The objective was to analyze anthropometric and physical performance variables as a function of chronological age and biological maturity in young Chilean tennis players. The study was observational, cross-sectional, with descriptive and analytical characteristics. Eighty-seven tennis players were evaluated (58 men 15.1 ± 0.8 years and 29 women, 15.3 ± 0.8 years). The measured anthropometric variables were a sprint test of 20m; a modified agility test; a sit-and-reach test and shoulder flexibility; manual grip strength; horizontal jump in feet; a medicine ball throw; a countermovement vertical jump; an abalakov vertical jump and a 20-m shuttle-run test. The growth velocity acceleration peak (APHV), skeletal muscle mass and fat mass were calculated, R2 and standard error of estimate (SEE) were examined. The results show that chronological age explained the anthropometric variables between 1 and 23% in men and 1 and 29% in women; by biological age, variables were explained between 3 and 53% in men and 2 and 42% in women. Of the physical performance variables, chronological age described between 2 and 24% of them in men and 1 and 29% in women; the same were explained by biological age between 1 and 19% in men and 1 and 26% in women. We conclude that anthropometric variables showed a better relationship with biological age, except for volume of fat tissue, while physical performance variables showed low association with both biological and chronological age.

In tennis, it is common for young male tennis players to spend several weeks away from their local training camps during the competition season, which could affect their performance. The purpose of the study was to analyze the effects of a six-week international tour on physical performance and body composition in young Chilean tennis players. Twenty-four men between the ages of 14 and 16 participated in this research. In body composition and anthropometric measurement, body weight, height, skinfolds, and perimeters were measured. Body fat percentage (BFP) and skeletal muscle mass (SMM) were calculated. For physical performance, 5-m and 10-m sprints, modified agility test (MAT test), countermovement jump (CMJ), and medicine ball throw (MBT) were evaluated. Results show that, in body composition, BFP and SMM significantly decreased post-tour (p < 0.05; effect sizes ranging from 0.23 to 0.33, respectively). In physical performance, agility and 5-m and 10-m sprints significantly decreased (p < 0.05, effect sizes ranging from −0.63 to 1.10). We conclude that after a six-week international tour, BFP, SMM, agility, and speed (linear sprint) tend to decrease significantly, with a greater effect in the sprint tests.

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El estudio tuvo como objetivo analizar la relación entre la fuerza muscular y composición corporal con la masa ósea en tenistas jóvenes chilenos. El estudio fue observacional, transversal, con características descriptivas y analíticas. La muestra estuvo compuesta por 51 tenistas jóvenes chilenos de sexo masculino (15.5±0.7 años) que fueron seleccionados de forma no probabilística y por conveniencia. Se midieron variables antropométricas de peso, estatura, estatura sentada, pliegues cutáneos (tríceps, muslo anterior y pierna medial), perímetros (brazo, muslo y pierna), diámetro del fémur y longitud del antebrazo, junto con la fuerza de prensión manual (FPM), lanzamiento de balón medicinal (LBM) y salto con contramovimiento (CMJ). Se calculó el pico de aceleración de la velocidad de crecimiento (APVC), la masa músculo esquelética (MME), el porcentaje de grasa (GC), la densidad mineral ósea (DMO) y contenido mineral óseo (CMO). Los resultados muestran que, en las variables de composición corporal, la MME se asocia mejor a la DMO (R2= 25% p˂0.01) y CMO (R2= 20%; p˂0.01). En las pruebas de fuerza muscular, el CMJ presenta la mejor relación con los indicadores de masa ósea, DMO (R2= 14%; p˂0.01) y CMO (R2= 19%; p˂0.01). Se concluye que la MME es el indicador que muestra mejor relación con la DMO y CMO en los tenistas evaluados, por su parte el CMJ, es la prueba de fuerza muscular que mejor relación muestra con estos indicadores de masa ósea. Palabras clave: desarrollo óseo; fuerza muscular; masa músculo esquelético; adolescentes; tenis. Abstract. The study aimed to analyze the relationship between muscle strength and body composition with bone mass in young Chilean tennis players. The study was observational, cross-sectional, with descriptive and analytical characteristics. The sample consisted of 51 young Chilean male tennis players (15.5±0.7 years old) who were selected non-probabilistically and for convenience. Anthropometric variables of weight, height, sitting height, skinfolds (triceps, anterior thigh, and medial leg), perimeters (arm, thigh, and leg), femur diameter, and forearm length were measured, along with hand grip strength (FPM), medicine ball throw (LBM), and countermovement jump (CMJ). Peak acceleration of growth velocity (APVC), skeletal muscle mass (MME), percentage of fat (GC), bone mineral density (DMO) and bone mineral content (CMO) were calculated. The results show that, in the body composition variables, MME is better associated with DMO (R2= 25% p˂0.01) and CMO (R2= 20%; p˂0.01). In the muscle strength tests, the CMJ presents the best relationship with the indicators of bone mass, DMO (R2= 14%; p˂0.01) and CMO (R2= 19%; p˂0.01). It is concluded that the MME is the indicator that shows the best relationship with DMO and CMO in the evaluated tennis players, while the CMJ is the muscle strength test that shows the best relationship with these indicators of bone mass. Key words: bone development; muscle strength; skeletal muscle mass; young boys; tennis.

