The exercises you are planning will strengthen you for the pounding you will take on the way down into the canyon, but they will do nothing to acclimatize you to the altitude. Only time at altitude will acclimatize you. Strong unacclimatized athletes often have greater problems than weaker unacclimatized athletes.

Here's a plan. Drive to the Canyon slowly. Stop in Flagstaff and spend a day hiking leisurely on one of the mountains around there (like O'Leary Peak) - don't go too high, but get up to around 8000 feet or so. Come back down and sleep overnight in or near Flag. The mantra for acclimatization is "climb high, sleep low." Then drive to GC, and hang around the rim for a day. Then start your hike. You will feel a lot better..

I think your "leader" is anything but that. I am glad you avoided misfortune. I hope you have many more enjoyable trips. <img src="/forums/images/graemlins/grin.gif" alt="" />