Sex-Based Differences In Lifting Technique Under Increasing Load Conditions: A Principal Component Analysis
Sheppard, Phillip S.
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The objectives of the present study were: 1) to determine if there is a sex-based difference in lifting technique across increasing load conditions; and, 2) to examine the use of body size-adjusted tasks and back strength-adjusted loads in the analysis of lifting technique. Eleven male and 14 female participants (n=25) with no previous history of low back pain participated in the study. Participants completed freestyle, symmetric lifts of a box with handles from the floor to table height for five trials under three load conditions (10%, 20%, and 30% of their individual maximum isometric back strength). Joint kinematic data for the ankle, knee, hip, and lumbar and thoracic spine were collected using a two-camera Optotrak 3020 system (NDI, Waterloo, ON). Joint angles were calculated using a three-dimensional Euler rotation sequence and PCA was applied to assess differences in lifting technique across the entire waveform. A repeated measures ANOVA with a mixed design revealed no significant effect of sex for any of the PCs. This was contrary to previous research that used discrete points on the lifting curve to analyze sex-based differences but agreed with more recent research using more complex analysis techniques. There was a significant effect of load on lifting technique for six PCs of the lower limb (p<0.005). However, there was no significant difference in lifting technique for the thoracic and lumbar spine. It was concluded that, when load is standardized to individual back strength characteristics, males and females adopted a similar lifting technique. In addition, as load increases participants used more of a semi-squat or squat lifting technique.