Muscles trained under anaerobic conditions primarily increase in which of the following?

Muscles trained under anaerobic conditions primarily increase in mass, strength, and power. This type of training involves short bursts of intense activity where the body relies on energy sources stored in the muscles rather than oxygen. Anaerobic exercises, such as weightlifting or sprinting, lead to muscle hypertrophy (an increase in muscle size) and improve the overall strength and power output of the muscles. This is because these activities create a high level of tension in the muscles, prompting them to adapt by growing larger and stronger to handle future stressors more efficiently.

Additionally, the anaerobic energy systems utilized during such activities contribute to increased muscle power, which is the ability to exert force rapidly. Consequently, this training enhances the muscle's capabilities in producing short, explosive movements, distinguishing it from endurance training that primarily benefits aerobic capacity and stamina.