Bicycle magazine: Core

Your bulging quads and razor-cut calves are the envy of your pack, and you start every ride strong. As the ride progresses, though, your hips seesaw in the saddle, your lower back aches, and you slow in corners. The problem? Your core cries uncle long before your legs wear out. Although a cyclist's legs provide the most tangible source of power, the abs and lower back are the vital foundation from which all movement, including the pedal stroke, stems.
"You can have all the leg strength in the world, but without a stable core you won't be able to use it efficiently," says Graeme Street, founder of Cyclo-CORE, a DVD-based training program, and a personal trainer in Essex, Connecticut. "It's like having the body of a Ferrari with a Fiat chassis underneath."
Read the rest here in Bicycle magazine.
It's true. The core muscles needed for cycling aren't the most obvious. You need the whole machine to do with the work, of course, but the legs get all the attention. Working the core will help you work more efficiently and powerfully.
Happy spinning, y'all.