Editor’s Note: Irene Lewis-McCormick is a graduate student in health and human performance. If you would like to ask a fitness-related question, please send an e-mail request to: [email protected].

Q: Does the time of day that exercise takes place have anything to do with one’s ability to perform?

A: The time of day and your response to the training can be affected by how regularly you train. If your goal is to improve your high-intensity performance, be certain that you train in high-intensity mode at a specific time of day on a regular basis. A basic and often ignored principle of training is that adaptations take place relative to the type of training performed. This is called the “specificity principle.”

For example, if you would like to be a better runner, general cardiovascular training, like aerobic dance, is not the most appropriate mode of exercise. Rather, running would be the most appropriate type of training because the goal is to become a better runner. The muscles used and the mode and speed of exercise is important if you are trying to achieve a specific goal.

Researchers at the Department of Kinesiology at the University of North Texas set out to discover if training adaptations also might be specific to the time of day of training.

Twelve female college students were divided into two groups. One group engaged in morning training, and the other group was trained in the afternoon. Both groups participated in high-intensity exercises, and those activities were individualized according to their body weight.

They exercised four days a week for five weeks — a total of 20 workouts.

The results indicated that the time to exhaustion and the oxygen deficit were not statistically higher for the a.m.-trained group. They were, however, statistically higher in the afternoon for the p.m.-trained group.

The maximum amount of oxygen that could be taken up, VO2max and the greatest amount of expired air, VE max were higher in the p.m. group than in the a.m. group.

Typically studies have concluded that time to exhaustion and anaerobic capacity are slightly higher in the afternoon than in the morning. This has led to the idea that afternoon, rather than the morning, is a better time to train.

The purpose of this study was to find out if high-intensity exercise training, like a cycling class or an advanced step aerobics class, would be affected by training regularly at a given time of day. This study found evidence of “temporal specificity.”

Participants in the afternoon group had a better work capacity, and participants who exercised in the morning did not have a greater capacity.

“In summary, there was a significant effect of the time of day of training on the a.m.-p.m. pattern in work capacity in high-intensity exercise. These results suggest that greater improvements seem to occur at the time of day when high intensity exercise is regularly performed,” according to the article in Medicine & Science in Sports and Exercise.

Best advice to you: Whether it be a.m. or p.m., just train.

Source: Medicine & Science in Sports & Exercise. Vol. 30 (3).

March, 1998.