BACKGROUND: To date, an assessment of the differences in the deep abdominal muscles among adolescent volleyball players at rest and during the abdominal drawing-in maneuver (ADIM) has not been performed.
OBJECTIVE: The aim of the study was to assess the thickness of the transversus abdominis (TrA) and internal oblique (OI) muscles at rest and during the ADIM in healthy adolescent volleyball players.
METHODS: Ninety-two secondary school students and members of volleyball sports clubs participated in the study. Measurements of the thickness of the muscles at rest and during ADIM were made in the supine position with ultrasound imaging.
RESULTS: The TrA was thicker in the volleyball group versus controls by 0.50 mm (95% CI: 0.09-0.99; p= 0.02). The OI was thicker in the volleyball group by 1.02 mm (95% CI: 0.34-1.71; p< 0.001). The analysis of the TrA preferential activity ratio showed that it was significantly higher, by an average of 0.03 (95% CI: 0.01-0.04; p< 0.001), in the volleyball group. The TrA contraction ratio was also significantly higher in the volleyball group, by an average of 0.20 (95% CI: 0.02-0.34; p= 0.03).
CONCLUSIONS: Adolescents who participate in volleyball training have higher TrA and OI thickness. The study showed higher values of the TrA preferential activation and contraction ratios in the volleyball group.
