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How Does WHOOP Strain Work?

May 17, 2022

Strain 101: Everything you want to know about how WHOOP quantifies the workload your body takes on.



Below we’ll discuss exactly what our strain metric is, how it’s calculated, factors that play into determining your strain for a whole day and for various activities, WHOOP averages for each, as well as the relationship between strain and recovery.


What is WHOOP Strain?

WHOOP strain is a measure of cardiovascular exertion that quantifies the amount of physical and mental stress you’re putting on your body. We track your strain on a 0-21 scale, both for your entire day and for specific workouts and activities.

Inspired by Borg’s Rating of Perceived Exertion, strain numbers can be loosely broken down as follows:

whoop strain scale 0-21

WHOOP measures your strain on a 0-21 scale. the higher it gets the harder it is to build more.

LIGHT (0-9): Minimal stress put on the body, room for active recovery

MODERATE (10-13): Moderate stress on the body, generally good for maintaining fitness

HIGH (14-17): Increased stress and activity level, ideal for making fitness gains when training

ALL OUT (18-21): Significant stress, often overreaching, likely very difficult to recover from the next day

Why WHOOP Doesn’t Count Steps


What Causes Strain & How Does WHOOP Calculate It?

When your heart rate begins to rise, you start building strain. The higher your HR gets and the longer it stays elevated, the more strain you accumulate. In this sense, your strain is calculated based on the length of time you spend in various heart rate zones (percentages of your max heart rate).

Beyond exercise and other physical exertion, anything that gets your heart pumping will boost your strain. Regular daily activities like work, commuting, running errands, and parenting may all cause strain. So can stress, anxiety, excitement, or feeling nervous–even being a sports fan is strenuous.

whoop app strain screen

WHOOP Calculates Your strain for the entire day, and for specific periods of exercise or activity.

FAQs About WHOOP Strain


Activity Strain vs. Day Strain

When WHOOP notices a spike in heart rate and movement for a sustained period of time, it will automatically detect your activity or workout and give you a strain value for it (you can also add other activities manually and see their strain).

Your total day strain provides you with additional insight into the cardiovascular load your body takes on outside of exercise. For example, a presentation at work or a busy afternoon with the kids might raise your day strain above average, even on a day you don’t work out.

activity strain vs day strain

WHOOP detects your workouts and tells you how strenuous they are. YOUR Day strain is not the sum of your activities.

If you have multiple workouts in a day, the strain of your activities does not add up to your total day strain. The WHOOP strain algorithm is logarithmic, meaning the higher your strain gets the harder it becomes to build more.

As illustrated by the top graphic above, it is much easier to go from a 0 to 10 strain than it is to go from a 10 to 20. Hypothetically, running a marathon might lift your day strain to 20.4 or 20.5, but then running a second one that day could only increase it to 20.6 or 20.7.

Podcast: The Science of Strain with Dr. Andy Walshe


What is a “normal” amount of strain?

The strain average for all WHOOP members is right around 11.0 per day. To no surprise, the number tends to decrease with age. Below you can see what daily average strains are by age and gender:

The average daily strain for WHOOP members is about 11.0, It decreases with age.

When it comes to individual workouts, more intense aerobic exercise leads to higher strain than less intense activity. The average strain for 1 hour of running is roughly 12.0, while an hour of walking is about 6.5.

Because strain is a product of your elevated heart rate, cardio-based workouts increase it faster than weightlifting or other strength-based training that doesn’t impact your HR as significantly (although the toll they take on your body is still reflected in your daily recovery). The average strain for 1 hour of functional fitness is 10.1.

Average Strain of 10 Most Popular Activities


Strain is Highly Individualized

Strain is calculated from your personal HR metrics and accounts for your individual fitness level. Since it quantifies how hard your body works and not what your body does, two people who complete the same activity may have very different strains.

For example, a 90-minute hike that registers a 10 or 11 strain for the average person might be just a 5 or 6 for a highly conditioned athlete. Along the same lines, as your fitness improves you’ll start to see lower strains for that same activity.

Quantifying the Strain of NFL Football with Patrick Mahomes’ WHOOP Data


Strain & Recovery

The higher your recovery is, the more strain your body is ready to take on.

Recovery determines WHOOP strain recommendations

The amount of STRAIN YOUR BODY IS READY TO HANDLE is dictated by your recovery each day.

You may notice strain accumulate faster on days when you have a low recovery, because your body is not as prepared to handle it. A workout routine that usually gives you a 9.5 might be a 10.5 when you’re in the red.

The Strain Coach suggests an optimal amount for you to take on each day based on your recovery. It’s a recommended level of strain intended to let you maintain fitness and still adequately recover the following day.

WHOOP recovery and strain balance


If you go above this amount you are “overreaching” (good for making fitness gains, but likely detrimental to your next-day recovery), and if you stay below it you are “restoring.”

In turn, the amount of strain you take on today then affects what your recovery will be tomorrow.

Podcast: Understanding WHOOP Strain


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