The aim of this experiment was to evaluate bilateral motor performance effects from training the non-dominant leg of competitive soccer players. The subjects were 39 soccer players, 15-20 years of age, performance-matched and randomly divided into a training group (n = 18) and a control group (n = 21) both belonging to the same team. Both groups were tested by using two standardised foot-tapping tests and three soccer-specific tests. The training intervention consisted of the experimental group participating in all parts of their soccer training except full play, using the non-dominant leg for 8 weeks. Statistical analyses for the soccer-specific tests revealed that the experimental group improved significantly as compared to the control group from the pre-test to the post-test period in their use of the trained non-dominant leg. Somewhat unexpectedly, the experimental group also improved significantly in the tests, which made use of the dominant side. The standardised foot-tapping tests revealed similar results. The results might be explained by improved generalised motor programmes, or from a Dynamic Systems Approach, indicating that the actual training relates to the handling of all the information available to the subject in the situation, and that the body self-organises the motor performance.

Motion sickness induced using linear visual oscillatory stimuli exhibited sex differences greater than those that have been reported in field studies. Sex differences in motion sickness may vary as a function of the type of motion stimulation (linear versus angular).

Motion sickness is more common among women than among men. Previous research has shown that standing body sway differs between women and men. In addition, research has shown that postural sway differs between individuals who experience visually induced motion sickness and those who do not and that those differences exist before exposure to visual motion stimuli. We asked whether sex differences in postural sway would be related to sex differences in the incidence of visually induced motion sickness. We measured unperturbed standing body sway before participants were exposed to visual motion stimuli that induced motion sickness in some participants. During postural testing, participants performed different visual tasks. Results revealed that postural sway was affected by visual tasks, consistent with the literature. In addition, we found a statistically significant three-way interaction between visual tasks, sex, and (subsequent) motion sickness status. These results suggest that sex differences in motion sickness may be related to sex differences in the control of postural balance.

BACKGROUND Sea travel leads to well-known changes in gait, but these effects have not been evaluated using quantitative data obtained through controlled experiments. We obtained quantitative data on step-timing patterns as experienced maritime crewmembers walked on a ship at sea. METHODS Using a within-subjects design, crewmembers walked back and forth along straight line paths (11 m long) that were parallel with the ship’s long (i.e., fore-aft) and short (i.e., athwart) axes. Using contact switches attached to the feet, we measured temporal parameters of gait, including stride time, the variability of stride time, and the coefficient of variation. We also evaluated the temporal dynamics of stride times using detrended fluctuation analysis. RESULTS The variability of stride time differed between walking fore-aft (mean = 0.10 s) and walking athwart (mean = 0.28 s). The coefficient of variation also differed between walking fore-aft (mean = 11%) and walking athwart (mean = 43%). CONCLUSIONS We obtained direct evidence that ship motions in roll and pitch differentially affect the timing of stepping patterns in human gait. This novel finding motivates new research on quantitative parameters of gait at sea.