[The impact of local muscle fatigue and foot strike techniques on kinematic features and plantar pressure distribution while walking].

Abstract

Although numerous studies have been performed, there are no clear findings providing a meaningful statement about how foot strike changes as a result of muscular fatigue. In studies on running fatigue, it is not possible to differentiate which kinematic or kinetic changes are a direct result of local muscle fatigue and varied speeds. This study aimed to investigate the effect of foot strike technique and localized muscle fatigue of the plantar and dorsal flexors on plantar pressure distribution and selected kinematic features of treadmill running. Twenty-six voluntary forefoot and rearfoot runners of similar age and body mass participated in the study. Each group completed two tests with a time interval of 3-7 days. The kinematic data was measured with the help of a three-dimensional measuring and analysis system while the volunteers ran on the treadmill. The fatigue protocol included an isometric maximal force test and an isokinetic endurance test. In order to check the differences, a variance analysis with repeated measurements was used. The strength values of the two groups of runners showed significant average differences in the plantar flexors in the endurance test and in the fatigue index for both the left and right legs. The results of the strength values are surprising because the plantar flexors of this group of runners should be well-trained due to the forefoot strike during regular running. In response to fatigue, the pressure maxima decreased under the exposed foot regions, i.e. under the forefoot at forefoot strike and under the heel at rearfoot strike. The two groups of runners differed in foot angle at foot-on with higher values measured in the forefoot runners. The larger foot angle of the forefoot runners improved shock absorption and can thus reduce the risk of injury.