The purpose of this study was to investigate the relationship between sprint performance of front-crawl swimming and muscle fascicle length in 23 male young swimmers. The sample was divided into two groups by 25-m sprint front-crawl swimming performance: 14.6-15.7 s (S1, n=11) and 15.8-17 s (S2, n=12). Muscle thickness and pennation angle and fascicle length of the Biceps Brachii (only muscle thickness) and Triceps Brachii and Vastus Lateralis and Gastrocnemius Medialis and Lateralis muscles were measured by B-mode ultrasonography. S1 had a significantly greater Vastus Lateralis, Gastrocnemius Lateralis, and Triceps Brachii muscle thickness. Pennation angle only in Triceps Brachii was significantly smaller in S1. S1 in Vastus Lateralis, Gastrocnemius Lateralis, and Triceps Brachii muscles had significantly absolute longer fascicle length and in Vastus Lateralis and Triceps Brachii muscles, had relatively (relative to limb length) longer fascicle length. There was a significant relationship between sprint performance of front-crawl and absolute and relative fascicle length in Vastus Lateralis (absolute: r = -0.49, relative: r = -0.43) and Gastrocnemius Lateralis (absolute: r = -0.47, relative: r = -0.42). It is concluded that muscle fascicle length is one of the effective factors on the sprint front-crawl swimming in young swimmers.
