Averaged EMG profiles in jogging and running at different speeds

EMGs were collected from 14 muscles with surface electrodes in 10 subjects walking 1.25–2.25 m s⁻¹ and running 1.25–4.5 m s⁻¹. The EMGs were rectified, interpolated in 100% of the stride, and averaged over all subjects to give an average profile. In running, these profiles could be decomposed into 10 basic patterns, 8 of which represented only a single burst. Muscles could be divided into a quadriceps, hamstrings, calf and gluteal group, the profiles of which were composed of the same basic patterns. The amplitude of some bursts was constant, but other ones varied with running speed. This speed dependency was generally different between muscles of the same group.

Many muscles show a similar profile in running as in walking. The most notable exception is the calf group, which shows activation in early stance (86–125%), together with quadriceps, instead of in late stance (26–55%) as in walking. This is also visible in low-speed running, ‘jogging’, where stance extends to 46% or 57%, instead of 30–37% as in normal running. Jogging shows some additional differences with normal running, related to this prolonged stance phase.