How running apps calculate your pace: VDOT and zones honestly explained

In the 1970s, running coach Jack Daniels faced a practical problem: lab VO2max tests are expensive — but his athletes raced constantly, and race times are mercilessly honest measurements. His solution, together with Jimmy Gilbert: a table that assigns every race performance a number — VDOT — and derives all training paces from it. Run 5k in 25:00 and you get a VDOT around 38 — and from that your easy, marathon, threshold and interval paces.

The double trick: first, no lab needed — just an honest race or test time. Second, VDOT is smarter than a pure VO2max measurement — because whoever runs a given time has automatically proven the right mix of engine (VO2max), fuel efficiency (running economy) and sustainable output (threshold). Two runners with identical lab VO2max can be minutes apart in a race; two runners with the same VDOT cannot.

Sports physiology has described endurance performance with three quantities for decades: VO2max (how much oxygen your body can process at maximum — our VO2max article explains why that number matters even for life expectancy), running economy (how much oxygen you burn at a given pace) and the threshold (the pace beyond which fatigue snowballs). A useful fourth quantity is vVO2max — the pace at which oxygen uptake reaches its maximum — which has become a practical yardstick for interval training.

Race-time tables like VDOT work because a race result condenses all these quantities into a single number. And the zones work because each training pace targets one of the engines: easy runs build the base (zone 2), threshold runs push the fatigue limit outward, intervals near vVO2max stress the engine itself. Successful endurance athletes distribute this strikingly consistently: mostly easy, a little hard — the much-quoted 80/20 pattern. Important caveat for recreational athletes: a large individual-participant-data network meta-analysis from 2025 and a further 2024 meta-analysis show that a pyramidal distribution (mostly easy, some moderate-pace work, a little hard) performs equally well or even slightly better for them than the strictly polarized version. That changes little for the zone logic itself — the lion's share stays easy regardless of the exact distribution pattern.

As good as the foundation is, the limits deserve honesty. First: tables do not know your daily form. Heat, poor sleep, stress or a brewing infection make the "correct" pace wrong on some days — the talk test (easy pace = conversation possible) beats any second-exact number on those days. Second: the race-time-to-zones mapping is an average model; individual outliers (great economy, weak threshold or vice versa) deviate. Third — and this is the big one: the formulas say nothing about how fast you should progress. Recovery needs change with age, training years and life circumstances; many apps ask for your age but do not use it in the progression — with the familiar result that plans get too hard too fast for beginners beyond 50.

That is exactly our angle: our upcoming running module uses the same open science (race-time anchor, zones, 80/20) — combined with what our app already does: a check-in before every session, feedback after every session, and a progression that takes age and recovery seriously.

• Step 1 — honest test: run 5k (rested, warmed up) as evenly fast as you can. That time is your anchor — more realistic than any guess.
• Step 2 — derive zones roughly: your easy pace is typically 1:15–2:00 min/km slower than your 5k race pace; your threshold pace about 10–20 sec/km slower than 5k pace. For intervals, a starting point: short segments around 5k pace with generous recoveries.
• Step 3 — cross-check with your body: easy means full sentences; threshold means short sentences only. If feel and math disagree, feel wins.
• Step 4 — retest every 6–8 weeks: zones are snapshots. As you get faster, every pace moves with you — the most motivating proof that it works.

For your ego: the easy pace will feel embarrassingly slow at first — for almost everyone. It is right anyway; running every run in the grey zone reliably makes you tired instead of faster. For a joint-friendly start: starting to run with excess weight.