i just turned 60 and am now 7 years post emergency bypass surgery. if you are perfectly comfortable playing squash with your heart rate that high not out of breath not breathing hard or panting no chest pain then you simply have fantastic fitness. its a whole body activity utilizing legs and tush as you move about the floor and back and ab muscles as you lean in all directions to move for the ball and start and stop. just be sure you eat a very healthy diet plenty of anti-oxidant rich foods every day and keep a lid on saturated fats in the diet. with a bad diet your heart can develop an alternative capillary network that feeds it as major arteries become blocked from bad diet with good exercise. this does not happen to every one but i have this and i know of a fellow about 60 miles away who does also. he also recently had bypass surgery.
my heart rate often goes as high as 170 beats per minute when i exercise. i am in my mid-60s. should i worry about this? i monitor my blood saturation and it sometimes drops into the low 90s. i have been doing this same kind of workout (squash) for 18 years.