Changes in EEG during Ultralong Running

There are only a few studies using human electroencephalograms (EEGs) to investigate bioelectrical changes in the brain during exercise (running or cycling). These studies report an increase in EEG alpha amplitude during and immediately after exercise. However, only exercises within a relatively short time interval of approximately 1 hour have been investigated. Thus, we focussed on long-lasting exercise and report three single case studies, performed on the same participant, during extended exercise and under different thermal conditions. EEG was recorded during a 12-, 24-, and 56-hour ultramarathon. The 56-hour race was performed under extreme thermal stress in Death Valley, CA, with temperatures well above 55uC/131uF. Analyzing the centre gravity frequency of the EEG alpha rhythm yielded a gradual decrease with time for the 12and 24-hour races. In the 56-hour race, the centre frequency decreased only until the first sleeping period. Alpha amplitude, on the other hand, did not vary systematically. For all three races, the lowest alpha amplitude was observed during the last test session. This decrease is most likely due to cognitive and emotional changes but not to thermal stress, exhaustion, or sleep deprivation.