Exercise intensity: How to measure it
Date Updated: 06/17/2021
When you exercise, are you working hard or hardly working? Exercising at the correct intensity can help you get the most out of your physical activity — making sure you're not pushing too hard or too little. Here's a look at what exercise intensity means, and how to maximize your workout.
Choosing your exercise intensity
How hard should you be exercising? The Department of Health and Human Services recommends these exercise guidelines for most healthy adults:
Aerobic activity. Get at least 150 minutes a week of moderate aerobic activity — such as brisk walking, swimming or mowing the lawn — or 75 minutes a week of vigorous aerobic activity — such as running or aerobic dancing. You can also do a combination of moderate and vigorous activity. It's best to do this over the course of a week. You can achieve more health benefits if you ramp up your exercise to 300 minutes or more of moderate aerobic activity a week.
Even small amounts of physical activity are helpful, and accumulated activity throughout the day adds up to provide health benefits.
- Strength training. Do strength training for all major muscle groups at least twice a week. Consider free weights, weight machines or activities that use your own body weight — such as rock climbing or heavy gardening. Or try squats, planks or lunges. Aim to do a single set of each exercise, using a weight or resistance level heavy enough to tire your muscles after about 12 to 15 repetitions.
Your exercise intensity must generally be at a moderate or vigorous level for maximum benefit. For weight loss, the more intense or longer your activity, the more calories you burn.
Balance is still important. Overdoing it can increase your risk of soreness, injury and burnout. Start at a light intensity if you're new to exercising. Gradually build up to a moderate or vigorous intensity.
Consider your reasons for exercising. Do you want to improve your fitness, lose weight, train for a competition or do a combination of these? Your answer will help determine the appropriate level of exercise intensity.
Be realistic and don't push yourself too hard, too fast. Fitness is a lifetime commitment, not a sprint to a finish line. Talk to your doctor if you have any medical conditions or you're not sure how intense you should exercise.
Understanding exercise intensity
When you're doing aerobic activity, such as walking or biking, exercise intensity correlates with how hard the activity feels to you. Exercise intensity is also shown in your breathing and heart rate, whether you're sweating, and how tired your muscles feel.
There are two basic ways to measure exercise intensity:
- How you feel. Exercise intensity is a subjective measure of how hard physical activity feels to you while you're doing it — your perceived exertion. Your perceived exertion level may be different from what someone else feels doing the same exercise. For example, what feels to you like a hard run can feel like an easy workout to someone who's more fit.
- Your heart rate. Your heart rate offers a more objective look at exercise intensity. In general, the higher your heart rate during physical activity, the higher the exercise intensity.
Perceived exertion may not always be similar to your heart rate level, and it depends on the individual. But it can be a general guide to measure your exertion level. If you think you're working hard, your heart rate is probably higher than usual.
You can use either way of gauging exercise intensity. If you like technology, you can check your heart rate with an activity tracker that includes a heart rate monitor. If you feel you're in tune with your body and your exertion level, you'll likely do fine without a monitor.
Gauging intensity by how you feel
Here are some clues to help you judge your exercise intensity.
Moderate exercise intensity
Moderate activity feels somewhat hard. Here are clues that your exercise intensity is at a moderate level:
- Your breathing quickens, but you're not out of breath.
- You develop a light sweat after about 10 minutes of activity.
- You can carry on a conversation, but you can't sing.
Vigorous exercise intensity
Vigorous activity feels challenging. Here are clues that your exercise intensity is at a vigorous level:
- Your breathing is deep and rapid.
- You develop a sweat after only a few minutes of activity.
- You can't say more than a few words without pausing for breath.
Beware of pushing yourself too hard too often. If you are short of breath, are in pain or can't work out as long as you'd planned, your exercise intensity is probably higher than your fitness level allows. Back off a bit and build intensity gradually.
Gauging intensity using your heart rate
Another way to gauge your exercise intensity is to see how hard your heart is beating during physical activity. To use this method, you first have to figure out your maximum heart rate — the upper limit of what your cardiovascular system can handle during physical activity.
You can calculate your maximum heart rate by subtracting your age from 220. For example, if you're 45 years old, subtract 45 from 220 to get a maximum heart rate of 175. This is the average maximum number of times your heart should beat per minute during exercise.
Once you know your maximum heart rate, you can calculate your desired target heart rate zone — the level at which your heart is being exercised and conditioned but not overworked.
