Why Exercise Intensity Is Important

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Exercise intensity is one of the important components of your workout program. It's the "I" in the F.I.T.T. (Frequency, Intensity, Time, Type) Principle, a set of guidelines that can help you set up a workout routine. Measuring your workout intensity and using that information to plan your future workouts can help you reach your fitness goals.

What Is Exercise Intensity?

Intensity is probably the most important element of your workout. When you work out at a sufficient intensity, your body grows stronger and you'll see changes in your weight, body fat percentage, endurance, and strength. Exercise intensity is usually described as low, moderate, or vigorous.

Low Intensity Exercise

Low intensity exercise raises your heart rate mildly and then keeps it steady. It is fairly slow-paced. Examples of low intensity exercises include:

  • Walking at a leisurely pace
  • Riding a bike on flat ground
  • Lifting light weights
  • Using an elliptical machine at a slow pace

Moderate Intensity Exercise

A moderate intensity workout raises your heart rate. You will be sweating, breathing heavier, and moving at a quicker pace. You may not be able to talk easily, and you will feel warm. Examples of moderate intensity exercises are:

  • Hiking
  • Brisk walking
  • Biking at 10 miles per hour or less
  • Water aerobics

Vigorous Intensity Exercise

Vigorous intensity exercise gets your heart pumping, elevates your heart rate, and leaves you breathing hard. When working out at more intense levels, you will likely not be able to talk for long stretches without needing to take a breath. Examples of vigorous intensity exercises include:

  • Running
  • Swimming
  • Jumping rope
  • Cycling faster than 10 miles per hour

Benefits of Moderate and Vigorous Intensity Exercise

Increasing the intensity of your workouts can have many benefits. Regular moderate to vigorous exercise offers health advantages.

  • Improved mood: Studies have shown that increasing the intensity of a physical activity can have a positive impact on mood and lower symptoms of depression.
  • Increased calorie burn and metabolic rate: A small study examined 10 male subjects and found that 45-minute vigorous exercise resulted in higher calorie burn and a post-workout energy expenditure that lasted for 14 hours.
  • Lower mortality risk: A 2019 research review examined how vigorous and moderate exercise affected mortality risk and found that higher intensity workouts, in particular, lowered the risk of death.

How Hard Should You Work?

How hard you work out during any fitness session depends on a variety of factors. Your current fitness level, any physical limitations, and your fitness goals all affect desired workout intensity. And it's also important to vary your workouts and intensity levels to decrease the risk of injury and burnout.

Adults should participate in both aerobic (cardio) and muscle-strengthening workouts every week to improve their health, according to the Centers for Disease Control (CDC). The CDC recommends at least 150 minutes of exercise per week (that's 30 minutes a day for five days, but you can schedule it any way that works for you).

Important Safety Precautions

If you begin to feel dizzy or nauseous, are experiencing any pain, have trouble breathing, or have sudden cramps, stop your workout. Rest momentarily and if your symptoms do not subside, contact a medical professional.

How to Measure Exercise Intensity

It's helpful to monitor your intensity while exercising to make sure you're getting an effective workout. Unfortunately, it's one of the harder elements of exercise to measure. There are several choices, but none of them are perfect. It often takes a combination of methods to really get a sense of how hard you're working.

Heart Rate

Using a percentage of your maximum heart rate (MHR) is probably the most widely used method of tracking intensity. It's simple, as long as you have a heart rate monitor device. For this method, you use a formula such as the Karvonen Formula to determine your target heart rate zone—the heart rate zone you try to work within to get the most effective workout.

The drawbacks: Formulas used to calculate target heart rate are imperfect and can be off by as much as 12 beats per minute. And you'll need a heart-rate monitor (with chest strap, for greater accuracy) or fitness tracker, unless you want to take your pulse regularly and do some calculations.

Heart rate monitors and fitness trackers that detect your heart rate use it as the basis for displaying your exercise intensity.

Talk Test

This is a very easy test to figure out your intensity: Just pay attention to how breathless you are. If you can easily talk, you're working at a light intensity, which is fine for a warm-up. If you can talk, but it's a little harder, you're getting more into the moderate zone. If you can only speak in short sentences, that's right about where you want to be for a vigorous workout.

If you're doing high-intensity interval training, that may include some breathless or anaerobic intervals where talking is out of the question. This is the high end of the intensity spectrum.

Perceived Exertion

Your rating of perceived exertion (RPE), refers to how hard an exercise feels. The standard scale is the Borg Scale of Perceived Exertion, which ranges from 6-20 and is designed to help you estimate your heart rate by multiplying the rating by 10. If you're at a 15 on the Borg scale, you're working pretty hard (say, running) and your heart rate is an estimated 150 beats per minute (15 x 10).

You could also use a 1-10 scale, which is a little simpler. The idea is to check in and ask yourself how hard you're working. If you're very comfortable, maybe you're at a level 3 or 4. If you feel like you're exercising, but are still just in your comfort zone, you may be at a level 5. If you're sweating and very breathless, you might be at a Level 8 or 9.

Frequently Asked Questions

How can you increase the intensity of exercise?

Increase the intensity of your workout by adding speed or difficulty. That could mean boosting your running speed, increasing the weight you're lifting, or walking or hiking at a steeper incline.

Where do muscles get their energy during high intensity exercise?

For quick bursts of energy, your muscles will pull from adenosine triphosphate (ATP) stores. Carbohydrates are most often converted into ATP for moderate and high intensity workouts.

How do you monitor exercise intensity?

You can monitor your exercise intensity by using any of the three main test methods: measuring your heart rate, doing the talk test, or checking your rating of perceived exertion.

A Word From Verywell

Exercise intensity is just one important aspect of fitness. Understanding the benefits of increased intensity and how to measure it can help you get the most out of your workout and achieve your fitness goals more efficiently.

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5 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Heart Association. American Heart Association recommendations for physical activity in adults and kids.

  2. Noh J-W, Lee SA, Choi HJ, Hong JH, Kim MH, Kwon YD. Relationship between the intensity of physical activity and depressive symptoms among Korean adults: Analysis of Korea Health Panel data. J Phys Ther Sci. 2015;27(4):1233-1237. doi:10.1589/jpts.27.1233

  3. Knab AM, Shanely RA, Corbin KD, Jin F, Sha W, Nieman DC. A 45-minute vigorous exercise bout increases metabolic rate for 14 hours. Med Sci Sports Exerc. 2011;43(9):1643-1648. doi:10.1249/MSS.0b013e3182118891

  4. Rey Lopez JP, Gebel K, Chia D, Stamatakis E. Associations of vigorous physical activity with all-cause, cardiovascular and cancer mortality among 64 913 adults. BMJ Open Sport Exerc Med. 2019;5(1). doi:10.1136/bmjsem-2019-000596

  5. Centers for Disease Control and Prevention. How much physical activity do adults need?.

Additional Reading
  • American Council on Exercise. ACE Personal Trainer Manual, 5th Edition. American Council on Exercise, 2014.