Figure 2. [PCr] responses of a typical subject in the rest-to-heavy exercise condition (A) and the rest-to-moderate exercise and moderate-to-heavy exercise condition (B).

The residuals for the model fits are shown at the foot of each plot. Note the progressive slowing of the time constant (τ) from rest-to-moderate exercise (26 s), rest-to-heavy exercise (41 s), and moderate-to-heavy exercise (66 s). Note also that, in this example, the delayed-onset [PCr] slow component evident in the rest-to-heavy exercise condition is absent in the moderate-to-heavy exercise condition.