Specific biomechanical characteristics in 110 m hurdlers: Asymmetrical hip flexor/extensor muscle size and hip joint torque

Sprint hurdle races differ from other sprint events in that obstacles are placed on the running lane. In the hurdling, hurdlers carry out asymmetrical motions. Therefore, hurdlers may have obtained asymmetrical muscle size through their training. In addition, if muscles of hurdlers have hypertrophied, hurdlers are likely to show specific muscle strength together with the morphological characteristics. The purpose of this study was to investigate the asymmetrical characteristics of hip flexor and extensor muscle size and strength in 110 m hurdlers. To investigate this issue, three independent experiments were conducted in this study. In the first experiment, we determined the size of the psoas major muscle, hamstrings and gluteal muscles. In the second experiment, we determined the isometric hip joint flexion and extension torque. In the third experiment, we determined the hip joint flexion and extension moment of the lead leg in the hurdling phase and investigated whether the cross sectional area (CSA) of the psoas major muscle and hamstrings of the lead leg significantly influence hip joint flexion and extension moment of the lead leg. The CSA of the psoas major muscle of the lead leg and the gluteal muscles of the trail leg were significantly greater than that of the other leg except for the hamstrings (p < 0.05, 0.01 respectively). Isometric hip joint flexion and extension torque of the lead leg was significantly greater that of the trail leg (p < 0.05, respectively). There were no significant correlations between the hip joint flexion moment during hurdling phase and the CSA of the psoas major muscle at any levels. Hip joint extension moment of hurdling phase was significantly correlated with the CSA of the hamstrings at the level of 30% distal thigh length (p < 0.01). These results suggest that hurdlers had obtained competition-specific morphological and muscle strength characteristics through the training unique to hurdling.