Heart rate training effect with pacemaker

I haven't been able to form a useful Google search for this question, so I'm hoping someone here will have an answer.

Most athletes understand the concept of the "training effect" -- challenge the body (including the heart) to perform at a higher-than-comfortable level over a number of intervals, to accustom/train/strengthen it so the higher level becomes the "new normal"... and repeat.

So I'm wondering, since the pacemaker controls the heart rate more or less independently of the body's requirements, does gradually increasing one's efforts *with* a pacemaker still lead to the same improvements as it would without one?

Before my pacemaker, I was walking on a treadmill 5 miles a day, 5 days a week, at about 3.5 mph/17 minutes/mile and 3.0% grade. It's been about 10 months since implantation, and I'm back up to about 3 mph/20 minutes/mile and 3.0% incline. 

The HR monitor on the treadmill isn't very accurate, but it does seem to be consistent from day to day. If my current program results in a heart rate around 95BPM and I push the pace up to 3.5mph over several weeks, such that my heart rate initially goes above 95, can I expect that eventually the training effect will bring it back down to around 95 at the new pace?

Thanks for any insight on this! 



The effect of exercise

by IAN MC - 2019-10-01 13:09:48

Whether you have a pacemaker or not, the more exercise you do, the fitter you will become.  Exercise makes your heart work more efficiently.

If you are fit , every heart beat delivers a greater volume of oxygen to your muscles than if you are not fit  i.e. you will have a larger " stroke volume ". The heart will then need to beat less to do the same job ; this is why fit people tend to have lower heart-rates

You  are wrong when you say that " the pacemaker controls the HR independently of the body's requirements ".  This is only true if the Rate Response feature is switched off . It should only be switched off if your heart -rate is  is naturally increasing when you exercise. If it isn't you are suffering from "chronotropic incompetence " and Rate Response needs to be switched on ... this  will trigger your PM to increase your HR when required.

Around half of all PM recipients have RR switched on so their PM attempts to measure their body's requrements and then determines their heart-rates.  Hopefully the other half have their heart-rates increasing naturally when they exercise without the need for  RR  ( but I doubt it ! )


Body's requirement

by AgentX86 - 2019-10-01 14:53:25

No, a pacemaker does not control the heart rate dependent on the body's requirement.  Rate response tries to guess at what the body requires but it really has no clue how much oxygen is needed. The time spent at a higher heart rate will still increase muscle and improve pumping efficiency but without changes to the PM's settings, the heart rate won't change with fitness. A normal sinus node uses blood pCO2, which is a measure of the body's oxygen demand, as a feedback mechanism. A pacemaker has no such direct feedback.

With rate adaptive pacing, and the same settings you won't see a 'fitness' drop in HR

by crustyg - 2019-10-01 17:32:12

The rate response of a modern PM can't measure what cardiac output you need.  So for a given amount of exercise and the same rate response settings then no, you won't see a reduction in HR over time as your heart becomes 'fitter'.  In fact, having your heart rate driven higher than perhaps your body needs can increase your blood pressure, over the long term.

But there is one thing that your body and heart can do as a result of regular exercise and training, and that's make each beat more or less powerful.  You have probably noticed that sometimes your heart beats are more powerful than others.  This is *not* because you've had a particularly powerful electrical stimulation to make the heart beat - the pulse generator in your PM is very carefully designed to avoid this.

But your heart muscle receives nerve signals - sympathetic nerves to increase heart contraction strength and vagus, or parasympathetic, to slow (not relevant with a PM) and reduce the contraction strength.  And of course there are hormones - adrenaline, amongst others - which increase the strength of each contraction - probably.  I suspect that they are much better at increasing heart rate than heart contraction strength.

So having answered your question, I'm going to adjust my answer.  As you improve your fitness, you may relax and work your voluntary, skeletal muscles less hard to achieve your treadmill performance target - you've heard sports commentators talk about runners tensing up or 'running tight'.  And if you find it easier, you *may* produce less input to the PM sensor(s) so that the software in your PM drives your heart to a lower rate.  Which would look as though your heart was needing to work less hard because it's 'fitter'.  But that's not the actual mechanism.

Thanks, crustyg.

by ffranny - 2019-10-01 17:53:40

Not only have I heard sports commentators talk about running tight, I've done it -- and learned from experience to try not to. I was a runner (not very fast) for 40+ years, so I've pretty much been there, done that for any kind of running experience a non-elite athlete can have.

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