Start in a standing position, knees slightly bent, with the barbell in your hands at hip-height. Your feet should be hip-width apart and maintain a slight retraction of your shoulder blades. Keeping your arms straight, begin to hinge at the hips lowering the bar. Your spine should not change form and keep your knees in the same slight bend you started with. The moment you feel your spine start to round is the moment you should reverse the exercise, return to standing and then repeat.