Is high-intensity exercise always best?

Experts explain the difference between low-, moderate-, and high-intensity exercise (and the health benefits of each).

Fitness is about starting to move your body. It’s not just about how much and what type of exercise you do, but how hard you do it. Exercise and physical activity are often divided into three different types of intensity: low, moderate, and high (sometimes called “vigorous”). But knowing exactly which type of activity falls into which intensity bucket can be tricky.

For example, the World Health Organization (WHO) 2020 guidelines on physical activity and sedentary behavior recommend that able-bodied adults get between 150 and 300 minutes of moderate-intensity exercise per week (i.e. about 21 to 43 minutes per day) or 75 to 150 minutes per week. minutes of high-intensity aerobic exercise. 1 But how can you be sure that the exercise you choose is really vigorous enough? Are your cardio levels too vigorous? Is high intensity always best, or can a good low-impact walk get the job done? Do the same guidelines apply to beginners and fitness enthusiasts? So many questions.

Knowing what each type of exercise intensity means and learning how to structure your fitness program accordingly will help you get the most out of the workouts you do. We asked health and fitness experts to break them down, explain why they’re important, and share how you can apply them to your everyday life.

1. Overview of exercise intensity
Intensity has to do with how hard you’re working out when you exercise, or actually, how hard your heart is working. The three levels run from easiest to hardest, and there are two ways to measure them, either a “talking test” or measuring your heart rate.

The talk test is probably the easiest way to gauge intensity, since you just have to figure out how easy it is to speak in whatever activity you’re doing. At low intensity, you’re moving, but you’re still able to carry on a conversation.

While you shouldn’t be completely out of breath when you get into moderate-intensity activity, you won’t be able to carry on a conversation easily. Your sentences may be interrupted slightly by intermittent but controlled, heavier breathing. If you move with high or violent intensity, you won’t be able to carry on a conversation at all).

Exercise intensity can also be more technically determined by heart rate: the rate at which your heart beats in a minute (that is, beats per minute). Heart rate monitors make measuring your resting and working heart rate a simple task (smartwatches like the Apple Watch often have this handy feature). But if you don’t have a monitor, you can do some old-fashioned counting. Simply find your pulse on your wrist or neck and count the number of heartbeats for 10 seconds; then multiply that number by 6 to get beats per minute.

2. Know your maximum heart rate and exercise intensity
Knowing all of this, the next step is to calculate your maximum heart rate (MHR): the point of maximum intensity you should reach during exercise.

Exercise intensity is calculated as a percentage of your maximum heart rate during physical activity, the higher the percentage, the harder your body is working.

To determine what your body’s maximum heart rate should be, subtract your age from 220.

For example, if you are 40, your estimated MHR is about 180 beats per minute. Now, once you know your personal MHR, you can use it to gauge how many beats you should be striving for during activities, depending on their intensity. Here’s the breakdown:

low intensity
Low intensity is calculated as working around 30% to 50% of the MHR. Multiply your MHR by 0.30 and then by 0.50 to determine your heart rate zone, Walker says.

Sticking with the example above, if you are 40 and the MHR estimates about 180 beats per minute, multiply 180 by .30 (=54), then by .50 (=90). The results of it? A hypothetical healthy 40-year-old should maintain a heart rate between 54 and 90 beats per minute during low-intensity exercise. Low-effort cardio usually involves repetitive moves at a slower, more steady pace: leisurely walking (where you can still have a conversation), light yoga, low-resistance cycling, or laps at a leisurely pace. You’re moving, but you’re not panting and panting.

medium intensity
With moderate-intensity aerobic exercise, your heart works harder — though not at maximum capacity — at about 50 to 70 percent of your MHR. Common activities include brisk walking or hiking, aerobic dancing, doubles tennis, biking (slower than 10 mph, according to the American Heart Association), and even strenuous yard or housework.

high strength
Finally, high intensity means you’re training at 75 to 100 percent of your MHR (the average 40-year-old’s heart should be beating between 135 and 180 beats per minute). This type of strenuous exercise often involves short, quick bursts of practice in which you quickly lose track of your goals, Walker says. You should be working hard, breathing fast and heavily, sweating, and unable to maintain a conversation. For example, you might jump rope, run the stairs, do a HIIT (high-intensity interval training) workout, play singles tennis, run, or bike at 10 miles per hour or faster.

3. Benefits of each intensity level
Each type of exercise intensity affects the body differently. While they all have benefits, what you do with each depends largely on your current fitness level and goals.

low intensity
Beginners should start with a low intensity, which is good not only for fitness novices, but also for experienced athletes. Think of low-intensity exercise as setting the stage for more intense activity.

Low-intensity exercise can reduce the risk of injury while preparing your body for more intense activity, adding that it primarily burns fat cells as a fuel resource. It also builds your stamina, which you’ll need as you progress through your fitness program, as it activates your aerobic system. It is also critical for athletes of specific sports. “If you’re training for any sport that requires prolonged activity, you need aerobic training to handle that level of fitness required.”

medium intensity
When you switch to moderate-intensity exercise, your body starts using fat, carbohydrates, and sugar as fuel sources. “Burning calories from all of these sources can help achieve faster weight loss,” Walker says. More moderate activity is required to reap more health benefits (the higher the intensity, the less time it takes to achieve those exercise rewards).

high strength
However, once you get into high-intensity exercise, you will reach your full potential. Not only will this stimulate your body’s optimal response to fat loss and muscle gain, it will also boost your metabolism for hours after your workout. With maximal volume training, you increase your potential for muscle growth and weight loss by breaking down more muscle fibers, adding that it’s an excellent way to maintain lean muscle mass and improve body composition.

4. Apply it to your fitness routine
So, how do you know what intensity to play when exercising? While it depends on your health, current fitness level and personal goals, some guidelines can help. (Note: Always consult your physician if you have any questions or concerns about the strength that is right for you and your health.

According to the 2018 Physical Activity Guidelines for Americans, which echo WHO global guidelines, adults should get at least 150 to 300 minutes per week of moderate-intensity activity, 75 to 150 minutes of vigorous-intensity exercise, or a combination of both. (Guidelines also recommend that you engage in muscle-strengthening activities at least two days a week. Even the American Heart Association and American College of Cardiology have exercise prescriptions that recommend 30 minutes of moderate-intensity exercise five to seven days a week.

Of course, if you’re just starting an exercise program, always start with low-intensity exercise and work your way up. This also applies if you’re recovering from a health issue like an injury or heart attack.

Once you get past this point, your personal goals will largely determine your exercise program and the intensity of your workouts. Follow the guidelines above if you want to achieve optimal health. However, if you have sport-specific goals, you may need something different.

The only thing to watch out for? While high-intensity exercise is good for the body, including your heart, you don’t want to overdo it. Extreme cardio is taxing on the body and it takes time for the body to recover from it. Walker recommends no more than three high-intensity workouts per week, spaced one day apart.

On the other hand, prolonged periods of low-intensity exercise unfortunately don’t confer the same benefits as high-intensity activity (even moderate intensity). These two intensity levels stimulate different responses in the body, and while you may improve your cardiovascular fitness if you do too much low-intensity exercise, you may deplete your muscle tissue, Walker says.

The most important thing, though, is not to get too attached to the numbers – find the motivation to get up and exercise regularly, as much as you can. Intensity aside, all movements count.