Purpose. The aim of the present work was to identify factors and neurophysiological mechanisms that may determine a robust and very stable postural control in athletes. Basic procedures. Postural performance in quiet stance was compared in 23 volleyball players from the Polish second league with 24 age-matched healthy physically active male subjects (controls). All participants stood quietly for 20 s on a force plate with their eyes open, while the center of pressure (COP) was recorded with the sampling rate of 20 Hz in both: the anterior-posterior (AP) and medial-lateral (ML) planes. From the recorded signals the COP dispersion measures, postural frequency and stiffness were computed. Main findings. The players displayed lower COP variability in the ML plane (p < 0.05) and lower COP range than controls in both planes (p < 0.01). Their COP mean velocity was higher in the AP plane (p < 0.0001) and the ML plane (p < 0.01) than in controls. Together, these findings indicated the presence of an additional low-amplitude and high-frequency signal superimposed on the COP in athletes but not in controls. Superior body stability and different mode of automatic postural control observed in the players challenge recent views on the relationships between attention resources allocation and its consequences to the selection and implementation of postural strategies. Conclusions. The volleyball players have superior body stability and different mode of automatic postural control as compared with the control group. Postural strategies of athletes may result from slight muscular adjustments that adopt mechanisms similar to stochastic resonance to monitor an instantaneous body vertical with greater efficiently.
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Purpose. The aim of the paper was to determine the effect of respiration on body balance in quiet standing. Basic procedures. Postural performance during quiet standing was compared in 37 young healthy subjects in two trials on a force plate: first with natural breathing, and then with accelerated high-volume breathing at the rate of 1 Hz. Each trial included 20 s quiet standing with eyes open, and the center of pressure (COP) was recorded with the sampling rate of 20 Hz in both anterior-posterior (AP) and mediallateral (ML) planes. Based on the recorded signals the COP dispersion measures and postural frequency were calculated. Main findings. The forced respiration contributed significantly to the increase in all COP stability measures in the AP plane: dispersion (p < 0.01), range (p < 0.001) and mean velocity and frequency (p < 0.00001). In the ML plane only mean velocity (p < 0.001) and frequency (p < 0.01) were affected. Conclusions. In view of the evidence provided by other authors that stress tests increase the amplitude- and frequency-based stability measures, our results indicate that the contribution of natural accelerated breathing after strenuous physical exercise will bias the results of stabilographic studies, rendering them worthless in understanding the role of neuromuscular fatigue in stability deterioration. Such studies must use data collected after the respiration returns to normal rate. However, if the study aims at overall assessment of postural stability post-fatigue, the postural testing may be performed immediately after the stress test.
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Purpose. The study compares the sway variables after continuous CMJs eliciting different level of proprioceptive stimulation determined by percentage of max height of the jump. Basic procedures. A group of 11 aerobic dancers performed in random order repeated jumps with maximal effort until the jump height dropped to 75%, 50%, and 25% of previously established max jump achieved in non-fatigued conditions. The height of CMJs was calculated from flight times registered by FiTRO Jumper. Thirty seconds prior to and two minutes after exercises the COP velocity was registered at 100 Hz by means of posturography system FiTRO Sway Check based on dynamometric platform. Main findings. Results showed that max height of the jump (MJ) decreased from 27.7 ± 2.8 cm to 20.1 ± 2.6 cm when subjects matched 75% of 1MJ, to 13.8 ± 1.6 cm at 50% of 1MJ, and to 6.9 ± 0.8 cm at 25% of 1MJ. The COP velocity was significantly (p ≤ 0.01) higher after jumps dropped to 75% of 1MJ as compared to baseline (from 9.2 ± 1.6 mm/s to 14.5 ± 2.4 mm/s). Its further significant (p ≤ 0.05) increase was observed after jumps dropped to 50% of 1MJ (to 19.6 ± 2.6 mm/s). However, there was only slight increase in COP velocity after jumps dropped to 25% of 1MJ (to 21.4 ± 3.2 mm/s). Conclusions. Taking into account a gradual increase in sway velocity after jumps matched 75% and 50% of 1MJ and its no further increase after jumps matched 25% of 1MJ, it may be assumed that post-exercise balance impairment is not linearly related to the level of proprioceptive stimulation.
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The aim of this study was to investigate the effect of an increasing number of training hours of specific highintensity karate training on postural sway in preadolescent karate athletes. Seventy-four karatekas were randomly assigned to 1 of 2 groups: Karate Group (KG=37): age 10.29±1.68 yrs; or Control Group (CG= 37): age 10.06±1.77 yrs. The KG performed two sessions per day for 1 week in total, while the CG performed only 3 sessions during the same period. The center-of-pressure length (COPL) and velocity (COPV) were recorded under four different experimental conditions: open eyes (EO), closed eyes (EC), open eyes monopodalic left (EOL), open eyes monopodalic right (EOR), pre as well as post training intervention. Post-camp results indicated significant differences between the groups in the COPL p<0.001; an interaction of training type×time in the COPV (p<0.001) and an interaction of training type×time (p=0.020). The KG revealed an improvement in the COPL from pre to post-camp under conditions of EO [-37.26% (p<0.001)], EC [-31.72% (p<0.001)], EOL [-27.27% (p<0.001)], EOR [-21.44% (p<0.001)], while CG revealed small adaptations in conditions of EO (3.16%), EC (0.93%), EOL (-3.03%), EOR (-0.97%). Furthermore, in the KG an improvement in the COPV from pre to post-camp was observed in conditions of EO [-37.92% (p<0.001)], EC [-32.52% (p<0.001)], EOL [-29.11% (p<0.001)], EOR [-21.49% (p<0.001)]. In summary, one-week of high intensity karate training induced a significant improvement in static body balance in preadolescent karate athletes. Karate performance requires high-levels of both static and dynamic balance. Further research dealing with the effect of karate practice on dynamic body balance in young athletes is required.
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