What adaptation occurs in muscle fibers as a result of sustained anaerobic training?

Sustained anaerobic training primarily targets type II muscle fibers, which are responsible for explosive and powerful movements. As an individual engages in consistent anaerobic exercises, such as heavy weightlifting or sprinting, there is an increased recruitment of these type II muscle fibers. This adaptation allows for enhanced strength and power output during short bursts of high-intensity activities.

While other adaptations may occur within the muscle, such as changes in fiber density or muscle size, the cornerstone of anaerobic training's effect lies in the recruitment and activation of type II fibers. This recruitment leads to improved performance in activities that require quick, powerful movements, signaling the importance of increasing this fiber recruitment as a primary adaptation from sustained anaerobic training.

The other options could potentially relate to other training adaptations but do not accurately summarize the specific physiological change that occurs with anaerobic training. For instance, increased type I muscle fiber density is more associated with endurance activities, while decreased mitochondrial volume is not a typical adaptation of anaerobic training. Enhanced capillary density around slow-twitch fibers ties back to aerobic training adaptations rather than those resulting from anaerobic exertion. Therefore, the focus on type II muscle fiber recruitment stands out as the most relevant and accurate response in the context of anaerobic