Knowing your target heart rate every year is important because this rate changes as you get older. The rate for a 40-year-old man or woman at the beginning of middle age is lower than for younger adults and higher than older adults. Exercising within your target rate helps you get the most from your workout while limiting your chance of overtraining.
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Cardiovascular exercise, also known as endurance, cardio or aerobic exercise, raises your heart rate. In this form of exercise, you rhythmically use your large muscles for a sustained time. Aerobic exercise includes brisk walking, running, biking or active sports such as basketball. If the activity raises your heart rate to its target level and you can keep it up for 20 to 30 minutes, it counts as aerobic. Adults of any age should engage in at least 150 minutes of aerobic exercise each week -- and more is better.
Calculating Heart Rate
For any age, the complete zone for a target heart rate begins at about 55 percent of your maximum heart rate, or MHR, and ends at about 85 percent. The numbers can vary by about 5 percent on either side. To find your MHR, subtract your age from 220. For a 40-year-old person, this number is 180. Next, multiply that number by both the low and the high percentages. For example, 180 x 0.55 gives you a starting rate of 99 beats per minute, or bpm. The ending rate of your range, 180 x 0.85, is 153 bpm. If you exercise regularly and are fit, work at the upper end of the zone. Otherwise, begin at the lower end and increase your intensity as your stamina increases.
Fat-Burning and Aerobic Zones
You can adjust your heart rate for fat burning or cardiovascular fitness. Treadmills often have a chart that indicates target heart rates for each. The fat-burning zone is between 55 and 70 percent of MHR. A 40-year-old who wants to emphasize burning fat would exercise to achieve a heart rate between 99 bpm and 126 bpm. The aerobic zone is between 70 and 85 percent of MHR -- for cardio fitness, a 40-year-old man would aim for a heart rate between 126 bpm and 153 bpm.
A study published in the October 2009 issue of the “Journal of Strength and Conditioning Research” found the fat-burning zone between 67.6 and 87.1 percent of MHR and the aerobic zone between 58.9 and 76.2 percent of MHR. The study concluded that because of the significant overlap between the two zones, you can both burn fat and increase aerobic fitness by keeping your heart rate in the overlap range. For a 40-year-old, the range is between 122 bpm and 137 bpm.