Influence of Time of Day on Anaerobic Capacity

12 volunteers performed exhaustive exercise tests in the morning and afternoon. Paired-means t tests indicated that anaerobic capacity, as reflected by maximal accumulated oxygen deficit, was 26% higher (p < .01) in the afternoon than in the morning. VO2max appeared higher and VO2 kinetics seemed faster in the afternoon, but differences did not attain statistical significance. Thus, the time of day affects anaerobic capacity and may influence other responses to exercise.