We recently invited the WHOOP community to ask us anything about WHOOP strain: the metric you see in your app each day that ranges from 0 to 21.
We’ve talked in-depth about strain on the WHOOP podcast and show notes, and we’ve covered topics such as the Borg Scale of Perceived Exertion and heart rate training zones to help the WHOOP community better understand what it all means. If you haven’t had a chance to listen or read yet, we encourage you to do so to get the most out of your WHOOP data.
Below, we’ve selected 15 specific questions from WHOOP members about strain. Whether you’re a long-time member or you've just joined, we hope you find this information valuable and relevant to your training!
1. I’ve had days where I hit 15+ strain and burn 2500 calories, and other days where I hit 4000 calories. Why? -@baby_drew77
There’s more than one way to get a 15 strain based on the heart rate training zones you’re operating in. For example, one day you could spend most of your time in a light training zone: active, but not overdoing it. Another day you could be resting in the morning with a period of hard to max training in the afternoon, which will rapidly increase your strain and calories burned. It’s important to note that the rate at which you build strain and burn calories does not always scale the same.
2. How many high strain days should you have in a row? -@geologist_who_wods
There is no strict guideline for how many days you should spend getting a high strain. What’s more important is how your body is recovering and adapting to training. If you have consistently high strain, but over time you notice you are struggling to recover adequately, then WHOOP recommends you reduce your strain to let your body rest and heal. There are many endurance athletes who regularly have high strain, but their bodies have adapted to that kind of cardiovascular training.
3. What’s the correlation between muscle strain and body strain? How can we extrapolate muscle strain from HRV readings and total body strain? -@amiin_
WHOOP measures strain based on cardiovascular output and time spent in various heart rate zones. Therefore, if you’re doing a strength-based workout with minimal reps and periods of rest (such as Olympic weightlifting), you will have a lower strain if your heart rate is not elevated for extended periods of time. Many WHOOP members have wondered how their data will reflect a strenuous strength session, so here’s the breakdown:
- Increasing weight and adding new strength exercises to your routine will likely cause soreness and muscle fatigue, otherwise known as delayed onset of muscle soreness (DOMS). This microtrauma from eccentric lengthening of the muscle fibers typically causes a reduction of heart rate variability (HRV) the following morning, especially if your body is not used this kind of stressor.
- Fatigued muscles often result in a higher strain as you go about your day, because your body is working harder to recover as it responds to disturbances of your homeostatic state.
In order to read true muscle strain following a workout, you’d likely need an additional tools such as an EMG or blood test.
4. If I have a daily strain above 17, can I expect my recovery to tank the next day? -@raised_in_baseball
While your chance of reduced recovery the next day is elevated due to the high-strain day, one day of high strain does not guarantee a poor next-day recovery. There are many athletes who are well-conditioned and regularly achieve high strain and are able to bounce back quickly. Additionally, there are many other internal and external factors that affect recovery beyond cardiovascular strain, such as diet, sleep quality, psychological stress, and more.
5. Is the strain based on a fixed formula or does it have iterations to respond to trends? -@mars_mapper
The WHOOP strain algorithm is not fixed. It adjusts to your personal baseline, which is why two people can do the same workout and have vastly different strains. Your strain will adjust to changes in fitness level, so as your fitness improves the same workouts will create less strain. Within your app, you can swipe right on the homescreen to see your 30-day baseline overview.
6. I have 3 activities in a day, but the total strain does equal the sum of each. Why? -@duffy_wan
We cover this in the podcast linked above, but strain does not operate on a linear scale. You can have multiple activities throughout the day, but they will not add up to a total day strain. Just because you have 2 relatively easy activities at 6 strain, for example, does not mean it equates to a 12 strain on your body. More likely, you’ll end up with an 8 or 9 strain in culmination with the rest of your day.
7. If I take an ice bath, do yoga or cryo, do I get strain reversed? -@notthefakedrew
Physiologically speaking, the cardiovascular strain on your body can’t be reversed once you’ve put your body through it. There is no way to retroactively reduce your WHOOP strain; it will only build throughout the day. However, activities such as naps, cryotherapy, or ice baths can certainly aid your recovery.
8. How do we accumulate strain even when we haven’t done a workout? -@adamgeering
Day strain is a measure of the strain you have accumulated over the course of an entire day. There are numerous factors beyond your workouts that affect the strain on your body, including stress, your commute, your job, yardwork, chores around the house, etc. In fact, many WHOOP members have noticed that on particularly taxing days (being on their feet all day or a stressful day at work) their WHOOP strain is noticeably higher, even if they haven’t worked out.
9. I workout in the morning. Is there a way to use my strain to ensure I still have enough energy for the rest of the day without being overly exhausted? -@305jm9055
We’d recommend using the Strain Coach feature in your WHOOP app. It will suggest an optimal strain range for the day based on your recovery. If you know your day will be particularly taxing, you can adjust your workouts accordingly based on what the strain coach is telling you.
10. Why does my WHOOP sometimes record a strain of 3 or 4 when I first wake up? -@jwysokowski43
Your WHOOP cycle begins when you fall asleep, then resets the next time you fall asleep (some other wearables operate on a fixed 24 hour cycle, which isn’t an accurate portrayal of your body’s routine). Therefore, you’ll wake up with a relatively low strain, since your body is still using energy and burning calories while you’re asleep.
11. Why does strain build faster some days than others when activity level is close to the same? - @josh_moses79
Strain can accumulate differently based on your body’s recovery. If you wake up in the red, your body will work harder to achieve the same performance results than if you were in the green. Additionally, because strain can be affected by things like stress and diet, no two days are exactly the same, even if you’re doing the same activities.
12. What information gives me my average day strain? Mine is about 15.8 -@sanzoeb
Your average day strain (seen on your profile overview when you swipe right) is a basic average calculation from your past 30 days of data on WHOOP. It is a good indication of your baseline and what your body is used to.
13. What factors make strain different from person to person? - @drbrandonbrown
Just like all of the data you collect on WHOOP, strain is personal to your physiology. Strain can be affected by things like fitness level, diet, hydration, stress, illness, injury, alcohol, health conditions, training loads, and more.
14. Why is it impossible to reach 21? -@atlrel
The strain scale is set based on the mathematical limit: if you were operating at your max HR for 24 hours, you would earn a 21. However, that’s physiologically impossible, so while you technically “can” get a 21, no one ever will.
15. How is HRV used to calculate available daily strain? -@loots_of_war
HRV does not factor into WHOOP strain, only into your recovery. HRV constantly fluctuates throughout the day based on internal and external stressors, which is why WHOOP measures HRV every night during the last cycle of your slow wave (deep) sleep for the most accurate, consistent reading.
We hope these answers helped you better understand the #scienceofstrain. Thanks again for all your questions!