How to Do a Running Threshold Test Properly

Short answer: run a 30-minute effort on your own, as steadily as you can, and press the lap button at the 10-minute mark. As coaches use the term, threshold is roughly the hardest effort you can hold steadily for about an hour. A 30-minute effort runs slightly faster than that, so the results are useful estimates for setting your first training zones, not direct measurements of lactate threshold. Your average heart rate for the last 20 minutes approximates your lactate threshold heart rate (LTHR), and your average pace for the whole 30 minutes is your 30-minute test pace, an upper estimate of threshold pace (1). The heart rate average skips the first 10 minutes, which is the convention in Friel's method; heart rate still climbing early on is one reason. That is the field test described by Joe Friel, and it needs nothing but a flat route and a watch.

Those two numbers set your training zones, the heart rate and pace bands for each run. Zones set too high turn easy days into moderate ones. As a suggestion, retest every 6–8 weeks, especially if you are newer to training, when your fitness changes faster.

Which threshold test should I do?

For most amateurs, the answer is the 30-minute solo time trial. It is free, it is repeatable, and it gives you both a pace and a heart rate in one go. In a study of 27 competitive runners and triathletes, the average speed from a 30-minute time trial did not differ significantly from a laboratory-measured lactate threshold (a blood lactate of 4 mmol/L), but individual estimates were not exact (2).

Use the field test if:

• you can run steadily for 30 minutes without stopping;
• you are healthy and have been training consistently for a few weeks;
• you have a heart rate strap or a watch you trust.

Skip it, or ask a doctor first, if you are ill, injured, or returning from a break; if you have a heart condition or have had chest pain or fainting on exercise; or if you are new to hard running. In those cases, build a few easy weeks first and use an effort-based estimate for now (a pace that feels comfortably hard). During the test, stop if you feel chest pain, dizziness, unusual breathlessness or sharp pain, and speak to a doctor before trying again.

What do I need to do on test day?

Choose a day when you are fresh: after an easy day or a rest day, not after your longest run of the week. Eat as you would before a hard session, and keep caffeine, food and sleep the same before every test, so results are comparable.

Pick the route. Flat is best: a track, a flat loop in a park, or a straight path. Hills change both your pace and your heart rate in ways that make the numbers hard to compare next time.

Check the conditions. Heat pushes heart rate up, and wind changes the pace you get for the same effort. If it is very hot or windy, move the test.

Run it alone. Friel's protocol is a solo effort, so nobody drags you into their pace (1).

Treadmill? It removes wind, hills and traffic. As a common convention, set about 1% incline, and use the same setup every time.

The protocol, step by step

1. Warm up for 15–20 minutes. Run easy, then add four or five 20-second pick-ups, with a minute of easy running between them.
2. Start your watch and run the 30 minutes. The effort is the hardest pace you could hold evenly for the full 30 minutes. It should feel very hard by the end, and you should not be able to hold a conversation beyond a word or two.
3. Pace it evenly. The classic mistake is to start too fast. Aim for the same effort from the first minute to the last, and keep something in reserve until the last five minutes. If you must misjudge, start slightly too easy.
4. Press lap at 10 minutes. Do not stop the watch; just mark the lap.
5. Finish and record. At 30 minutes, stop the effort. Note your average heart rate for the last 20 minutes (the second lap) and your average pace for the whole 30 minutes.
6. Cool down for 10 minutes of easy jogging or walking.

Your LTHR is approximately the average heart rate for the last 20 minutes, and your 30-minute test pace is the average pace for the whole 30 minutes (1). Both are estimates.

If you do not have heart rate, use effort alone: the pace you could just hold for 30 minutes, hard but steady. Threshold intervals later feel "comfortably hard": you can say a short sentence but not chat.

Common mistakes that spoil the result

• Uneven pacing. Starting too fast makes the second half collapse and gives you a pace you cannot repeat; if your last 10 minutes were much slower than your first, the test is not clean. A big negative split means you started too easy, so your last-20-minute heart rate may understate your LTHR.
• Testing when tired. A heavy week, poor sleep or a hard session the day before lowers your pace and distorts your heart rate. Rest and repeat.
• Trusting a doubtful heart rate reading. Wrist sensors can misread at high effort. If the number looks wrong, use a chest strap.
• Changing conditions between tests. Heat raises heart rate at the same pace, so a hot test followed by a cool one is not comparable.
• Treating one test as the truth. One test is one data point. If the number is far from the last one, check fatigue, pacing and conditions before you rebuild your zones.

How do I turn the result into zones?

With your LTHR, set your heart rate zones as percentages of it. As a rule of thumb from Friel's system (1), for running; other platforms, including your watch, may draw the boundaries differently, so do not mix systems:

Zone	What it is	% of LTHR
1	Recovery	below 85%
2	Aerobic (easy)	85–89%
3	Tempo	90–94%
4	Sub-threshold	95–99%
5	Threshold and above (Friel splits this further)	100% and up

For example, suppose your test gives an average pace of 4:30 per km over the 30 minutes and an average heart rate of 170 beats per minute over the last 20. Zone 2 is then about 145–151 beats per minute, so easy runs should stay at or below about 151, and zone 4 is about 162–168. Friel's zones treat your LTHR as the threshold anchor; because the test is an estimate, treat them as a guide. Use heart rate as a guide for easy runs, alongside breathing and effort. Slow down when heat or fatigue push it up, and do not force a pace just to stay in a zone. Zones are sport-specific, so do not reuse a running LTHR for the bike.

Your test pace is a reference point, not a set of pace zones. What you can run in a session also depends on its length, terrain, weather and effort.

How do I read my results over time?

