B.C.
Stairs.
Lot's of stairs.
I use to go to the high school football field and run up and down the bleachers.
When it gets easy, wear a backpack with some heavy books in it.
I was in 11th grade when I worked clean up crew at an 80,000 seat stadium.
I was carrying up to 3 sacks of trash on my back (wet blankets get HEAVY) up and down all those lovely stairs.
The weather was sometimes hot, sometimes cold, sometimes wet, the work was always stinky, and even with work gloves pushing the brooms gave me blisters but my legs/behind NEVER looked so good as when I had that job.