A recent study investigated the effects of progressively increasing training on health and performance measures, revealing the potential drawbacks of excessive training. The research suggests that going overboard with workouts may have adverse effects on overall well-being.
The study enlisted 11 participants who engaged in regular endurance and strength training. These individuals were not professional athletes but maintained an active lifestyle. The participants underwent a 4-week training program that incorporated high-intensity interval training (HIIT) using a cycle ergometer. The program gradually increased the number and duration of training sessions each week, resulting in higher weekly training volume. A recovery week with reduced training volume was also included. Various assessments, including blood samples and muscle biopsies, were conducted before and after the program, as well as at the end of each week.
The overall training program led to performance improvements, with increased power output. However, performance did not further improve during the week with the highest training volume, suggesting that excessive training can hinder progress. After the recovery period, performance reached its peak, demonstrating "super-compensation."
Mitochondrial Function and Overreaching
The study focused on changes in muscle mitochondria, the cellular powerhouses responsible for energy production during exercise. Endurance training and HIIT generally increase the number of mitochondria, enhancing performance. However, the study found that several mitochondrial markers plateaued or declined after the week of excessive training. These markers are associated with good health and dysregulated in conditions like type-2 diabetes. Intrinsic mitochondrial respiration (IMR), a marker of mitochondrial function, decreased by 40% after the week of excessive training.
Glucose Tolerance and Overreaching
The study explored the impact of IMR changes on insulin sensitivity by conducting an oral glucose tolerance test (OGTT). Blood glucose levels rose after the excessive training week, indicating decreased effectiveness in removing glucose from the bloodstream. This impaired glucose tolerance parallels mechanisms observed in type-2 diabetes.
The study also analyzed blood glucose levels in elite athletes. The results showed that elite athletes experienced prolonged periods of high and low blood glucose levels compared to the control group. Despite engaging in more training and exercise, the athletes exhibited worse blood glucose control. It is worth noting that elite athletes frequently engage in overreaching during training, potentially affecting blood glucose regulation.
The study suggests that individuals who are not high-level athletes are unlikely to engage in the same level of excessive training. A week of low-volume training allowed health markers and mitochondrial function to recover. However, for elite athletes, intensive training is unlikely to pose significant long-term health concerns. Careful management of training volume and incorporating recovery periods can help mitigate the negative effects of excessive training, maintaining a balance between exercise intensity and long-term well-being.
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