Critical pace, from your own runs
A critical pace calculator usually asks you for a couple of race times. Lapline works it out from your actual running instead: for each length of effort from 1 to 60 minutes, the fastest pace you really held, found in the .fit and .gpx files you import.
What critical pace means
The longer you run, the slower the pace you can hold. Plot your best pace against how long you held it and you get a curve that drops steeply over the first few minutes and then flattens. In running science, critical pace (or critical speed) is roughly where that curve levels off: about the fastest pace you can keep up for a long time without steadily tiring, typically somewhere around your 30 to 60-minute race pace. It's a useful anchor for threshold and interval training.
How Lapline builds your curve
- It looks at seven lengths of effort: 1, 5, 10, 20, 30, 45 and 60 minutes.
- For each one it scans every second of every run in the date range you choose and finds the fastest stretch of that length, whether or not it was a lap, a race or a personal record.
- It draws the same curve for the period just before, so you can see where you've got faster or slower.
Because it comes from what you actually ran, the curve is only as good as your recent efforts: if you haven't run hard for 20 minutes lately, the 20-minute point shows your best easy running, not your potential. A hard session or a race fills it in. Lapline shows the measured curve; it doesn't fit a mathematical model to it or predict race times.
Where to find it
Import your runs, then open Records. The critical pace curve sits under your personal records, with the current period in teal and the previous one in grey. Change the range at the top (4 weeks, 12 weeks, a year) to compare different periods.
Private by design
Your runs are read and analysed in your browser and stored on your device. Nothing is uploaded, and there's no account to create. Estimates like this one are training guidance, not medical advice.