Buy, and use, a
scooter.
No, not a motorised one, but one of the ones like a skateboard with handlebars.
This mode of transport is popular with young urban professionals and hepcats as the scooters are easy to steer and don't take as much skill as riding one of those fang-dangled skateboards those crazy kids with green hair and body-piercing and Blink 182 T-shirts use.
Because a lot of scooter riders can only push off with one leg comfortably they neglect to strengthen and firm up their other side, which results in what we in the industry* call una dimidium gluteus adamanteus .
Yes, that dreaded one half-hard, one half-flabby butt condition.
Scooter riders: Do yourself a favour and learn to use both legs to push off.
* The industry that churns out lazy, unskilled university graduates, that is. Most of whom only use the scooter to go to the nearest corner shop or pub.