Kind of inspired by the 'how do we get fitter' thread, I've often wondered how come the heart doesn't seem to get tired.
Or maybe it does?
But let's say we lead a sedentary lifestyle. The heart never has to work too hard. (Well actually it does. It works very hard all the time. But I mean relatively speaking).
But then we start doing cardio work. Our superficial muscles will fatigue quote quickly. They may even end up quite sore. The next day they might feel barely able to move. Yet during the exercise that fatigued the superficial muscles, the heart was working a lot harder than usual. In fact it continues to work a lot harder than usual for some hours after the exercise stopped, as it still has to supply the increased blood flow to deal with the fatigued superficial muscles.
OK. I know the heart can fatigue and in extreme cases you get a heart attack. But generally speaking, major cardiac events aside, how come the heart doesn't ever seem to get DOMS, or how come you never seem to walk up one morning with your heart barely able to beat because it's tired?