I guess I shouldn't have used "rigorous" as a word. My trainer is great and has been working very carefully with me. We only work one of 5 muscle groups per day. Those muscles then rest till their next turn. He's started me off with low weights and reps, but enough different activities to keep me sweating but not straining for the whole time. I've been doing different typed of cardio to not stress any given muscle group further, the most being Zumba. Sweaty but not stressful. I'm quite active in my job and haven't felt stressed by any of this, quite the opposite, full of energy and seeing results already.

But thank you for the book recommendation, it looks pretty great