This study was designed to clarify the relationships between the muscle cross-sectional area of the trunk and thigh and 400-m hurdle time in 12 young adult male athletes include a bronze medalist in the world championships (height 175.4 ± 6.0 cm, body mass 67.9 ± 5.8 kg, 400-m hurdle time 47.89―55.41 s). Crosssectional images from the origin to insertion of the trunk and thigh muscles were obtained using magnetic resonance imaging (MRI). These images were used to calculate the absolute cross-sectional areas of each muscle as indices of muscularity. Stepwise multiple regression analysis was performed to examine the association between the indices and 400-m hurdle time. This analysis produced an equation (adjusted R2 = .868) with the semitendinosus (β = −0.611, P = .001), quadratus lumborum (β = −0.300, P = .044) and adductor brevis (β = −0.395, P = .014) as the explanatory variables. It was concluded that individual differences in 400-m hurdle performance can be explained by the semitendinosus, quadratus lumborum and adductor brevis.
