Figure 1. Fatigue occurs more rapidly after recovery without glucose.

Original data traces of force (upper panels) and [Ca²⁺]_i (lower panels) obtained in single fast-twitch mouse muscle fibres during fatigue induced by repeated tetanic contractions (100 Hz, 350 ms). This type of fatiguing stimulation resulted in marked decrease in glycogen to ∼30% of the control value (Chin & Allen, 1997). Force and [Ca²⁺]_i were well maintained during a second fatigue run after 60 min of recovery in 5.5 mm glucose (A), which restored glycogen to pre-fatigue levels. Conversely, force and [Ca²⁺]_i were not fully restored and fatigue occurred more rapidly after 60 min of recovery without glucose (B), where glycogen stores remained depleted. Adapted from Figs 5 and 6 of Chin & Allen (1997).