Torii, J., Shinkai, S., Hino, S., Kurokawa, Y., Tomita, N., Hirose, M., Watanabe, Shuichiro, Watanabe, Seiichiro, & Watanabe, T. (1992). Effect of time of day on adaptive response to a 4-week aerobic exercise program. Journal of Sports Medicine and Physical Fitness, 31, 348-352.

Healthy men were assigned to groups that trained in the morning (N = 4; 9:00 to 9:30 AM), afternoon (N = 4; 3:00 to 3:30 PM), or evening (N = 4; 8:00 to 8:30 PM). Ss worked by pedaling a cycle ergometer for 30 minutes at 60% VO2max.

The following were found.

• The afternoon group increased VO2max and decreased the blood lactate response in exercise.
• The evening group decreased the blood lactate response in exercise.

Implication. This study suggests that aerobic training is most effective in the afternoon. Training effects are less in morning or late evening practices. Performing at those times is probably best designed for physiological maintenance rather than change.

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