I am 65 years old and play a lot of good standard tennis. I am also a soccer ref and assistant. Recently I have been feeling absolutely shattered after doing these sports. My heart rate is up in the 80s for a few hours after the activity but it is usually 58- 60 bpm. Should I take beta blockers which have been suggested. I did the suggested manoeuvre for lowering the heart rate and it dropped to normal straight away.