Does side dominance affect the symmetry of barbell end kinematics during lower-body resistance exercise?

The aim of this study was to examine whether ground kinetic asymmetries significantly affected measures of bar end power output during bilateral lower-body resistance exercise. Vertical ground reaction forces (GRFs) from both feet and power outputs from both ends of the bar were recorded using force platforms and high-speed cameras simultaneously during the back squat performance of 10 experienced male volunteers with 30, 60, and 90% of their 1 repetition maximum. Side dominance was determined according to perceived left- and right-side handedness, dominant left- and right-side GRFs, and barbell power output side dominance. The dominant and nondominant side average concentric phase GRFs and barbell end power outputs were compared at each loading condition using 2-way analysis of variance. Pearson product-moment correlations were also performed to assess the relationship between average GRF and bar end differences. The results showed that although differences between the dominant and nondominant side GRFs reached 21% in some cases, there were no significant differences between the left- and right-side bar end power outputs, which did not exceed 3.4%. There were no consistent correlations between the dominant and nondominant side average GRFs and average bar end power differences. In addition to this, progressive loading did not significantly affect differences between the dominant and nondominant side GRFs or bar end power output differences. It was concluded that although apparently healthy individuals demonstrate considerable side dominance at the foot-floor interface, these tend not to be reflected in the symmetry of bar end power output.