Let me start of by saying that Utkatasana is my least favorite of all yoga postures, however, this posture helps to build stamina and strengthens the thighs. I use this posture in classes to have students focus inward, control their breath, and concentrate.
Stand in Tadasana or Mountain Pose. Inhale and raise your arms perpendicular to the floor. Either keep the arms parallel, palms facing inward, or join the palms.
Exhale and begin to bend your knees, trying to take the thighs as nearly parallel to the floor as possible. The knees will project out over the feet, and the torso will lean slightly forward over the thighs until the front torso forms approximately a right angle with the tops of the thighs. Keep the inner thighs parallel to each other and press the heads of the thigh bones down toward the heels.
Firm your shoulder blades against the back. Take your tailbone down toward the floor and in toward your pubis to keep the lower back long.
Stay for 30 seconds to a minute. To come out of this pose straighten your knees with an inhalation, lifting strongly through the arms. Exhale and release your arms to your sides into Tadasana.
Strengthens the ankles, thighs, calves, and spine
Stretches shoulders and chest
Stimulates the abdominal organs, diaphragm, and heart
Reduces flat feet