There's no good WHOOP strain score for everyone. Aim for strain that matches this morning's recovery: High (14 to 17) or All Out is fine on green days if your plan calls for it, Moderate (10 to 13) on yellow days and Light (0 to 9) on red days. Treat the target as a range, and judge training over weeks.
You finished a long ride, saw a 20.1, and felt a little proud and a little worried. Or you've been sitting at 9s and 10s all week and wonder if you're doing enough. Either way, the question is the same: what number should you actually be aiming for?
It comes up again and again in the WHOOP subreddit, with threads like "How often do you guys go over 19 or 20 strain?" (Reddit) and "20.1 Strain. Should I be concerned?" (Reddit). The honest answer is that the right number depends on your recovery that morning, your fitness and what the rest of your week looks like.
How does the 0 to 21 strain scale work?
WHOOP measures strain on a 0 to 21 scale, split into four zones: Light (0 to 9), Moderate (10 to 13), High (14 to 17) and All Out (18 to 21) (WHOOP).
The scale is logarithmic, which means each point is harder to earn the higher you go. Going from 16 to 17 takes far more work than going from 4 to 5. It also means workouts don't simply add up. WHOOP's example: a run at 10.2, a strength session at 8.4 and a walk at 5.1 might leave you with a Day Strain of about 14.1, not 23.7. One marathon might score 20.4, and a second marathon the same day would only take it to about 20.6 (WHOOP).
So a 20 is rare by design. WHOOP says most members reach All Out only on race or competition days, and it can take one or more days of recovery (WHOOP). A 20 after a big day doesn't mean something is wrong. It means the next few mornings matter.
What strain should you aim for on each recovery color?
WHOOP's own guidance ties strain to your recovery color (WHOOP):
- Green (67% or higher): High (14 to 17) or All Out (18 to 21) strain is fine if your training plan calls for it.
- Yellow (34 to 66%): Aim for Moderate strain (10 to 13).
- Red (0 to 33%): Keep it Light (0 to 9).
WHOOP is clear that "there is no universally good Strain score" (WHOOP). A 15 can be just right on a green day and too much on a red one. This is what strain vs recovery on WHOOP comes down to: the right number depends on the morning.
That's because your body doesn't respond to the same session the same way every day. WHOOP's example: a session that scores 9.5 on a green day can feel more like a 10.5 on a red day (WHOOP). It's also why it helps to check recovery before a hard session rather than after. Strain only goes up through the day, so once it's done, it's done (WHOOP).
Research on HRV-guided training points the same way. A meta-analysis of eight studies found that adjusting training day to day based on HRV improved vagal HRV more than following a fixed plan, with fewer people responding badly to training. The edge in fitness and performance was small and not statistically significant, so it's no magic trick, but it's a sensible way to avoid stacking hard days on a tired body (Manresa-Rocamora et al., 2021).
Why your 14 isn't someone else's 14
Strain is calibrated to your own cardiovascular baseline, so the same workout gives different numbers to different people. A fitter heart works less to hold the same pace (WHOOP). WHOOP's example: a 90-minute hike might score 10 to 11 for one member and 5 to 6 for someone very well conditioned (WHOOP).
The same applies to you over time. As you get fitter, the same workout tends to score lower. WHOOP suggests comparing yourself against your own patterns, not other people's. If your usual 5K run scores less strain than it did a few months ago, that's a sign your fitness is improving, not that you're slacking (WHOOP).
The target is a range, not a finish line
WHOOP's Strain Target turns your morning recovery into a recommended strain range, and it updates through the day as you take on strain. You can set an intent: restorative or taper, maintenance (the default) or overreaching (WHOOP).
The target is a range on purpose. In a WHOOP podcast episode, WHOOP scientist Greg Grosicki puts it simply: "The body cannot tell the difference between a 12.3 and a 12.6." You don't need to hit the top of the range every day (WHOOP). WHOOP's advice is that if you hit your target partway through a workout, it's worth considering wrapping up (WHOOP).
The bigger point from that episode is easy to forget: "There are no benefits at all that are coming from Strain. The benefits come after the Strain" (WHOOP). Training is the stimulus. Getting fitter happens while you recover. A higher number is only better if you can recover from it.
