Methods: Eight male endurance performance athletes performed 3 trials CMJ in force platform before and after fatigue protocol high intensity intermittent running (PFAI) (fatiguing to the maximum possible rate of work for each repetition Protocol). A total of 8 variables were analyzed through CMJ and the biomarker CK before and after fatigue protocol. Results: No significant differences for the variables of mean force MF (P = 0,62. d = 0,03), time to peak force TTPF (P = 0,46. d = 0,43), jump height JH (P = 0,19. d = 0,65), flight time FT (P = 0,26. d = 0,58), relation flight time: contraction time FT: CT (P = 0,74. d = 0,59) and CK (P = 0,79. d = 0,31). Significant differences in variables of peak power (p = 0.008. d = 1,37) and contraction time (p = 0.01. d = 0,76) were found. Finally, Spearman’s correlation (Spearman’s Rho) for non-parametric tests was performed between peak power (PP) (p = 0.002) (r = 0.92) and contraction time (CT) (p = 0.001) (r = 0.97). Conclusions: There is a neuromuscular fatigue state in the acute phase determined of CMJ variables, independent of lineal relation CK production. Likewise, it is highlighted a major parameter the reduction of peak power and increment of contraction time in the neuromuscular performance.

El objetivo de este estudio fue describir un perfil antropométrico, aeróbico y de potencia muscular de basquetbolistas juveniles costarricenses según sexo, posiciones de juego y categoría de edad. Se evaluaron 99 jugadores juveniles (43 mujeres y 56 hombres; 18 bases, 51 aleros y 30 pívots; 42 categoría U16 y 57 categoría U18) de ocho equipos diferentes. La experiencia deportiva de los jugadores fue de 6.5 ± 3.1 años. Se realizaron las siguientes evaluaciones: altura, peso, índice de masa corporal, masa músculo-esquelética, porcentaje de grasa, prueba de contramovimiento (CMJ) y prueba de Yo-Yo de Recuperación Intermitente Nivel I. Los principales resultados mostraron valores significativamente mayores en hombres que en mujeres en peso, talla, masa músculo-esquelética, distancia recorrida en la prueba Yo-Yo, en el VO2max, altura en el CMJ y en el tiempo de vuelo. El porcentaje de grasa fue mayor en mujeres que en hombres. Los jugadores pívots presentaron significativamente mayor estatura, peso corporal y porcentaje degrasa que las otras posiciones de juego. Los bases y los aleros cubrieron más metros en la prueba Yo-Yo y tuvieron mayor VO2máx que los pívots. Entre las categorías U16 y U18 no se encontraron diferencias significativas en ninguna variable. Modelos de regresión mostraron la influencia del peso, porcentaje de grasa corporal, masa músculo esquelética y la edad sobre el VO2máx y CMJ. Como conclusión, según el sexo y las posiciones de juego de los jugadores, estos indicadores variaron. Además, esta información será útil para procesos de promoción, desarrollo y diseño de entrenamientos de baloncesto juvenil en Costa Rica.

Taurine (2-aminoethanesulfonic acid) is a semi-essential sulphur-containing amino acid abundant in skeletal muscle. Taurine supplementation is popular among athletes and has been purported to enhance exercise performance. This study aimed to investigate the ergogenic effects of taurine supplementation on anaerobic (Wingate; WanT) performance, blood lactate, ratings of perceived exertion (RPE), and countermovement vertical jump (CMJ) in elite athletes. For this study, randomized, double-blind, placebo-controlled crossover designs were used. Thirty young male speed skaters were randomly assigned to either taurine (TAU; single dose of 6 g) or placebo (PLAC; single dose of 6 g) 60 minutes before testing. Following a 72-hour washout, period participants completed the opposite condition. TAU improved peak (Δ% = 13.41, p < 0.001, d = 1.71), mean (Δ% = 3.95, p = 0.002, d = 1.04), and minimum power output (Δ% = 7.89, p = 0.034, d = 0.48) compared to placebo. Further, RPE (Δ% = -10.98, p = 0.002, d = 0.46) was significantly lower following the WanT in the TAU condition compared to placebo. There were no differences between conditions for the countermovement vertical jump. In conclusion, acute TAU supplementation augments anaerobic performance in elite speed skaters.

