a, Pattern of lever movement. Frequency of 0.5 Hz and peak-to-peak amplitude 18% Lo (10% Lo). Lo is the fibre bundle length at which isometric force was greatest. Values for cow experiments are in parentheses, where they are different than those for wildebeest. b, Stimulus duty cycles used in the experiments. Top to bottom, duty cycle of 0.1, 0.2, 0.3 and 0.4 (0.2 and 0.3). c, Stimulus phases used in the experiments. Top to bottom: phase −0.2, −0.1, 0, 0.1, 0.2 and 0.3. (−0.2 to 0.1). Phase = 0.0 corresponds to the stimulus starting when shortening starts. In this example, DC = 0.4.