Althought not addressing the specifics of Q's post, I also agree that the specifics of training are unimportant. I think that lower body aerobics are the ticket, but you do what you have available.

BobR has continually impressed me with his experience with people who have not trained. It requires patience.

Optimal is hiking with weight, both uphill and downhill, for sustained distances. That is the best for the specific muscles and body parts.

Any aerobic activity works for the lung part.

When it comes time for the actual performance, optimally, one goes at a less intense level than the practice, with much in reserve, in case of problems.