Abstract

The purpose of this study was to describe kinematic changes that occur during an actual marathon. We hypothesized that (1) certain running kinematic measures would change between miles 5 and 25 of a marathon and (2) fast runners would demonstrate smaller changes than slow runners. Subjects (n = 179) were selected according to finish time (Range = 2:20:47 to 5:30:10). Two high-speed cameras were used to measure sagittal-plane kinematics at miles 5 and 25 of the marathon. The dependent variables were stride length, ground time, peak knee flexion during support and swing, and peak hip flexion and extension during swing. Two-tailed paired t-tests were used to compare dependent variables between miles 5 and 25 for all subjects, and regression analyses were used to determine whether faster runners exhibited smaller changes (between miles 5 and 25) than slower runners. For all runners, every dependent variable changed significantly between miles 5 and 25 (p < 0.001). Stride length increased 1.3%, ground time increased 13.1%, peak knee flexion during support decreased 3.2%, and peak hip extension, knee flexion, and hip flexion during swing decreased 27.9%, increased 4.3%, and increased 7.4%, respectively (p<0.001). Among these significant changes, all runners generally changed the same from miles 5 to 25 except that fast runners decreased peak knee flexion during support less than the slow runners (p < 0.002). We believe these kinematic changes were an attempt by all runners (fast and slow) to decrease energy expenditure and enhance performance at the late stage of the race. The fact that fast runners maintained knee flexion during support more consistently might be due to their condition on the race day. Strengthening of knee extensor muscles may facilitate increased knee flexion during support throughout a marathon.

Degree

College and Department

Life Sciences; Exercise Sciences

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