## 4 Discussion  
The main finding of this study is that anaerobic fatigue induced by sport-specific exercise deteriorates postural control in highly-trained adolescent road cyclists. What is also of significance in this research is that deterioration of postural control was visible as an increase in the positional parameters of body sway (EA, AP\({}_{\text{R}}\), and ML\({}_{\text{R}}\)) as well as a decrease in MF, but not a change in MV. To best of our knowledge, this is the first study in which the effect was examined of anaerobic fatigue induced by sport-specific exercise on postural control in adolescent road cyclists. In our study, anaerobic fatigue induced a significant increase in the majority of positional body sway parameters (i.e., EA, AP\({}_{\text{R}}\), and ML\({}_{\text{R}}\)), both with eyes open and closed. It was only the AP\({}_{\text{R}}\)/ML\({}_{\text{R}}\) ratio with eyes open that did not increase substantially after the effort. Similar changes were also observed by other authors when anaerobic fatiguing protocols were used: the Wingate Anaerobic test (young judokas [17]; 13-year-old alpine skiers [18]); repeated sprint ability test among soccer players [19]; U19 basketball players [20]); and the Bosco protocol (recreationally trained volunteers [21]). All these protocols linked (beyond the anaerobic background) the involvement of a large number of muscles (general exercise type) mainly in the lower extremities. Therefore, the probable explanation for postural control disturbances may be that high-intensity general exercise such as cycling, running, or jumping deteriorates the quality of sensory information (proprioceptive, visual, vestibular, and plantar cutaneous inputs) and/or their integration, while potentially decreasing the efficacy of the muscular system [34; 35; 36]. Metabolic products diminish the facilitation of muscle spindle afferents and thus reduce the efficiency of the myotatic loop during postural regulation. [PERSON] [37] specifies that the action of the chemosensitive group III and IV muscle afferents reduces the motor resolution in response to any input, which might lead to less efficient control and reduced motor output accuracy. Another explanation may be the decrease of lower limb muscle strength (the median fatigue index registered in our study was 41.2%). [PERSON] and [PERSON] [38] and [PERSON] et al. [39] reported that the decrease in the strength of the ankle or knee musculature as a result of fatigue significantly disturbed postural control, and manifested in increased EA, AP\({}_{\text{R}}\), as well as ML\({}_{\text{R}}\). Another important aspect which should be addressed while explaining changes in postural control induced by cycling exercises is neck musculature fatigue [25; 40]. The cycling position, which require extreme trunk horizontal flattening [41], predisposes one to fatigue in the neck muscles [42]. It has been reported that nociceptive sensorial inputs induced by fatigue of the neck muscles deteriorate the ability to correctly perceive verticality and, moreover, the fatigue degrades spatial body orientation, influencing postural balance [25; 43; 44]. Postural control disturbances may also be the effect of a large acid-base imbalance [45]. The applied effort induced large increases in BL concentration among the studied athletes (the median BL concentration was 12.9 and 11.9 mmol \(\times\) L\({}^{-1}\) during the third and sixth minutes, respectively, following the effort). Interestingly, in our study, MV did not significantly change after the effort, while MF decreased substantially. Other authors using anaerobic exercise to induce fatigue obtained different results, i.e., increased MV [17; 18; 19; 20], and no changes in MF [17; 20]. We have suggested that divergent results may be caused by the different time intervals between the end of the effort and body sway measurements.