You are 72 years old your heart beat rate is 42-48 are you in trouble?

yes, if you are not doing any exercise because your maximum heart rate is 220 minus your age, so 220-77=143 then the amount you exercise is never 0% so even if you are doing 20% exercise your heart rate is still pretty low. Plus if you are on high blood pressure pills that also slows down your pulse rate. you should still ask your doctor.