Training Pace Zones

Training zones explained (Billat model)

• Zone 1: Recovery / Easy (60-75% MAS): slow jogging, active recovery. Very comfortable, you can hold a full conversation.
• Zone 2: Aerobic base (75-82% MAS): long runs, endurance base building. Comfortable but requires attention. The zone where most kilometers should be run.
• Zone 3: Tempo (82-87% MAS): sustained, comfortably hard. Marathon race pace, tempo runs. Develops lactate threshold.
• Zone 4: Threshold (87-93% MAS): half-marathon effort. Hard but sustainable for 20-60 minutes. Significantly raises lactate threshold.
• Zone 5: VO₂max intervals (95-100% MAS): short intervals (3-5 min). Very hard. Maximizes aerobic capacity.
• Zone 6: Speed / Neuromuscular (105-120% MAS): short repetitions (30-60 s). Develops running economy and neuromuscular power.

How to use training zones

Most endurance training plans follow an 80/20 rule: about 80% of training volume at low intensity (zones 1-2) and 20% at high intensity (zones 4-6). Running too much in the middle (zone 3) is the most common mistake, it produces fatigue without delivering the full benefits of either easy or hard training.

Entering from MAS vs threshold pace

MAS (km/h): enter your Maximal Aerobic Speed from a Cooper test or VMA calculator. This is the most direct input.

Threshold pace (min/km): your 1-hour race effort, approximately equivalent to 87% of MAS. Use this if you do not know your MAS but have run a recent 10K or half-marathon time.

The 80/20 rule: science behind the split

The 80/20 training distribution was first documented systematically by Norwegian sports scientist Stephen Seiler (University of Agder) based on analysis of elite endurance athletes across rowing, cross-country skiing, cycling, and running. He found that world-class athletes consistently spend roughly 80% of their training at low intensity (zones 1-2, below the first lactate threshold) and 20% at high intensity (zones 4-6, above the second lactate threshold). Training too much in zone 3, the "moderate-hard" grey zone, produces fatigue comparable to hard training but fewer adaptations. The 80/20 split became popular in UK running coaching after publication of Matt Fitzgerald's "80/20 Running" (2014).

parkrun as a free threshold benchmark

parkrun (free, weekly 5K every Saturday across the UK) gives runners a consistent fitness snapshot without race-day costs or logistics. A parkrun time can serve as a rough threshold estimator: multiply your parkrun pace (min/km) by approximately 1.12 to estimate your marathon pace, or use the pace calculator on this site to translate the 5K time into an estimated MAS. Tracking parkrun times over months is one of the clearest ways to measure fitness progression for UK runners.

Jack Daniels VDOT system

The training paces in this tool are based on the Billat 6-zone model built from MAS (Maximal Aerobic Speed). An alternative widely used in English-language coaching is Jack Daniels' VDOT system, which derives training paces from recent race results rather than MAS. The two systems are complementary: both prescribe easy runs at about 60-75% of maximum effort, tempo at about 83-88%, and VO2max intervals at 95-100%. The VO2max Race Predictor tool on this site uses the Daniels/VDOT system.