Fig. 5. The temporal organization of wakefulness and nonrapid eye movement (NREM) sleep varied as a function of aerobic capacity. Asterisks indicate statistically significant differences between high capacity runners (HCR) and low capacity runners (LCR). (A ) The number of transitions between NREM sleep and wakefulness (Wake) was significantly greater in LCR rats than in HCR rats. (B ) Across the 24-h sleep recordings LCR animals also had significantly more wakefulness episodes. (C ) Averaging the duration of the NREM sleep episodes revealed a shorter duration in LCR than HCR rats.