The purpose of this study was to describe an anthropometric, aerobic and muscle power profile of young Costa Rican basketball players according to sex, play positions and age. The assessment was carried outa on 99 young players (43 women and 56 men; 18 guards, 51 forwards and 30 centers; 42 in the U16 category and 57 in the U18 category) from eight different teams. The sports experience of the players was 6.5 ± 3.1 years. The following parameters were assessed: height, weight, body mass index, skeletal muscle mass and body fat percentage, countermovement test (CMJ) and Yo-Yo Intermittent Recovery Test Level I. The main results showed significantly higher values in men than in women in terms of weight, height, skeletal muscle mass, distance covered in the yo-yo test, VO2max, height in CMJ and in flight time. Body fat percentage was higher in women than in men. Centers showed significantly higher height, weight and body fat percentage than other play positions. Guards and forwards covered more meters in the yo-yo test and showed higher VO2max than centers. No significant differences were found between the U16 and U18 categories in any variable. Regression models showed the influence of weight, body fat percentage, skeletal muscle mass and age on VO2max and CMJ. In conclusion, these indicators varied according to the sex and play position of the players. Additionally, this information will be useful for processes of promotion, development and training design of youth basketball in Costa Rica.

(1) Background: Leg length discrepancy (LLD), regardless of its origin, is a very common pathology that can contribute to low back pain. Various authors have pointed out its relationship with the lack of activation of both the gluteus medius (GM) and the ipsilateral erector spinae (ES). The purpose of this study was to identify the activation of the ES and GM with different simulated LLDs, correlating this activation with LBP. In turn, we evaluated whether ES and GM activity has an effect on jumping ability using a CMJ test. (2) Method: A sample of healthy subjects was selected to whom an artificial LLD was applied using 0.5, 1, and 1.5 cm insoles. These three heights were measured using EMG while the subjects walked and performed a counter movement jump (CMJ). The measurements of the insole heights were carried out in random order using a Latin square. Muscle activation patterns were recorded for 30 s at each of the insole heights while the patients walked at 5.7 km/h and they were compared with the maximum voluntary contraction (MVC), both on the ipsilateral and contralateral sides. These muscles were then measured under the same circumstances during the performance of the CMJ. (3) Results: We found statistically significant differences in the flight heights in both the CMJ and DJ. In the comparison, significant differences were found in the flight heights of the CMJ and the DJ using the 5 mm insoles, and in the case of the DJ, also without insoles, with respect to the MVC. We found statistically significant differences in the activation of the GM with the differences in insoles, but not in the activation of the Es in relation to the different insole heights. (4) Conclusions: Insoles of different heights caused activation differences in the medius on the side where the insoles were placed. We can relate this difference in activation to LBP. In relation to the ES, no significant differences were found in the activation of the ipsilateral side of the insole.

