The Beta-Blocker and the Numbers That Don't Add Up
Marcus, 69, is 12 weeks into your program after a cardiac event. He takes a beta-blocker and reports he feels 'great.' He has started pushing hard on the stationary bike because he read that he should reach 70-85% of his maximum heart rate. Using the 220-minus-age formula, he calculates a target of about 106-129 bpm and is frustrated that he 'can't get there' even when working hard. He has begun adding resistance and longer sessions on his own to try to hit the numbers, and last week he felt lightheaded after a session.
1. Explain why his target heart rate approach is misleading and what he should use instead.
Read the worked answer
The 220-minus-age formula is a rough population estimate with large individual error, and his beta-blocker further lowers his heart-rate response to exercise. Chasing a heart-rate target derived from that formula can push him to work harder than is appropriate while his heart rate stays deceptively low.
Replace heart-rate targets with perceived exertion and the talk test. Teach him to rate effort on a 6-20 RPE scale and to work at a level where he can still speak in short sentences. These tools reflect his actual physiological effort better than a formula-based heart-rate zone when heart rate is blunted.
His lightheadedness after a self-escalated session is a warning sign; he should not add intensity or duration on his own without guidance.
2. He is self-escalating to hit numbers and had lightheadedness. What do you change now, and how do you coach the behavior?
Read the worked answer
Immediately pull back his self-directed progression: set a defined intensity ceiling using RPE and the talk test, cap session duration, and have him stop and report any lightheadedness, dizziness, or unusual symptoms. Reinforce that he should not increase workload on his own between sessions.
The lightheadedness warrants attention; document it and advise him to raise it with his cardiology team before further progression. Do not simply ignore it because he 'feels great' otherwise.
Coach the behavior by explaining the mechanism in plain terms: his medication keeps his heart rate low, so the numbers he is chasing do not measure what he thinks they measure. Give him a simple, concrete rule (effort level and ability to talk) he can apply himself, and praise him for reporting symptoms rather than pushing through them.