The Department of Health and Human Services (HHS) published the “Physical Activity Guidelines for Americans” in 2008 and updated and reissued these Guidelines in 2018.
“For substantial health benefits, adults should do at least 150 minutes (2 hours and 30 minutes) to 300 minutes (5 hours) a week of moderate-intensity aerobic physical activity…
OR at least 75 minutes (1 hour and 15 minutes) to 150 minutes (2 hours and 30 minutes) a week of vigorous-intensity aerobic physical activity…
OR an equivalent combination of moderate- and vigorous-intensity aerobic physical activity per week.
Preferably, aerobic activity should be spread throughout the week.”
These HHS Physical Activity Guidelines provide clear, quantifiable measures of “how often” you exercise, “how long” you exercise and “how hard” you exercise. In other words, the Guidelines define the recommended “minimum” frequency (weekly), duration (# of minutes) and intensity (“moderate” or “vigorous” levels of intensity — based on “measured heart rate exertion” during exercise).
The “frequency” and “duration” measures can be easily calculated (i.e. minutes per week). However, the “intensity” measure is determined by the individual’s pulse rate or heart rate, in terms of heart “beats per minute” (bpm). The simplest method for someone to measure their heart rate during exercise is to briefly “pause” and take their pulse at their wrist.
Fortunately, advances in portable wrist-mounted heart rate monitors simplify the measurement of exercise intensity and do not require “pausing” exercise to do so. These portable heart rate monitors, which are inexpensive and user-friendly, provide real-time, continuous and uninterrupted heart rate measurement of “exercise intensity” during the entire “duration” of an exercise session. These monitors also have record-keeping and summarized reporting features for demonstrating compliance with the Physical Activity Standards.
Going back to the physical activity intensity guidelines established by HHS and the definition of two different levels of exercise “intensity,” differences among individuals regarding their ability to safely exert their heart, needed to be taken into account. These individual differences are based on their age. The maximum heart rate of a young person is higher than the maximum heart rate of an older individual. The established and accepted formula for determining the individual’s “age related” maximum heart rate is to subtract the individual’s age from 220. (A twenty year old individual would have a maximum heart rate of 220-20 = 200 bpm. A 45 year old individual would have a maximum heart rate of 220 – 45 = 175 bpm.)
In addition, as exercise intensity varies during physical activity, the guidelines were required to define a range of heart rates, with lower and upper limits for determining and differentiating “moderate” versus “vigorous” levels of exercise intensity
The estimated “age related” exercise intensity measure is then defined in the form of a “lower and upper percentage range” of the individual’s maximum heart rate that is reached and maintained during exercise. For “moderate intensity” exercise, the range is from 64% to 76% of the individual’s age determined maximum heart rate. For “vigorous intensity” exercise, the range is from 77% to 93% of the individual’s age determined maximum heart rate.
The exercise intensity measure for the individual is calculated as a percentage of the individual’s age related maximum heart rate.
Fortunately, The Center for Disease Control and Prevention (CDC) has defined and published the “target heart rate range” for both moderate physical activity and vigorous physical activity, in terms of the percentage of a person’s maximum heart rate.
Heart Rate Monitored Measurement of Exercise Intensity
For moderate-intensity physical activity, the target heart rate range should be between 64% and 76% of the individual’s age-related maximum heart rate.
The above identified 45 year old person with estimated maximum heart rate of 175 bpm would be required to maintain a heart rate range of 112 beats per minute (0.64 x 175) to 133 beats per minute (0.76 x 175)
For vigorous-intensity physical activity, the target heart rate range should be between 77% and 93% of the individual’s age-related maximum heart rate.
The above identified 45 year old person with estimated maximum heart rate of 175 bpm would be required to maintain a heart rate range of 135 beats per minute (0.77 x 175) to 163 beats per minute (0.93 x 175)
As physicians begin to introduce and adopt a Cardio-respiratory Fitness (CRF) Vital Sign for patient visits, the HHS Physical Activity Guidelines provide a frame of reference for their adoption and use of standardized and structured Exercise Prescriptions (Rx) for patients who have low measures of Cardio-respiratory Fitness (CRF).
A highlighted summary of the current HHS Physical Activity Guidelines can be found here: Physical Activity Guidelines Summary
A link to the full HHS Physical Activity Guidelines publication on their website can be found here: