Longevity Briefs: How Much Exercise Is Too Much?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: We all know that exercise is good for us. Research suggests that even a small amount of moderate intensity exercise can boost lifespan, and that more is generally better. Exercise training improves the ability of mitochondria to produce the cellular fuel ATP, and also improves the body’s ability to control blood sugar, making it excellent for the prevention and treatment of conditions such as type II diabetes and obesity. However, the benefits of exercise are subject to diminishing returns. At what point does exercise stop being beneficial, and can too much exercise be harmful?

What did the researchers do: In this small study, 11 healthy volunteers participated in increasingly strenuous high-intensity interval training over a 4 week training period. Researchers took weekly muscle biopsies to study the energy-producing capacity of the participants’ mitochondria, and also monitored their physical exercise capacity and ability to control blood sugar. Additionally, researchers compared blood sugar measurements for a separate group of 15 professional endurance athletes to those of 12 non-athletes.

Key takeaway(s) from this research: As exercise intensity increased, so too did participants’ athletic performance, as well as the ability of their mitochondria to produce energy. However, following the week with the highest exercise load, participants experienced a decline in athletic performance, reduced mitochondrial function, and reduced blood sugar control. In the group of professional athletes, researchers found similar average blood sugar levels over a 24 hour period when compared with the control group, but blood sugar fluctuated more throughout the day among athletes, suggesting that it is less well controlled in this group.

This research supports the idea that excessive exercise training can be harmful for the metabolism. How much exercise is excessive? It’s difficult to say based on this study alone. During the week of “excessive training” in this study, participants were instructed to exercise to achieve ‘maximum average power output’ for periods of 4 to 8 minutes, separated by short breaks and totalling 152 minutes over the course of the week (compared to 90 minutes the week before). More research is needed to confirm the results of this study, and to establish the effects of other forms of exercise training besides high intensity interval training. Unfortunately, the effects of high intensity exercise on health and lifespan remain poorly understood due to the sparsity of data and the number of confounding factors involved.

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