A target heart rate is the measure of how hard you need to exercise to get the maximum benefits from your workout.
For years, men and women have used the same formula: Subtracting your age from 220. But some men and women's bodies don't react the same, even if the workout is identical.
One researcher says the number 206 subtracted from 88 percent of her age equals her maximum heart rate.
Whatever the number may be, experts say it's best to consult with your doctor before beginning any exercise program.