Effects of muscle fatigue of the quadriceps femoris on kinematic parameters of human gait

Abstract

The present study was designed to identify the abnormal gait of limping from the view of the leg muscle strength whose loss caused kinematic changes of leg motions to carry the body weight. The limping was simulated by muscle fatigue of the quadriceps femoris after repetitive knee extensions in the isometric contraction.

Eighteen healthy male sutudents aged 20.0 ± 2.1 years old performed three different exertions, when the muscle strength of left knee extensor decreased to 60, 40 and 20 % BW (body weight). Their normal and abnormal gait were videotaped to measure the joint angle changes of knees and ankles. In addition, selected kinematic parameters such as left and/or right step lengths were analyzed in a gait cycle.

The most severely fatigued condition of 20 %BW trial showed significantly (p<0.05) different 1) velocities during both left (fatigued leg side) stride and right-to-left step, 2) ranges of knee and ankle angles from those in the normal gaits. On the other hand, the least fatigued 60 %BW trial showed significantly different range of ankle angle, while the intermediately fatigued 40 %BW one in both knee and ankle angles.

The present results suggest that the muscle strength of knee extensors of around 40 to 60 %BW are necessary to perform normal gait, which could be target values to be achieved by patients in a rehabilitation program.