What adaptations occur in muscles with aerobic training?

With aerobic training, one of the key adaptations in muscles is the increase in mitochondrial density and capillary supply. This adaptation enhances the muscles' ability to utilize oxygen more efficiently during prolonged exercise.

Mitochondria are the cellular organelles responsible for producing energy through aerobic metabolism, so an increase in their number means that more energy can be generated in the presence of oxygen. Additionally, a greater capillary supply allows for more effective transport of oxygen to the muscle fibers and removal of metabolic waste products, further improving performance during endurance activities. This physiological change is fundamental for athletes and individuals engaging in endurance sports, as it directly contributes to an improvement in aerobic capacity and overall endurance.

In contrast, options related to increased adipose tissue, decreased mitochondrial density, and reduction in muscle fiber size do not align with the expected physiological responses to aerobic training. Instead, aerobic training aims to enhance energy efficiency and endurance, prompting beneficial changes rather than a reduction in muscle function or an increase in fat storage.