Engage Gluteus Maximus for Piriformis Injury?

I was googling piriformis and roller skiing yesterday because I thought I might go out for an inline skate (don't have roller skis) instead of a run. I came across this page, a personal testimony of how one guy (thinks that he) solved his piriformis injury. His logic goes

1. I never get butt soreness when I alpineer

2. I always wear a backpack when I alpineer

3. Wearing a backpack causes me to activate my gluteus maximus

4. Therefore, activating the gluteus maximus has allowed me to alpineer injury free

5. Consequently activating the gluteus maximus during activity will allow me to recover from piriformis injury and remain injury free in the future.

Hmm? #4 simply doesn't follow from the premises (#1-3). Its a typical case of post hoc ergo propter hoc. Lots of things occurred prior to his not getting injured. Maybe it was the pollen from the lovely alpine flowers. But I guess it allows us to start somewhere. But a problem is that the gluteus maximus is activated during running but runners get piriformis injury. Lots of sights claim downhill running can aggravate the piriformis - is this because the g. maximus is not active?