La velocidad de sprint y la capacidad de salto vertical son requisitos fundamentales para alcanzar el alto rendimiento en fútbol. Existe controversia sobre el tipo de ejercicio de fuerza (bilateral o unilateral) que permite mayor transferencia a estos gestos. El objetivo del presente estudio fue comparar el efecto del entrenamiento de fuerza utilizando sentadillas vs. estocadas sobre la velocidad de salto vertical y el sprint lineal en 20 metros en jugadores de fútbol de categoría juvenil. Participaron en el estudio 79 sujetos divididos aleatoriamente en tres grupos: entrenamiento con estocadas (GE) (n = 28; edad = 16,5 ± 1,2 años); entrenamiento con sentadillas (GS) (n = 24; edad = 16,3 ± 1,4 años) y grupo control (GC) (n = 27; edad = 16,5 ± 1,2 años). GE y GS realizaron entrenamiento de fuerza dos veces por semana durante 12 semanas. Previo y posterior a la intervención todos los sujetos fueron testeados en velocidad máxima en CMJ y sprint lineal de 20m. Los tres grupos mejoraron significativamente el rendimiento (p < ,05) en el sprint en 20m, siendo la mejora significativamente superior en los grupos experimentales en comparación con GC (p < ,05), sin diferencias entre los primeros. No se verificó una mejora significativa en la velocidad máxima en CMJ para ninguno de los grupos. Tanto el entrenamiento de fuerza bilateral como el predominantemente unilateral parecen ser beneficiosos para la mejora del rendimiento en velocidad de desplazamiento horizontal en jugadores de fútbol de categoría juvenil, sin que existan diferencias significativas entre los mismos. Palabras clave: Fútbol juvenil. Entrenamiento de fuerza bilateral. Entrenamiento de fuerza unilateral. Rendimiento deportivo. Sprint lineal. CMJ. Abstract. Sprint speed and vertical jumping ability are fundamental requirements to reach high performance in soccer. There is controversy about the type of resistance exercise (bilateral or unilateral) that allows greater transfer to these gestures. The aim of this study was to compare the effect of strength training using squats vs. lunges on vertical jump speed and 20-meter linear sprint in youth soccer players. Seventy-nine subjects randomly divided into three groups participated in the study: lunge training (GE) (n = 28; age = 16.5 ± 1.2 years); squat training (GS) (n = 24; age = 16.3 ± 1.4 years) and control group (GC) (n = 27; age = 16.5 ± 1.2 years). GE and GS performed strength training twice a week during 12 weeks. Before and after the intervention, all subjects were tested for maximum speed at CMJ and linear sprint of 20m. All three groups significantly improved performance (p < .05) in the 20m sprint, with the improvement being significantly greater in the experimental groups compared to GC (p < .05), with no differences between the former. No significant improvement in maximum speed at CMJ was verified for either group. Both bilateral and predominantly unilateral strength training appear to be beneficial for the improvement of sprint speed performance in youth soccer players, with no significant differences between them. Keywords: Youth Soccer. Bilateral resistance training. Unilateral resistance training. Athletic Performance. Lineal sprint. CMJ.

Player performance in an intense sport such as basketball is known to be related to attributes such as speed, agility, and power. This study presents a comparative analysis of associations between anthropometric assessment and physical performance in different age groups of elite youth basketball players, while simultaneously identifying the predictors for speed and agility in these players. U14 (n = 44), U15 (n = 45), and U16 (n = 51) players were tested for anthropometry, lower-body power, speed, and agility. U16 players were found to be taller, heavier, more muscular than U14 and U15 players. In addition, the U16 group showed better performance in all performance tests. Age had a significant positive correlation with countermovement (CMJ) and drop jump (DJ) performance in U14 players, and a significant negative correlation with 15m and 20m sprint times in the U15 group. CMJ and DJ emerged as the most significant predictors for sprint and agility variables, respectively. Body fat percentage was found to be a significant predictor for the speed and agility tests in all age groups, but a negative lower-body power predictor. Therefore, besides all sport-specific and fitness tests, it is essential to place emphasis on the percentage of body fat when designing players’ individualized training programs, and during team selection.

El objetivo de este estudio fue comprobar el efecto de dos periodos de preparación diferenciados por los medios de entrenamiento de la fuerza (con/sin carga externa añadida-pesas), en deportistas de natación sincronizada. Se valoraron las variables rendimiento (altura) en salto vertical (CMJ) y los test específicos de boost y tintorera. Un grupo de nadadoras de categoría infantil/júnior (14 ± 1 años), sin experiencia en el entrenamiento de fuerza, fueron las participantes en el estudio (n = 10). Durante el primer periodo de preparación se trabajó la fuerza sin carga externa añadida. En el segundo, se trabajó la fuerza con carga externa añadida (cargada, sentadilla y saltos con carga). Las deportistas fueron testadas al finalizar la pretemporada (datos referencia) y tras cada periodo de intervención (14 semanas). El análisis estadístico mostró cambios significativos en el boost (p

