I'm on a cardiac rehabilitation course following bypass surgery. One of the cardiac nurses running the course explained they've had many people with angina symptoms, and those people are often surprised at the relatively high level of exercise they can achieve during the course without suffering any angina pain.
Her explanation was very interesting and I thought I'd pass it on in case anyone found it relevant.
The nurse pointed out that we always complete an extended, 15 minute long, warm-up routine. During that warm-up the arteries will naturally dilate and allow more blood to pass. Consequently many people with angina find that with pre-dilated arteries they can perform much more strenuous activities than they were used to. This learning has application outside the course, say someone with angina was faced with a number of tasks like putting the bins out or changing the bed sheets. Her advice was take 15 minutes walking on the spot to throughly warm up, but then complete ALL the tasks without cooling down between each one.
Her point was that going cold into a task will almost certainly trigger angina pain, where as a proper warm up will dilate the arteries more throughly than a GTN spray and allow you to complete more than you thought you could without angina pain.
Hope someone finds that of interest.