I already take multi-vitamins. Some say these are good, others say
they are just garbage and don't help you in any way. They already
contain calcium.

The stair climbing does not hurt my knees at all. I'm careful not to
hurt them when doing any exercise. Today I had to do only half of what
I usually do because the lower back was a little weak. I thought it
was better to stop instead of hurting it. I did my climbing in the
morning before breakfast. I think I should have eaten something maybe
one or two hours beforehand. I also have more energy at around 10 or
11PM than in the morning.