Everyone reacts to chemo in different ways. I've tried to exercise straight after chemo, even though I'm feeling "spaced out", then 30 mins the next day. After that, I'm lucky to manage a walk for the next few days until symptoms subside. When I start to feel better I do gentle weights or a Step class & just let my body be my guide as to what I can cope with. I don't always get through a class, but I'm definitely exercising 5-6 days per week. I find the more I do, the better I feel.
Good luck, do what you can!
Kristy