Endurance training is beneficial. Regular workouts not only improve physical fitness and well-being, but also trigger profound muscle remodeling. This is reflected in typical training effects: muscles fatigue less quickly, provide more energy, and use oxygen more efficiently.
"The adaptation of muscles to physical activity is a well-acknowledged phenomenon," says Prof. Christoph Handschin, who has long been researching muscle biology at the Biozentrum of the University of Basel. "We wanted to understand what exactly happens in the muscle during exercise training."
Training state is reflected in genes
In the current study, Handschin's team compared muscles of untrained with those of trained mice and investigated how gene expression changes in response to exercises. "Since endurance training induces substantial muscle remodeling, we assumed that the adaptations would be reflected in gene expression," says first author Regula Furrer. "However, in contrast to our expectations, the expression of relatively few, about 250 genes, was changed in trained compared to untrained muscles. Strikingly, about 1,800 to 2,500 genes were regulated after an acute bout of exercise. How many and which genes respond largely depends on the training state.”
Muscles respond differently to physical stress
In untrained muscles, for example, endurance training activates inflammatory genes, triggered by tiny injuries causing what we know as muscle soreness. "We couldn’t observe this in trained mice; instead, genes that protect the muscle are more active. Thus, trained muscles respond completely different to exercise stress," explains Furrer. "They are more efficient and resilient – in short, they can cope better with the physical load."