RESUMEN
Bioceramic fabrics have been claimed to improve blood circulation, thermoregulation and muscle relaxation, thereby also improving muscular activity. Here we tested whether bioceramic fabrics have an effect on postural control and contribute to improve postural stability. In Experiment 1, we tested whether bioceramic fabrics contribute to reduce body-sway when maintaining standard standing posture. In Experiment 2, we measured the effect of bioceramic fabrics on body-sway when maintaining a more instable posture, namely a handstand hold. For both experiments, postural oscillations were measured using a force platform with four strain gauges that recorded the displacements of the center of pressure (CoP) in the horizontal plane. In half of the trials, the participants wore a full-body second skin suit containing a bioceramic layer. In the other half of the trials, they wore a 'placebo' second skin suit that had the same cut, appearance and elasticity as the bioceramic suit but did not contain the bioceramic layer. In both experiments, the surface of displacement of the CoP was significantly smaller when participants were wearing the bioceramic suit than when they were wearing the placebo suit. The results suggest that bioceramic fabrics do have an effect on postural control and improve postural stability.
Asunto(s)
Cerámica , Vestuario , Gimnasia/fisiología , Equilibrio Postural/fisiología , Postura/fisiología , Adolescente , Adulto , Método Doble Ciego , Femenino , Humanos , Masculino , Adulto JovenRESUMEN
Proprioceptive signals are of prime importance in kinesthesia. However, in conditions of visuo-proprioceptive conflicts, strong visual-evoked biases can be observed. In three experiments, we parsed the interaction between visual and proprioceptive afferents using the 'mirror box' paradigm. Participants' left arm, the image of which was reflected in a mirror, was passively moved into flexion/extension or remained static. In Experiment 1 proprioceptive afferents of the unseen static right arm were masked with diffuse arm vibration. In Experiments 2 and 3, afferent signals were enhanced by muscle vibration of biceps or triceps stretch receptors. Illusory arm movements were evaluated with subjective reports and matching adjustments. Results revealed that participants did not experience kinesthetic illusions when the mirror reflected the image of a static arm while proprioceptive afferents conveyed signals of a moving arm (Experiment 2). In this specific case, vision apparently contributed much more strongly to the final percept than proprioceptive signals. However, in most circumstances, the percept reflected integration of both afferent signals (Experiments 1-3). For instance, when both sensory channels conveyed signals of arm displacement but in the opposite direction, kinesthetic illusions occurred but were either proprioceptively (vibration illusion) or visually driven (mirror illusion), according to individual sensorial preferences (Experiments 2 and 3). These results indicate that kinesthesia is the product of cooperative integration processes in which the final percept strongly depends on the experimental conditions as well as sensorial preferences. The observed changes in the relative contribution of each input across experimental conditions likely reflect reliability-dependent weights.
Asunto(s)
Cinestesia/fisiología , Propiocepción/fisiología , Desempeño Psicomotor/fisiología , Vibración , Visión Ocular/fisiología , Percepción Visual , Adolescente , Adulto , Análisis de Varianza , Femenino , Antebrazo/inervación , Humanos , Masculino , Modelos Biológicos , Músculo Esquelético/inervación , Adulto JovenRESUMEN
Using galvanic vestibular stimulation (GVS), we tested whether a change in vestibular input at the onset of goal-directed arm movements induces deviations in arm trajectory. Eight head-fixed standing subjects were instructed to reach for memorized visual targets in complete darkness. In half of the trials, randomly-selected, a 3 mA bipolar binaural galvanic stimulation of randomly alternating polarity was triggered by the movement onset. Results revealed significant GVS-induced directional shifts of reaching movements towards the anode side. The earliest significant deviations of hand path occurred 240 ms after stimulation onset. The likely goal of these online deviations of arm trajectory was to compensate for a vestibular-evoked apparent change in the spatial relationship between the target and the hand.