MinuteMetric

Pace, Effort and Race Prediction

Endurance training runs on two numbers: how fast you're going and how hard it feels. The calculators here convert between the two — turning target times into required paces, splits into projected finishes, and heart rate into training zones — so you can plan sessions around intent rather than guesswork.

Race prediction deserves a note. Formulas that project from one distance to another, such as Riegel's, assume you have the specific endurance for the longer event. Predicting a 10K from a strong 5K is usually reliable. Predicting a marathon from a 5K assumes months of long-run training you may not have done, and the further you extrapolate, the more optimistic the number becomes.

Training Principles Behind the Numbers

• Most training should feel easy. The common pattern among endurance athletes is a large majority of volume at conversational effort, with a small proportion genuinely hard. Training everything at a moderate middle pace is the classic mistake.
• Increase load gradually. Connective tissue adapts more slowly than your cardiovascular system, which is why fitness often outruns durability and injuries appear during enthusiastic build-ups.
• Conditions change the maths. Heat, humidity, wind, hills and altitude all shift the pace a given effort produces. Run to effort on days when the number won't cooperate.
• Adaptation happens in recovery. Sleep and easy days are when training turns into fitness, not the sessions themselves.