Comparisons of increases in knee and ankle joint moments following an increase in running speed from 8 to 12 to 16km·h(-1.).

BACKGROUND

Knowledge regarding knee and ankle joint load across a range of running speeds is important, if running related injuries are to be prevented. The purpose of the present study was to test the hypothesis that peak plantar flexion moment increases relatively more than peak knee extension moment when running speed is increased.

METHODS

Kinematic and ground reaction force data were collected from 33 recreational runners during steady-state running at three different speeds: 7.96km·h(-1) (SD 0.18), 11.92km·h(-1) (SD 0.25) and 15.91km·h(-1) (SD 0.36). Peak plantar flexion moment and peak knee extension moment were calculated using a standard three-dimensional inverse dynamics approach.

FINDINGS: There was a significant interaction between the joint location and the running speed (P=0.03): When running speed increased from 7.96 to 15.91km·h(-1), mean peak plantar flexion moment increased by 0.74N·m·kg(-1) (95% CI: 0.64; 0.85) which was more than the 0.52N·m·kg(-1) (95% CI: 0.42; 0.63) increase in mean peak knee extension moment.

INTERPRETATION: A greater increase in biomechanical load occurs for the plantar flexors of the ankle joint than for the extensors of the knee joint when running speed increases. This may indicate that at an excessive running speed, the structures at the posterior part of the lower leg and underneath the foot are relatively more vulnerable to injury compared with the structures at the anterior part of the knee. As a considerable load reduction is achieved, a decrease in running speed may benefit rearfoot striking recreational runners experiencing pain in the posterior lower leg or underneath the foot.