The American College of Sports Medicine (ACSM) recommends that healthy adults engage in 30 minutes of moderately intense activity most days of the week to maintain their well-being.

To figure out your exercise intensity, simply check your heart rate. As defined by the ACSM, moderate intensity is 65 to 75 percent of your maximum heart rate. A reasonable estimate of your maximum heart rate can be found by subtracting your age from 220.

Figured in this way, a 40-year-old’s maximum heart rate would be 180 beats per minute. That 40-year-old’s heart rate reflecting moderate exercise intensity would be 117 beats per minute (65 percent of 180) to 135 beats per minute (75 percent of 180). Here’s a math breakdown:

• Maximum heart rate = 220 – your age
• Heart rate range reflecting moderate exercise intensity = Maximum heart rate x 0.65 to Maximum heart rate x 0.75

To check whether you’re within your range for moderate exercise intensity, stop your workout, and using the pads of your index and middle fingers, press lightly on the underside of your opposite wrist, below the base of the thumb.

Count your pulse for 10 seconds, then multiply that number by 6. This is your heart rate. Remember that this range is only a guide. And always check with your doctor before starting or upping the intensity of an exercise program. [source: YHN]