The American Heart Association generally recommends a target heart rate of:
- Moderate exercise intensity: 50% to about 70% of your maximum heart rate
- Vigorous exercise intensity: 70% to about 85% of your maximum heart rate
If you're not fit or you're just beginning an exercise program, aim for the lower end of your target heart rate zone. Then, gradually build up the intensity. If you're healthy and want to exercise at a vigorous intensity, opt for the higher end of the zone.
How to determine your target heart rate zone
Use an online calculator to determine your desired target heart rate zone. Or, here's a simple way to do the math yourself. If you're aiming for a target heart rate in the vigorous range of 70% to 85%, you can use the heart rate reserve (HRR) method to calculate it like this:
- Subtract your age from 220 to get your maximum heart rate.
- Calculate your resting heart rate by counting how many times your heart beats per minute when you are at rest, such as first thing in the morning. It's usually somewhere between 60 and 100 beats per minute for the average adult.
- Calculate your heart rate reserve (HRR) by subtracting your resting heart rate from your maximum heart rate.
- Multiply your HRR by 0.7 (70%). Add your resting heart rate to this number.
- Multiply your HRR by 0.85 (85%). Add your resting heart rate to this number.
- These two numbers are your average target heart rate zone for vigorous exercise intensity when using the HRR to calculate your heart rate. Your heart rate during vigorous exercise should generally be between these two numbers.
For example, say your age is 45 and you want to figure out your target heart rate zone for vigorous exercise using the HRR method. Follow these steps:
- First, subtract 45 from 220 to get 175 — this is your maximum heart rate.
- Next, check your resting heart rate first thing in the morning. Say it's 80 beats per minute. Calculate your HRR by subtracting 80 from 175. Your HRR is 95.
- Multiply 95 by 0.7 (70%) to get 66.5, then add your resting heart rate of 80 to get 146.5.
- Now multiply 95 by 0.85 (85%) to get 80.75, then add your resting heart rate of 80 to get 160.75.
- Your target heart rate zone for vigorous exercise is 146.5 to 160.75 beats per minute.
How to tell if you're in the zone
So how do you know if you're in your target heart rate zone? You can use an activity tracker to check your heart rate regularly while you exercise.
Or use these steps to check your heart rate during exercise:
- Stop briefly.
- Take your pulse for 15 seconds. To check your pulse over your carotid artery, place your index and third fingers on your neck to the side of your windpipe. To check your pulse at your wrist, place two fingers between the bone and the tendon over your radial artery — which is located on the thumb side of your wrist.
- Multiply this number by 4 to calculate your beats per minute.
Here's an example: You stop exercising and take your pulse for 15 seconds, getting 37 beats. Multiply 37 by 4, to get 148. If you're 45 years old, this puts you in the target heart rate zone for vigorous exercise, since the target zone for that age is between 146.5 and 160.75 beats per minute using the HRR method. If you're under or over your target heart rate zone, adjust your exercise intensity.
Target heart rate tips
It's important to note that maximum heart rate is only a guide. You may have a higher or lower maximum heart rate, sometimes by as much as 15 to 20 beats per minute. If you want a more specific range, consider discussing your target heart rate zone with an exercise physiologist or a personal trainer.
Generally only elite athletes are concerned about this level of precision. They may also use slightly different calculations that take into account sex differences in target heart rate zones. These differences are so small that most casual athletes don't need separate calculations for men and women.
Also note that several types of medications, including some medications to lower blood pressure, can lower your maximum heart rate, and then lower your target heart rate zone. Ask your doctor if you need to use a lower target heart rate zone because of any of your medications or medical conditions.
Interestingly, research shows that interval training, which includes short bouts (around 15 to 60 seconds) of higher intensity exercise alternated with longer, less strenuous exercise throughout your workout, is well tolerated. It's even safe for those with heart disease and type 2 diabetes. This type of training is also very effective at increasing your cardiovascular fitness and promoting weight loss.
Reap the rewards of exercise intensity
You'll get the most from your workouts if you're exercising at the proper exercise intensity for your health and fitness goals. If you're not feeling any exertion or your heart rate is too low, pick up the pace. If you're worried that you're pushing yourself too hard or your heart rate is too high, back off a bit.
Before starting a vigorous exercise program, you may want to talk with your doctor. He or she may suggest that you have certain tests first. This may be the case for people who have diabetes or more than one risk factor for heart disease, and for men over age 45 and women over age 55.