Figure 1. Intramuscular [PCr] and V̇_O2 dynamic responses to two square wave forcings of moderate intensity exercise in a representative subject (subject 1).

The response shows an ‘exponential-like’ fall of [PCr] and the associated ‘exponential-like’ rise in V̇_O2 to a new steady state from a resting value in two successive bouts of 6 min duration, separated by a 6 min rest period. The residuals to a linear fit of gradient zero are shown in the relevant regions. The vertical dotted lines indicate onset or cessation of exercise.