Fig. 9.

Average normalized fiber velocity () and period of highest activation of 11 muscles during gait at four walking speeds and four running speeds (N=5). Colors indicate gait speed in walking (1.00–1.75 m s⁻¹) and running (2.00–5.00 m s⁻¹). Thick horizontal lines indicate portions of the gait cycle when a muscle's activation exceeded 80% of the maximum value for that speed. Vertical lines on the abscissa indicate the instant of toe off for each of the eight speeds. When fibers are shortening, is positive; when fibers are lengthening, is negative.