As a rough guide, if your test pace improves but your heart rate barely changes, you are probably fitter: update your pace reference and keep your heart rate zones. If a result is far from your last test, check sleep, heat, fatigue, pacing and route first. Retest only when you are recovered and can match the conditions, in place of that week's threshold session. If your heart rate at the same pace is lower, that may be fitness or just a rested day, so confirm it the same way.

How does this fit into a normal training week?

Many runners do well with mostly easy running and, when training history and recovery allow, one controlled quality session a week to start, with experienced runners sometimes adding a second; threshold work is one option, not a requirement. For example:

• Monday: rest or easy 30–40 minutes.
• Tuesday: 15 minutes warm-up, then 3 × 8 minutes (newer runners can start with 3 × 5 or 2 × 8) at a controlled, comfortably hard effort with 2 minutes' jog recovery, 10 minutes cool-down. Go by effort and pace first: as a rough guide, a little slower than your test pace, perhaps 10–15 seconds per kilometre (4:40–4:45 per km in the example above). Heart rate is a secondary check; it lags, so expect it to climb through each repetition towards zone 4 and the bottom of zone 5 (about 95–100% of LTHR). That offset is a starting point, not a universal conversion; the test's own typical error is about the same size, so adjust by effort.
• Thursday: easy 40–50 minutes.
• Saturday: long run at easy effort, 60–90 minutes.
• Other days: rest or cross-train.

How often you do threshold work depends on your training history, weekly mileage, injury risk and your other hard sessions. As a starting point, newer runners could do one every one to two weeks, and experienced runners one or two a week.

If a session fails, and you cannot hold the pace in the second or third interval, do not push through. Cut the last repeat, finish the session easy, and ask whether you are tired or whether your threshold pace was set too optimistically. If most sessions feel too hard, repeat the test.

Reviews of mostly competitive distance runners suggest that keeping most running easy (roughly zones 1–2; the studies define intensity in their own ways) appeared more effective than building training mainly around threshold work (3, 4). Treat that as direction, not a prescription.

Tito connects to Strava, tracks your fitness, fatigue and form, and builds a training plan that adapts every week.

The science behind it

This section is optional reading. You do not need it to run the test.

Why threshold matters. In a classic review of the factors behind endurance performance, Bassett and Howley described three things that matter: maximal oxygen uptake (the most oxygen your body can use per minute), running economy (how little energy a given pace costs you) and the fraction of that uptake you can use for a long time. They concluded that the speed at lactate threshold combines all three and is the best physiological predictor of distance running performance (5). That makes it a sensible anchor, though the review is about prediction, not zones.

What "threshold" actually means. The word covers several related ideas. (Lactate is a substance your muscles make during effort, and you can measure it in blood.) The first lactate threshold is where blood lactate begins to rise above baseline. The second is higher, near the maximal lactate steady state, the highest intensity at which lactate stays stable (6). LTHR and threshold pace in this article refer to the second. Critical speed (the running version of critical power) is a different, modelled boundary that Jones and colleagues say can be held for only about 20–30 minutes (7). A maximal 30-minute run therefore sits near critical speed, which may be a little above the pace you could hold for an hour. Depending on how threshold is defined, your sustainable threshold-session pace may be slower than your test pace. Jones's paper does not test field protocols; this application is our inference.

What the training studies say. A systematic review of 16 studies of middle- and long-distance runners found that pyramidal and polarised training appeared more effective than threshold-focused training, although some of the best marathon runners in the world use threshold-heavy work (3). A second review concluded that about 70% or more of volume at low intensity seems necessary to optimise adaptations in these runners; that split is the authors' conclusion, not a direct comparison, and studies measured intensity in different ways, so the figures are approximate (4).

What the test study found. McGehee and colleagues compared a 30-minute time trial with a laboratory test in 27 competitive runners and triathletes. The time trial's estimates of speed and of heart rate at lactate threshold did not differ significantly from the criterion, a blood lactate of 4 mmol/L, though the typical individual error was 0.21 m/s in speed and 8 beats per minute (2). At 4:30 per km, 0.21 m/s is roughly 15 seconds per km, and 8 beats is about the width of one heart rate zone. No significant difference across 27 people does not make the methods interchangeable for one runner. Four mmol/L is only one definition of threshold, the sample was competitive athletes, and the abstract does not say which part of the time trial was averaged, so results may differ for newer runners and for this protocol.

Limits. The test is a practitioner's field protocol: useful, not exact. We found no study testing Friel's exact averaging rules (last 20 minutes for heart rate, whole run for pace) or testing newer runners.

References

1. Friel J. The Triathlete's Training Bible. VeloPress; 2016.
2. McGehee JC, Tanner CJ, Houmard JA. A comparison of methods for estimating the lactate threshold. J Strength Cond Res. 2005. doi:10.1519/15444.1
3. Kenneally M, Casado A, Santos-Concejero J. The Effect of Periodization and Training Intensity Distribution on Middle- and Long-Distance Running Performance: A Systematic Review. Int J Sports Physiol Perform. 2018. doi:10.1123/ijspp.2017-0327
4. Campos Y, Casado A, Vieira JG, et al. Training-intensity Distribution on Middle- and Long-distance Runners: A Systematic Review. Int J Sports Med. 2022. doi:10.1055/a-1559-3623
5. Bassett DR, Howley ET. Limiting factors for maximum oxygen uptake and determinants of endurance performance. Med Sci Sports Exerc. 2000. doi:10.1097/00005768-200001000-00012
6. Jamnick NA, Pettitt RW, Granata C, et al. An Examination and Critique of Current Methods to Determine Exercise Intensity. Sports Med. 2020. doi:10.1007/s40279-020-01322-8
7. Jones AM, Burnley M, Black MI, et al. The maximal metabolic steady state: redefining the 'gold standard'. Physiol Rep. 2019. doi:10.14814/phy2.14098