If you have had a cardiac event like a heart attack, then you may want to attend physical therapy in a specialized cardiac rehabilitation program. During cardiac rehab, you will work closely with a physical therapist, your doctor, and other health care workers to help improve your fitness level and cardiovascular endurance. That way, you can quickly and safely return to your previous level of function.
One important goal of phase one cardiac rehab is for you to learn how to measure your exercise intensity. When you understand how hard your body is working during exercise (and other everyday tasks) you can adjust the intensity to make sure that it is right for you. Too much intensity during a task or exercise may overstress your heart; not enough intensity will stress your heart too little to help it recover from your cardiac related injury.
One way to know how hard your body is working during exercise is to measure your heart rate. Heart rate measurements give you an idea of how much stress your heart is under during activity.
Maximum Heart Rate
Before measuring your heart rate during exercise, it may be helpful to know what your maximum heart rate should be. That way, your exercise intensity can be represented as a percentage of your maximum heart rate. Typically, it is recommended that you exercise at an intensity that is 65-85% of your maximum heart rate. Of course if you have had an acute cardiac event, you may not start out exercising at such an intensity, so it is important to work closely with your physical therapist and doctor to understand the correct intensity of exercise for your specific condition.
To measure your maximal heart rate, you can use a simple formula:
220 - your age.
This is known as your "age related estimated maximum heart rate." So, if you are 40 years old, your estimated maximal heart rate should be 180 beats per minute. An exercise intensity of 65% of your maximal heart rate would be 117 beats per minute. During exercise, you would need to measure your heart rate and adjust the intensity of your workout to maintain a heart rate of 117 beats per minute.
This simple formula is a bit controversial as some cardiac rehab specialists argue that it is not accurate enough. Another formula to measure maximal heart rate is:
206.9 - (.67 x age).
A more complicated formula to use is called the Karvonen formula which uses your resting heart rate to determine your exercise level heart rates. Again, work closely with your cardiac rehab team to understand your maximal heart rate and correct exercise intensity levels.
How to Measure Your Own Heart Rate
While exercising, the simplest way to measure your own heart rate is to palpate, or touch, your pulse in your wrist. It is easy to do. Here's how:
- Place your index and middle fingers on your wrist near the point where your thumb and wrist meet.
- You should feel your pulse beating in an artery called your radial artery.
- Each time you feel a pulse, count one beat.
- Watch a clock, and count the number of beats that occur over 10 seconds.
- Multiply that number by 6 to obtain the number of times your heart beats each minute.
Make sure you use your index and middle fingers, and not your thumb, to measure your pulse. There is a pulse in your thumb that you may feel when pressing on your wrist, and this could give you inaccurate results.
Using a Heart Rate Monitor
Another easy way to measure your heart rate is to use a heart rate monitor. These are inexpensive devices that include a strap that wraps around your body to measure heart rate. A special watch is then worn that gives you a heart rate readout.
Basic heart rate monitors start in a price range of about $30.00 (US). Monitors with more functions, like GPS tracking and time keeping, are a little more expensive.
Heart rate monitors work well, but occasionally the belt worn around your body may slip down and out of place. Also, sweat or body oils may interrupt the signal sent from the monitor to the wrist readout device, leading to inaccurate measurements of heart rate.
During cardiac rehabilitation, your physical therapist may use a portable monitor that is placed on your finger to measure your heart rate. This monitor uses light passed through your finger to measure your heart rate, and it can also measure your pulse oximetry, or the amount of oxygen in your blood.
These devices can be very accurate and simple to use, but if you are wearing nail polish, they may not work properly.
Learning how to measure your own heart rate is an essential step in monitoring your exercise intensity level. By spending the time to understand the importance of heart rate monitoring and how to do it properly, you can be sure that you are exercising correctly through all phases of your cardiac rehabilitation.
Sources: Jackson, Andrew S. Estimating Maximum Heart Rate From Age: Is It a Linear Relationship? Med Sci Sports Exerc. 39(5):821, May 2007.
Hillegas, E., & Sadowski, H. S. (1994). Essentials of cardiopulmonary physical therapy. (1 ed.). Philadelphis: W.B. Saunders