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Philippe C. Dixon and David J. Pearsall

The purpose of this study was to determine the effect of cross-slope on gait dynamics. Ten young adult males walked barefoot along an inclinable walkway. Ground reaction forces (GRFs), lower-limb joint kinematics, global pelvis orientation, functional leg-length, and joint reaction moments (JRMs) were measured. Statistical analyses revealed differences across limbs (up-slope [US] and down-slope [DS]) and inclinations (level; 0°; and cross-sloped, 6°). Adaptations included increases of nearly 300% in mediolateral GRFs (p < .001), functional shortening the US-limb and elongation of the DS-limb (p < .001), reduced step width (p = .024), asymmetrical changes in sagittal kinematics and JRM, and numerous pronounced coronal plane differences including increased US-hip adduction (and adductor moment) and decreased DS-hip adduction (and adductor moment). Data suggests that modest cross-slopes can induce substantial asymmetrical changes in gait dynamics and may represent a physical obstacle to populations with restricted mobility.

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Sarah M. Coppola, Philippe C. Dixon, Boyi Hu, Michael Y.C. Lin and Jack T. Dennerlein

This study examined the effects of 4 micro-travel keyboards on forearm muscle activity, typing force, typing performance, and self-reported discomfort and difficulty. A total of 20 participants completed typing tasks on 4 commercially available devices with different key switch characteristics (dome, scissors, and butterfly) and key travels (0.55, 1.3, and 1.6 mm). The device with short-travel (0.55 mm) and a dome-type key switch mechanism was associated with higher muscle activities (6%–8%, P < .01), higher typing force (12%, P < .01), slower typing speeds (8%, P < .01), and twice as much discomfort (P < .05), compared with the other 3 devices: short-travel (0.55 mm) and butterfly switch design and long travel (1.3 and 1.6 mm) with scissor key switches. Participants rated the devices with larger travels (1.3 and 1.6 mm) with least discomfort (P = .02) and difficulty (P < .01). When stratified by sex/gender, these observed associations were larger and more significant in the female participants compared with male participants. The devices with similar travel but different key switch designs had difference in outcomes and devices with different travel were sometimes not different. The results suggest that key travel alone does not predict typing force or muscle activity.