Which statement best describes the typical impact of endurance training on the oxidative capacity of skeletal muscle?

Which statement best describes the typical impact of endurance training on the oxidative capacity of skeletal muscle?

• A. It increases oxidative enzyme activities and mitochondrial density, enhancing oxidative capacity
• B. It reduces mitochondria and oxidative enzymes
• C. It only increases glycolytic enzymes
• D. It decreases overall aerobic capacity

Answer: (A)

Endurance training boosts the muscle’s ability to produce energy aerobically by increasing the number and quality of the structures that carry out oxidative metabolism. With regular aerobic work, muscle fibers accumulate more mitochondria (mitochondrial density) and raise the activity of oxidative enzymes involved in the aerobic pathways of glucose and fat oxidation. This combination means ATP can be generated more efficiently during sustained activity, improving overall oxidative capacity. You may also see accompanying improvements like greater capillary density and better fat utilization, which support prolonged aerobic performance. It would not be accurate to say endurance training reduces mitochondria or oxidative enzymes, or that it only increases glycolytic enzymes, or that aerobic capacity would decrease.

Endurance training boosts the muscle’s ability to produce energy aerobically by increasing the number and quality of the structures that carry out oxidative metabolism. With regular aerobic work, muscle fibers accumulate more mitochondria (mitochondrial density) and raise the activity of oxidative enzymes involved in the aerobic pathways of glucose and fat oxidation. This combination means ATP can be generated more efficiently during sustained activity, improving overall oxidative capacity. You may also see accompanying improvements like greater capillary density and better fat utilization, which support prolonged aerobic performance. It would not be accurate to say endurance training reduces mitochondria or oxidative enzymes, or that it only increases glycolytic enzymes, or that aerobic capacity would decrease.