Why do athletes track resting heart rate?

Answer: Indicates recovery and overtraining

Indicates recovery and overtraining ✓ — Correct! Resting heart rate, taken on waking, is one of the simplest windows into how the body is coping with training. Over months, a falling resting rate usually means the heart is getting fitter; many endurance athletes sit around 40 to 60 beats a minute. Day to day, a reading several beats above an athlete's own usual baseline can hint at incomplete recovery, poor sleep, stress, dehydration or an oncoming illness. It is a nonspecific signal, so one high morning is not an order to rest, but a rise that persists for a few days, together with heavy legs or poor sleep, is a good reason to ease the next session.

Calculates calorie burn accurately — Resting heart rate says little about calories; energy use depends on how hard and how long you move, which is why calorie estimates use heart rate during exercise, body size and pace rather than the morning pulse.

Measures muscle strength gains — A low resting rate reflects an efficient heart and circulation, not strong muscles. Strength is measured by what you can lift or how far you can jump; a weightlifter may have a perfectly ordinary resting pulse.