Utkatasana is a great blend of strengthening the legs as you squat while keeping your heart open as you lift your arms to the sky. Add in a twist to each side for great cleansing benefits as you release energy and massage the internal organs. It builds a lot of heat in the body, and fast!
Benefits (from yogajournal.com)
Strengthens the ankles, thighs, calves, and spine
Stretches shoulders and chest
Stimulates the abdominal organs, diaphragm, and heart