Ruiz Garrigós, A., Durán, A. y Sánchez - Pay, A. (2020). Influencia de dos tipos de calentamiento sobre la fuerza explosiva del tren inferior en estudiantes de educación física. PENSAR EN MOVIMIENTO: Revista de Ciencias del Ejercicio y la Salud, 18(1), 1- 13. El objetivo del presente Internacionalestudio fue determinar las posibles influencias de dos tipos de calentamiento (tradicional y específico) sobre la fuerza explosiva del tren inferior. Se realizaron dos pruebas (salto con contramovimiento -CMJ- y sprint 5 metros) sobre tres grupos: grupo sin calentamiento (GSC); grupo de calentamiento tradicional (GCT), que incluía movilidad articular, carrera continua y estiramientos estáticos; y grupo de calentamiento específico (GCE), que incluía movilidad articular, carrera continua, estiramientos dinámicos y pliometría. Se realizó un pre y post test y se utilizó la prueba de ANOVA de medidas repetidas para0020comparar la influencia del tipo de calentamiento sobre las pruebas entre los diferentes grupos. Posteriormente, se calculó el tamaño del efecto a través de g de Hedges. Los resultados mostraron diferencias estadísticamente significativas entre el pre y post test en el GCT y en el GCE; además, se encontraron diferencias estadísticamente significativas (p < .05) entre GSC y el GCE en el posttest solo en la prueba de salto. Realizar estiramientos dinámicos y pliometría como parte del calentamiento parece influir positivamente en la capacidad de salto vertical. Los datos sugieren que los profesores de educación física deberían utilizar calentamientos con estiramientos dinámicos y pliometría para mejorar el rendimiento en actividades que incluyan el salto.

The ability to generate force in the lower body can be considered a performance factor in sports. This study aims to analyze the test–retest and between-device reliability related to the location on the body of the inertial measurement unit Vmaxpro for the estimation of vertical jump. Eleven highly trained female athletes performed 220 countermovement jumps (CMJ). Data were simultaneously captured by two Vmaxpro units located between L4 and L5 vertebrae (hip method) and on top of the tibial malleolus (ankle method). Intrasession reliability was higher for ankle (ICC = 0.96; CCC = 0.93; SEM = 1.0 cm; CV = 4.64%) than hip (ICC = 0.91; CCC = 0.92; SEM = 3.4 cm; CV = 5.13%). In addition, sensitivity was higher for ankle (SWC = 0.28) than for the hip method (SWC = 0.40). The noise of the measurement (SEM) was higher than the worthwhile change (SWC), indicating lack of ability to detect meaningful changes. The agreement between methods was moderate (rs = 0.84; ICC = 0.77; CCC = 0.25; SEM = 1.47 cm). Significant differences were detected between methods (−8.5 cm, p < 0.05, ES = 2.2). In conclusion, the location of the device affects the measurement by underestimating CMJ on ankle. Despite the acceptable consistency of the instrument, the results of the reliability analysis reveal a significant magnitude of both random and systematic error. As such, the Vmaxpro should not be considered a reliable instrument for measuring CMJ.

Objective Various nutritional strategies are adopted for athletes to maintain and to improve performance during the competition season. Betaine may enhance performance during a competitive season by increasing the testosterone to cortisol ratio and reducing systemic inflammation. The aim of this study was to investigate the effect of betaine supplementation on the bio-motor abilities in young professional soccer players. Methods Twenty-nine young professional soccer players (age, 15.5±0.3 years) were matched by position and randomly assigned to one of two groups for 14 weeks: betaine (BG, 2 g/day; n=14) or placebo (PG n=15). Diet was standardized by a nutritionist, and measures of muscular power (countermovement jump: CMJ), change of direction: modified 5-0-5), acceleration (10 m sprint), sprint performance (30 m sprint time: SpT), muscular strength (leg press and bench press one repetition maximum: 1-RM), repeated sprint ability (running-based anaerobic sprint test: RAST), and aerobic capacity (30-15 intermittent fitness test) were assessed in the pre (P1), mid (P2) and post (P3) season over the course of 5 days. All subjects participated in one soccer match and five training sessions per week. Results Significant (p < 0.05) group x time interactions were found for maximal oxygen uptake (VO2max), anaerobic peak power, and muscular strength favoring BG at P2 and P3 compared to P1. There were meaningful (p < 0.05) group x time interactions for CMJ, SpT, and peak power during the RAST that favored the BG. Conclusions 14-week of betaine supplementation increased predicted 1-RM, VO2max, and repeated sprint ability performance in youth professional soccer players. Betaine supplementation seems to be a useful nutritional strategy to improve and to maintain performance during a competitive soccer season.

