Fig. 4. (A) Mean EMG spike amplitude (MSA) for the LG (top), pMG (middle) and dMG (bottom). The black and grey bars represent strides at 0.5 and 2.0 m s^–1, respectively. Strides on the level surface are on the left of each panel and strides on the inclined surface are on the right. Asterisks indicate a significant effect of locomotor speed from an ANOVA (P<0.05). Values are means ± s.e.m. (N=4). (B) Regressions of MSA versus maximum muscle force for the LG (top), pMG (middle) and dMG (bottom). Force and MSA were significantly, and positively, correlated for the LG (r²=0.52, P<0.001), pMG (r²=0.31, P<0.001) and dMG (r²=0.58, P<0.001). LG, y=152.9x+10.8; pMG, y=110.7x+19.1; dMG, y=98.3x+26.3.