Heart rate variability, or HRV, is the small variation in time between one heartbeat and the next, and for endurance athletes, it’s most useful as a trend that shows how well the body is handling training and life stress, not as a one-off score that tells you whether today is good or bad. Used well, HRV can help you decide when to push, when to hold steady, and when to back off, but it only becomes genuinely useful when you judge it against your own normal range and combine it with sleep, soreness, mood and the demands of your training.












