Electroencephalographic Changes after a Marathon at 4300 M of Altitude

Abstract

Running at altitude is gaining greater popularity but it may expose participants to the risk of acute mountain sickness (AMS). The study investigated electroencephalographic (EEG) changes and eventual symptoms suggestive of AMS in 5 well-trained lowland native male runners (average age, 38.2 ± 4.6 years; VO 2 peak 61.4 ± 2.7 mL·kg -1 ·min -1 at sea level; best marathon performance at sea level under 3 hours), who completed a marathon at 4300 m altitude. EEG, percentage of peripheral arterial oxygen saturation (% SpaO 2 ) and heart rate (HR) were recorded during wakefulness at rest (supine position) and in comfort: 1) at sea level; 2) at 3600 m after 32 -38 hours of acute acclimatization; 3) at 4300 m after 145 -153 hours of chronic acclimatization; and 4) at 4300 m immediately after a marathon race. Symptoms of AMS were evaluated with the Lake Louise questionnaire before any ECG recording. There was a significant decrease in low-voltage high-frequency activities at rest after acute hypoxic-hypobaric exposure at 3600 m as compared to sea level. After six days of acclimatization at 4300 m there was a significant increase in the power of low-voltage high-frequency activities, particularly beta and gamma, indicating an aroused waking state and an integrated activity across widely distributed cortical regions. An increase in the power of low-voltage high-frequency activities over the entire cortex was observed, particularly after completion of the marathon at 4300 m. The increase in the high-frequency activities was probably due to direct and indirect reflex activation of the forebrain and reticular activating system involved in behavioral and metabolic integration of autonomic control and arousal and due to residual activation of the somatomotor and parietal cortex after the end of the marathon. Lake Louise score always resulted lower than 3, indicating no signs of AMS in all the runners. The results of this study indicate that in well-trained and acclimatized athletes, arousal has a protective role in preventing excessive oxygen deprivation also after an endurance exercise performed at high altitude. The absence of AMS fond in our study bear out that well trained and acclimatized runners, can safely participate in a marathon at high altitude that gives rise to temporary EEG changes without inducing paroxysmal phenomena.

Using Electroencephalography (EEG) Power Responses to Investigate the Effects of Ambient Oxygen Content, Safety Shoe Type, and Lifting Frequency on the Worker’s Activities

“…The results of the experiments for relative indices presented significant differences between the lifting frequencies at central cortex for alpha, safety shoes types, and interaction between ambient oxygen content, frequency, and replication at frontal and central cortexes for theta, safety shoes types at frontal and central cortexes for beta, and replications at frontal and central cortexes for gamma. These results are similar to the previous studies results which conclude that decreased in the power of the numerous bands of EEG at central and frontal cortexes related to increase the workload [53][54][55].…”

“…The experiment showed that EEG power of theta decreased as the ambient oxygen content decreased at frontal and central cortex. This finding is consistent with other researches that reported decreased of the alpha activities is one of the most features of cerebral hypoxia [54]. Accordingly, some researchers also found an increasing alpha activity during fatigue [6,56]; on the contrary, the alpha, beta, and gamma increased as the ambient oxygen content decreased at frontal and central cortex, but these decreases and increases in the brain signal were not significant because participants were subject to acclimatization sessions for 14 days.…”

Electroencephalogram (EEG) Alpha Power as a Marker of Visuospatial Attention Orienting and Suppression in Normoxia and Hypoxia. An Exploratory Study

“…Altered EEG recordings, considered by clinicians as indicators of cerebral metabolism and useful tools for evaluating hypoxia severity-i.e., hypoxia with or without ischemia-in individuals affected by such a condition (e.g., [24][25][26]), have generally been reported in many electrophysiological studies based on different types of both acute and chronic hypoxia. In human EEG studies of transient hypoxia, for instance, the latter was induced by low oxygen gas mixtures or hypoxic normobaric hypoxia (e.g., [27]), by simulated HA in hypobaric pressurized chambers (e.g., [28][29][30][31]), during rapid ascent to HA and lowland reoxygenation (e.g., [32][33][34]), and in HA natives [35]. Overall, a slowing activity of EEG in hypoxia with respect to normoxia has been generally advanced by all these studies.…”

Heart Rate Variability, Standard of Measurement, Physiological Interpretation and Clinical Use in Mountain Marathon Runners during Sleep and after Acclimatization at 3480 m

“…The endurance performance of mountain marathoners is appreciably reduced at high altitude. Based on their antropometrical characteristics, mountain marathoners may be considered a suitable group for studying possible pathological effects of stay and exercise at altitude [4][5][6][7][8][9][10][11][12][13].…”

“…Unlike the situation described in Lanfranchi and coworkers [2], the medical staff involved in this study, during the long-term follow-up of a group of mountain marathon athletes during training and athletic competition from sea level to 5500 m, has never recorded signs of acute mountain sickness (AMS) [4][5][6][7][8][9][10][11][12][13]. Regular exercise is thought to modify autonomic balance and accelerate the safe recovery of physiological sympathovagal interaction [1].…”