Exercise Intensity, Heart Rate, and Perceived Exertion
Cardiovascular exercise is typically performed to improve and maintain cardiovascular health. Aside from endurance competitors (triathletes, cyclists, marathon runners, etc.), recreationally active men and women should be exercising at an intensity that promotes optimal heart health. However, it is not always clear as to what intensities one should be exercising at to facilitate the greatest return. For years exercisers have been using both heart rate (HR) values and ratings of perceived exertion (RPE) to classify intensities during cardiovascular training. While both methods have proven to be valid, it is significantly more difficult using HR compared to RPE.
Training between 70% and 90% of your age-predicted maximum heart rate is considered optimal for cardiovascular health, though predicting maximum HR is not as accurate as knowing your actual max HR. Nonetheless, there are prediction equations that can provide values within 10 beats per minute of your actual heart rate. The equation 220 minus your age has been used in the past to calculate max HR, but an alarming amount of research has indicated that this equation is only valid in men, since women tend to have lower maximum heart rates. The latest equation for women is: Max HR = 206-(age x 0.88), which will produce more accurate estimates than the older equation. Once max HR is estimated, exercisers can calculate their optimal training zone. For example, a 40 year-old man and woman would have the following optimal training zones:
Max HR: 220 – 40 = 180
90% Max: 180 x 0.90 = 162
70% Max: 180 x 0.70 = 126
Optimal training range = 126 – 162 beats per minute
Max HR: 206 – (40 x 0.88) = 171
90% Max: 180 x 0.90 = 154
70% Max: 180 x 0.70 = 120
Optimal training range = 120 – 154 beats per minute.
Theoretically, the man and women here would simply need to strap on a heart rate monitor and keep their HRs within the calculated zones. However, there is a problem with using HR alone. Several factors can influence heart rate including room/air temperature, clothing, training status, anxiety, and obesity to name a few. Therefore, many trainers and exercisers prefer the RPE scale. Typically, the scale used ranges from 6 to 20, with 20 being something extremely difficult. Using this scale you should observe HRs in the optimal training range between rates of perceived exertion of 14 to 17. To assure you are training in the optimal zone, it is best to wear a HR monitor or exercise on a machine with a handheld HR monitor and take a mental note of how you feel on a scale from 6-20 when you are at 70% and at 90% of your estimated max HR.
After only a few training sessions you will be accustomed to the “RPE feeling” and will no longer need to know your HR. By using only RPE you are not limited to knowing your HR and can modify your training intensity based on how you feel. This becomes increasingly important when exercising outside in hot and humid environments and when you are exercising for long periods of time. Once you know what a 14-17 on the RPE scale feels like, you can exercise anywhere, on any piece of equipment, and be confident you are in your optimal training zone.
Dr. Moon is the Department Head of Sports Health and Fitness at the United States Sports Academy. He has trained athletes at all levels including professionals in Major League Baseball, the National Football League, and the National Hockey League, as well as college athletes and teams in addition to youth and fitness clients.