I am passionate about this... after spending $$$ with trainers and seeing no difference in my buttocks, I took myself to the street. I am walking the hills; taking longer, deliberate steps AND doing stairs. If your knees can tolerate skipping one step (thus creating longer, more challenging steps), I highly recommend it. In a couple of months, I noticed
a tremendous difference in my "bum" as you call it. It has lifted and doesn't look like a neighbor to the back of my knee!! OF COURSE, eating clean, non-greasy, low carb diet comes into play here, as well. Enjoy AND concentrate
on the area that you're working while you're working it!