What is the best way to gauge how much exercise is too much?
The general rule is that people need to pace themselves and limit their exercise based on their ability to do it. So if your mother is exercising and having chest pain, that's definitely too much. But as long as she's exercising with frequent resting so she's not exhausted, short of breath, or having angina symptoms, it's probably okay.
Think of it this way: She's not training to run a marathon, she's just exercising because it makes her feel good, and because staying active helps her to remain active. So how she exercises depends on what feels good. For some people, that may just mean going through the daily routine; for others, it may mean actual scheduled exercise like walking, from even just several feet to a few blocks. But the important thing is that she shouldn't push herself to the point of having symptoms or past the point of having symptoms. And she should definitely discuss her exercise program with her doctor.
I'm no expert, but I'd bet your mother will know. Keep an eye on the clock and watch for fatigue. Personally I wouldn't go for more than ten minutes to start and see how she's feeling then.
