Q&A - Heart of the matter
By Dr Giles P Croft | Friday, November 23, 2007 2.50pm
Q. I am 56 years old and this year have done some ten-mile TTs to keep my daughter company but have only managed times in the 28s. Because of high blood pressure I take ACE inhibitors (Ramipril).
A few crude tests (riding flat-out up a steep hill) show my maximum heart rate (MHR) in the 140s whereas last year it was in the 160s on the same hill. If this is down to the medication is it something I will have to live with (along with the 28s!)? I obviously couldn't ride at MHR anyway, but is my max possible effort over the ten miles being reduced?
Phil Clements, email
A. Rather than being a comment on your performance,'ACE'stands for angiotensin converting enzyme. Your medication prevents conversion of angiotensin I to angiotensin II; a natural substance in your body which causes constriction of small blood vessels, thereby increasing blood pressure.
Unlike other drugs which help lower blood pressure by making the heart work less (beta blockers, for example), ACE inhibitors are exercise-friendly and have been shown to have no effect on oxygen uptake or metabolism during exercise. The only common side-effect that might affect exercise is a dry cough.
None of which explains your lower maximum heart rate this year. Such reductions are not uncommon and can be due to a myriad of causes. How is your general fitness compared to last year? Have you had any recent illnesses? Have you been performing your tests of MHR under exact conditions? Whatever the reason, it's important to distinguish between max HR (essentially just a number) and maximum possible effort, which is more subjective but easy enough to measure when you're riding.
Don't be a slave to your heart rate monitor though, and if your new MHR really is persistently in the 140s, then adjust your training zones accordingly. Many coaches would recommend using lactate threshold heart rate rather than maximum for such calculations anyway, as it's a more important physiological marker during exercise.
I'm sure improvements will be possible in your time trialling: focus on position, technique, diet, goal-focused training and, above all, consistency. Good luck, and enjoy the family competition!
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