At one point in our lives, we have all been introduced to the concept of heart rate; whether it was middle school health class or stepping on a treadmill for the first time and seeing a picture depicting the different heat rate zones. Those graphs displayed on cardio equipment and the gym posters show what's called a fat burning zone. Most people think in order to burn fat; they need to keep their heart rate in a specific range.
But, heart rate is one of the most misunderstood concepts when it comes to fitness. To understand it, first you have to know how to find it and what it means. You can measure your resting heart rate by locating an artery’s pulse. The easiest ones to find are on the neck and on the wrist. The number is based on how many times the lower chambers of the heart contract per minute.
Heart rate is affected by your body’s need for oxygen, your fitness level, what activity you are doing, if you are standing up or lying down and if you are under stress. Even the temperature and medication can affect the number. A normal resting rate has a pretty big range: anywhere from 60 to 100 beats per minute. Between 68 and 72 tends to be the average, with athletes logging even lower numbers, often in the 40s. In most cases, a low heart rate is indicative of good cardiovascular health. It means more efficient heart function (your heart is working less but still doing its job) and a higher level of fitness.
When trying to determine exercise intensity, many people try to calculate the heart rate maximum. There are a couple formulas that health professionals use, but, the easiest one is take the number 220 and subtract your age. So, for a 20 year old, an estimated heart rate max would be 200 beats per minute. Remember, this is just an estimate.
So, back to the fat burning theory… there is a perpetuating myth that if you stay within a certain percentage of your heart rate max (it can range anywhere from 50-65%) you will burn strictly fat for fuel. But it’s not all that simple.
What your body uses for fuel depends on a whole set of factors and its too simplistic to state that remaining within a certain set of numbers is going to guarantee 100 percent fat loss. It depends on how much you just ate and what that meal comprised of, how long you are exercising for, and if you are doing weights, cardio, or a combination of both. Plus you have to take in account if you used stimulants or medication, both which effect heart rate.
But, assuming normal metabolic function and hormone levels, you don’t burn as many calories at a lower heart rate. After all, your body isn’t working as hard. At the end of the day, to lose fat you are going to have to be in a deficit. So, it doesn’t make much sense to work at a low heart rate for 60 minutes and burn 200 calories, if you can work at a medium to high intensity heart rate for 60 minutes and burn 500 calories. Over a period of time, that higher deficit is going to result in more fat loss.
In addition to fat loss, knowing your heart rate can improve your cardiovascular health. In this case, you want to exercise in what's called your Target Heart Rate Zone. Some call this the Aerobic Zone; others Zone 3. Don't get caught up on the title; just know it's usually between 65% to 80% of your maximum heart rate. Exercising in this zone increases your aerobic capacity allowing you to exercise longer and workout harder at lower heart rates.
If you perform work at roughly 80 to 90% of your heart rate or more you are doing High Intensity exercise and have moved into the Anaerobic Zone. Many athletes work in this zone and it places a high demand on your cardiovascular system. It doesn't burn much fat; instead it draws upon other fuel sources. You can't sustain this heart rate very long. In fact, a great example of when you might reach these numbers is interval training...where you sprint hard for 30 seconds, then recover, and repeat.
If you want to measure your heart rate, you can purchase a monitor from a sporting goods store. There are also several companies that sell special devices you can wear all day to calculate your heart’s output and estimate calorie burn based on that. You can also grab hold of the metal handles on cardio machines every couple of minutes to get an idea of where your heart rate falls. Those tend to be less accurate, but can give you an idea if you are curious how hard you are working.
Of course, how hard and how often you exercise depend on your goals. But, at the end of the day you’re doing well if you have a healthy resting heart rate and make some effort to get cardio in a few times a week. For ideas on how to get started, email the author at firstname.lastname@example.org.
Michelle Fiscus writes a regular column for fredericknewspost.com. Michelle and her husband own a personal training and nutrition business based in Frederick County and hold industry certifications and credentials.