If you regularly run on flat terrain, it's time to hit the hills. FitSugar recommends hill repeats to jump-start your conditioning. You don't need to kill yourself on a steep, 30-degree hill. Find a medium, 5-6 percent grade incline and incorporate this series of hill climbs, runs, and finally, sprints. Don't forget your warm-up and cool-down.

Not sure there are inclines in your area? Try Map My Run -- a fantastic tool to locate running routes with the nitty-gritty details on elevation, grade and a variety of map views (hybrid, street, terrain, satellite, topo). If you're a Saucony-clad map and compass running freak, this site is for you.

Get ready to burn bunches of calories running hills, too.