
A really good measure of how wrecked you are is your body’s “heart rate variability” (HRV). This is the difference between the gap between your heart beats. So if you imagine: BEAT (GAP) BEAT (GAP) BEAT (GAP), HRV is the difference of length of those gaps. Strangely, and counter-intuitively, a low (and therefore more regular) HRV is worse.