ECSS Paris 2023: OP-AP19
INTRODUCTION: Sustained cognitive activity (SCA) induces perceived cognitive fatigue and alters affect, arousal, motivation, and boredom. While studies have shown that SCA impairs endurance performance, limited evidence exists on the modifying effect of training status. This study tested the resistance to perceived cognitive fatigue in male competitive endurance trained vs. untrained participants using a 3000-m time trial (TT). To further elucidate the underlying mechanisms, the temporal dynamics of perceptual responses and prefrontal cortex oxygenation during SCA were analysed for both groups. METHODS: In a randomised, counterbalanced cross-over design, 16 males (25.3 ± 5.7 yrs, 8 competitive endurance athletes, 8 untrained males) completed an SCA task (30 min inhibitory control task, AX-CPT) and a control task (30 min, neutral video). Thereafter, a 3000-m TT was performed. Perceived cognitive fatigue and effort were assessed using visual analogue scales pre, during (3x) and at SCA termination. Prefrontal cortex oxygenation was monitored using functional near-infrared spectroscopy (fNIRS). Data were analysed using repeated measures ANOVA. RESULTS: A significant time × condition interaction was observed for perceived cognitive fatigue (p ≤ .001; ηp2 = .755) and cognitive effort (p ≤ .001; ηp2 = .806). No interactions were found for affective valence, arousal, motivation and boredom. No main effect of group (training status) was determined for any of the perceptual responses. Prefrontal oxygenation (TSI%) showed a main effect of time irrespective of condition. In the 3000-m TT, a significant condition × group interaction was observed for running time (p = .039; ηp² = .269). There was a trend towards significance for the percentage change in running time between groups (p = .060). Average and maximum heart rates did not differ between conditions. CONCLUSION: Findings suggest that 30 min of SCA increased perceived cognitive fatigue and cognitive effort compared to control task. Both conditions resulted in a transient elevation of prefrontal oxygenation (TSI%), irrespective of training status. Despite comparable physiological responses, the subsequent 3000-m TT performance significantly decreased after SCA in comparison to control. The decline in 3000-m TT performance was less pronounced among runners with a higher training status than those with a lower status. This finding aligns with previous research demonstrating the protective potential of endurance training against performance declines in the presence of cognitive fatigue. Further multiparametric assessment is necessary to elucidate the psychophysiological effects of SCA on subsequent cognitive or motor performance and the causal mechanisms involved in the different performance declines between trained and untrained subjects.
Read CV Martin SchlegelECSS Paris 2023: OP-AP19
INTRODUCTION: While sex-related differences in fatigability are established in temperate conditions [1], the influence on exercise responses under heat stress remains less understood [2]. This study aimed to investigate sex-related differences in fatigability induced by exercise under heat stress. METHODS: Twelve females (F) and fourteen males (M) of similar training status (maximal oxygen uptake: 45.2 and 53.4 mL/kg/min; maximal metabolic steady state: 59 and 62% of peak power output, for F and M, respectively) completed cycling trials to task failure in the heavy domain in temperate (CONT; 21°C, 52% RH) and hot (HEAT; 42°C, 33% RH) environments. During exercise, core temperature and rate of perceived effort were recorded every 2- and 4-min, respectively. Before, after 30-min of exercise, and at task failure, brief (3-s) and long (1-min) maximal voluntary contractions (MVCs) of the knee extensors were performed with peripheral nerve stimulation delivered during along with electromyography activity (EMG) of vastus lateralis being recorded. Where necessary, repeated-measures ANOVA with three (condition, time, sex) or two (condition, sex) factors were used to evaluate the effects of environment, exercise, and sex on the outcomes. Statistical significance was set at p<0.05. RESULTS: There was no difference in time to task failure (TTF) between sexes in either CONT (F= 97±26 min; M= 89±26 min) or HEAT (F= 37±8 min; M= 35±5 min – condition×sex interaction, p=0.54). Throughout exercise in HEAT, F and M showed similar increases (i.e., linear slope) in core temperature (F=+0.03°C/min; M=+0.04°C/min) and perceived effort (F=+0.12 a.u./min; M=+0.14 a.u./min – condition effect, p<0.01; condition×sex interaction, p>0.20). After 30-min of effort, heat stress exacerbated reductions in voluntary activation during brief MVCs (−5%) along with decrements in mean force and in the ratio of the root mean square of EMG to the amplitude of the evoked M-wave (RMS/M-wave) during long MVCs (−13% and −33%, respectively – condition×time interaction, p<0.01). These changes were similar between sexes (condition×time×sex interaction, p>0.42). At task failure, F presented greater reduction in RMS/M-wave during brief MVC than M (−39% and −13%, respectively), whereas M presented greater reduction in M-wave than F (−32% and 3%, respectively – condition×time×sex interaction, p<0.02). Specifically in F, heat-induced changes in TTF correlated (p<0.05) with both heat-induced exacerbation of perceived effort (r=¬−0.66) and the decline in RMS/M-wave during long MVC (r=0.78). CONCLUSION: Heat stress reduced TTF similarly for both sexes but exacerbated central fatigue in F and worsened the impairment in sarcolemma action potential propagation in M. Correlational results suggest that the heat-induced increase in perceived effort and exacerbation of central fatigue may contribute to impaired performance of F when exercising under heat stress. 1. Ansdell et al., 2020 2. Périard et al., 2021
Read CV Yago DutraECSS Paris 2023: OP-AP19