Buzz
Physical activity is a vital and arguably indispensable aspect of a healthy lifestyle. Public health guidelines recommend targeting a minimum of 150 minutes of ‘moderate’ exercise weekly, with ‘vigorous’ exercise counting twice as much. This naturally leads to the question: What exactly constitutes ‘moderate’ exercise? How can you determine if you’re engaging in it?
Heart rate isn’t the primary factor
A simplified, though not entirely precise, explanation is that ‘moderate’ exercise aligns with ‘zone 2’ cardio, as I’ve detailed before. (Zone 2 represents the second-lowest intensity in a five-zone framework, and identifying your zone requires a heart rate monitor.)
Although ‘zone 2’ and ‘moderate’ encompass broad intensity ranges, they share considerable overlap. If I were to identify which heart rate zone best aligns with ‘moderate’ exercise, I’d choose zone 2. However, this doesn’t imply they are identical.
Scientifically, ‘moderate’ and ‘vigorous’ are quantified using METs
The studies underpinning these guidelines didn’t rely on heart rate as the primary metric. Instead, researchers utilized metabolic equivalents, or METs, to gauge exercise intensity.
One MET represents the energy your body consumes at rest—the oxygen, calories, and other resources required to sustain basic life functions like breathing. (Since oxygen is used in calorie burning, officially, a MET equals 3.2 milliliters of oxygen per kilogram of body weight per minute.)
By fitting individuals with oxygen masks, researchers can measure oxygen consumption during activities like running, walking, playing guitar, and more. If an activity doubles the oxygen usage compared to resting, it’s rated at two METs. Below are some examples (sourced from this scientific paper):
2 MET: doing the dishes, engaging in a game of croquet
3 MET: strolling at 3 miles per hour (a standard walking speed)
4 MET: playing ping pong, gliding on ice skates
5 MET: contemporary dance, energetic ballroom dancing
6 MET: playing volleyball, engaging in singles tennis
7 MET: light jogging, skipping rope
The MET values increase beyond this range. Speed skating, for instance, reaches 15 MET. It’s important to note that you won’t measure METs directly during your workouts. These studies are conducted in controlled lab environments to help us understand the typical MET values associated with various exercises.
Moderate exercise ranges from 3 to 6 MET, while vigorous exercise is classified as 6 MET or higher
According to the physical activity guidelines, ‘moderate’ exercise is defined as activities with at least 3 MET but under 6. Vigorous exercise, on the other hand, starts at 6 MET and above.
Since METs are tied to the activity itself rather than individual fitness levels, it’s most practical to consider METs in relation to your running pace or the settings on your treadmill or cardio equipment. Below are examples of paces and activities that fall within the 3 to 6 MET range:
Walking at a pace of 3-4 mph (equivalent to a 15 to 20-minute mile)
Cycling with an effort between 50 to 100 watts
Practicing basketball shots
Engaging in a game of baseball
Participating in a low-impact aerobics session
The following activities are considered vigorous (6 MET or higher):
Race walking at speeds over 5 mph
Hiking uphill
Walking while carrying a 12-pound backpack
Jogging (a 12-minute mile equals 8.0 MET; increasing speed raises the MET value)
Cycling at 12 mph or faster
Swimming continuous laps
Playing competitive sports like basketball, soccer, or hockey
How can I determine if I’m engaging in moderate exercise without measuring METs?
Let me reiterate: Your fitness tracker cannot measure METs. This is why many recommend aiming for ‘zone 2’—it’s not entirely accurate, but it’s a straightforward metric you can easily monitor on your device.
In practice, this approach has two limitations: (1) various devices and systems apply different thresholds to define "zone 2", and (2) for many individuals, zone 2 encompasses not only moderate activities but also some vigorous ones. For instance, if you’re fairly fit, you might jog at a 12-minute-mile pace while staying within zone 2 heart rate. However, this pace is considered “vigorous” in terms of METs.
Another reason heart rate isn’t a precise indicator is its variability due to multiple factors. Exercising in hotter conditions can elevate your heart rate, as can feelings of nervousness or stress. Additionally, as your fitness improves, you’ll perform the same activities at a lower heart rate. While these activities may feel easier, they still require the same effort.
This is why it’s helpful to consult the bulleted lists above or refer to a more detailed chart like this one. To summarize a few key distinctions:
Walking qualifies as moderate, while jogging or running falls under vigorous.
Cycling is moderate if you’re riding below approximately 12 mph on flat terrain
Indoor cycling is moderate when the power output stays around 100 watts or less
Ultimately, there’s no need to overcomplicate things. The guidelines referencing “moderate” and “vigorous” activities aren’t expecting you to track your heart rate or any specific metrics. Instead, they encourage you to think in broad terms: walking versus running, a relaxed bike commute versus an intense spin class.
Truthfully, if monitoring your heart rate feels simpler than keeping track of the details mentioned earlier, that’s perfectly acceptable. For the majority of people, logging 150 minutes in Zone 2 will likely equate to at least 150 minutes of moderate exercise. By adhering to this guideline, you’ll not only meet but exceed expectations.
