Begin by holding a dumbbell vertically between both hands at chest height. Feet should be shoulder-width apart. Brace your core and keep your chest up. With your right leg take a wide step directly out to the side, whilst simultaneously bending at the knee. Drive your hips back and down as if you are going to sit on a chair. Lower slowly with control until your thigh is parallel to the floor or deeper depending on your range, making sure your knee is pointing in the same direction as your foot and that your lower back doesn't collapse. Inhale throughout this lowering phase. Pause at the bottom, then push through your right foot to extend your leg 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. Repeat the movement on the leg and keep alternate legs for the required amount of reps (or time).