Changes in EEG activity before and after exhaustive exercise in sedentary women in neutral and hot environments

• Published in: Applied ergonomics Vol. 41; no. 6; pp. 806 - 811
• Main Authors: Ftaiti, Foued, Kacem, Asma, Jaidane, Nadia, Tabka, Zouhair, Dogui, Mohamed
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2010; Elsevier; Elsevier Science Ltd
• Subjects: Applied physiology; Biological and medical sciences; Blood; Brain; Case-Control Studies; Electroencephalography; Ergonomics; Ergonomics. Work place. Occupational physiology; Exercise; Exercise - physiology; Exercise - psychology; Exercise Test; Fatigue; Fatigue - psychology; Female; Heat Stress Disorders - psychology; Human physiology applied to population studies and life conditions. Human ecophysiology; Humans; Hyperthermia; Hyperthermia, Induced; Medical sciences; Oxygen Consumption; Sedentary Lifestyle; Studies; Women; Young Adult; Women; Fatigue; Hyperthermia; Physical exercise; Human; Temperature; Effort; Electrophysiology; Environmental factor; Electroencephalography; Heat; Ergonomics; Vision; Reaction time; Female
• ISSN: 0003-6870; 1872-9126
• DOI: 10.1016/j.apergo.2010.01.008

This study examined the effect of hyperthermia on brain electrical activity measured with encephalography during prolonged exhaustive exercise in a group of sedentary women (VO 2max = 35 ± 4 mL kg min −1). Two strenuous cycling exercises were performed either in neutral (N-Ex) or in heat (H-Ex) conditions. Tympanic temperature (Tty), heart rate (HR), body mass loss (BML), plasma volume decrease, and brain electrical activity [EEG: α (8–13 Hz) and β(13–30 Hz)-band and α/ β index of fatigue: the ratio between EEG activity in the α band and β-band] were recorded throughout the cycling sessions. The Tty increase 1.0 °C in the N-Ex and 1.8 °C in H-Ex. HR increased in both sessions but with significantly higher values during the H-Ex session when compared with the N-Ex session ( p < 0.001) (from 85 ± 4 beats min −1 to 164 ± 6 beats min −1 and from 83 ± 6 beats min −1 to 181 ± 8 beats min −1, respectively in N-Ex and in H-Ex). This was associated with a significantly higher BML ( p < 0.05) and a higher plasma volume decrease in the H-Ex session ( p < 0.01). The α/ β index increased significantly during both trials particularly during the H-Ex session ( p < 0.05). This was associated with a significant decrease of time to exhaustion (−34%). We suggest that exhausting work in the heat induced a change in gross brain activity (alpha/beta ratio) compared to a longer, less thermally demanding exposure. Fatigue in the heat could be attributed to central factors as well as thermal, cardiac and hydro-electrolytic impairment.