Three days after a myocardial infarction, what upper-limiting guideline should be used for inpatient exercise intensity?

• A. Maximum oxygen consumption
• B. Resting respiratory exchange ratio
• C. Rate of perceived exertion of 18
• D. Resting heart rate plus 20 beats per minute

Answer: (D)

After a myocardial infarction, keeping activity levels safely conservative is essential to prevent ischemia and excessive cardiac strain. Using a simple, individualized ceiling based on the patient’s resting heart rate plus about 20 beats per minute provides a practical upper limit for inpatient exercise. This method adjusts for daily fluctuations in resting HR and avoids pushing the heart into higher workloads that could be unsafe in the early post-MI period. It’s safer and more feasible at the bedside than aiming for maximum oxygen consumption or a near-maximal rating of perceived exertion. In practice, the patient should stay below that resting HR plus 20 bpm, and exercise should be stopped if chest pain, undue shortness of breath, dizziness, or abnormal rhythms occur.