Analysis of gait differences in healthy runners and runners with chronic Achilles tendon complaints

Differences in lower extremity movement characteristics are stated as a reason for overuse injuries. The causal assignment of biomechanical quantities to the onset of complaints is still subject of debate in gait analysis. The purpose of this study was therefore to compare biomechanical gait characteristics by means of plantar pressure distribution (PPD), EMG and ground reaction forces (GRF) in healthy runners and in runners with chronic Achilles tendon complaints (AT). Fourteen healthy runners and 8 runners with AT were examined at 12 km/h. Surface EMG, in-shoe PPD and GRFs were evaluated on a treadmill mounted on force transducers. Subjects ran barefoot and with a reference shoe in random order. EMG time and amplitude quantities, characteristics of the path of the center of pressure (CoP), vertical and a-p forces and impulses were extracted. In AT no differences in CoP-characteristics between barefoot and reference shoe were observed, compared to corresponding significant differences in the control group. Compared to the AT group, the control subjects had a higher activity EMG-amplitudes in the extensor loop during weight acceptance phase, a higher braking impulse and a lower pushing impulse. It is thus concluded that healthy runners differ from AT patients in terms of movement characteristics especially in running.