Picture this: a single move that not only strengthens your key leg muscles (quads, hamstrings, and glutes) but also improves your balance, coordination, and yes, gets your heart pumping like a cardio ...

The best way to avoid common problems like runner’s knee is to strengthen the muscles that support this important joint.

Relatively simple but effective exercises are often particularly popular. Step-ups definitely fall into this category, primarily working our glutes and legs. They also burn calories at the same time.

"Hearst Magazines and Yahoo may earn commission or revenue on some items through these links." Ready to sweat? Keep reading to find out more benefits of single-leg exercises, as well as the best ones ...