Your lactate switch, from your race times.

Enter two or more recent all-out races. The calculator fits your critical speed and reserve, then uses the model in Running Metabolism to estimate the speed at which your working muscles' mitochondria run out of room. It also predicts your race times and shows what training each dial would buy you. Free, no sign-up.

The book behind the calculator

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Lactate switch (LT1)

Critical speed

Fastest pace you can hold steadily

Reserve above it, D′

Estimated V̇O₂max

mL O₂ per kg per min

Training zones

The three intensity domains, with their boundaries set by your own numbers.

Race predictions

From the fit d = s_c·t + D′, valid from 1500 m to the marathon.

Distance	Time	Pace

Speed and duration

How long each speed can be held. Your races should sit on the curve.

What if you trained?

Move the dials the book says training acts on and see your predicted times move.

Mitochondria in the running muscles:

Volume and easy mileage. About ×2–3 over a career.

Lactate clearance elsewhere:

Heavy-domain and interval work. About twofold.

Running economy:

Cost of a kilometre. 5–15 %, plus footwear.

Distance	Now	After	Faster by

What would a goal take?

Each dial alone, as if it had to do the whole job. The realistic answer is a mixture.

Distance

Target time

This link restores your inputs. Nothing is stored on a server.

By the author of the model

Paperback Kindle