The danger of falling arises when the unsuspecting climber shifts his center of gravity, causing the ladder’s elevated rear leg, to impact the ground. This is likely to occur when the user lifts one foot while stepping from one level to the next or shifts his weight while working. When this happens, large and rapid forces and the user’s overcompensating reflexes can cause him to lose his balance and fall….
Based on our research, Type II racking can easily lead to the…three-legged condition, even when a stepladder meets the present ANSI (Type-I) racking standard. Based on dynamic testing, a vertical rear leg lift of as little as 1 inch is sufficient to cause a ladder user to fall upon unanticipated crossover. This scenario is consistent with many accident investigations and offers a likely explanation for stepladder fall accidents when there is no obvious cause. We have found that the minimum leg lift-off required to cause a ladder user to fall upon crossover is less than 1 inch and also depends greatly on the agility of the ladder climber.