This study evaluated the reliability and sensitivity of a set of different common strength and power tests in a healthy adult population in a span of 9 weeks. Seventeen subjects (24.2 ± 2.2 years, 1.75 ± 0.10 m, 68.6 ± 14.2 kg, seven women) participated in the study. We tested countermovement jumps, reactive hops, and the maximal voluntary contraction (MVC) of handgrip and isometric knee extension. The tests were conducted in three separate sessions across a nine-week period, with one week between the first two sessions and eight weeks between the second and the third. Reliability and sensitivity statistics for each test were calculated for both the average of three trials and the best result during each session. The MVC of isometric knee extension and handgrip, as well as the countermovement jump test, demonstrated very high reliability and sensitivity over the nine-week period. The peak force of the reactive hops demonstrated high reliability but high sensitivity only for the average but not for the best result. The average contact time of reactive hops was neither a sensitive nor reliable measurement. In conclusion, isometric maximal knee extension and handgrip tests, as well as countermovement jumps and peak force of reactive hops, can be used as reliable and sensitive measurements of isometric and reactive strength and power over time periods of up to eight weeks. We recommend the use of the average results of three trials instead of the best performance value for longitudinal studies, as this procedure produces more consistent results and a lower measurement error.

In this study, we aimed to assess the countermovement jump (CMJ) using a developed instrument encompassing an off-the-shelf Inertial Measurement Unit (IMU) in order to analyze performance during the contraction phase, as well as to determine the jump height and the modified reactive strength index (RSImod), using force plate (FP) data as reference. Eight athletes (six males and two females) performed CMJs with the IMU placed on their fifth lumbar vertebra. Accuracy was measured through mean error (standard deviation), correlation, and comparison tests. The results indicated high accuracy, high correlation (r), and no statistical differences between the IMU and the FP for contraction time (r = 0.902; ρ < 0.001), negative impulse phase time (r = 0.773; ρ < 0.001), flight time (r = 0.737; ρ < 0.001), jump time (r = 0.708; ρ < 0.001), RSImod (r = 0.725; ρ < 0.001), nor minimum force (r = 0.758; ρ < 0.001). However, the values related to the positive impulse phase did not have the expected accuracy, as we used different devices and positions. Our results demonstrated that our developed instrument could be utilized to identify the contraction phase, jump height, RSImod, and minimum force in the negative impulse phase with high accuracy, obtaining a signal similar to that of an FP. This information can help coaches and athletes with training monitoring and control, as the device has simpler applicability making it more systematic.

