Prolonged inactivity triggers rapid muscle loss and metabolic decline
Research by human movement scientist Moritz Eggelbusch of VU Amsterdam reveals how physical inactivity, such as prolonged bed rest during hospitalization or microgravity in space, causes rapid muscle loss and metabolic decline. His research highlights how just six days of inactivity can induce insulin resistance and, over time, inflammation in muscle tissue, paving the way for chronic diseases like diabetes.
“My research focused on understanding how physical inactivity and systemic inflammation affect skeletal muscle mass and metabolism, with relevance to clinical and extreme conditions such as hospitalization, prolonged bed rest, and space flight,” movement scientist Moritz Eggelbusch explains. Skeletal muscle accounts for about 40% of body mass in a healthy weight individual, and is essential for metabolic health and physical function. “Inactivity, even over just a few days, can lead to rapid muscle loss and metabolic decline, increasing the risk of chronic diseases such as obesity, diabetes, and cardiovascular conditions.”
Eggelbusch’ research shows that when people are physically inactive, such as during extended hospital stays with bed rest, their muscles shrink quickly, and fats and sugars start to accumulate within muscle tissue. Eggelbusch: “Remarkably, early signs of insulin resistance, a precursor to diabetes, can appear after just six days of bed rest. This underscores how hospitalization-related inactivity can significantly impact health, contributing to metabolic issues such as diabetes.” His findings reveal that this process involves not only muscle loss but also triggers inflammation and changes within muscle cells, making it more challenging for muscles to recover and utilize nutrients effectively. “We identified a specific inflammation-related factor that contributes to this muscle wasting and tested a promising therapeutic approach to reduce it, paving the way for potential new therapies.”
The implications of Eggelbusch’ research are highly relevant for healthcare strategies targeting muscle preservation and metabolic health in elderly and critically ill patients. “For example, strategies that prevent the accumulation of unhealthy fats in muscle during physical inactivity could help mitigate muscle deterioration.” The research showed that although fat accumulation in muscle coincides with metabolic decline, additional fat build-up over time did not further impact insulin sensitivity, challenging conventional views on how type 2 diabetes mellitus develops.
To investigate the effects of physical inactivity on muscle health, Eggelbusch used a mix of methods and experiments. One of them was a human bed rest study conducted at the German Aerospace Center in Cologne, Germany, in collaboration with the European Space Agency (ESA) and NASA. “In this study, 24 healthy volunteers stayed in bed for 60 days, lying down for all activities, including eating and leisure, to replicate the effects of extreme physical inactivity on skeletal muscle.”
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