The core musculature in male prepubescent tennis players and untrained counterparts: a volumetric MRI study.

The effects of exercise on the core musculature have not been investigated in prepubescents. The main purpose of the present study was to determine the volume and degree of asymmetry ofrectus abdominis, obliquesandtransversus abdominis, quadratus lumborum, iliopsoas, gluteusandparavertebralismuscles in prepubescent tennis players and in untrained boys. The muscle volume was determined using magnetic resonance imaging (MRI) in 7 male prepubescent tennis players and 10 untrained controls (mean age 11.0 ± 0.8 years, Tanner 1–2). After accounting for height and body weight as covariates, the tennis players had 14–34% greater volume than the controls in all the muscles analysed (P < 0.05) except inparavertebralis, dominantquadratus lumborumand non-dominantgluteus, which had similar volumes in both groups (P = NS). Compared to controls, the tennis players displayed a greater degree of asymmetry inquadratus lumborumandrectus abdominis(3% vs. 15%,P < 0.01 and 8% vs. 17%,P = 0.06, respectively). The level of asymmetry ofobliquesandtransversus abdominis, iliopsoas, gluteus andparavertebralismuscles was similar in both groups (P = NS). In conclusion, tennis playing at prepubertal ages induces a selective hypertrophy of the core musculature and exaggerates the degree of asymmetry ofquadratus lumborumandrectus abdominiscompared to untrained boys. [ABSTRACT FROM PUBLISHER]