Too Much Exercise Leads to a Decline in Mitochondria Function and Glucose Tolerance
Written by Thin Han
Edited by Charan Karthik
July 31st 2021
Edited by Charan Karthik
July 31st 2021
Whether it be to get fresh air, become healthy, or lose weight, exercising has many positive effects. However, a group of scientists have discovered that exercising too much is actually bad for your metabolism and muscular functions (Flockhart et al., 2021). They also found that it decreases your tolerance toward glucose, thereby increasing your risk of developing type 2 diabetes. They explained that excessive exercising has been linked to heart complications such as myocardial fibrosis, arrhythmia, and an increase in coronary artery calcification.
The experiment the scientists conducted involves increasing the exercise load of healthy volunteers, six females and five males, over a four week period in five different phases (baseline, light/moderate/excessive training, recovery). During that time period, they measured various factors such as glucose tolerance, mitochondrial function, and metabolism of the volunteers using tests such as muscle biopsies and oral glucose tolerance tests. They hypothesized that there was a curvilinear relationship between exercising and all the factors listed above; essentially after a certain threshold (achieved during the excessive training (ET) phase), the benefits of exercising will be minimal compared to the negative effects.
Their hypothesis turned out to be correct where they found that once people hit the limit in the ET phase, both their metabolic health and physical performance hit a decline (Flockhart et al., 2021). This is due to the shutdown of intrinsic mitochondrial respiration (normally increases the respiratory capacity of muscles) and hydrogen peroxide production in the mitochondria. Even after the excessive training period has finished, the recovery of disturbance in glucose control and mitochondrial respiration never recovered fully.
Additionally, they also help solve a controversy surrounding mitochondrial function and insulin resistance. Scientists used to believe that mitochondrial impairment was a secondary response to insulin resistance, but the results of this experiment actually reveal that it actually was the cause behind resistance to insulin. All things considered, they explained that reaching the limit in the ET phase involves going all-out on a daily basis, which is hard to maintain long term, so there is little to no risk of most people ever reaching this limit. In conclusion, you can continue exercising as usual without worrying about your mitochondria breaking down, but just remember that too much of a good thing can be a bad thing.
Works Cited
Flockhart, M., Nilsson, L. C., Tais, S., Ekblom, B., Apró, W., and Larsen, F. J. (2021). Excessive
exercise training causes mitochondrial functional impairment and decreases glucose tolerance in healthy volunteers. Cell Metabolism, 1–21, https://doi.org/10.1016/j.cmet.2021.02.017
Image Source: “Set of Active Multiethnic People Training in Gym Free Vector” by katemangostar
licensed under Freepik License
licensed under Freepik License