Endurance training affects lactate metabolism by increasing capacity for aerobic respiration and reducing reliance on the lactate system. Which option best describes this adaptation?

• A. Increases capacity for aerobic respiration and reduces reliance on the lactate system
• B. Increases reliance on anaerobic glycolysis
• C. Decreases capillary density
• D. Reduces VO2 max

Answer: (A)

Endurance training boosts the muscles’ oxidative capacity. More mitochondria and oxidative enzymes, plus greater capillary density, mean ATP can be produced efficiently through aerobic respiration. As this aerobic system handles more of the energy demand, the contribution from anaerobic glycolysis—and thus lactate production—decreases at submaximal efforts. Any lactate that is produced is cleared and oxidized more readily, shifting the lactate threshold to a higher intensity and delaying fatigue.

This is why the statement that endurance training increases capacity for aerobic respiration and reduces reliance on the lactate system is the best description. The other options describe adaptations that don’t occur with endurance training: greater dependence on anaerobic glycolysis, reduced capillary density, or a lower VO2 max would all contradict what endurance training does.