Today, I did the taiji form first, then Five Golden Coins, then the first four of the 8 pieces of brocade (from memory). Reversing the order of the activities (although not the order of the postures in each form), allowed me to work up a sweat. Not that I need to — last night was hot and steamy and uncomfortable. The weather was sort of chilly when I went to bed, and by morning I had thrown off all the covers except a single sheet. It’s going to be a hot, hot summer.
Anyway, that’s sort of drifting away from the main point, which is that by doing things in a different order from time to time, you’re preventing your muscles from getting too comfy with one pattern. By doing some taiji first, and then qi gong, or doing your forms in a reversed order, you’re strengthening the core and your periphery by challenging them to work in a different way than usual.