While resting heart rate has long been the gold standard to measure an athlete’s general state of stress and recovery, heart rate variability (HRV) takes biofeedback to the next level by delivering more nuanced readings that accurately reveal conditions like hyper-arousal or burnout.I’m so enthusiastic about promoting the concept of HRV that I partnered with the industry leaders at Sweetbeat Life LLC to create a customized iPhone app called PrimalBeat HRV.

(This Mark's Daily Apple article was written by Mark Sisson, and is narrated by Brock Armstrong)