Relationship of The Knee Extensor Strength But Not The Quadriceps Femoris Muscularity With Sprint Performance in Sprinters: A Reexamination and Extension

Purpose: This study examined the relationships of the knee extensor strength and quadriceps femoris size with sprint performance in sprinters. Methods: : Fifty-eight male sprinters and 40 body size-matched male non-sprinters participated in this study. The knee extensor isometric and isokinetic strengths were measured using a dynamometer. The isokinetic strength measurements were performed with slow and fast velocities at 60°/s and 180°/s, respectively. The quadriceps femoris muscle volume (MV) was measured using magnetic resonance imaging. The relative values of the knee extensor strengths and quadriceps femoris MV were normalized to body mass. Results: : The absolute and relative values of the two velocity isokinetic strengths, but not of isometric strength, of the knee extension were significantly higher in sprinters than in non-sprinters (both P s < 0.05). Such a significant difference was also observed for the relative quadriceps femoris MV ( P = 0.018). In sprinters, there were significant correlations between all three knee extensor strengths and quadriceps femoris MV ( r = 0.421 to 0.531, all P s £ 0.001). The absolute and relative strengths of the fast-velocity isokinetic knee extension correlated with personal best 100-m sprint time ( r = -0.477 and -0.409, respectively, both P s £ 0.001). By contrast, no significant correlations were observed between absolute and relative quadriceps femoris MVs and personal best 100-m sprint time. Conclusions: : These findings suggest that despite the presence of the relationship between muscle strength and size, the knee extensor strength may be related to superior sprint performance in sprinters independently of the quadriceps femoris muscularity.