We studied the degree of dependence on vision of static postural control among ten male adult ironmen and ten healthy subjects (firemen, control group) who took part in regular physical activity, and the perturbations of equilibrium after prolonged exercise in ironmen. Static postural stability was measured during standing on a single-force platform alternating between eyes open and eyes closed. First, body sway was analysed on a force plate in both groups, and the athletes then took part in an ironman triathlon. The measurement was repeated after the race. The sway in both directions was subjected to spectral analysis. The frequency spectrum of the platform oscillations was calculated by fast Fourier transformation in the intervals 0-0.3, 0.3-1 and 1-3 Hz. The sway path in both directions and the total path were significantly lower in the ironmen than in the control group without vision, and the absence of visual control caused a significant increase in sway in both directions in the control group, but not in the ironmen. The frequency analysis revealed a higher level of stability in the medio-lateral direction with closed eyes. The endurance race caused increases in both the total sway path only with closed eyes, and these changes were significant at higher frequency bands. These results indicate that ironmen are more stable and less dependent on vision for postural control than the control subjects, and the prolonged stimulation of the proprioceptive, vestibular and visual inputs in the endurance race causes a significant disturbance in postural control.

The changes in postural control in elderly people after an 8-week training course were characterized. Static postural stability was measured during standing on a single force platform first with the eyes open and then with the eyes closed. Body sway was analysed on a force plate in groups of elderly and of young subjects. Half of the elderly subjects then took part in the training course. The posturographic measurements were repeated after the course. The sway in anteroposterior (AP) and mediolateral (ML) directions was subjected to spectral analysis. The frequency spectrum of the platform oscillations was calculated by fast Fourier transformation in the intervals 0.1-0.3, 0.3-1 and 1-3 Hz. It was found that the sway path was longer and the frequency power was higher in the elderly group. The training caused a significant improvement in functional performance, but a significantly longer sway path was observed after the training in the ML direction. The frequency analysis revealed a significantly higher power after 8 weeks without visual control in the ML direction in the training group in the low and the middle frequency bands. The results suggest that the participants' balance confidence and the control of ML balance improved in response to the training. The higher ML frequency power exhibited after the training may be indicative of a better balance performance. Thus, the increase in the sway path in this age group did not mean a further impairment of the postural control.

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Gene-environment interactions have an important role in the development of psychiatric disorders. To generate and validate a new substrain of rats with signs related to schizophrenia, we used selective breeding after postweaning social isolation and chronic ketamine treatment through several generations of animals and compared the subsequent strain to naive rats that were not genetically manipulated. We further investigated whether social isolation and ketamine treatment augmented the appearance of schizophrenic-like signs in these rats. Four experimental groups were studied (n=6-15 rats/group): naive rats without any treatment (NaNo); naive rats with postweaning social isolation and ketamine treatment (NaTr); 15th generation of selectively bred animals without any treatment (SelNo) or selectively bred rats with both isolation and ketamine treatment (SelTr). The startle reaction, tail-flick and novel object recognition tests were used to classify the animals into low- or high-risk for schizophrenia. Reduced pain sensitivity, higher degree of the startle reaction, disturbed prepulse inhibition, altered motor activity and decreased differentiation index in the memory test were observed in the 15th generation of the substrain, along with enhanced grooming behavior. Five functional indices (TF latency, startle reaction, prepulse inhibition, differentiation index, and grooming activity) were rated from 0 to 2, and the analysis of the summarized score revealed that the NaNo group had the lowest overall indication of schizophrenic-like signs, while the SelTr animals scored the highest, suggesting that both heritable and environmental factors were important in the generation of the behavioral alterations. We assume that further breeding after this complex treatment may lead to a valid and reliable animal model of schizophrenia.

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