Heart rate's dropped due to meds - will it slow me down?

[Chris249]

Hi all.

I've been on some meds for reasons not related to any significant issues. The first ones I tried reduced my heartrate from high 50s to mid 40s; I didn't notice it until I felt dead doing some hillclimbs. I had been feeling tired but thought it was due to other issues.

The new meds have my heartrate in the low 50s and I'm feeling fine. I don't feel dead on the bike but I'm not riding too much, not racing at all, and just trying to build up some fitness again.

The question is, will a medication-induced drop in RHR to low 50s cause problems with my performance on the bike, as seemed to happen when it went below 50? I know I should ask the doc but I forgot to!

To give some background I'm 51, was winning in B Grade at my old "all ages" club three years ago, and when I had to quit racing due to another illness last November I was doing OK in local veterans track racing. So I'm not real slow and not real fast, and also not really experienced in racing or in measuring HR. My location, training and fitness have all changed and I have no HRM or other data to use as a measure.

[sogood]

on some meds for reasons not related to any significant issues...

Not sure what kind of trivial condition would demand the use of a medication that gives you a significant cardiac effect. Otherwise yes, medications that affect the regulation of HR can certainly affect one's sports performance.

[nickobec]

As somebody who rode and raced on beta blockers (the general term for a group of drugs that lower your heart rate), yes they will effect your performance.

Simply because your heart can not beat as fast as before to deliver oxygen and fuel to your muscles.

I had a heart attack (Myocardial infarction) five years ago, was prescribed beta blockers and only came off them a few months ago. I only started racing a couple of years ago, so no previous performances to compare to. Also I track max HR rather than resting HR. Currently my resting HR is low 50s, on beta blockers it was mid 40s.

When I started racing, I was taking my tablets in the morning. If my HR hit 150 early in a race I would blow up. At the end of a race I would hit 160 and max out at 170.

On the advice of my doctor, I started taking my tablets in the afternoon. I could easily hold 150 during a race, ride at 160 at the end of the race and max out close to 180. I went from being at the back of my grade, to competing for wins.

A couple of months ago, I stop taking my beta blockers (in consultation with my doctor) after 5 years . Now hold 160 during a race, can ride at 170 for 15 minutes and my max HR is 185. And I am racing a grade higher than before and being competitive in that grade.

So from my experience, taking beta blockers is probably worth a grade.

[chriscole]

Your cardiac output is determined by your stroke volume and your heart rate. Decrease either one, and your cardiac output (and consequently your VO2) drops, definitely adversely affecting performance.

[sogood]

Another way to look at this is, with the medication and cardiac regulation, the rider may slow right down in an ambo and hospital. With, the heart will run a good pacing strategy like in an ITT and go on and on, optimised and no slowing.

[ValleyForge]

Many men tolerate beta-blockers (the likely medication responsible for the lower HR) poorly. Early onset muscle fatigue and erectile failure are the two most commonly cited reasons. The muscle fatigue especially affects the proximal muscles (quads & gluteals).

The main current indication for beta-blockers is reducing mortality post myocardial infarct (heart attack) especially in males. The group also reduces muscular tremor and sweating related to performance anxiety; also works to reduce migraines and premature ejaculation for some.

There are newer drugs for blood pressure control that have better utility for active men. A good GP will try not to use beta-blockers in men for blood pressure control.

So, while a lower heart rate is a therapeutic effect, there are a wide range of compensatory mechanisms that will maintain you cardiac output during exercise. Any slowing down is more likely due to the muscle fatigue effect that is reported by patients.

[sogood]

Key is, was it prescribed for BP control or for the management of risks to other cardiovascular states? So once again we go back to OP's "significant issues", an undefined term.

[Chris249]

Thanks guys. I've been late replying because I was setting up a new computer.

Ironically, my heart rate seems to have returned to normal now, although I haven't been checking it much. I will keep monitoring it and if it goes back to being a touch too low I will do some more research to find out how to handle it. If I am interpreting SG's last post correctly it appears that a lowered HR may not affect disciplines like ITTing as much as it may affect sprints, which is something I had considered.

VF's post about the compensatory mechanisms was interesting, too. Thanks.

I had my first group ride for ages yesterday and my performance seemed to be back on track; the A Graders I tagged onto at first by mistake got away up a 1.1km 8.5% climb but that's just to be expected. When I found the right (medium-pace) group I felt very competitive, and definitely much improved on my performance under the first meds.

BTW the use of the medication is not related to heart issues, blood pressure issues, erectile disfunction, performance anxiety or anything else.

[nickobec]

Chris the real question is what drugs are you taking?
Are they beta-blockers designed to slow your heart rate ie atenolol or metropolol or another type of drug which has side effects of slowing your heart rate.