Do betablockers affect physical performance? My own story

  • Creator
  • #52748

    I am 79 and I exercise regularly. Typically, I run 6 km three times a week, in addition to biking and windsurfing. In winter, I train on an elliptical machine. I try to work out as much as possible outside the “comfort “zone, within the limits of my age, of course.
    Based on my experience, I’d like to make a few observations regarding the effects of certain commonly prescribed drugs on athletic performance.
    Currently, I have been on betablockers (Metoprolol, 2x 25 mg/day) for three years, following one isolated episode of A Fib.
    Before going on Metoprolol, according to the age charts, my suggested h.r at 80% of my maximum capacity was about 112 bpm. But, no doubt because of my excellent cardio conditioning , it felt ridiculously low, almost like walking, for effective cardio vascular training.

    Because of this, before going on Metoprolol, I had stepped up my training to 130-135 bpm, with occasional peaks to 140-145 bpm.
    After going on Metoprolol, not only did my rest h.r. substantially drop to about 60 bpm, which was expected, but it also reached a ceiling at 115 bpm for the same effort level of before , with the same resistance setting and the same duration on the elliptical machine.

    All this was expected, but I am also surprised that with such an artificial, chemically induced, lower pulse caused by Metoprolol, it looks like my cardio efficiency has significantly improved, because I can now easily push my Watts expenditure well beyond 60-65 Watts, even to 80-85 Watts, without significantly increasing my h.r.

    I have had a similar experience with Metformin, a drug that is commonly prescribed at the pre-diabetic stage to treat insulin resistance. My doctor prescribed it about three years ago as a precaution and, here too, I noticed an effect similar to that of Metoprolol
    To be more specific, In the past, on the same jogging track I have been using for years, my heart rate would always rise to the strain zone after three or four lapses ( approximately 1 mile) , even at the best of my training. I would then stop to catch my breath.

    Surprisingly, a week or two after going on Metformin, I was doing 10 lapses, even though I had stopped my usual running routine for about three weeks as I had gone on vacation.

    The only explanation I could come up with was that Metformin had somehow improved the glucose absorption by the cells, therefore making more oxygen ( =energy) available for the body..This was confirmed by my cardio watch showing a significantly lower pulse and calories count.

    I spoke to my GP. She said that I was perhaps right, but there is no clinical evidence, because not enough clinical studies have been conducted regarding the effects of Metformin on physical performance.

    It would be interesting to know if, short of a medical opinion, which may not be easy to find in a Forum, other people have had the same experience.



  • Participant
    russes011 on #52761

    RE: Metformin

    This drug blocks glucose production in the liver, as well as increases glucose uptake by the cells of the body. These two effects yield a lower blood glucose. Metformin can also increase your blood lactate level, irrespective of exercise stress or oxygen availability. Lactate builds up due to Metformin blocking glucose production in the liver, as well as its ability to block oxidative respiration (aerobic respiration) in the mitochondria. Lactate, which is just buffered lactic acid, is an excellent fuel source for muscles, among other organs. Lactic acidosis from Metformin, however, is uncommon and unpredictable, and is generally associated with more serious medical problems. Nevertheless, maybe some extra lactate helped you? (pure speculation here), or more likely, perhaps it simply encouraged more blood sugar to enter your cells (you became less insulin resistant)

    RE: Metoprolol

    HR monitoring is probably not an accurate way to determine effort, or your body’s aerobic efficiency per work load, or power output, when on a beta-blocker. It’s honestly not even a super reliable marker when one’s not on beta-blockers. In general beta-blockers will blunt your VO2max by blunting your max HR as well as your bodies other pro-performance responses to adrenaline. The other issue is that maybe the metoprolol prevented you from going in and out of afib during exercise, which is often asymptomatic, thereby increasing your stroke volume and efficiency in delivering oxygen to your muscles. Some new heart rate wrist watches, like the apple watch, can actually alert you to certain arrhythmias occurring. Some doctors are recommending them because they are cheaper than other more expensive, medical-grade, arrhythmia monitoring devices.

    Anyway–they both seemed to improve your performance, so good news regardless.

    vifra on #52783

    Thanks Steve
    Your answer is well informed and I am glad you agree with me on the Metformin issue.
    Regarding the Metoprolol, yes, going by the HR of the cardio watch may not be an accurate way to determine effort or my body’s aerobic efficiency, but I also go by the perceived effort level, which is an unmistakable indicator of improved efficiency, as I am now able to do many more lapses. Or perhaps is this still the effect of Metformin?

    Regarding the possibility that Metoprolol prevent me from going into Afib when exercising, therefore triggering physiological processes resulting in a perceived higher efficiency, I have to say that, based on my medical history, I would not expect A Fib to occur that frequently, even less during each running session.

    In fact, I had it for the first time about three years ago, and, again, two weeks ago, in both cases without any untoward symptoms (difficulty in breathing, chest pains or other.) except for an abnormally high pulse, between 100-130, briefly peaking, occasionally, to 160.
    It lasted a few days, but when I finally decided to go to E.R., it was back to normal and the ECG did not show any problems. I am sure that if it happened again, I’d certainly pick it up from my cardio watch or by taking my pulse, which I frequently do.

    Thank you so much for your comments


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