L4/L5 COMPRESSIVE LOADING IN MALE PAIR FIGURE SKATERS DURING PRESSURE AND WAIST LOOP LIFTS

Abstract

Pair skating is highlighted by overhead lifts, in which the lady is held 2 metres in the air or more above her male partner's head. Because younger and younger skaters are attempting overhead lifts, safety concerns arise related to the potential for back injury. The purpose of this study was to estimate the L4/L, compressive forces on young male pair figure skaters at the onset of two sagittal plane overhead lifts using a 2-dimensional, quasi-static biomechanical model (WATBAK). Results were compared with industrial lifting guidelines of the National Institute for Occupational Safety and Health (NIOSH, 1981). Three male pair figures skaters and their partners were videotaped on the ice performing 2 different overhead lifts: a pressure lift and a waist loop lift. The posture of interest was of the male at the moment when the female's blade just left the ice. The males' body segment endpoints were digitized using the Peak 2D system. To calculate the L4/L, compressive force, the load on the hands was required. This was determined statically as the female partner's body weight and dynamically by entering the maximum force generated by the female when executing the lift take-off from a force platform in an off-ice lift in the laboratory. Static lifts produced lower compressive forces than dynamic lifts and loop lifts tended to produce lower overall compressive loads than pressure lifts. All of the static lifts were below the NIOSH Maximum Permissible Limit (MPL), while the MPL was exceeded by two subjects in both of the dynamically modelled situations. One subject's compressive loads were lower than the other two, possibly because his partner's mass was only 46% of his own mass, while the other partners were 66% and 53 % of the males' masses. While the dynamic lifts exceeded the NIOSH MPL, these forces were only sustained for very short periods of time. Based on the results of this study, it was recommended that skaters not practice several successive lifts in one session, but intersperse lifts with other non-lifting activities. This study confirms the well-established practice of teaching young male pair skaters waist loop lifts before pressure lifts.