Exercise Intensity for Weight Loss
If you want to jumpstart or sustain weight loss by enhancing your workout routine, most trainers and therapists will recommend increasing your exercise intensity to a moderate or high level. The higher the exercise intensity, the more calories will be burned during a set period of time.
However, all calories are not created equal, and the safest, most appropriate level of exercise intensity for you depends on your health. To reap the most benefits of exercise intensity and improve your physical fitness while shedding excess calories, you need to know where you fall on the spectrum.
What is exercise intensity?
Exercise intensity is the amount of energy the body uses to exercise. The more intense an exercise is, the more physical power someone must expend in order to complete that workout. For example, lifting a 300lb barbell or cycling uphill is more intense than lifting 20lbs or pedaling across a flat stretch of road.
The most accurate measurement of exercise intensity is oxygen consumption (V02), which is the volume or amount of oxygen the body is able to consume. How difficult an exercise feels, or perceived intensity, is generally correlated to heart rate, not oxygen consumption.
Every person has a maximum rate of oxygen consumption (referred to in training forums and on some pedometers as V02 Max) that represents his or her threshold of physical fatigue.
Levels of exercise intensity
There are three levels of exercise intensity: low, moderate, and high. All of these depend on the physical fitness of the individual who is working out.
For a person in average health, low intensity can be achieved during a long, rambling walk. Moderate intensity can be achieved through a brisk walk or jog, and high intensity can be achieved through running.
For someone who is extremely fit, however, a brisk walk may seem like a low-intensity workout, whereas someone who is obese may perceive a long rambling walk as moderate or even high intensity.
Effects of exercise intensity during workouts
When you increase the intensity of aerobic exercises like running, swimming, and cycling, you raise heart rate, oxygen intake, and metabolism, all of which can improve your overall fitness and burn the calories that contribute to weight loss and body composition.
Your level of exercise intensity also determines the type of calories you burn. Low to moderate exercise intensity mainly burns fat, whereas high intensity exercise burns carbohydrates.
If you want to lose fat, you may jump to the conclusion that moderate intensity exercise is best for fat loss. This is only true for obese individuals, as their carbohydrate metabolism differs drastically from that of healthy individuals.
Individuals who have already achieved a healthy weight should focus on high intensity exercise that burns carbohydrates. This will condition the body to spare carbohydrates during rest and burn fat instead.
High intensity exercise also results in higher overall fitness, which allows you to exercise at a higher percent of oxygen intake without reaching your point of fatigue. The longer you exercise at these high V02 levels, the more calories you’ll burn in a given time period.
Effects of exercise intensity after workouts
The intensity and duration of exercise increases oxygen intake after as well as during workouts. This elevation is different than that which occurs mid-workout; metabolic processes like replenishing energy stores in the cells, converting lactate back into glycogen, and re-loading oxygen into muscles help the body adjust to its non-working out state.
Low intensity exercise does not create much oxygen debt, but on average, people who perform moderate to intense exercise for more than 60 minutes have elevated oxygen intake for up to 24 hours afterward. However, these elevated V02 levels burn negligible calories (up to 75 calories for every 80 minutes of exercise).
The real benefit of these lingering effects is your ability to recover more quickly. The fitter you are, the faster VO2 will return to resting values and the sooner you can complete another round of intense exercise.
What exercise intensity is right for me?
Your overall health and fitness level must dictate your approach to intensity training. It is very possible to overextend yourself and suffer burnout or setbacks. The goal is to be able to exercise consistently and repeatedly at a high to moderate level, increasing your overall fitness and capacity for high intensity training over an extended period of time.
Although it’s true that higher intensity exercises will burn more calories, obese individuals can focus on burning fat calories at moderate intensity. Remember, the difficulty of a workout is determined largely by your own perceived exertion.
Healthy weight individuals, on the other hand, should aim for high intensity workouts that train their bodies to burn carbohydrates during exercise and fat during rest while contributing to fast recovery times and their overall fitness.
As always, consult your doctor or physical therapist before embarking on a new fitness program.
McArdle, Katch, and Katch Exercise Physiology: Nutrition, Energy, and Human Performance 7th Edition. Lippincott Williams & Wilkins, Philadelphia 2010.
Mayo Clinic Staff. Exercise Intensity: how to measure it. Mayo Clinic. http://www.mayoclinic.org/healthy-living/fitness/in-depth/exercise-intensity/art-20046887