Brain activity and fatigue during prolonged exercise in the heat

Citation
B. Nielsen et al., Brain activity and fatigue during prolonged exercise in the heat, PFLUG ARCH, 442(1), 2001, pp. 41-48
Citations number
29
Categorie Soggetti
Physiology
Journal title
PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY
ISSN journal
00316768 → ACNP
Volume
442
Issue
1
Year of publication
2001
Pages
41 - 48
Database
ISI
SICI code
0031-6768(200104)442:1<41:BAAFDP>2.0.ZU;2-O
Abstract
We hypothesized that fatigue due to hyperthermia during prolonged exercise in the heat is in part related to alterations in frontal cortical brain act ivity. The electroencephalographic activity (EEG) of the frontal cortex of the brain was measured in seven cyclists [maximal O-2 uptake (V-O2max) 4.8 +/-0.1 (SE)1 min(-1)] cycling at 60% V-O2max in a hot (H, 42 degreesC) and a cool (C, 19 degreesC) environmental. Fast Fourier transformation of the E EG was used to obtain power spectrum areas in the alpha (8-13 Hz) and beta (13-30 Hz) frequencies. The ratio alpha/beta was calculated as an index of arousal level; an elevated alpha/beta index reflects suppressed arousal. In H, subjects fatigued after 34.4 +/-1.4 min coinciding with an oesophageal temperature (T-oes) of 39.8 +/-0.1 degreesC, an almost maximal heart rate ( HR 192 +/-3 beats(.)min(-1)), a rating of perceived exertion (RPE) of 19.0 +/-0.8 and significantly elevated alpha/beta index (188-+/- 71% of the valu e after 2 min of exercise; P <0.05). In C, subjects cycled for a similar pe riod while T-oes was below 38 degreesC, HR and RPE were low and the alpha/b eta index was not significantly elevated (59 +/- 27% of 2 min value; P=NS). Increases in the odp index were strongly correlated to increases in T-oes (r(2)=0.98; P=0.0001).