hi,
thank you for providing the brief history of you.
as you mentioned you are facing the
rapid heart rate and weakness of the
limbs upon exertion. your age is 65 right?
now ageing is a process where nothing is constant. As the old tyre of the car has wear and tear the human body tissues do have the same wear and tear. And as age passed by, due to lack of exercise there is a weakness.
Also, loss of muscle mass is a common physiological process which all face. some looks bulky but the muscle fibres present in the muscle are actually lower.
memory loss is also an ageing factor. as the number of neural cells and the neural activity is reduced as Age progresses.
also, increase in heart rate while performing mild exertion is related to the endurance. when the endurance in the muscle is low it will lead the cardiac to work harder as the need for
oxygen is more in the cell for the muscle performing movement.
to help you out of this ageing process, you need to follow three basic things which keeps body at optimum at this age.
1. Meditation
2. breathing exercises
3. body conditioning.
all three when performed in a balanced equation gives a suport to the physiological system.
with the grace of God I wish you a good health