What is a common measure of cardiovascular fitness?

Resting heart rate is a vital measure of cardiovascular fitness because it provides insight into how efficiently the heart operates at rest. A lower resting heart rate generally indicates a more efficient heart, which is typically seen in individuals who engage in regular cardiovascular exercise. This efficiency is due to the heart becoming stronger and more capable of pumping blood with each beat, consequently requiring fewer beats to maintain adequate circulation while at rest.

In contrast, muscle mass, cholesterol levels, and bone density, while important health indicators, do not directly measure cardiovascular fitness. Muscle mass relates more to strength and body composition, cholesterol levels are indicative of heart health but do not reflect cardiac function, and bone density pertains to bone health rather than cardiovascular efficiency. Thus, resting heart rate remains a standard and straightforward measure that reflects one's cardiovascular fitness and overall heart health.