Weight Loss & Heart Rate

Heart rate training is one of the most effective ways to reach weight loss and fitness goals. Heart rate, in combination with perceived exertion, is a targeted way to measure your energy output as you exercise. Each heart rate "zone" uses a specific energy system of the body, and each energy system has its own specific source of energy. Knowing when your body utilizes fat as fuel is the key to smart weight loss.

Maximum Heart Rate

Heart rate is a function of age, genetic background and current fitness level. Your maximum heart rate (MHR) is used to calculate your heart rate training zones. MHR isn't a static number. Generally, it decreases with age and increases with fitness. One way you can find your MHR is by using the age-predicted method: subtract your age from 220. According to this method, the MHR of a 50-year-old is 170. This method doesn't take a high fitness level into consideration, however. An aerobically fit body may have a MHR several beats higher than the age-predicted number. In such cases, physical exertion in a MHR test provides a way to find an accurate number.

Heart Rate Zones

The parameters of the three heart rate training zones --- labeled zone one, two and three --- are individualized based on personal MHR. Heart rate zone one is the purely aerobic training zone. Using perceived exertion, you should be able to hold a steady conversation while exercising in this zone. Using heart rate training, this zone is 65 to 75 percent of your MHR. For a MHR of 170, the aerobic zone takes place between 110 and 128 beats per minute. Zone two is both aerobic and anaerobic and takes place at 80 to 85 percent of MHR. Zone three is completely anaerobic, at 86 to 90 percent of MHR.

Fat as Fuel

During extended periods of aerobic --- or zone one --- training, the body uses muscle glycogen, which is a store of carbohydrates in the body's tissues, and fat as its primary sources of fuel. In zone two, the body uses muscle glycogen and lactic acid for fuel. In zone three, it sources muscle glycogen and creatine phosphate, a substance in the body used for high-intensity bursts. Exercisers interested in losing excess body fat should spend at least 75 percent of their work out time in zone one, performing aerobic workouts.

Anaerobic Threshold

The body must continually adapt and progress within its workouts to avoid reaching a plateau, overtraining or injury risk. As fitness levels increase, so does the body's anaerobic threshold. The anaerobic threshold is the point at which the exercising body cannot produce the energy needed by the muscles with a normal intake of oxygen. At that point, the body's preferred fuel switches from fat to lactic acid. Knowing your heart rate number at the anaerobic threshold allows you to workout just below it, burning the highest amount of calories from fat as possible.

Further Benefits

In addition to promoting easier weight loss, consistent aerobic exercise also keeps the pounds off. According to the Mayo Clinic article "Aerobic Exercise: Top 10 Reasons to Get Physical," it also reduces fatigue; increases energy; helps the heart muscle pump more efficiently; elevates the immune system; reduces risk for type 2 diabetes, heart disease and high blood pressure; and increases lifespan.