La investigación tuvo como objetivo analizar la relación entre indicadores de agilidad con la composición corporal y la fuerza muscular explosiva de los miembros inferiores en mujeres jóvenes tenistas. El estudio fue de tipo observacional, transversal, correlacional, y con características descriptivas. La muestra estuvo compuesta por 22 jóvenes tenistas chilenas (15.3±0.7 años), seleccionadas en un muestreo no probabilístico por conveniencia. Se midieron variables antropométricas de peso, estatura, pliegues cutáneos (tríceps, muslo anterior y pierna medial) y perímetros (brazo, muslo y pierna). Se calcularon la masa músculo esquelética (MME) y el porcentaje de grasa corporal (GC). Además, se aplicaron pruebas de rendimiento físico; test 505 con arranque estacionario (505), test modificado de agilidad (MAT), salto horizontal a pies juntos (SH), salto con contramovimiento (CMJ) y Abalakov (ABK). Los resultados mostraron que las pruebas de agilidad (MAT y 505) se asocian mejor con el SH, test 505 (R2= 34% p˂0.01) y test MAT (R2= 22%; p˂0.05), además, por cada centímetro de aumento del SH disminuye el tiempo de ejecución en ambas pruebas de agilidad (β= − 0.02 s). En cambio, la MME, GC, CMJ y ABK, no muestran relaciones significativas con la agilidad (p>0.05). Se concluye que la agilidad muestra una mejor asociación con la prueba de SH en tenistas jóvenes chilenas, por lo que las pruebas de agilidad (test 505 y MAT) podrían ser un método específico de evaluación en tenistas mujeres. Palabras clave: fuerza muscular; composición corporal; agilidad; mujeres; adolescentes; tenis. Abstract. The objective of the research was to analyze the relationship between agility indicators with body composition and lower-extremity explosive muscle strength in young female tennis players. The study was observational, cross-sectional, correlational, and with descriptive characteristics. The sample consisted of 22 young Chilean tennis players (15.3±0.7 years old), selected in a non-probabilistic sampling for convenience. Anthropometric variables of weight, height, skin folds (triceps brachial, anterior thigh, and medial leg) and perimeters (arm, thigh, and leg) were measured. Body fat percentage (GC) and skeletal muscle mass (MME) were calculated. In addition, physical performance tests were applied; 505 with stationary start test (505), modified agility test (MAT), horizontal jump (SH), countermovement jump (CMJ) and Abalakov jump (ABK). The results showed that the agility tests (MAT and 505 tests) are better associated with the SH, 505 test (R2= 34% p˂0.01) and MAT test (R2= 22%; p˂0.05), in addition, for each centimeter of increase in the SH there is a decrease in the execution time of both agility tests (β=−0.02 s). On the other hand, the MME, GC, CMJ and ABK, do not show significant relationships with agility (p>0.05). It is concluded that agility shows a better association with the SH test in young Chilean tennis players, so that agility tests (505 and MAT) could be a specific method of evaluation in female tennis players. Key words: muscle strength; body composition; agility; women; young boys; tennis.