Endurance athletes usually have a lower heart rate at rest due to _____ .

Endurance athletes typically exhibit a lower resting heart rate primarily due to a greater stroke volume. Stroke volume refers to the amount of blood pumped by the heart with each beat. In endurance training, the heart becomes more efficient; the muscle mass of the heart, particularly the left ventricle, increases, allowing it to pump more blood with each contraction.

As a result, when the stroke volume is higher, the heart does not need to beat as frequently to deliver an adequate blood supply to meet the body’s metabolic demands at rest. This is beneficial for endurance athletes, as lower heart rates are associated with improved cardiovascular efficiency and better overall fitness levels.

While other factors like fat metabolism and hormone levels play roles in overall cardiovascular and metabolic adaptations, the primary determinant of the lower resting heart rate in endurance athletes is their enhanced stroke volume due to improved heart function from consistent aerobic training.