College of Massage Therapists of British Columbia (CMTBC) Practice Exam

What aspect of skeletal muscle fibers aids in their endurance capability?

1. Higher capillary density

2. Increased diameter

3. Greater number of motor units

4. Less myoglobin content

The correct answer is: Higher capillary density

Higher capillary density is a key factor that enhances the endurance capabilities of skeletal muscle fibers. This increased density of capillaries allows for improved blood flow to the muscle tissue, which in turn facilitates a greater supply of oxygen and nutrients while also promoting the removal of metabolic waste products like carbon dioxide and lactic acid. In muscles that are designed for endurance, such as those used in long-distance running or cycling, having a rich capillary network is essential. It ensures that the muscle fibers can sustain prolonged activity by efficiently delivering oxygen, which is critical for aerobic metabolism. This metabolic pathway is utilized during steady-state activities where energy needs to be met over an extended period. Other options like increased diameter or a greater number of motor units typically refer to strength and power capabilities rather than endurance. A larger muscle diameter may correlate with greater force production, while the number of motor units influences how strength is generated but does not directly enhance endurance. Additionally, less myoglobin content would actually be detrimental to endurance, as myoglobin is vital for storing and facilitating oxygen transport within muscle cells.