Exercising in the evening or in the morning does not have the same effects on our metabolism. Explanations.
Morning jogging, gym after work… The impact of physical exercise on our body varies depending on when we start moving. Those are conclusions of two teams of researchers, which confirm existing results.
50% of our metabolism is circadian
Concretely, performance tends to be better in the early evening, but sport has more positive effects on the body in the late morning. For scientists, these differences are explained by the circadian cycles (or biological clock), which dictate to the body to fall asleep when it is dark and to wake up when it is day.
“Almost every aspect of our physiology and metabolism is dictated by the circadian clock,” notes Gad Asher, lead author of the study. “Previous studies have indicated that at least 50% of our metabolism is circadian and that 50% of the metabolites in our body oscillate according to the circadian cycle. It makes sense that exercise is influenced,” adds one of his collaborators.
Improved athletic performance
The two teams first worked on mice, having them run on a treadmill at different times of the day. Animals performed better in the evening, when levels of a compound called “ZMP” were higher. ZMP activates the metabolic pathways that lead to the breakdown of glucose and fatty acids, and is therefore thought to be responsible for improving the sports performance of mice in the evening. “Interestingly, ZMP is an analogue of a compound that some athletes use for doping,” says Gad Asher.
The researchers then used these findings to analyze the performance of 12 humans, who were also better in the evening. In contrast, glucose breakdown and fat burning were greater in the late morning. However, these conclusions can be offset by the nature of each. “Being in the evening or in the morning also affects physical activity”, conclude the scientists.
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