Training Pace Calculator

The 80/20 principle

Research on endurance athletes suggests spending around 80% of training time at easy intensity and 20% hard. The pace bands here make that split concrete and repeatable.

Why each training pace exists

Easy pace builds aerobic capacity with minimal fatigue, threshold pace raises the effort you can sustain before lactate accumulates, interval pace develops VO2 max, and repetition pace sharpens speed and economy. Each band targets a specific adaptation, and running them at the wrong pace blunts the benefit.

The most common error is running easy days too fast, which adds fatigue without adding fitness and leaves you too tired to hit the hard sessions that actually drive progress.

The 80/20 principle in practice

Research on endurance athletes repeatedly points to spending roughly 80% of training time at easy intensity and 20% hard. The pace bands here make that split concrete: keep the bulk of your week in the easy range, and reserve threshold, interval, and rep paces for two or three quality sessions. Polarising your training this way produces more improvement than running everything at a moderate, grey-zone effort.