I'd like to make a device that could be used to temporarily stimulate a pacemaker's accelerometer, to be used during low-impact exercise.
"Adaptive" pacemakers are intended to increase a person's heart rate when the person exerts himself, for people like me whose heart doesn't speed up like it should (chronotropic incompetence). Most adaptive pacemakers use an accelerometer to estimate exertion -- if the accelerometer senses that the person is acceleration activity, the pacemaker takes that as an indicator of exertion.
That works for higher impact exercise like running, but unfortunately not for low impact exercise like bicycling. So for low impact exercise, it would be useful to deliberately get the pacemaker to raise heart rate.
Unfortunately, a person cannot adjust their pacemaker's settings manually. That is done (wirelessly) in the doctor's office, using specialized manufacturer-specific systems.
So I would like to make a device that can temporarily simulate high impact activity -- as far as the pacemaker's accelerometer is concerned -- by thumping or patting a person's chest over the site of their pacemaker, for use during low impact exercise like a bike ride.
There's an easy proof of concept. If I use my hand to continuously clap or pat my pacemaker (through the skin of my chest), a few times per second (roughly the rate at which your feet impact the ground while running), my pacemaker will gradually raise my heart rate.
The target area on the chest is a circle about 1.5-2 inches in diameter, where the pacemaker is lurking under the skin.
I'm imagining something like a battery-powered motor driving (gently) a piston, but I'm basically clueless, and looking for suggestions.
My first thought would be to try something similar to how a speaker works. Wrap wire around a tube and pass alternating current through it at the frequency of foot falls while running. Attach a magnet to a rod inside the tube and it'll move back and forth withe the current. I don't know the equations that govern that interaction off the top of my head, but I imagine there's a size vs force trade off. In order to get the acceleration you need, you might need a long stroke or tons of current. I'd be wary of electronic interference with the pacemaker. Good luck, from one cyclist to another.