What Actually Counts As “moderate Exercise”
Physical exercise is a healthy and, one might say, necessary part of our lives. Recommendations from public health organizations say that you should aim for at least 150 minutes of “moderate” exercise each week , and that every minute of “vigorous” exercise has double value. This begs the question: What the heck is “moderate” exercise? How do you know when you do this?
It’s not about the heart rate
The short answer, which is only slightly incorrect, is that “moderate” exercise is the same as the “zone 2” cardio I talked about earlier . (Zone 2 is the second highest intensity in the five-zone system, and you’ll need a heart rate monitor to know which zone you’re in.)
Although “zone 2” and “moderate” are broad intensity ranges, there is some overlap. If I had to choose which heart rate zone most closely corresponds to “moderate” intensity exercise, I would choose zone 2. But that doesn’t mean they’re the same thing.
Science measures ‘moderate’ and ‘vigorous’ MET scores
The study that led to these recommendations did not use heart rate as an indicator. Instead, these scientists measured exercise in terms of metabolic equivalents, or METs.
One MET is the energy expended at rest – the amount of oxygen, calories, etc. needed to keep you alive and breathing. (We use oxygen in the process of burning calories, so the official MET is 3.2 milliliters of oxygen per kilogram of body weight per minute.)
Researchers can then put an oxygen mask on a person and measure how much oxygen they use while running, walking, playing the guitar , etc. If an activity requires twice as much oxygen as sitting still, it is said to require two METH. Here are some examples (taken from this research paper ):
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2 MET: washing dishes, playing croquet.
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3 MET: Walking at 3 mph (a fairly typical walking pace).
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4 MET: table tennis, ice skating.
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5 MET: modern dance, fast ballroom dance.
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6 MET: volleyball, tennis in singles.
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7 MET: running, jumping rope.
The numbers go up from there. Speed skating starts at 15 MET. To be clear, you will not be measuring MET directly during exercise . MET studies are conducted in laboratories so that we can use this information to understand what MET values each common type of exercise has.
Moderate physical activity ranges from 3 to 6 METs, and vigorous physical activity is 6 or more.
Physical activity guidelines define “moderate” physical activity as at least 3 METs but less than 6 METs . Vigorous – 6 METS or more.
Since METs depend on the type of activity and not how fit you are, it makes sense to think about METs in terms of the pace of your run or the settings you use on the treadmill or other cardio equipment. Here are the rates and activities that were recorded as 3 to 6 MET:
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Walk at 3 to 4 mph (15 to 20 minute mile)
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Cycling, 50 to 100 W.
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Shooting baskets
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Play baseball
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Low impact aerobic exercise
And these are energetic (6 or more METs):
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Race walking (5+ mph)
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Go uphill
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Walking with a 12 lb Backpack
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Jogging (12 minute mile – 8.0 MET; the faster you run, the higher the MET)
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Cycling at 12 mph or faster
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Swimming rings
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Playing basketball, football or hockey
So how do I know I’m doing moderate exercise if I can’t measure my MET?
I’ll say it again: your fitness watch can’t measure MET. This is why people so often advise targeting “zone 2” instead – it’s not entirely correct , but at least it’s a simple measurement you can read on your watch.
This is actually untrue for two reasons: (1) different gadgets and systems use different thresholds to define “zone 2” and (2) for most of us, zone 2 includes most moderate activities, but also some energetic activities. If you’re fit, you can jog at a pace of 12 minutes per mile while maintaining your heart rate in zone 2. However, from a MET perspective, this is a “vigorous” activity.
Another reason why heart rate is not accurate for this task is that heart rate changes for various reasons. The hotter it is during exercise, the higher your heart rate. The same thing happens when you are nervous or stressed. And as you get fitter, you’ll be able to perform the same activities at a lower heart rate. These steps may seem easier than before, but they are just as much work.
That’s why you should refer to the bullet points above or a more detailed chart like this one . Let’s summarize a couple of dividing lines:
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Walking is moderate, jogging or running is vigorous.
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Cycling is considered moderate if the speed on level ground is less than 12 mph.
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Indoor cycling is considered moderate if its power is around 100 watts.
With all that said, you don’t need to think too much about it. These recommendations, which refer to “moderate” and “vigorous” exercise , do not require you to monitor your heart rate or any other numerical indicator . They want you to think in general terms: walking instead of running, taking a leisurely bike ride instead of sweating it out in the spin studio.
And honestly, if it’s easier to monitor your heart rate than worry about the above, that’s fine. For most of us, 150 minutes of Zone 2 is at least 150 minutes of moderate exercise. So follow this rule and you will succeed.