Exercise expenditure is categorized into several different zones, which correspond to various percentages of your maximum heart rate. Your maximum heart rate (MHR) is the highest number of beats per minute your heart would beat if you were running as fast as possible. The process for obtaining your MHR can be as simple as using a predictive formula or as involved as a comprehensive test that measures your endurance capacity (VO2 Max).
Fitness expert Mackie Shilstone, executive director of the Fitness Principle with Mackie Shilstone at East Jefferson General Hospital, explains that by measuring VO2 Max through specialized equipment and testing, experts at the Fitness Principle can pinpoint, among other variables, the MHR and therefore have the most accurate data for determining appropriate heart rate zones to optimize fat utilization. "Our goal is to determine the ventilatory threshold or defection point, which will help us to determine when we shift toward higher carbohydrate utilization and less fat as a fuel source," Shilstone says.
The average person interested in target heart rate zones for weight control and fitness can probably forgo high-tech testing. People interested in weight control can opt for the Karvonen method, a simple calculation anyone can use to estimate his or her MHR and target heart rate zones.
Heart rate zones are based on a percentage of your MHR. According to the American Heart Association, optimum heart rate zones for fitness should be between 50 and 85 percent. Although these numbers vary from individual to individual and even within the course of a person's life, most people cannot sustain a heart rate of 90 percent or higher for very long. Conversely, heart rates under 50 percent may not be high enough for effective exercise.
To calculate target heart rate zones, you must establish your resting heart rate (RHR), your maximum heart rate (MHR) and your heart rate reserve (HRR). First find your resting heart rate by taking your heart rate first thing in the morning before you get up or by taking it after lying down for 20 minutes. To establish your maximum heart rate, subtract your age from 220. The MHR equation for a person 30 years of age is 220 - 30 = 190.
Find your heart rate reserve by subtracting your resting heart rate from your maximum heart rate. For example, if a 30-year-old has a resting heart rate of 70, the equation for HRR would be 190-70=120
Then, to determine a heart rate zone at 60 percent, multiply your heart rate reserve by 60 percent and add it back to your resting heart rate. For this example, the formula would be (120 x .60) + 70= 142. In this scenario, a heart rate of 142 means this person is exercising at 60 percent. Repeat this equation for 70, 80 and 90 percent to determine all of your target heart rate zones.
"The higher you go above your defection point heart rate, the less you rely on fat as fuel," Shilstone says. That is not to say you aren't burning plenty of calories when you exercise at higher rates, but you tend to burn more carbohydrates and less fat stores. "Sometimes less is more if you can go longer," Shilstone says. The key for calorie burning is to move your body at a specific intensity for at least of 270 minutes a week.
Shilstone recommends an easy, safe and effective technique to help you optimize fat utilization during exercise. Known as the talk test, the method is derived from track coach and Nike cofounder Bill Bowerman and simply means pushing your body to a point below becoming breathless. You should be able to carry on a conversation with yourself out loud, thus remaining below your ventilatory threshold.
"Optimizing your energy system management can be as simple as talking to yourself or as scientific as the testing performed at the Fitness Principle," Shilstone says.