What increases the density of mitochondria and capillaries in skeletal muscle?

The increase in the density of mitochondria and capillaries in skeletal muscle is primarily associated with aerobic training. This type of training enhances the muscle's ability to utilize oxygen efficiently, which is crucial for endurance activities.

Aerobic training leads to physiological adaptations that result in an increase in the number of mitochondria, which are responsible for energy production through aerobic metabolism. This also includes an increase in capillary density, improving blood flow and nutrient delivery to the muscle fibers, thereby enhancing overall endurance and performance during prolonged physical activities.

Resistance training focuses more on increasing muscle strength and size through hypertrophy, which does not have the same effect on mitochondrial and capillary density as aerobic training does. Flexibility training primarily improves the range of motion and elasticity of the muscles rather than impacting mitochondrial or capillary density. While cardiovascular training generally refers to aerobic conditioning, it is important to note that the term can sometimes be used interchangeably with other types of physical activity, which might lead to confusion with resistance training in this context.