Fig. 5. Mean±S.E.M. values of net work, average force, net fascicle strain, and average velocity for the lateral gastrocnemius (LG) and peroneus longus (PL) muscles in all turkeys running at a steady speed of 2 m s^–1 on a level, incline, and decline. Filled symbols for the LG and PL are averages over the period of stance; open symbols for the LG are averages over the period of force production in stance. For clarity, S.E.M. values for open symbols are not shown; hidden open symbols for LG net work are the same as the stance values. Net work output for the LG and PL changed significantly with running slope (P<0.05; r²=0.99 for LG and r²=0.97 for PL). On steeper inclines, LG and PL did increasingly greater amounts of net positive work; on steeper declines, both muscles did increasingly greater amounts of net negative work. Average muscle force in stance remained constant across all slopes for both the LG and PL (P>0.05), whereas net fascicle strain, expressed as percentage length change relative to resting fascicle length, and average muscle velocity changed significantly with running slope, in parallel with the changes in net work output. For net fascicle strain, P<0.01; r²=0.99, LG and r²=0.98, PL; for average muscle velocity, P<0.01; r²=0.99, LG and r²=0.98, PL. L, fascicle length; L₀, resting segment length.