Performance & Training

The first three are genuinely actionable — they change what you do in a session. The fourth is the one to hold most loosely, for reasons worth being explicit about.

MET-based estimates and wrist trackers both produce a confident-looking figure with a wide error. The definition of a MET itself overestimates resting rate by around 20% for the average adult, the values describe an activity rather than a person, and the Stanford evaluation of seven wrist devices found none with an energy-expenditure error below 20%.

On top of that, the reported figure is gross rather than net — it includes the resting metabolism you would have spent anyway — and some of the burn is offset by moving less afterwards. The practical rule that follows is simple: do not eat the number back.

Whether lifting or running, the common error is the same: too much moderately-hard work and not enough at either end. Easy sessions creep upward because they feel unproductive; hard sessions drift downward because the legs are tired from the last one. Everything converges on the middle, which generates fatigue without a strong signal in either direction.

• Easy should be genuinely easy. Conversational pace, or the low end of your heart-rate zones. Most volume belongs here.
• Hard should be genuinely hard, and rare. Two sessions a week is plenty for most people not competing.
• Progress the load, not the estimate. When a working weight becomes easy, add weight — do not re-test your max.
• Fuel it. Strength and speed work in a steep deficit is a poor trade; keep the deficit moderate and protein high.