La fuerza explosiva de los segmentos inferiores tiene un importante papel en los karatekas. Para su medición, los tests de salto Abalakov (ABK) y el salto con contramovimiento o Countermovement Jump (CMJ) son los más aceptados en las investigaciones. El objetivo de este estudio es analizar las horas de entrenamiento semanal y los resultados obtenidos en el salto vertical CMJ y ABK de 28 karatekas de categoría juvenil españoles (15 hombres y 13 mujeres), con edades comprendidas entre los 12 y 13 años, todos ellos participantes en la fase final del Campeonato de España de Karate. Se compararon los resultados en función del sexo por medio de la prueba T de Student, así como se realizó el ANOVA para conocer la relación entre el IMC y los resultados en los saltos. Para conocer la correlación entre horas de entrenamiento y los valores de fuerza explosiva se empleó la prueba Rho de Spearman. Los valores de horas de entrenamiento semanales son superiores en las chicas (horas de entrenamiento= 10.46 ± 3.04) frente a los chicos (horas de entrenamiento= 6.16 ±3.19). Los chicos tienen mayores valores medios en los resultados del salto CMJ (chicos 0.31 ±0.57; chicas 0.28 ±0.03) y ABK (chicos 0.35 ±0.06; chicas 0.33 ± 0.06). No existen diferencias significativas en los datos de salto CMJ y ABK en función del sexo de los karatekas. Abstract. Explosive strength of the lower segments plays an important role in karatekas. For its measurement, the Abalakov jump (ABK) and the counter-motion jump or Countermovement Jump (CMJ) are the most accepted test in research. The objective of this research work was to describe and analyze the results in CMJ and ABK tests of 28 Spanish youth category karatekas (15 boys and 13 girls), aged between 12 and 13 years, all of them participating in the final phase of the Spanish Karate Championship. Results were compared by gender using the Student's T test, as well as ANOVA was performed to assess the relationship between BMI and results in the jump tests. The Spearman Rho test was used to evaluate the correlation between training hours and explosive strength values. The values of weekly training hours are higher in girls (training hours = 10.46 ± 3.04) compared to boys (training hours = 6.16 ± 3.19). Boys have higher average values in CMJ jump results (boys 0.31 ± 0.57; girls 0.28 ± 0.03) and ABK (boys 0.35 ± 0.06; girls 0.33 ± 0.06). There are no significant differences in CMJ and ABK jump data by gender of the karatekas.

The aim of the present study was to compare the effects of countermovement jump (CMJ) and drop jump (DJ) training on the volleyball-specific jumping ability of non-professional female volleyball players. For that purpose, 26 female volleyball players (15–32 years) were assigned to either a CMJ (20.4 ± 3.1 years, 171.0 ± 3.0 cm) or a DJ training group (22.0 ± 4.4 years, 168.2 ± 5.0 cm), which performed a six-week jump training (two sessions per week, 60 jumps per session). Each group performed 20% of the jumps in the jump type of the other group in order to minimize the influence of enhanced motor coordination on the differences between groups regarding the improvements of jump performance. Before and after the training, jump height was assessed in four jump types, including the trained and volleyball-specific jump types. Although both training forms substantially improved jump height, the CMJ training was significantly more effective in all jump types (17 vs. 7% on average; p < 0.001). This suggests that, at least for non-professional female volleyball players and a training duration of six weeks, training with a high percentage of CMJs is more effective than one with a high percentage of DJs. We hypothesize that this might be related to the slower stretch-shortening cycle during CMJs, which seems to be more specific for these players and tasks. These findings should support volleyball coaches in designing optimal jump trainings.

Background: The importance of vertical jumps has been extensively recognised in sports. Furthermore, the main indicator of success in vertical jumps is the attained height, however, there is lack of knowledge on how the eccentric and concentric force-time curve variables affect the jump height. Objective: The objective of this study was to assess the relationships between eccentric and concentric variables of the force-time curve and jump height in youth volleyball players. Methods: Twelve elite volleyball players (male, Iranian national youth volleyball players, 17 ± 0.7 years) have participated in this study. The correlations between the force-time variables, including the peak force, relative peak force, peak power, average power, relative peak power, peak velocity, and modified reactive strength index, of the eccentric and concentric phases and jump height have been assessed based on Pearson's correlation coefficient. Results: Results showed that the average power (r = .70, p = .034), relative peak power (r = .75, p = .029) and peak velocity (r = .98, p = .004) of the concentric phase and modified reactive strength index (r = .83, p = .014) significantly correlated with the jump height. Conclusions: Relative peak power and average power of the concentric phase are shown to affect jump height in young volleyball players, whereby the vertical jump is their integral part.

