As the American Heart Association (AHA) explains, a heart rate zone — measured in beats per minute — is a number range based on your age that reflects your ideal heart rate during various activities. You can maximize workouts by making sure that your heart rate falls in the appropriate zone. If your heart rate is too low, you may want to increase the intensity of your workout. But if your heart rate is too high, the strain might cause problems. Studies have shown that athletes who exercise too intensely have longer recovery times and can experience problems such as irregular heartbeats.