Training Pace Zones

Five paces, five jobs

Every zone exists to produce a specific adaptation at a specific cost:

• Easy (E) — conversational, ~65–78% max HR. Builds aerobic base, capillaries, and fatigue resistance while costing the least recovery. This is where 70–80% of weekly volume belongs.
• Marathon (M) — goal marathon pace. Trains fuel efficiency and race-specific mechanics. Use sparingly outside plans: M-pace runs are "comfortably hard" for a reason.
• Tempo / Threshold (T) — "comfortably hard," the pace you could hold ~60 minutes. Raises the lactate threshold — the strongest single predictor of distance performance.
• Interval (I) — 3–5K race pace, 3–5 minute reps. Develops VO₂max. Expensive; one session weekly is plenty.
• Repetition (R) — mile-pace or faster, short reps. Economy and speed mechanics. Small doses, full recovery.

Zones derive from your race, not your ambitions

The calculator converts your recent result through the Riegel equation to equivalent performances, then anchors each zone to physiology — easy at the pace where conversation stays comfortable, threshold at the hour-race pace, intervals at current 3–5K fitness. Age-grade tables and "average paces for your age" cannot know your fitness; a recent race can.

The error everyone makes

Easy days drift 30–60 seconds per mile too fast — because they feel fine — and then interval sessions underperform because fatigue borrowed from tomorrow arrived early. The discipline that produces breakthroughs is unglamorous: run easy paces easy enough to make hard paces truly hard. If you can't hit interval targets, the problem is usually the easy days, not the intervals.