The physiology behind the platform.

HRV-guided training

Morning heart rate variability, read as a 7-day mean against each athlete's own normal range, tells you how they are handling load. Inside the range: carry on. A sustained drop below it: back off or hold. A rise in a recovery week: the block is working.

Endurance Signals builds that range from each athlete's own history, pairs it with resting heart rate and day-to-day variation, and recommends whether the next block should push or consolidate. Race weeks are never moved. Read the full guide.

Metabolic profiling without a lab

Lab tests are expensive and hard to repeat. Peak power over short and long durations, from everyday training, gives a good estimate of an athlete's aerobic and glycolytic capacity, fat and carbohydrate use, and the zones that follow from them.

Try the VO2 max calculator to compare the published models with the one I use.

This replaces the INSCYD testing I used to sell here. The same thinking runs in FuelingSense and inside Endurance Signals. Read how the field test works.

Durability

Whole-session efficiency breaks down once threshold work disrupts the heart rate to power relationship. Measuring efficiency only in steady zone 2 to 3 work gives a cleaner signal of aerobic fitness and fatigue.

Daily fuelling

Energy and carbohydrate targets should follow the day's training, not a fixed number. Daily Fuel, in development, calculates them from planned load and the athlete's metabolic profile.