Training zones
Training zones: power, heart rate and pace
Training zones divide effort into bands set as a percentage of your threshold in each sport: FTP on the bike, threshold pace on the run, Critical Swim Speed (CSS) in the pool, and threshold heart rate.
They turn "go steady" or "go hard" into a target you can hit, repeat and compare, and they are the language almost every training plan is written in.
At a glance
| Sport | Anchor | What it means | A common field test |
|---|---|---|---|
| Bikepower | Functional Threshold Power (FTP) | Roughly the highest power you can hold for about an hour | 95% of your average power for a 20-minute all-out effort |
| Runpace or power | Threshold pace | Roughly the fastest pace you can hold for about an hour | A solo 30-minute time trial on flat ground |
| Swimpace | Critical Swim Speed (CSS) | A pace you can hold in a long continuous swim without fading | A 400 m and a 200 m time trial |
| Any sportheart rate | Threshold heart rate (LTHR) | Your heart rate at threshold, which differs by sport | Average heart rate over the last 20 minutes of a 30-minute effort |
How do training zones work?
Find one anchor number per sport, then set each zone as a percentage of it. Your threshold sits close to the point where effort stops being sustainable for long. Below it you can go for hours; above it the clock starts running down quickly. Zones slice the range either side into named bands, so a plan can ask for "20 minutes at Sweet Spot" and mean the same thing every time.
The catch is that there is no single zone system. Andrew Coggan's power levels use seven bands. Many heart-rate systems use five. Research papers usually use three, set by two physiological thresholds. So "Zone 2" can mean an easy endurance ride in one app and something noticeably harder in another. When you compare advice, check which system it uses before you compare the numbers.
What if you've had a lactate test?
Then you can set zones from your own turn points instead of a percentage. A lactate test finds two points as effort rises: LT1, where blood lactate first rises above resting, roughly the top of easy effort; and LT2, where it starts climbing steeply, close to threshold. Your heart rate, pace and power at each become the edges of your zones. See lactate thresholds and lactate testing for how it works.
Which zones does LOAD use?
Five zones in every sport: Recovery, Endurance, Tempo, Threshold and VO2 Max. Each sport's zones are set from its own threshold, and shown as power, pace or heart rate wherever they apply. We use five rather than seven because zone edges are fluid for real athletes, and a few wider zones are honest about that. Where a finer distinction matters, it sits inside a zone rather than becoming a zone of its own.
On the bike, the ranges are adapted from the power zones TrainerRoad publishes:
| Zone | % of FTP | What it feels like |
|---|---|---|
| Z1 Recovery | Below 55% | Barely working. Spinning the legs out. |
| Z2 Endurance | 55–75% | Easy and conversational. Could go for hours. |
| Z3 Tempo to Sweet SpotTempo 76–87% · Sweet Spot 88–94% | 76–94% | From steady and purposeful to comfortably hard. |
| Z4 ThresholdSupra-Threshold 101–105% | 95–105% | Hard. Sustainable for tens of minutes, not hours. |
| Z5 VO2 Max and above | Above 105% | Very hard to maximal. Efforts of a few minutes or less. |
Zone 3 on the bike is called "Tempo to Sweet Spot" because it spans both, and the two feel and train differently. Tempo and Sweet Spot are still marked inside it, so a session can target either one. The top of Zone 4 is marked as Supra-Threshold in the same way.
Worked example
A rider with an FTP of 250 W, and a swimmer who covers 400 m in 6:00 and 200 m in 2:50.
| Target | Calculation | Result |
|---|---|---|
| Z2 Endurance | 250 × 0.55 to 250 × 0.75 | 138–188 W |
| Z3 Tempo to Sweet Spot | 250 × 0.76 to 250 × 0.94 | 190–235 W |
| Sweet Spot, inside Z3 | 250 × 0.88 to 250 × 0.94 | 220–235 W |
| Z4 Threshold | 250 × 0.95 to 250 × 1.05 | 238–263 W |
| CSS speed | (400 − 200) m ÷ (360 − 170) s | 1.05 m/s |
| CSS pace | 100 m ÷ 1.05 m/s | 1:35 /100 m |
CSS comes from the difference between the two swims, so a fast 200 m on its own doesn't inflate it. Pace both swims evenly, or the number drifts.
Power, heart rate, pace or feel?
Each measures something different, so each is wrong in a different way.
- Power is external: it measures what you are producing, instantly. It doesn't know how tired you are, so 200 W on a fresh morning and 200 W at the end of a hard week read the same.
- Heart rate is internal: it measures what the effort is costing you. It lags behind changes in effort by a minute or more, and it drifts upward with heat, dehydration and long sessions.
- Pace is simple and honest on flat ground, but hills, wind, surfaces and pool length all bend it.
- Lactate, measured with a portable meter, is internal like heart rate: it shows what the effort is doing inside you. Some athletes now pace sessions to keep lactate in a set range, rather than to a power or pace target.
