http://www.sloh.org/increasing-athletics-oblivion/
Where to get athletics into oblivion?
I heard that you can increase your athletics into oblivion for swimming, but there is a safe place to swim without being attacked?
Well there is a little trick I discovered for this … Works to level up Sneak too. Sign at an inn … (Or else a limited both will be safe from danger) then put your controller upside down but make sure the control lever is stuck forward making your character run. This works best on a shag rug. If you can not get to stay stuck, try to launch an elastic band in the country. Once you have it nice and stuck, go watch TV or something. Back in an hour or two, and voila! Your athlete should be much higher. If you are using the PC version is the easiest way … Simply press the race car. If you want to do it manually all, then circles swimming in the pond on the anvil. It's a pain though.
Oblivion – Increase Acrobatics Faster