It turned out that a kids summer camp was making a field trip to the Big City ED, and the doc needed a volunteer to undergo an ultrasound demonstration. More than happy to strip in the support of education, I headed over to the trauma bay and hopped on the stretcher. Listening to the oohs and ahhs as the attending narrated a tour through my liver, gall bladder, and lungs, I noticed a pause once she switched to the cardiac probe.
As my heart valves opened and closed on the monitor, the attending leaned towards me and asked in a slightly concerned and doubtful tone if I was an athlete. With a resting pulse in the 40s, I reassured her that my bradycardia was perfectly normal.
Apparently I have the running down, it's just the physique part I have to work on.