MAS and ASR Calculator

Turn a short maximal run into MAS, your anaerobic speed reserve, six pace zones, rep targets and race predictions. Everything updates as you type.

This tool is a guide only. It estimates paces from a short test and your races. It can't see an athlete's training, health, or recovery, and it doesn't replace a coach or a periodised program. Use it to frame sessions, then coach the athlete in front of you.

What it measures and how to use it

MAS is your speed at VO₂max, from a short maximal run. It sets your training from easy running through to VO₂max intervals.

ASR is the gap between MAS and your top sprint speed. It sets the fast work above MAS, so speed reps fit the athlete rather than a shared percentage.

Pace zones turn both into training paces, from recovery through threshold to VO₂max, so any session lands in the right effort.

1

Your test

From a test I know my MAS

Load example Clear

Test distance (m)

Distance covered in an all-out 4 to 6 minute run.

Test time (mm:ss)

Duration of that run.

MAS (m/s)

From a lab test, the 30-15 IFT, or a known value.

2

Sprint speed (optional)

Needed only for the anaerobic speed reserve and speed-zone reps. The aerobic zones (easy through VO₂max) don't use it. Time a flying sprint and the tool works out the speed, or enter a known value.

Flying sprint distance (m)

A short run-up, then time this fly zone.

Flying sprint time (s)

Both fields set the sprint speed.

or max sprint speed directly (m/s)

Work it out as distance divided by time from a flying sprint (metres / seconds). As a rough guide, distance runners sit around 7 to 9 m/s and trained sprinters 10 to 11+ m/s. GPS max velocity works too.

3

Your profile

MAS

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-

ASR (MSS − MAS)

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-

Speed reserve ratio

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MSS ÷ MAS

Add a sprint speed in Step 2 for the anaerobic speed reserve and speed zone. The pace zones below work without it.

Pace zones Rep targets Sessions Reference Races How it works

Two boundaries are measured: critical speed (top of Z3) and MAS (top of Z5). The severe domain between them splits into 5 km to 3 km intervals (Z4) and a tight VO₂max band at MAS (Z5), so VO₂max isn't stretched down to threshold pace. Z6 is anaerobic, set by %ASR, and appears once a sprint speed is entered.

Intensity 90% MAS 95% MAS 100% MAS 105% MAS 110% MAS 120% MAS Δ25% ASR Δ50% ASR Δ75% ASR

Set by Distance (m)Time (s)

Distance (m)

Rep speed-

Time-

Pace-

Target time per rep (mm:ss)

Rep (m)	95% MAS	100% MAS	110% MAS	Δ25% ASR	Δ50% ASR

Turn the numbers into training. These build from the paces above and update live. Templates to adapt, not fixed prescriptions.

% MAS grid

% MAS	Speed (m/s)	Speed (km/h)	Pace (/km)

% ASR table (target = MAS + %ASR × ASR)

% ASR	Speed (m/s)	Speed (km/h)	Pace (/km)

Optional. Enter two or more race or time-trial results to measure critical speed and predict other distances.

Distance (m)	Time (h:mm:ss)	Pace (/km)

Critical speed

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from your 1.6 to 10 km efforts

D′ capacity

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anaerobic distance (m)

Predicted times (Riegel, from your 5 km)

Distance	Predicted	Your result

Where your real result is faster than the model, trust your result. It means you're stronger at that distance than a projection from 5 km assumes.

Critical speed is cleanest from efforts of about 2 to 15 minutes. Add a 1 km or 3 km result for a sharper value.

When to use MAS or ASR

Use MAS to set everything at or below MAS: easy running, tempo, threshold, and VO₂max reps around MAS. It's the anchor for aerobic and VO₂max training. Use ASR for anything faster than MAS: short speed reps, speed endurance, and finishing speed. Above MAS a shared percentage misreads effort between athletes, because two runners at the same %MAS above MAS can sit at very different fractions of their reserve, so %ASR sizes the fast work to the individual. Simple rule: at or below MAS, prescribe from MAS and the pace zones; above MAS, prescribe from ASR on the Rep targets tab.

How the six zones are set

Running intensity splits into three domains, moderate, heavy and severe, divided by the first lactate threshold (LT1) and the second (LT2). LT2 is effectively critical speed, so the tool anchors the top of threshold (Z3) to critical speed and the top of VO₂max (Z5) to MAS, both measured. The severe domain between critical speed and MAS is wide in pace terms, so it splits into an intervals zone (Z4, roughly 5 km to 3 km pace) and a tight VO₂max band at MAS (Z5), which stops VO₂max from reaching down to threshold pace. Z6 is the anaerobic work above MAS, set by %ASR.

Where critical speed comes from

When you enter two or more race or time-trial results, the tool fits critical speed from them. A 2025 systematic review of field-based methods (Lipkóva et al.) found the time-trial test to be a reliable way to determine critical speed in runners when conditions are controlled, which is the method used here. With no race data, the tool falls back to an estimate of 0.86 × MAS. That specific ratio still traces to Billat et al. (1998), who measured critical velocity at 86% of velocity at VO₂max in trained runners, because no higher-evidence single ratio has replaced it. The fallback is only a placeholder, so enter races to measure critical speed properly.

Limits

These are model estimates, not guarantees. MAS from a short test and critical speed from races are only as good as the efforts behind them, and thresholds shift with training and fatigue. Retest as the athlete changes, and check the paces against recent sessions before building a block around them.