Eight healthy men, unacclimated to heat, were submitted to variations in body hydration. The subjects were kept euhydrated, dehydrated by controlled passive hyperthermia or exercise on a treadmill up to a weight loss of 2.8%, or hyperhydrated using a solution containing glycerol, with a total ingested volume equal to 21.4 ml/kg of body weight. On completion of a 90-min recovery period, the subjects were assigned a pedaling exercise on an arm-crank ergometer. Psychological tests were administered 30 min after the phase of hydration variation and 15 min after the arm crank exercise. Both dehydration conditions impaired cognitive abilities (i.e., perceptive discrimination, psycho-motor skills, and short-term memory) as well as subjective estimates of fatigue, without any relevant differences between them. Short-term memory was significantly greater following hyperhydration when compared to euhydration (P < .05). Following arm crank exercise, further effects of dehydration were found for tracking performance only (P < .05). Moreover, long-term memory was impaired in both control and dehydration situations, whereas there was no decrement in performance in the hyperhydration condition.
This study investigates whether the vertical orientation may be predominantly used as an amodal reference norm by the visual, haptic, and somato-vestibular perceptual systems to define oblique orientations. We examined this question by asking the same sighted adult subjects to reproduce, in the frontal (roll) plane, the vertical (0 degree) and six oblique orientations in three tasks involving different perceptual systems. In the visual task, the subjects adjusted a moveable rod so that it reproduced the orientation of a visual rod seen previously in a dark room. In the haptic task, the blindfolded sighted subjects scanned an oriented rod with one hand and reproduced its orientation, with the same hand, on a moveable response rod. In the somato-vestibular task, the blind-folded sighted subjects, sitting in a rotating chair, adjusted this chair in order to reproduce the tested orientation of their own body. The results showed that similar oblique effects (unsigned angular error difference between six oblique orientations and vertical orientation) were observed across the three tasks. However, there were no positive correlations between the visual, haptic, and somato-vestibular oblique effects. Moreover, in some oblique orientations, there was a tendency to overestimate the angle between the oblique orientation and the vertical orientation. This effect varied according to the orientation value and the modality. Taken together, these findings suggest that although vertical orientation is used as a reference norm in the visual, haptic, and somato-vestibular systems to define oblique orientations, specific processing mechanisms seem to be at work in each perceptual system.
International audienceBioceramic fabrics have been claimed to improve blood circulation, thermoregulation and musclerelaxation, thereby also improving muscular activity. Here we tested whether bioceramic fabrics have aneffect on postural control and contribute to improve postural stability. In Experiment 1, we testedwhether bioceramic fabrics contribute to reduce body-sway when maintaining standard standingposture. In Experiment 2, we measured the effect of bioceramic fabrics on body-sway when maintaininga more instable posture, namely a handstand hold. For both experiments, postural oscillations weremeasured using a force platform with four strain gauges that recorded the displacements of the center ofpressure (CoP) in the horizontal plane. In half of the trials, the participants wore a full-body second skinsuit containing a bioceramic layer. In the other half of the trials, they wore a ‘placebo’ second skin suitthat had the same cut, appearance and elasticity as the bioceramic suit but did not contain thebioceramic layer. In both experiments, the surface of displacement of the CoP was significantly smallerwhen participants were wearing the bioceramic suit than when they were wearing the placebo suit. Theresults suggest that bioceramic fabrics do have an effect on postural control and improve posturalstability
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