The objective of this investigation was to examine the influence of body mass in the calculation of power and the subsequent effect on the load-power relationship in the jump squat, squat, and power clean. Twelve Division I male athletes were evaluated on their performance across various intensities in all the 3 lifts. Power output was calculated using 3 separate techniques: (a) including the contribution of body mass in force output (IBM), (b) including the contribution of the mass of body less the mass of the shanks and feet in force output (IBMS), and (c) excluding the contribution of body mass in force output (EBM). Peak power, peak power relative to body mass, and peak force calculated using EBM were significantly (p <= 0.05) lower than outputs calculated with IBM and IBMS. The load that maximized power output was unchanged between the 3 techniques in the jump squat (0% 1 repetition maximum [1RM]) and power clean (80% 1RM) but was shifted from 56% (IBM and IBMS) to 71% 1RM (EBM) in the squat. Across all 3 movements, the shape of the load-power curve was affected when derived via the EBM method as a result of the underrepresentation of power output at light loads. This was due to the majority of the load being neglected when the mass of the body was removed from the system mass used in the calculation of force. This study indicates that not only is the actual power output significantly lower when body mass is excluded from the force output of a lower body movement, but the load-power relationship is altered as well. Therefore, it is imperative that the mass of the individual being tested is incorporated into the calculation of force used to determine power output during lower-body movements.
(C) 2007 National Strength and Conditioning Association