Directional asymmetry in handedness and hand efficiency
Several studies analyse anthropometric dimensions of the hands, but few look at how they influence hand performance or hand efficiency. In this analytic cross-sectional study conducted amongst 162 preclinical medical students, directional asymmetry was evaluated in relation to hand preference and hand efficiency in order to determine whether it can be used as an indicator for outcomes of hand dominance. Directional asymmetry (DA) was established by calculating differences in the mean hand measurements and the mean hand volumes. Hand preference was assessed using the modified Edinburgh Handedness Inventory, and handedness categories determined by applying the Geschwind Score. Hand dominance was categorized from the laterality score obtained from differences between left and right hands. Differences in hand dimensions were evaluated in relation to hand preference and hand efficiency. An apparent similarity in the morphology of the hands was suggested by the highly positive statistically significant result in the paired samples correlation test across all the parameters (p < 0.001). A positive association (not statistically significant) was noted between the handedness categories and the demonstrated directional asymmetry. No gender disparity was found in the relationship between DA and Hand efficiency by grip strength testing. The EHI-GS hand preference category positively indicated the preferred hand but did not on its own designate hand dominance or hand proficiency. Notwithstanding the gender, EHI-GS handedness neither predicted DA nor hand efficiency. Similarly, neither EHI-GS hand preference nor hand efficiency by grip strength testing could predict DA in males and females alike.
Key words: Hand performance, Hand proficiency, Hand dominance, Grip strength testing, Laterality