A clear plan, all the way to the start line
Two runs on the track are enough. They tell you where you stand, which paces to train at, what to work on over the coming weeks and how to pace your race. This page shows what is behind it.
Too much knowledge, too little plan
Preparing for a race, most people do not have too little information but too much: zone models, plans, studies, watches that show a new number every day.
- Ten answers to every question.
Training for a half marathon, a marathon or a triathlon, you find ten answers to every question. In the end many train by feel, too often in the middle range and without a clear goal for the week.
- The formula from the internet does not fit everyone.
220 minus your age or a fixed percentage of your 10 km time can be far off for an individual runner.
- A test that rarely happens shows no progress.
A lab test takes an appointment, travel and money. So hardly anyone retests during their preparation, and nobody knows whether the training works.
- Finish strong instead of surviving.
Start without a plan and without pacing, and you often go out too fast, eat too little and live through the second half of the race as a fight.
What we do differently
- One goal, one direction.
The starting point is always your race. Everything in the report, from the zones to the weekly plan, is built around it.
- Training guidance, not training science.
We translate the research into a few clear rules: your paces, your focus, your key sessions. You don't have to read the studies; we did that for you.
- A clear plan.
Week by week until the retest, with the one thing that moves you forward most: your development focus.
- Progress you can measure.
The test can be repeated at any time on any 400 m track. After 6 to 10 weeks you see in black and white what has changed.
- Prepared at the start.
Target time, pacing, heart-rate range and fuelling per hour are settled before you stand at the start line. With the race plan, even section by section on your real course.
- Honest about every number.
Every value says whether it is measured, modelled or estimated.
From your first test to the start line
For runners and triathletes training for a specific race, from a first half marathon to the long distance. And for coaches who want to test their athletes regularly.
Your details. Sex, age, weight, maximum heart rate, your target race with its date and the days you can train.
Two maximal runs. A short run of 3 to 4 minutes and a long one of 12 to 17 minutes, ideally on a track. Which distances suit you depends on your 5 km time.
Your report. Profile, predictions, zones, metabolism, fuelling, development focus and the weekly plan up to the test week.
Retest after 6 to 10 weeks. With the same distances and the same routine. The report shows the trend and adjusts paces and plan.
Race plan. Pacing and fuelling in the report and, if you like, section by section on your own GPX course.
The full test protocol with the distance table →
Your report plans up to the test week. If you are linked to a coach, we remind them after 6, 8 and 10 weeks, as long as no new test has come in.
Critical Speed and D′: the boundary that matters
There is a pace you can hold steady for a long time, and one that only lasts a limited time. Critical Speed, CS for short, is the boundary between them: the highest speed at which your metabolism still settles into balance. Just above it, oxygen uptake climbs to its maximum and the run ends after a predictable time.
D′ (D prime) is your reserve of distance you can run faster than CS: a distance in metres, not a pace. The further above CS you run, the faster it is used up. That is why a pace just above CS lasts many minutes, and a much faster one only briefly.
Two maximal runs of different length set both values. The curve through them is a hyperbola: for every duration it shows the pace you can hold, flattening out towards CS. Everything else follows from it, from the predictions to the zones.
Critical Speed & D′
- Critical Speed
- 4:07 /km
- D′
- 152 m
- Two maximal runs: 1000 m and 3000 m
- The hyperbola through both: the pace you can hold for each duration
- Critical Speed: the boundary of balance
- Faster than CS only works for a while: 37 s/km faster lasts 1000 m, 12 s/km faster lasts 3000 m. Both runs spend the same 152 m of D′.
A worked example: 1000 m in 3:30 and 3000 m in 11:45. The long run lasts more than three times as long as the short one, so D′ is well defined too. Your report works with your own two runs.
Progress you can see.
From test to plan in six steps
The basis is always the same model: your Critical Speed and your D′.
Check. Are the two runs usable? Each lasts 2 to 18 minutes, the long one at least three times as long as the short one. Between two and three times the test can still be evaluated, D′ then comes with a range, and we suggest distances for the next test.
Fit the model. Critical Speed and D′ from your two runs.
Predictions. Times from 800 m to the marathon, each with a range instead of a falsely exact number. With a race time of your own over a longer distance, the long-distance prediction becomes personal.
