Stand tall with your core braced and a flat back, holding a dumbbell in each hand. Feet should be shoulder-width with your toes pointed forward. This is your start position. Brace your core and keep your chest up. Bending at the knees, drive your hips back and down as if you are going to sit on a chair. Lower slowly with control until your thighs are parallel to the floor, making sure your knees are pointing in the same direction as your feet and that your lower back doesn't collapse. Inhaling throughout this lowering phase. Pause at the bottom, then push through your feet to extend your legs and drive your hips forward to return to the start position, exhaling as you do so. Do not lock out your knees at the top.