Your nervous system needs time to bounce back after hard work. A review of how cardiac parasympathetic activity recovers after exercise found it took up to 24 hours after low-intensity aerobic sessions, 24 to 48 hours after threshold work, and at least 48 hours after high-intensity sessions (Stanley et al., 2013). That's one reason two hard days in a row can leave you with a lower recovery the next morning. It's also one of the usual reasons for low WHOOP recovery after good sleep.
Consistency beats peaks
For general fitness, WHOOP suggests meeting your maintenance target four to five days a week. If you're newer to training, two to three workout days a week is a good start (WHOOP). WHOOP also says that, among its members, meeting strain targets over 12 weeks has been associated with improvements in HRV and lower resting heart rate (WHOOP).
All Out days have their place, like races or big events. Just plan for the recovery that follows, and don't stack them.
It's also worth watching the bigger picture. If your last seven days of strain are running well above your last four weeks while HRV drifts down, that's a sign to ease off for a week. We cover that in when to deload using 7- vs 28-day strain and HRV trends.
When strain climbs without a workout
Sometimes strain is higher than you expected on a rest day. WHOOP notes that strain reflects everything that makes your heart work harder, including stress, illness, heat, caffeine, chores and poor sleep, not just exercise (WHOOP).
If your strain is running high while you're resting, your resting heart rate is up and HRV is down, it may be worth taking it easy. Here's what WHOOP can show when you're getting sick, and when to train again after being sick.
A simple way to pick today's strain
Before your session, run through this:
- Check your recovery first. Green: high strain is fine if your plan calls for it. Yellow: moderate. Red: light.
- Look at the last two or three days. If you've already had back-to-back hard days, a moderate day is often the better choice even on green.
- Treat the target as a range. Once you're in it, you've done the job. Consider wrapping up.
- Account for other stress. A hard day at work, a bad night or a drink the night before all count. More on that in how long alcohol affects WHOOP recovery.
- Plan the recovery too. A big day needs a good night after it. A steady sleep schedule helps, as we explain in WHOOP sleep consistency and recovery.
- Judge it over weeks. Look at how often you hit your range and how HRV is trending, not at one day's number. If you're not sure what a healthy trend looks like, here's what a good HRV on WHOOP is.
If you plan your training the night before, it also helps to know how much of tomorrow's recovery you can predict.
Frequently asked questions
There's no universally good score. WHOOP suggests matching strain to recovery: High or All Out on green days if your plan calls for it, Moderate on yellow days and Light on red days.
Not by itself. All Out strain is rare by design and usually happens on race or competition days. It can take one or more days of recovery, so plan easier days after it.
Not often. All Out days are best saved for races and big events. For general fitness, WHOOP suggests meeting your maintenance target four to five days a week rather than chasing peaks.
As you get fitter, your heart works less hard for the same effort, so the same workout tends to score lower. It's usually a sign of improving fitness.
No. The target is a range, and you don't need to reach the top of it every day. Consistently meeting your targets over weeks matters more than any single day.
Strain reflects everything that makes your heart work harder, including stress, illness, heat and caffeine. If it's high while resting heart rate is up and HRV is down, take it easy.
This article is general information, not medical advice. If something feels off, talk to a qualified professional.
Know how hard to go today
The hard part isn't knowing the zones. It's knowing how much you can take on today without paying for it tomorrow.
That's one of the reasons we built ZONAL, a free web app in beta that works with WHOOP through a read-only WHOOP sign-in. It gives you a daily go, caution or swap call for training, and its Strain fit view checks every finished day against that morning's recovery, counting the days you landed in range, above it or below it, by week or month. Tap Be green tomorrow and it turns tomorrow's recovery forecast into a plan: a strain limit for today that keeps you green, or gets you as close as it can, an asleep-by time for tonight and your chance of a green morning. It also shows the next-morning HRV cost of each workout, compares your last 7 days of strain with your last 28, and uses Signal watch to flag mornings when several of your signals drift from your normal at once, so you know when to take it easy.
ZONAL started after one of our founders had strep throat and wanted to see what their data had been doing in the days before, and to know when it was safe to push again. If you'd like to know how hard to go today, you can try ZONAL free while it's in beta.
ZONAL is an independent app that works with WHOOP through a read-only WHOOP sign-in. It is not affiliated with, endorsed by, or sponsored by WHOOP, Inc. WHOOP is a trademark of WHOOP, Inc.