Zones and thresholds. Training zones as percentages of your CS, plus the aerobic threshold, the pace of peak fat burning (FatMax) and your heart-rate zones.
Metabolism and fuelling. Oxygen demand, fat and carbohydrate use at each pace, your glycogen store and how many grams of carbohydrate per hour you need in the race. The report also shows when the store would run low without fuelling.
Focus and plan. Your profile and what your target race demands give your development focus, and from it the weekly plan up to the test week.
Measured, modelled, estimated
Not every number in the report is equally certain. That is why every value says where it comes from.
| Value | Origin | Basis |
|---|---|---|
| Time and distance of your runs | measured | your watch; on a track, the laps |
| Critical Speed and D′ | modelled | from your two runs |
| Predictions from 800 m to the marathon | modelled | from CS and D′, with a range |
| Training zones, aerobic threshold, FatMax | modelled | anchored to your CS |
| Heart-rate zones | modelled | from your maximum heart rate |
| VO₂max and running economy | estimated | from pace, level and sex |
| Fat, carbohydrate, glycogen, fuelling | estimated | from pace, weight and level |
The race plan: pace the effort, not a fixed speed
Your course's GPX file and your report make a plan for each section. What is planned is the effort: uphill the pace gets slower, downhill faster, and on steep ground you walk when walking is cheaper. Altitude, surface and fatigue over the race come on top.
The elevation profile comes from swisstopo's terrain model, not from your watch's GPS. How hard you can run overall follows from the race duration your report predicts. Short climbs may be a little harder, as long as your D′ is not used up.
For every section you get pace, heart rate, feel and fuelling, plus a plan B for a bad day.
A mountain half marathon, section by section
- Plan
- 2:24:54
- Ascent
- 529 m
- climb
- flat
- gentle descent
- Above each section: the planned pace per kilometre
An example from the race plan: a sample runner on a mountain half marathon. On the steepest climb it plans walking, because brisk walking is just as fast there and saves strength.
Where our report stops being reliable
The report works with the time and distance of your runs. Four things bound its accuracy:
Your distanceOn a track the laps give it. On the road GPS estimates it, and a few percent of distance error shift Critical Speed by the same amount. For retests: same route, same watch, similar conditions.
Your pacingEvery run has to be truly maximal for its distance and evenly paced, not a sprint followed by a collapse. The mathematics does not correct mistakes; it works with what you ran.
D′It is the least certain number in the report and varies more from test to test than CS. Read it as a rough figure for your reserve, not as a measurement to the metre.
Your healthThis is not a medical screening. The report detects neither cardiac risk nor anaemia, overtraining or infection. If you feel ill or completely exhausted, the test is the wrong tool at that moment.
What remains is the decisive advantage: a repeatable measurement of your boundary, with the watch you already own, often enough to see real development.
Key references
- Monod, H. & Scherrer, J. (1965). The work capacity of a synergic muscular group. Ergonomics, 8(3), 329–338.: the linear work–time model, in running as distance and time.
- Poole, D. C., Burnley, M., Vanhatalo, A., Rossiter, H. B. & Jones, A. M. (2016). Critical power: an important fatigue threshold in exercise physiology. Medicine & Science in Sports & Exercise, 48(11), 2320–2334.: CP and CS as the boundary between intensity domains.
- Nixon, R. J., Kranen, S. H., Vanhatalo, A. & Jones, A. M. (2021). Steady-state V̇O₂ above MLSS: evidence that critical speed better represents maximal metabolic steady state in well-trained runners. European Journal of Applied Physiology, 121(11), 3133–3144.: CS as the boundary of balance in running.
- Galbraith, A., Hopker, J., Lelliott, S., Diddams, L. & Passfield, L. (2014). A single-visit field test of critical speed. International Journal of Sports Physiology and Performance, 9(6), 931–935.: CS and D′ from a field test on the track.
- Gilgen-Ammann, R., Schweizer, T. & Wyss, T. (2020). Accuracy of distance recordings in eight positioning-enabled sport watches: instrument validation study. JMIR mHealth and uHealth, 8(6), e17118.: how accurately GPS watches measure distance.
Test yourself on the track
Two runs are enough to see what the models above say about you.