Whether walking the red carpet or hitting the stage, country singer Carrie Underwood has been known to rock her share of super-short frocks. (Have you seen her legs?!) The key to keeping them slim and strong: body-quivering, lower-half moves, like this three-part lunge series. “You’re targeting your quads, hamstrings, glutes, and calves,” explains Underwood’s on-the-road trainer, Eve Overland.

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Start with feet hip-width apart. Step right foot forward and lower down into a lunge until both legs form 90-degree angles; begin pulsing, up 2 inches, down 2 inches (A). Keeping abs tight and spine aligned, shift weight and torso forward; continue pulsing (B). Return to A and shift weight and torso back (C); continue pulsing. Try each position for 20 seconds; rest and repeat on the opposite leg.