Bonj, as usual, talking bollocks.
I once did clinical trials with a bunch of averagely fit aussies and kiwis. All keen sportsmen, none of us super-athletes.
The trials involved spending hours at a time on our beds wired up to hospital monitors.
The alarms on the monitors would regularly go off as our HRs dropped to 35, 33, 32bpm. The nurses would dart out from their station, expecting an adverse reaction to the drug we were testing, only to find us reading, or dozing or something.
After a while, as a courtesy to the nurses, we'd do a few half-situps or something to keep the HR in the mid-40s.