Purpose: This study aimed to investigate how the cross-sectional areas (CSA) of the quadriceps femoris (QF)3, hamstrings (Ham), and psoas major (PM) in junior sprinters are related to mean running velocity (MV100m) calculated from official records of 100-m races.
Methods: In 44 sprinters (22 boys and 22 girls) aged 14-17 yr, cross-sectional images were taken at the upper thigh and midthigh and midway between the fourth and fifth lumbar vertebrae using magnetic resonance imaging. CSA of the three muscles located in both sides were analyzed. For each muscle, the mean values of the CSA of the right and left sides were calculated and used for regression analyses of the relationships between CSA variables and MV100m.
Results: Stepwise multiple-regression analyses produced prediction equations of MV100m with independent variables of QF CSA at the midthigh and PM-to-QF CSA ratio at the upper thigh for boys (R2 = 0.38) and PM-to-QF CSA ratio at the midthigh for girls (R2 = 0.33). In the regression model for boys, QF CSA at the midthigh had a negative regression coefficient.
Conclusion: For junior sprinters of both genders, the higher development of PM relative to QF, rather than absolute muscle size, is a factor in achieving a better performance in 100-m race performance.
1Sports Photonics Laboratory, Hamamatsu Photonics K.K., Iwata-City, JAPAN; 2Department of Life Sciences (Sports Sciences), University of Tokyo, Tokyo, JAPAN; and 3Department of Sports Sciences, School of Human Sciences, Waseda University, Tokorozawa, JAPAN
Address for correspondence: Yoshihiro Hoshikawa, Sports Photonics Laboratory, Hamamatsu Photonics K.K., 2150-1 Iwai, Iwata-City, Shizuoka 438-0016 Japan; E-mail: firstname.lastname@example.org.
Submitted for publication December 2005.
Accepted for publication June 2006.