Wearable Metrics Explained

Your Apple Watch is a remarkable little instrument. Every day it captures VO2 max, heart rate variability, resting heart rate, sleep stages, activity rings, and a growing list of derived scores. The trouble is that the watch hands you the numbers but rarely tells you what to do with them. A 42 ml/kg/min VO2 max — is that good? Your HRV dropped 15ms overnight — should you skip the gym, or push through? Most people end up either ignoring the data entirely or staring at it anxiously without a framework for action. This pillar exists to close that gap. Each topic underneath takes one wearable metric, explains what it actually measures, how Apple's sensors derive it (and where they fall short), what a meaningful change looks like for someone your age and training level, and — most importantly — the specific decision the number should drive in your day. We treat your wrist as a sensor, not an oracle: the goal is to make the data improve your training, recovery, and longevity outcomes rather than to add a layer of anxiety on top of an already busy life. Dorsi is built on this same philosophy. Our AI coach reads your wearable signals in real time and turns them into a single concrete recommendation — train, modify, or rest — so you don't have to interpret the dashboard yourself. The articles below give you the underlying mental models; Dorsi automates the daily decision.