Isometric strength assessment, part I: static testing does not accurately predict dynamic lifting capacity.

OBJECTIVE To determine if isometric (static) strength accurately predicts dynamic lifting capacity. PARTICIPANTS 107,755 male and 23,078 female prospective workers taking part in a post-offer employment test. METHODS Subjects were tested for strength three standard static lifts and attained physical maxima for four dynamic lifts. RESULTS The data confirms modest correlations between isometric and dynamic measures. However, the standard errors of estimate for all isometric-to-dynamic predictions make such predictions meaningless for the practical purpose for which they are most commonly used. CONCLUSIONS The Static Leg Lift, Static Arm Lift and Static Back (Torso) Lift are not appropriate for making predictions relative to dynamic lifting capacity. Given the likely degree of error in such predictions, and in light of potential safety concerns as reported by previous investigators, employers, clinicians and risk managers now have substantial objective evidence to call such testing into question.