Alterations in spontaneous electrical brain activity after an extreme mountain ultramarathon.

This study aimed to investigate the impact of an extreme mountain ultramarathon (MUM) on spontaneous electrical brain activity in a group of 16 finishers. By using 4-minute high-density electroencephalographic (EEG) recordings with eyes closed before and after a 330-km race (mean duration: 125 ± 17 h; sleep duration: 7.7 ± 2.9 h), spectral power, source localization and microstate analyses were conducted. After the race, power analyses revealed a centrally localized increase in power in the delta (0.5-3.5 Hz) and theta (4.0-7.5 Hz) frequency bands and a decrease in alpha (8.0-12.0 Hz) power at the parieto-occipital sites. Higher brain activation in the alpha frequency band was observed within the left posterior cingulate cortex, left angular gyrus and visual association areas. Microstate analyses indicated a significant decrease in map C predominance and an increase in the global field power (GFP) for map D at the end of the race. These changes in power patterns and microstate parameters contrast with previously reported findings following short bouts of endurance exercises. We discuss the potential factors that explain lower alpha activity within the parieto-occipital regions and microstate changes after MUMs. In conclusion, high-density EEG resting-state analyses can be recommended to investigate brain adaptations in extreme sporting activities.

Resting EEG Microstates and Autonomic Heart Rate Variability Do Not Return to Baseline One Hour After a Submaximal Exercise.

Recent findings suggest that an acute physical exercise modulates the temporal features of the EEG resting microstates, especially the microstate map C duration and relative time coverage. Microstate map C has been associated with the salience resting state network, which is mainly structured around the insula and cingulate, two brain nodes that mediate cardiovascular arousal and interoceptive awareness. Heart rate variability (HRV) is dependent on the autonomic balance; specifically, an increase in the sympathetic (or decrease in the parasympathetic) tone will decrease variability while a decrease in the sympathetic (or increase in the parasympathetic) tone will increase variability. Relying on the functional interaction between the autonomic cardiovascular activity and the salience network, this study aims to investigate the effect of exercise on the resting microstate and the possible interplay with this autonomic cardiovascular recovery after a single bout of endurance exercise. Thirty-eight young adults performed a 25-min constant-load cycling exercise at an intensity that was subjectively perceived as "hard." The microstate temporal features and conventional time and frequency domain HRV parameters were obtained at rest for 5 min before exercise and at 5, 15, 30, 45, and 60 min after exercise. Compared to the baseline, all HRV parameters were changed 5 min after exercise cessation. The mean durations of microstate B and C, and the frequency of occurrence of microstate D were also changed immediately after exercise. A long-lasting effect was found for almost all HRV parameters and for the duration of microstate C during the hour following exercise, indicating an uncompleted recovery of the autonomic cardiovascular system and the resting microstate. The implication of an exercise-induced afferent neural traffic is discussed as a potential modulator of both the autonomic regulation of heart rate and the resting EEG microstate.

A single-bout of Endurance Exercise Modulates EEG Microstates Temporal Features.

Electrical neuroimaging is a promising method to explore the spontaneous brain function after physical exercise. The present study aims to investigate the effect of acute physical exercise on the temporal dynamic of the resting brain activity captured by the four conventional map topographies (microstates) described in the literature, and to associate these brain changes with the post-exercise neuromuscular function. Twenty endurance-trained subjects performed a 30-min biking task at 60% of their maximal aerobic power followed by a 10 km all-out time trial. Before and after each exercise, knee-extensor neuromuscular function and resting EEG were collected. Both exercises resulted in a similar increase in microstate class C stability and duration, as well as an increase in transition probability of moving toward microstate class C. After the first exercise, the increase in class C global explained variance was correlated with the indice of muscle alterations (100 Hz paired stimuli). After the second exercise, the increase in class C mean duration was correlated with the 100 Hz paired stimuli, but also with the reduction in maximal voluntary force. Interestingly, microstate class C has been associated with the salience resting-state network, which participates in integrating multisensory modalities. We speculate that temporal reorganization of the brain state after exercise could be partially modulated by the muscle afferents that project into the salience resting-state network, and indirectly participates in modulating the motor behavior.