Calories are an important piece of information when trying to lose or gain weight. Knowing how many calories you consume versus how many you expend determines the rate at which you lose or gain. While it is fairly easy to record the calories that you consume, determining how many you expend presents a challenge. Heart rate watches can be helpful, as there is a linear relationship between your heart rate and oxygen consumption, and the watches can very accurately assess heart rate. Oxygen consumption may then be converted to calories burned. Always consult with your physician before beginning any exercise program.
Performing exercise at a heart rate of 50 to 60 percent of your maximum heart rate is considered low intensity. At this level of intensity, the body primarily utilizes calories stored as body fat for energy. While burning fat sounds ideal, it is important to note that not as many total calories are burned during a low-intensity bout of exercise compared to something of higher intensity. At this intensity, you will burn approximately three to five calories per minute, or 90 to 150 calories per 30-minute bout. Many heart rate watches require the user to stop, press a button on the watch and wait for a reading. This can be a challenge during very intense exercise but works well during low-intensity exercise, making a heart rate watch a reliable option for determining heart rate and calories burned.
Moderate-intensity exercise is exercise performed between 60 and 70 percent of maximum heart rate. This higher intensity is not quite as comfortable as low intensity but is not an all-out effort. At this rate, you can expect to burn between seven and nine calories per minute, or 210 to 270 calories per 30-minute bout. Performing moderate-intensity exercise not only burns more calories but it also allows for greater gains in fitness levels by challenging the cardiovascular system. In order for a heart rate watch to get an accurate reading, it needs to be placed snugly on the wrist and remain there for several seconds while a reading is taken. As exercise intensity increases, it is harder to remain still enough to get an accurate reading while continuing to exercise. It may be necessary to stop exercising for several seconds while a reading is being taken.
Exercising at 70 to 80 percent of maximum heart rate is considered high intensity. While this is the most challenging level to maintain comfortably, it is also the most effective at burning calories. At this level you can expect to burn between 10 and 12 calories per minute, or 300 to 360 per 30-minute bout. While exercising at a high intensity would seem ideal for burning calories and losing weight, it can be very challenging to maintain over time. At this level of intensity, you would have to stop exercising momentarily to allow a heart rate watch to measure heart rate and calories accurately. Exercisers who prefer higher-intensity activities should use a chest strap type of heart rate monitor for the most accurate heart rate and calorie burn assessments.
If the goal is to burn as many calories as possible, interval training may offer the best option. Mixing short bursts of high-intensity exercise between recovery periods of low or moderate exercise will allow you to exercise for a longer duration while still burning a higher rate of calories. Beginners should consider shorter intense bouts with longer recovery periods while more advanced exercisers should decrease the recovery or increase the intense bouts. Not only does interval training allow for maximum calorie burn, but it also works to strengthen the heart and improve your fitness level. Wristwatch heart rate monitors would work during intervals if readings were taken during the recovery periods when it is easier to keep the arm still. This would, however, skew the reported number of calories being burned, because the higher heart rates achieved during the intense bouts would not be recorded and converted into calories. As with intense exercise, strap heart rate monitors would be a more reliable option for interval training.
- American Council on Exercise: Are the Calorie Counts on Exercise Machines Accurate?
- American Council on Exercise: I’ve Heard That Performing Aerobic Workouts at a Low Intensity is Best for Losing Body Fat -- Is That True?
- American Council on Exercise: Heart Rate Myth
- American Council on Exercise: High-Intensity Interval Training
- Consumer Reports: Heart-Rate Monitors