BackgroundIn the context of a public health physical fitness (PF) examination in adolescence, a countermovement jump (CMJ) and a squat jump (SJ) are two vertical jump (VJ) tests widely used to evaluate lower limb muscle strength and power, respectively. The main criticism of both the CMJ and SJ test is the lack of test standardization. Therefore, the objectives of this review are: (a) to gather information about both jumps; (b) to investigate whether it is possible to identify common procedures referred to in the CMJ and SJ technical execution, and (c) to design standard operating procedures (SOPs) to promote CMJ and SJ standardization in an adolescent population aged 12–18 years.MethodsThe review partially adopted the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Statement (PRISMA). Due to growing attention in monitoring physical health through field tests in recent years, articles were collected using the PubMed, Web of Science, and Scopus databases from January 2009 to July 2019. Original articles in which CMJ or SJ were used to assess the muscular strength in adolescents were eligible for further analysis. Articles written in English was imposed as a limit.ResultsA total of 117 studies met the inclusion criteria. The description of the CMJ and SJ test procedures was different within the literature, with discrepancies in the jump technique, number of jumps, and measurement devices used.ConclusionsA lack of method standardization for both the CMJ and the SJ test was identified. Based on the literature, SOPs for both VJs were proposed. These are useful in the context of public health PF examination in adolescents, as they facilitate an unbiased comparison of jump performance data between published studies.

The aim of the study was to investigate the relationships between countermovement jump (CMJ) height and inertial power in squat and sprint variables with change of direction (COD) performance. Fifty young healthy active males participated in the study. To determine these relationships, we carried out a 10-m linear sprint test (T 10 m), vertical jump tests (CMJ and CMJ Abalakov), an assessment of power relative to bodyweight in a flywheel squat (Pbw), and 10-m COD sprints with two different turn types (COD-90° and COD-180°). T10 m showed statistically large and moderate correlations with T10 m COD-180° (r = 0.55) and T10-m COD-90° (r = 0.41), respectively. Moderate to large correlations between jumping height, linear sprinting, and sprints with COD were found (r = −0.43 to r = −0.59), and there were unclear correlations between jumping height and the loss of speed caused by executing COD (DEC-COD). Pbw showed a large correlation with CMJ Abalakov and CMJ jump height (r = 0.65 and r = 0.57, respectively), and a moderate and large correlation with T 10 m, T 10 m COD-180°, and T10 m COD-90° (r = −0.33, r = −0.38, and r = −0.54, respectively). Despite the existence of substantial correlations between variables, straight linear sprinting, jumping performance, CODs and squat power were, for the most part, separate motor qualities (R2 from 14% to 34%), suggesting that all of them should be specifically assessed and trained.

ResumenEl objetivo de este estudio es examinar los efectos agudos del entrenamiento con cargas pesadas, y del estiramiento estático sobre sujetos no entrenados y determinar si tiene un efecto positivo sobre el rendimiento en SJ y CMJ. 20 sujetos divididos en dos grupos (grupo de fuerza n:10 y grupo de estiramientos n:10). El grupo de fuerza realizó 3 series de 3 repeticiones con la máxima carga que puede soportar en 3RM y 3 min descanso entre serie. En el grupo de estiramientos los sujetos realizaban 3 series de 3 ejercicios de estiramientos correspondientes a flexores de rodilla, extensores de cadera y gemelos manteniendo el estiramiento pasivo durante 15 segundos en cada ejercicio. SJ y CMJ fueron medidos antes y después del ejercicio. La altura de salto se incrementó significativamente en el SJ después de los ejercicios de estiramiento (pAbstractThe purpose of this study were to examine the acute effects of strength training using heavy loads and static stretching for 15 seconds on SJ and CMJ. A population sample of 20 subjects was studied which was divided into two groups (strength training (ST) n=10- and static stretching training (SS) n=10-) ST group performed 3 sets of 3RM load with 3 min rest between all sets. SS group performed 3 stretching exercises, with each exercise held for 15 second repetitions. The stretches included a seated bilateral hamstring stretch; Standing unilateral quadriceps stretch and standing unilateral calf stretch. Vertical jump performance was measured before and after exercise. The height jump in SJ increased significantly after static stretching training (p