How does aerobic fitness influence overall metabolic rate?

Higher aerobic fitness levels can significantly influence resting metabolic rate (RMR) by increasing it. When a person engages in regular aerobic exercise, they typically build more muscle mass and enhance the efficiency and capacity of their cardiovascular system. This physiological adaptation contributes to a higher metabolic rate, even when the body is at rest.

Increased muscle mass is particularly important because muscle tissue requires more energy to maintain than fat tissue. As individuals improve their aerobic fitness through regular exercise, their body composition often shifts toward a greater proportion of lean mass. Consequently, this shift contributes to an elevated RMR, as the body burns more calories to sustain muscle tissue.

Moreover, consistent aerobic exercise can enhance mitochondrial density and enzyme activity within muscle cells, improving overall energy metabolism. This means that not only does the body become more efficient at utilizing calories during physical activity, but it also tends to remain more metabolically active independently of exercise.

The other options do not accurately encompass the relationship between aerobic fitness and metabolic rate. Decreasing the resting metabolic rate or calorie expenditure negates the benefits of aerobic training, while suggesting that its influence is limited to intense activities overlooks the broader implications of continuous aerobic conditioning on metabolism at rest.