Motor strength is often rated on a 0 to 5 scale: 0: No visible muscle contraction 1: Visible muscle contraction with no limb movement 2: Limb movement but not against gravity 3: Movement against gravity but not resistance 4: Weakness against resistance 5: Full strength Although these numbers seem objective, rating strength between 3 and 5 (the typical levels during early weakness, when diagnosis usually occurs) is rather subjective; if symptoms are unilateral, comparison with the unaffected side improves discrimination.