How to do it: Stand tall with your feet together, and brace your core. From here—holding onto a wall, counter, or sturdy chair for balance, if necessary—lift your right foot just off of the floor so that you’re standing on your left foot. Imagine a string through the crown of your head is pulling your spine straight toward the ceiling, and engage your core to avoid leaning to one side. Hold this position for 30 seconds or as long as you can, then repeat on the opposite side.
The other two, the medius and minimus, work together to aid your gluteus maximus in raising your leg to the side. Plus, those smaller glute muscles help rotate your thigh outwards when your leg is straight, and inwards when your hips are bent. Talk about a dream team! (To learn more about the workings of your glutes, check out The Women's Health Big Book of Exercises!)