Three race performances in, 400 m, 1600 m, 5000 m. Out comes a robust target-distance projection (median of three power-law fits), your 60-min threshold pace anchored to your 5K speed, and a full set of 9 Yousuli running zones from Easy through ATP-PC.
All-out efforts, recent (within 4–6 weeks), enter as mm:ss. Spread across short / mid / long is the point, using three time-trials at very similar distances breaks the model.
Three pairwise power-law fits, median projection, 5K-anchored threshold.
t = a · dk
Three pairs from your three points (400-1600 / 400-5000 / 1600-5000) yield three (a, k) fits. Each pair captures a different slice of your power-duration curve.
For your target race distance we project all three predictions and take the middle one. Median is robust to outliers, a sandbagged 5K won’t wreck the projection the way it would with just a single Riegel formula.
From each model we compute the speed sustainable for 60 min. Then we constrain it to the band 5K speed × [1/1.08 .. 1/1.03], physiology says 5K pace is 103–108% of threshold. If the raw fit pulls threshold faster than that, we cap (and flag) it.
Riegel’s single-effort predictor is fine. Three points let you see your power-duration shape, not just one point on it. Some athletes have flat curves (long-distance specialists), some have steep curves (sprinters trying to race long). The model picks up that signal.
Two patterns to watch in the output:
For honest test data: pick a flat course or treadmill, well-paced, well-rested. Same shoes, same surface, similar temperature. Spread the three across 7–10 days, not the same day.
Nine bands, nine different jobs. Train them on purpose.
Below the aerobic floor. Recovery runs, warm-ups, cool-downs. Should feel lazy, that’s the point.
Where mitochondrial density and fat oxidation get built. Long, frequent, conversational. Boring on purpose.
Steady-state at the top of aerobic. Marathon-pace work for most, race-pace for shorter events.
Comfortably-hard. Builds lactate clearance and the ability to hold pace under pressure.
Sustainable for 30–60 min. The classic 4×8 min or 5×10 min interval set lives here.
Just over the line. Used in cruise intervals; bridges threshold and VO₂max stimulus.
3–5 min reps. Pushes the oxygen ceiling. Feels brutal, should. 1 session/week max.
30 s – 2 min reps. Strength and lactate tolerance. Sparingly outside specific blocks.
< 15 s all-out reps. Neuromuscular speed, sprint mechanics. Long recoveries between reps.
Riegel-style 1-point prediction with Perfect/Normal/Poor columns. Simpler input, less precise.
Open → HR zones (LTHR-based)Pair the pace zones above with HR zones for a complete training prescription.
Open → All calculatorsBack to the full catalog, 30+ endurance calculators across performance, fueling, swim, bike, run.
Browse →Lab testing measures lactate threshold and VO2max directly, same morning, single visit. The pace zones you walk out with are anchored to your physiology, not an extrapolation. Worth its weight for marathon prep.
Spotted a bug or want a feature? Email info@yousuli.co.
