EXERCISE INTENSITY: How to measure it

Exercise intensity refers to how much energy is expended when exercising or defined by the amount of energy required for the performance of the physical activity per unit of time. Perceived intensity varies with each person. It has been found that intensity has an effect on what fuel the body uses and what kind of adaptations the body makes after exercise.

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

In order to determine the intensity level with which you need to exercise, you’ll first have to ask yourself what is the main reasons for you to exercise? What are you trying to archive? What is your goals? Your desired "results" are? Do you want to improve your fitness by increased strength and endurance, lose weight, train for a competition or do a combination of these? Your answer will help determine the appropriate level of exercise intensity and the effects of exercise are different at each intensity level.

All exercise is NOT created equal. Exercise has to force the body to make a positive adaptation.

But remember, 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.

Be realistic and don't push yourself too hard, too fast. Fitness is a lifetime commitment, not a sprint to a finish line. Make it as your lifestyle, a healthy lifestyle. 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 method to measure or determine the level of your exercise intensity:

1. Gauging by how you feel

2. Gauging by heart rate

Gauging Intensity by How You Feel

Here are some clues to help you to track of your exercise intensity.

Low intensity exercise

Easy activity feels so relaxing and comfortable:

• Your breathing easily.

• You develop a light sweat after about 30 minutes of activity.

• You can carry on a conversation comfortably.

Exercise example: a beginners' yoga class or tai chi, bike riding or using a cross trainer (aka an elliptical) at an easy pace.

Moderate intensity exercise

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.

Exercise example: weight training, or endurance exercise - things like jogging, cycling, or lap swimming.

Vigorous intensity exercise

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.

Exercise example: sprints in the park or up the length of the pool, HIIT & Tabata.

Exercise Intensity Level

Overexerting yourself

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 method 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.

Calculate your Maximum Heart Rate

You can calculate your maximum heart rate by subtracting/minus your age from 220. For example, if you're 20 years old, subtract/minus 20 from 220 to get a maximum heart rate of 200.

220 - 20 (your age) = MaxHR 200 bpm

Your Maximum HR (MaxHR) would be approximately 200 beats per minute/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.

Heart Rate Zones

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

Here's a simple way to do the math yourself. For moderate-intensity physical activity, your target heart rate should be between 65% and 75% of your maximum heart rate.

a) Calculate Maximum Heart Rate

Subtract your age from 220 to get your maximum heart rate.

For example, for a 20-year-old person, the estimated maximum age-related heart rate would be

220 - 20 (age) = MaxHR 200 bpm

b) Multiply percentage range of exercise intensity

• 65% : 200 x 0.65 = 130 bpm, and

• 75% : 200 x 0.75 = 140 bpm

This shows that moderate-intensity physical activity for a 20-year-old person will require that the heart rate remains between 130 and 140 bpm during physical activity.

b) Taking Your Heart Rate

Generally, to figure out whether you are exercising within the target heart rate zone, you can use an activity tracker to check your heart rate or take your pulse.

Here's how to do it:

1. Place your index and middle finger on your wrist or neck and press lightly over the artery. Refrain from moving or talking.

2. When you feel a consistent pulse, keep your two fingers in the same spot.

3. Using a timer to keep track, count your pulse for 30 seconds. Multiply that number by 2 to calculate your heart rate in beats per minute.

4. Start the count on a beat, which is counted as “zero.”

For example, if this number falls between 130 and 140 bpm in the case of a 20-year-old person, he or she is active within the target range for moderate-intensity activity. If you're under or over your target heart rate zone, adjust your exercise intensity.

Source: Centers for Disease Control and Prevention

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.