How it works Race predictions and threshold
Race predictions and lactate threshold
Your potential race times today, from 5K to marathon, plus your threshold pace and heart rate, which drive your workouts.
What Stamio uses
- Your VO2 max.
- Your best efforts over 5K, 10K, half marathon and marathon, found within your outdoor runs.
- Race results you enter for races run without your watch.
- Your heart rate during sustained efforts, and your max HR.
- With a chest strap paired with Stamio and your iPhone on you: the gap between each heartbeat during your runs.
How it's calculated
A time from your VO2 max
Published tables link VO2 max to the time you can hold at each distance. Stamio starts there, with a safety margin that narrows for highly trained runners.
A time from your runs
Each recent best effort is projected to the other distances using the published relationship between distance and race time. A strong run brings your times down, then its effect fades after 7 to 8 weeks.
The faster of the two
Your predicted time is the better of the two. So a strong race counts right away, even before your VO2 max moves.
Your threshold heart rate
It comes from your most recent sustained efforts (the highest heart rate you held for about ten minutes) and from a share of your max HR. A hard run raises it, then it drifts back down slowly.
Your threshold pace
It's derived from your predicted 10K time and holds at its best level for a few weeks rather than moving with every workout. The "Threshold" workouts in your plan are run around this pace.
Measured threshold, with a chest strap
At threshold, your breathing picks up and your heart rhythm becomes very regular: the gap between beats barely varies anymore. A chest strap reads your heart's electrical signal and timestamps each beat to the millisecond. During your run, Stamio spots the moment this variability drops below the level described in published research: your heart rate and pace at that moment give your measured threshold. One workout with 10 to 15 minutes near threshold is enough. This measurement is still labeled "Experimental".
Your heart rate zones
They're based on your heart rate reserve, between resting HR and max HR, and drive your easy runs, your run maps and your load.
When it changes
- After every outdoor run: a new VO2 max, maybe a new best effort.
- When you enter a race result (5K or longer, less than 200 days old).
- When a run raises your threshold, the run details say so: "New threshold".
- With a plan, each time also gets a race-day projection (see the Plan page).
What can throw it off
- The marathon takes endurance: its predicted time assumes you've trained for it, long runs included.
- A very hilly course, heat or wind: on race day you'll be slower than the flat-course prediction.
- A GPS distance that runs long: a best effort can look a little too flattering.
- A wrong max HR shifts your threshold heart rate and your zones.
- A watch, earbuds or an armband measure heart rate well, but can't time the gap between beats precisely enough to measure threshold: only a chest strap can.
- Dry electrodes at the start or a strap that slips can scramble a few beats: Stamio filters them out.
What you can set
- Add races you ran without your watch (My race results): they count toward your records too, marked "entered".
- Your max HR and resting HR, which set your zones.
- Pair a Bluetooth chest strap (Settings › Advanced › Chest strap), just once.
How it was checked
Predicted times were calibrated, then checked against a high-end GPS watch worn at the same time: under a 0.7% difference from 5K to marathon.
Just one runner so far: me. The beta will tell the rest.
Questions
My predicted marathon time seems too fast.
It shows what your fitness allows if you've trained for the distance. Without long runs, aim more conservatively: a marathon plan gives you a more accurate race-day projection.
Why did my times suddenly drop?
A strong recent run was factored in. Its effect fades over a few weeks, unless another run backs it up.
Do I need a chest strap for threshold?
No. Without one, your threshold is calculated from your heart rate and pace during your runs: a reliable estimate, within a few beats. With a chest strap, it can also be measured.
Further reading
- Daniels J., Gilbert J. (1979), Oxygen Power: Performance Tables for Distance Runners, Tempe (Arizona).
- Riegel P. S. (1981), "Athletic records and human endurance", American Scientist, 69(3), 285-290.
- Rogers B., Giles D., Draper N., Mourot L., Gronwald T. (2021), "Detection of the anaerobic threshold in endurance sports: validation of a new method using correlation properties of heart rate variability", Journal of Functional Morphology and Kinesiology, 6(2), 38.
Estimates for training: weather, course and how you feel on the day count too.