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This study examined the relationships between longitudinal changes in data obtained in the Yo-Yo intermittent recovery level 2 test (Yo-Yo IR2), maximal oxygen consumption (VO2max) and leg muscle size and function in pubescent soccer players. Forty-four soccer players with a mean age of 12.8±0.2 years participated, and were classified into three maturational groups (Late, Average and Early) according to their peak height velocity age. The Yo-Yo IR2 and five-jump tests along with measurement of VO2max and thigh muscle volume were conducted on two occasions 6 months apart. Performances in the Yo-Yo IR2 for the Late, Average and Early groups were 311±61, 371±88 and 411±72 meters at the first measurement, and 389±73, 509±117 and 621±69 meters 6 months later. Consequently, two-way repeated-measures ANOVA revealed a significant interaction whereby the improvement in Yo-Yo IR2 performance was larger in the Early group (51.3%) than in the Late group (24.8%). Greater increases of thigh muscle volume and the result of the five-jump test were found in the Early group, and these were correlated significantly (r=0.52, p<0.05; r=0.39, p<0.05) with improvement of Yo-Yo IR2 performance. In contrast, there was no relationship (r=−0.02, n.s.) between the increments of VO2max and Yo-Yo IR2 performance. These results suggest that performance in the Yo-Yo IR2 is affected by maturity to a great extent, early-maturing players having an advantage in terms of leg muscle development.

international journal of sport and health science

Yo-Yo Intermittent Recovery Level 2 Test Performance and Leg Muscle Growth in a Six-month Period among Pubescent Soccer Players at Different Stages of Maturity