Kinematic Analysis of the Lower Extremity During Sprinting at Maximum and Sub-maximum Speeds

Abstract

Hamstring muscle strains are one of the most frequent injuries in sports. They are thought to occur during the late swing phase of gait when the hamstring is lengthening and eccentrically contracting. PURPOSE: The purpose of this study was to assess the difference in injury risks during testing at maximum and sub-maximum speeds by identifying kinematic differences at the hip and knee during the late swing phase of both speeds. METHODS: Ten athletes (21.8 ±3.5 years, 1.78 ± 0.07m, 78.11 ± 13.90kg) with no history of lower extremity injuries in the past 6 months, who could run faster than 6.83m/s were tested. Informed consent was obtained prior to testing. Kinematic data was collected using an 8 camera motion capture system sampling at 240Hz. Five maximum speed trials were conducted, after which an average speed was calculated and 90% of this speed was used for the 5 sub-maximal speed trials. Sprinting speed was monitored using two sets of infrared photocells. Subjects ran within ±5% of the indicated speed for all trials. Analysis was performed on one gait cycle for each subject's dominant limb. A series of paired t-test were used to test for significant differences between the two test speeds (α=0.05). RESULTS: Significant differences existed between maximum and sub-maximum running speeds (p<0.01). The average stance phase as a percentage of the gait cycle was 16.96% and 18.17% for maximum and sub-maximum speeds, respectively (p=0.004). The maximum hip flexion angle was significantly larger for the maximum speed (76.97o) when compared to the sub-maximum (74.25o) speed (p=0.01). The knee flexion angle at the point of maximum hip flexion were 78.98° and 75.98° for the maximum and sub-maximum sprinting speeds, respectively (p=0.02). Therefore, the knee was more extended during the sub-maximum sprinting speed. The average stride length during sub-maximum sprinting was significantly longer than the stride length during the maximum sprinting speed (p=0.008). CONCLUSIONS: Based on the results of this study, joint kinematics are different between the maximum and sub-maximum speeds indicating the importance of completing biomechanical testing at a maximum speed when assessing the potential for hamstring injuries.