- Feel (rate of perceived exertion) folds in everything at once, including sleep and stress. It is the least precise and often the most informative.
The most useful habit is to use one as the target and another as the check. If power says Endurance but heart rate is climbing into Threshold, the gap between them is information worth having.
What changes for triathletes?
You have three thresholds, and they move independently. A winter on the turbo can lift your FTP while your run threshold stands still. Zones set from an old test in one sport quietly mislead you in that sport.
- Keep heart-rate zones per sport. Most triathletes reach a lower heart rate on the bike than on the run at the same effort. One set of heart-rate zones across all three will make rides look easier than they are, or runs harder.
- Treat swim heart rate with caution. Wrist sensors struggle in water, so pace against CSS is usually the better guide in the pool.
- Expect brick runs to read differently. Running off the bike, pace drops and heart rate rises for the same feel. That's normal, not a fitness problem.
- Stagger your retests. Testing all three sports in one week stacks a lot of hard efforts. Spread them across a recovery week or two.
Should you trust your zones?
Trust them as a shared language. Be sceptical of them as a map of your body. Zones are one of the most useful tools in endurance training, and one of the most over-precise.
What they get right
- They make sessions repeatable. You can do the same workout in March and June and see what changed.
- They protect easy days. The most common amateur mistake is easy sessions done too hard. A ceiling in watts or heartbeats stops that.
- They let coach and athlete mean the same thing. "Sweet Spot" is clearer than "push a bit".
Where they fall short
- The edges are invented. Your physiology doesn't change at 75% of FTP and something new begin at 76%. Effort is a continuum, and zone boundaries are conventions drawn across it.
- They rest on one test, on one day. Sleep, heat, motivation and pacing skill all move a test result. Every zone inherits that error, and it compounds when the number is out of date.
- The same percentage isn't the same state. Two riders at 90% of FTP can be in quite different places physiologically, because thresholds sit at different points in different people. A 2015 review by Thomas Stöggl and Billy Sperlich noted that zones set as a fixed percentage of maximum aerobic capacity can place quite different strain on different athletes.
- Methods disagree. The same review found that if you classify the same session by heart rate, lactate, percentage of maximum or feel, you can get different answers about how hard it was.
- Even a lactate test isn't fixed. LT1 and LT2 are points marked on a smooth curve, and the body doesn't change state as you cross them. They also move with fitness, fatigue, diet and heat, so a test is a snapshot of a moving target, not a set of permanent boundaries.
- They are easy to flatter. A well-paced test on a good day, rounded up, makes every zone harder. It feels like progress until the sessions start to break you.
- They describe intensity, not cost. Three hours in Endurance and one hour in Endurance are the same zone and very different days.
How to use them anyway
Use zones as guardrails, not instructions. Plan in zones, check against feel, and treat a mismatch as a question rather than a failure. When sessions keep feeling too easy or too hard for their zone, your threshold has probably moved. Retest it rather than forcing the numbers.
Common questions
What is Zone 2?
It depends on the zone system. In most five-zone systems, Zone 2 is easy aerobic work you could sustain for hours, which in LOAD's bike zones is Endurance, 55 to 75 percent of FTP. In three-zone research models, the same effort sits in Zone 1, which is why advice about Zone 2 is easy to misread.
How often should I retest my threshold?
Many athletes retest every six to eight weeks, or whenever sessions consistently feel too easy or too hard for their zone. In triathlon, spread the three sports' tests out rather than doing them in the same week.
Should I train by power or heart rate?
Use both if you can. Power shows what you are producing and responds instantly; heart rate shows what it is costing you but lags and drifts. Use one as the target and the other as a check, and pay attention when they disagree.
Why is my heart rate lower on the bike than on the run?
Most triathletes reach a lower heart rate cycling than running at the same effort, so heart-rate zones should be set separately for each sport rather than shared.
Related
Sources
- Allen H, Coggan AR, McGregor S. Training and Racing with a Power Meter, 3rd edition. VeloPress, 2019.
- Friel J. The Triathlete's Training Bible, 4th edition. VeloPress, 2016.
- Wakayoshi K, Yoshida T, Udo M, et al. A simple method for determining critical speed as swimming fatigue threshold in competitive swimming. International Journal of Sports Medicine. 1992;13(5):367–371. The critical-speed idea CSS builds on; the 400 m and 200 m test is a common simplified version.
- Stöggl TL, Sperlich B. The training intensity distribution among well-trained and elite endurance athletes. Frontiers in Physiology. 2015;6:295.
- Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? International Journal of Sports Physiology and Performance. 2010;5(3):276–291.
- Faude O, Kindermann W, Meyer T. Lactate threshold concepts: how valid are they? Sports Medicine. 2009;39(6):469–490.
- Impellizzeri FM, Marcora SM, Coutts AJ. Internal and external training load: 15 years on. International Journal of Sports Physiology and Performance. 2019;14(2):270–273.
- TrainerRoad. Cycling power zones: training zones explained. The basis of the bike zone ranges LOAD uses.