Hi Dr Jain Recently I spoke to a friend who had been a fitness fanatic, doing strenuous activity including hill walking, regularly until he was 80. Not long ago, his doctor diagnosed a hardening of the heart muscles, enlarging the heart overall, and causing a shortness of breath and lethargy. It seems to a non expert such as I that the symtoms are similar to arterial sclerosis around the heart, perhaps because the effects are similar, ie a reduced efficiency in the heart s operation. My question is: If the heart is a muscle, and can be grown and strengthened by exercise, can it be reduced in size again, by atrophy, perhaps reducing the heart to an appropriate size and regaining its flexibility and fuller function if the exercise level is reduced? If it is possible, how do you suggest one goes about it. My friend has been prescribed an increased dose of anti- high blood pressure pills, which he says make him very sleepy, which he does not like. He is not the kind of guy to stop taking the pills (or do anything else) without proper medical supervision, so please feel free to suggest anything appropriate. In my own inexpert view, I understand that the reduced function of the heart reduces oxygen flow between the lungs and other organs, through the blood, causing the lethargy etc. My simplistic mind wonders if breathing in extra oxygen might have some beneficial effect, but I recognise my limited expertise here and am expecting your greater knowledge to be able to explain why this would not work! Thank you. Mike Windsor