Relationships between hip range of motion, sprint kinematics and kinetics in track and field athletes
Hip range of motion (ROM) may influence movement kinematics and kinetics during sprinting. The purpose of this research was to investigate the relationships between hip ROM and measures of sprint kinematics and kinetics in track and field athletes, and to assess changes in these variables at different stages of the athletics season. Nineteen national-level track and field athletes undertook testing procedures for kinematic and kinetic assessment. Twelve participants returned to the laboratory 12 weeks later to carry out the same testing procedures. Clinical assessments of static and active hip ROM were conducted using a Thomas test and the active straight-leg raise. The kinematic data were collected from over-ground 40 m sprint trials recorded at 240 Hz and the kinetic data were obtained from a non-motorised treadmill with in-built load cells. The reliability of these assessments were analysed via intraclass correlation coefficients and typical error. Pearson correlation coefficients were used to examine the relationships between the kinematic and kinetic variables and the change scores between testing occasions were analysed by calculating the percentage change and effect sizes to make magnitude-based inferences. The results showed that all assessments had good reliability apart from hip extension (HE) angular velocity. Correlational analysis revealed very large correlations between dynamic hip flexion (HF) ROM and HE angular velocity (r = 0.76), and very large negative correlations between dynamic HF ROM and pelvic angle at peak HE (r = -0.71), as well as peak running velocity and ground contact time (r = -0.73). There was also a large correlation shown between dynamic HE ROM and pelvic angle at peak HF (r = 0.55), and large negative correlations shown between angular HF velocity and contact time (r = -0.61), and angular HE velocity and pelvic angle at peak HE (r = -0.69). Changes in the kinematic and kinetic variables were shown to be trivial between testing occasions. In conclusion, the high reliability shown for clinical measures of hip ROM and assessment of sprint kinematics and kinetics makes these tests useful for researchers and practitioners. Furthermore, the observed correlations between measures of hip ROM and sprinting kinematics and kinetics have implications for the development of technical sprinting abilities such as achieving a high degree of dynamic HF ROM to maximize HE angular velocity. The correlations between dynamic hip ROM and pelvic angle during running may also have implications for reducing vertebral impingement and hamstring strain injuries.