Although weight training doesn't offer the same cardio workout as other activities like running and swimming, you will still experience an increased heart rate when lifting weights. Your muscles need more oxygen when working hard, so your heart beats faster to meet those needs.
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Heart Rate Zones
Find your resting heart rate. Using two fingers, find the pulse on the thumb-side of your wrist. Count the number of beats in one minute. You can also count the beats for 15 seconds and multiply this by four. A heart rate between 60 and 100 beats per minutes is considered normal, advises the American Heart Association.
A lower resting heart rate typically indicates better heart health. Some athletes may have a heart rate as low as 40 beats per minute. A higher resting heart rate may indicate low fitness levels or high blood pressure.
To determine when you are in the heart rate zone you are looking for, start by determining your maximum heart rate. You can easily calculate this by subtracting your age from 220.
Use this number to find your target heart rate zones. If you are working out at a moderate-intensity, aim for 50 to 70 percent of your maximum heart rate. At a vigorous intensity, you want your heart rate to be between 70 and 85 percent of your maximum heart rate.
Unlike cardio activities, such as running, cycling or swimming, you are unlikely to maintain these target heart rates while weight lifting. You can use circuit training to get more cardio benefit from your weight training.
Read more: How to Determine the Baseline Heart Rate
Heart Rate During Exercise
Strength training such as weight lifting is an important part of any fitness routine. The U.S. Department of Health and Human Services Physical Activity Guidelines for Americans recommends doing strength training exercises for each of the major muscle groups at least two times per week.
Your heart rate during a bench press or other weight lifting exercise will increase as you workout. As your muscles work to do the lifts, they need more oxygen to generate energy and they produce more carbon dioxide as a byproduct. To meet these needs, you begin to breathe faster so that your lungs can bring in more oxygen and your heart beats faster to circulate blood to your muscles.
Although you may not be working in your target heart rate zone, strength training workouts still have heart benefits. Strength training helps you build muscle mass, which allows your body to burn more calories, even at rest, notes Harvard Health Publishing. Strength training also contributes to healthy body weight and avoiding obesity, which is a risk factor for cardiovascular disease.
Training With a Heart Condition
If you have heart disease or have had a heart attack, it may be frightening to experience the increased heart rate that comes with exercise. However, exercising is important to improve heart health and reduce risk factors that contribute to cardiovascular disease. Risk factors that can be improved with exercise include:
- Obesity and being overweight
- High blood pressure and cholesterol
- High blood sugar
Exercise makes your heart stronger and can decrease chest pain. Before you begin weight lifting or any other exercise program, be sure to consult your doctor to determine what types and intensity of exercise are safe for you.
Start slowly with lighter weights and increase the weight over time. If you are doing circuit training, start slowly and take breaks when needed if you experience symptoms such as:
- Chest pain
- Shortness of breath
- Irregular heartbeat
Monitor your heart rate closely and be sure to stay in the target heart rate range that your doctor has approved for you.
Slow Heart Rate and Exercise
If your heart rate becomes abnormally high or low while lifting weights, it may be a sign of a serious medical condition. Bradycardia, or a low heart rate, is usually a heart rate of fewer than 60 beats per minute; however, some athletes may have a normally slower heart rate.
The condition may be caused by a problem with the electrical signals in the heart, hypothyroidism or another metabolic condition or heart damage from heart disease, advises the American Heart Association. Some medications may also cause a slow heart rate.
When your heart beats too slowly, your heart isn't pumping enough blood to supply oxygen to your muscles and brain. An extremely low heart rate while strength training may cause symptoms such as fatigue, dizziness and shortness of breath. In extreme cases, cardiac arrest may occur.
If you experience symptoms of cardiac arrest, such as chest pain, palpitations, breathlessness and lightheadedness, seek immediate medical attention. In some cases, no treatment is required, but if the bradycardia is severe or ongoing, you may need a pacemaker to manage the condition.
Although you may not need treatment for mild cases of bradycardia, it is still important to seek medical attention if you experience symptoms. Complications from the condition may include problems with blood pressure, fainting, chest pain and heart failure.
Read more: What Is a Dangerously Low Pulse Rate?
Rapid Heart Rate and Exercise
If your heart beats fast when lifting weights and you exceed your target heart rate, take a break to lower your heart rate. If your heart rate is irregular or is faster than you would expect given the intensity you are exercising, it may be a sign of a medical condition.
Some conditions that may cause tachycardia, or a fast heart rate, include atrial fibrillation, atrial flutter and supraventricular tachycardia. Atrial fibrillation occurs when the electrical impulses that trigger your heart to beat become rapid and disorganized. Atrial flutter is a similar condition, but the signals are more organized than with atrial fibrillation.
If you have atrial fibrillation, you are at high risk for stroke. If you notice an irregular heartbeat, seek medical attention to get a diagnosis and proper treatment which may include daily aspirin.
Supraventricular tachycardia is characterized by a sudden racing heart with no obvious cause like stress or strenuous exercise. With this condition, the racing heart stops as suddenly as it began.
If the rapid heart rate is caused by a problem in the ventricles, your doctor may recommend an implantable cardiac defibrillator. This is implanted similarly to a pacemaker and the device monitors your heart rate and shocks the heart if it gets out of rhythm.
Some conditions may be successfully treated with electrophysiology study and ablation, which cauterizes the muscles tissues that are causing the problem.
- U.S. Department of Health and Human Services: "Physical Activity Guidelines for Americans, 2nd Edition"
- American Heart Association: "Bradycardia: Slow Heart Rate"
- American Heart Association: "Know Your Target Heart Rates for Exercise, Losing Weight and Health"
- Harvard Health Publishing: "Add Strength Training to Your Fitness Plan"
- European Lung Foundation: "Your Lungs and Exercise"
- University of Arizona Sarver Heart Center: "Diagnosing and Treating Heart Rhythm Problems"
- U.S. National Library of Medicine: "Being Active When You Have Heart Disease"