Write an exercise Rx to improve patients' cardiorespiratory fitness

The THR calculation is performed twice, once with a lower %intensity and again with a higher %intensity to develop a training zone based on HRR.

The HRR equation is more accurate than calculating HRmax from 220 – age, because HRR accounts for resting HR, which is often lower in people who are better conditioned.

Another method of calculating intensity for patients who are beginning a physical activity program is the rating of perceived exertion (RPE), which is graded on a scale of 6 to 20: Moderate exercise correlates with an RPE of 12 to 13 (“somewhat hard”); vigorous exercise correlates with an RPE of 14 to 16 (“hard”). By adding a zero to the rating on the RPE scale, the corresponding HR in a healthy adult can be estimated when they are performing an activity at that perceived intensity.²² Moderate exercise therefore correlates with a HR of 120 and 130 bpm.

The so-called talk test can also guide exercise intensity: Light-intensity activity correlates with an ability to sing; moderate-intensity physical activity likely allows the patient to still hold a conversation; and vigorous-intensity activity correlates with an inability to carry on a conversation while exercising.

An exercise prescription should be accompanied by a patient-derived goal, which can be reassessed during a follow-up visit. So-called SMART goals (Specific, Measurable, Achievable, Relevant, and Time-bound) are tools to help patients set personalized and realistic expectations for physical activity. Meeting the goal of approximately 150 to 300 minutes of moderate or 75 to 150 minutes of vigorous physical activity (or an equivalent combination) per week is ideal, but a patient needs to start where they are, at the moment, and gradually increase activity by setting what for them are realistic and sustainable goals.

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