# Acute Effects of Combined Hypoxia and Fatigue on Balance in Young Men
## 4 Discussion
The differences in body stability observed during these trials indicate whether the patient requires correct vision to maintain balance and whether they can inhibit incongruent visual information. In the next three conditions, the platform tilted according to the swaying of the subject. The moving platform disturbed the information coming from the proprioceptors. Each of the trials was performed in the same way as the first three trials under different visual conditions: with the eyes open, closed and with a moving visual surround. The last two allowed an isolated assessment of the vestibular organ. Exercise has a significant effect on the impairment of balance [9; 20; 30]. One reason for this is the increased respiratory rate immediately afterwards (ES1) [3; 13]. The increase in respiratory rate in response to lactate accumulation induces hyperventilation. Hyperventilation not only affects balance as a mechanical factor but is also responsible for interference with vestibular and somatosensory signals from the lower limbs [13; 31]. Static balance disturbances under the influence of intensive exercise are of a short-term nature, which is confirmed in our study, and has been observed by other authors [2; 13; 32]. The lack of significant differences in the trial excluding visual information, and the significant differences in the trials with full access to visual information may confirm this (ES 2). This would indicate a disturbing role of visual information on balance, or more broadly, on cognitive function and sensory integration [5; 33]. Our results do not correspond with those from studies indicating that strenuous exercise has a mild effect on balance and, at the same time, that vision is a sufficiently compensating factor for proprioceptive impairment. The exclusion of visual information did not significantly worsen balance in any conditions [2; 34]. On the contrary, the exclusion of visual and deep sensory information also improved stability in the groups exposed to hypoxia, as well as in those performing the exercise in hypoxia (ES 5). This indicates that the distractors used have a mobilizing effect on the vestibular organ. Furthermore, we did not find that the duration of the test had a degrading effect on balance [23; 26]. Improving stability scores in subsequent SOT tasks may indicate an adaptation of balance mechanisms to fatigue. However, this adaptation required allocating a larger proportion of cognitive resources to the active control of the balance task. This may explain the deterioration and subsequent improvement of balance under dynamic conditions [35]. In justifying such a sequence of events, the authors turn their attention to the noise in the input signal, which increases with fatigue. As a result of the adaptation of muscle spindles, this noise can be filtered out more effectively from the actual proprioceptive signal [35; 36]. However, this adaptation requires dedicating a greater proportion of cognitive resources to the active control of the counterbalancing task. Hypoxia as a stand-alone factor did not significantly affect balance degradation. This does not mean, however, that it did not have a modifying effect on sensory organization. The visual system first responds to oxygen deficiency [37], but our study indicates a significantly increasing role of visual information to the hypoxic groups (VIS). The observed increase in the hip strategy is confirmed by publications from authors who observed an increase in such responses in young athletes as a response to fatigue in the muscles around the ankle joint (triceps calf muscle, tibialis anterior) [38; 39]. We observed this preference especially in static conditions, both with and without visual support. This is most likely due to peripheral neuromuscular fatigue and hyperventilation, which affect multiple links in the kinematic chain [31; 39; 40]. The methods we used in this study mainly led to muscle fatigue in the lower limbs, and especially in the ankle area.