Your heart is a pump that circulates blood — and with it, oxygen and nutrients — throughout your body. When you work out, your muscles need more oxygen and nutrients to use as fuel, so your heart beats faster to power that increased circulation.
When you work out, your muscles need more oxygen and nutrients to use as fuel. Those are carried in your blood, and your heart is the pump that circulates blood through your body — so during a workout, your heart beats faster to accommodate that increased need.
Exercise and Your Heart
Your heart is a muscle — and just like the other muscles in your body, it gets stronger with exercise. Kaiser Permanente explains that when your heart gets stronger, it pushes out more blood with every beat — which means it doesn't have to work as hard to circulate adequate oxygen and nutrients when you exercise. So your heart rate will still rise with exercise, but it won't have to rise as much.
Regular exercise helps the rest of your circulatory system get more efficient too. This includes greater ability to utilize oxygen, better blood flow in small arteries around your heart and an improved cholesterol profile.
As Kaiser Permanente notes, if you haven't exercised in a long time or have a history of high blood pressure, stroke, dizziness, heart disease or exercise-related pain, you should talk to your doctor before working out.
Your resting heart rate can provide a useful glimpse into your heart health. Count your pulse for 60 seconds, after a good night's sleep and before you get out of bed. The result is your resting heart rate.
As the American Heart Association (AHA) notes, for most people who are sitting or lying down — calm, relaxed and not ill — a resting heart rate of 60 to 100 beats per minute (bpm) is normal. Your resting heart rate might be lower if you take certain drugs, such as beta blockers. Athletic people may also have lower resting heart rates, down to about 40 bpm, because their entire circulatory system works more efficiently.
The AHA warns that if you have a very low pulse or if you have frequent episodes of unexplained fast heart rates — especially if you also feel weak, dizzy or faint — you should consult a doctor to determine whether you're having a medical emergency.
Find Your Target Heart Rate
The AHA breaks down the basics of calculating your target heart rate for exercise. Start by subtracting your age from 220; the resulting number is your maximum heart rate. If you're 40 years old, it's 220 - 40 = 180 beats per minute (bpm).
The name "maximum heart rate" is a little misleading, because you don't actually want to reach that number. Instead, aim for 50 to 70 percent of that number for moderate-intensity physical activity and 70 to 85 percent for vigorous-intensity physical activity.
Continuing the example, that means for moderate-intensity exercise, a 40-year-old would aim for a heart rate between 180 x 0.5 = 90 bpm and 180 x 0.7 = 126 bpm. For vigorous intensity, that same 40-year-old would aim for a heart rate between 180 x 0.7 = 126 bpm and 180 x 0.85 = 153 bpm.
But this formula doesn't account for gender — and according to a 2014 summary of research from the American College of Cardiology, men's and women's hearts can respond differently to exercise. Based on data from 25,000 patients who underwent stress tests at the Mayo Clinic, the researchers recommended a new formula for calculating your maximum heart rate:
- For men, expect your maximum heart rate to be 216 minus 93 percent of your age.
- For women 40 to 89 years old, expect your maximum heart rate to be 200 minus 67 percent of your age.
There is no clear data for women younger than 40, due to an insufficient number of tests in that age range. Interestingly, the researchers note that "While everybody's peak heart rate declines with age, the decline is more gradual in women." They also discovered that men's heart rates rise more dramatically during exercise than women's do and return to normal more quickly.
- American Heart Association: "Know Your Target Heart Rates for Exercise, Losing Weight and Health"
- American Heart Association: "All About Heart Rate (Pulse)"
- American College of Cardiology: "The Heart Responds Differently to Exercise in Men vs. Women"
- Kaiser Permanente: "Exercise Helps Your Heart"
- Cleveland Clinic: How Does Blood Flow Through the Heart?