A metabolism-boosting workout that builds strength and tones your abdominals, back, thighs, butt and arms.

11 Exercises That Build Muscle Without Bulk

A metabolism-boosting workout that builds strength and tones your abdominals, back, thighs, butt and arms.

Twisting knee plank

Strengthens: Upper and lower body; arms, shoulders, abdominals, obliques, butt

Get into plank position (the up part of a push-up). Twist your lower body to the left, then to the right; return to center. Bring your left knee forward to touch your left elbow; hold for 1 second, then return to center and repeat on the right side. That's 1 rep; do 20 reps.