Skeletal Muscle Fiber Type, Fiber Size, and Capillary Supply in Elite Soccer Players

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Abstract
This study determined the fiber type composition, the fiber size, and the capillary characteristics of the vastus lateralis muscle in 11 young, elite, male soccer players and 8 sedentary male, age-matched controls. There were no significant differences (P < 0.05) in the fiber type percentages and fiber diameter between the soccer players and controls; however, all fiber types tended to be larger in the soccer players. The soccer players possessed a greater capillary supply; this was characterized by a significantly greater mean number of capillaries surrounding each fiber (5.7 ± 0.9 vs. 4.9 ± 0.4), a significantly larger capillary density (282.7 ±42.0 vs. 220.8 ±38.1), and a significantly higher capillary to fiber ratio (2.2 ± 0.6 vs 1.7 ± 0.1). The results indicate that soccer may be an appropriate stimulus for simultaneous adaptation to endurance and high intensity exercise.