COMPARING THE EFFECTS OF LOCOMOTOR MUSCLE FATIGUE AND MENTAL FATIGUE ON ENDURANCE PERFORMANCE IN CYCLISTS: A RANDOMIZED CROSS-OVER STUDY

Introduction This study compared the effects of mental fatigue and locomotor muscle fatigue on endurance performance, perception of effort and physiological responses in a group of well-trained and elite cyclists. Methods Seven performance level 4 and three level 5 (21.8 ± 2.7 yrs, 8 Male 68.4 ± 2.5 VO2Max and 438.8 ± 50.1 PPO, 2 Female 58.7 ± 5.4 VO2Max and 335.0 ± 14.1 PPO) have been recruited for this study. During the first visit to the laboratory, all participants performed an incremental ramp test on a cycle ergometer to determine the respiratory compensation point (RCP), VO2Max and Peak Power Output (PPO). In the subsequent three visits, participants performed TTE at the power corresponding to 95% RCP under three different conditions: 1) Mental fatigue (MF) induced by a 1-hour psychomotor vigilance task (PVT); 2) Locomotor muscle fatigue (LMF) induced by a 100-drop jumps protocol; 3) Watching documentaries was used as a control condition. The order of the three visits was randomly assigned. Physiological and psychological responses measured during the TTE test included heart rate (HR), VO2, ventilation, blood lactate concentration (La) and rating of perceived exertion (RPE). Manipulation checks included maximal voluntary contraction (MVC) of the knee extensors, PVT performance and perceived physical and mental fatigability scales. One-way (condition) or two-way (condition x time) repeated measure ANOVAs were used to analyse the data. Significance was set at p<0.05. The individual isotime method 1 was used to analyse the responses to the TTE test. Results Manipulation checks revealed mixed results, with only PVT performance influenced by MF (p<0.001) and only perceived physical fatigability affected by LMF (p<0.001). No significant differences in TTE were found between conditions (Control 989±122s, MF 1019±137s, LMF 973±145s, p=0.876). The RPE and HR at individual isotime in the LMF condition tended to be higher compared to the control condition but these effects were not significant (p=0.081 and p=0.090). No significant effects were found for the other physiological responses. Discussion The results of this study confirm previous investigations 2 suggesting that well-trained and elite cyclists are resistant to the negative effects of MF. The current study also suggests that well-trained and elite cyclists may also be resistant to the negative effects of LMF experimentally induced in the laboratory. Larger studies are required to confirm these findings and to investigate the “dose” of MF and LMF that may eventually reduce the performance of high-level cyclists. References 1. Nicolò, A. et al. A comparison of different methods to analyse data collected during time-to-exhaustion tests. Sport Sci. Health 15, 667–679 (2019). 2. Martin, K. et al. Superior Inhibitory Control and Resistance to Mental Fatigue in Professional Road Cyclists. PLoS One 11, e0159907 (2016).