I'm 66 and take a brisk walk every day, and swim two to three days a week.  Is this enough for heart health?  I've read about the need to get your heart pumping at a certain rate for a sustained period of time to receive any real benefit.  Should I check my pulse while exercising?  And what is the optimal heart rate we should achieve during exercise?
D000368:Aged; D015444:Exercise / Q000502:physiology*; D006304:Health Status; D006339:Heart Rate; D006801:Humans; D009043:Motor Activity; D011674:Pulse