Lumbar forces in male dancers during classical ballet lifts

Hopper, Luke BSc Honours, University of Western Australia, Perth, WA, Australia; Alderson, Jacqueline University of Western Australia, Perth,WA, Australia; Elliott, Bruce University of Western Australia, Perth, WA, Australia; and Ackland, Tim, University of Western Australia, Perth, WA, Australia

Lower back injuries (LBIs) are common in classical ballet dancers, allegedly more so in male dancers than in ballerinas due to the lifting requirements of the males (1,2,3). When applied to the lumbar spine anterior shear force has been attributed to the onset of LBI (4,5). This original research analysed the estimated level of peak shear and corresponding compression lumbar forces in 8 male dancers (WA Ballet & WAAPA) performing Full Press (FP) and Arabesque (AR) classical ballet lifts. 3D data was captured using a Vicon MX 3D motion analysis system (Oxford Metrics, Oxford, UK) and one AMTI force plate (AMTI, Watertown, MA, USA). The point of estimated peak shear lumbar force was identified using a customised 3D dynamic model. This occurred, irrespective of lift, at the beginning of the movement prior to vertical displacement of the ballerina?s approximated centre of mass position (Figure 1). Force magnitudes were estimated using a 3D Static Strength Prediction Package (3DSSSP) (University of Michigan, Centre for Ergonomics, 2006). Both lifts output compression forces greater than the National Institute of Occupational Safety and Health (6), Back Compression Design Limit (3400N). This indicates need for administrative controls to reduce the risk of LBI associated with the lifts. Peak shear and corresponding compression forces were significantly (p<0.05) higher in the FP than in the AR, which may be attributed to the dynamic nature of the lift and a significantly (p<0.05) larger horizontal distance between the male dancer and the ballerina. The distance between the male dancer and the ballerina was the only variable to appear in analyses of both the 3D dynamic model and 3DSSPP as a significant predictor (p<0.05) of peak shear force despite a range of less than 10 cm. Peak shear force magnitudes appear to be highly sensitive, therefore a fine balance appears to exist in training male dancers sufficiently to minimise lifting error without overtraining and risking a fatigue related injury.

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