Can We Train Our Bodies to Peak at Different Times of the Day?

Growing evidence suggests that the time of day we exercise can impact our performance and health. This article explores the research on circadian rhythms and how they affect athletic performance.


The Impact of Time-of-Day on Performance

Research has shown that the time of day we exercise can have an influence on our athletic performance. For example, a study conducted during four Olympic Games found that medal-winning swimmers had their fastest times when competing in the early evening, around 5:12pm. This is just one piece of evidence suggesting that physical performance is affected by the time-of-day. Recreational cyclists also complete faster time trials in the evening, and resistance exercise tends to peak between 4pm and 8pm.

These time-of-day effects on performance can also differ between men and women. Additionally, if your schedule only allows for morning workouts, there are indications that you can still optimize your peak performance.

One theory for the impact of time-of-day on performance is our circadian rhythms, which regulate various bodily functions throughout the day. These rhythms can be adjusted by cues such as light exposure and exercise, leading to changes in performance.

The Connection Between Exercise and the Circadian System

Our circadian rhythms are controlled by a central clock located in the hypothalamus of the brain. This clock responds to signals from the optic nerve, which is influenced by light exposure. The circadian clock then sends signals to peripheral clocks in other organs, muscles, and fat tissues, keeping the entire body in sync.

Exercise can directly affect these peripheral clocks, such as the 'skeletal muscle clock.' Regular exercise at different times of the day can tune this muscle clock and potentially optimize athletic performance. For example, mice that exercised in the morning were found to burn more fat, suggesting that exercising at specific times could maximize the metabolic benefits of exercise for individuals with metabolic diseases.

There have also been studies with humans that show performing specific exercises in the morning or evening can have different effects on health and performance. However, the research in this area is still evolving, and there is some inconclusive evidence regarding the advantageous time-of-day effect on exercise performance and health benefits.

Individual Variations and the Potential for Adjustment

One reason for the inconclusive evidence is the variations that exist between individuals. People have different chronotypes, meaning their internal clocks may run faster or slower than the standard 24-hour cycle. This can affect their peak performance times and response to exercise.

However, exercise does have the potential to 'reset' our muscle clocks, allowing individuals to adapt and potentially optimize their performance. Consistent endurance running training in the morning, for example, can shift the molecular clocks in skeletal muscle and lung tissues to an earlier time-of-day. It's still uncertain if this effect can be replicated in humans, but if it can, athletes could potentially recalibrate their muscle clocks with the right training.

Overall, routine seems to be a key factor in optimizing performance. Consistently training at the same time of day allows the body to adapt better and may provide an extra edge for athletes. However, it's important to note that exercising at any time is beneficial for overall health.