Related Experiment Videos
Inadequate heat release from the human brain during prolonged exercise with hyperthermia
Lars Nybo1, Niels H Secher, Bodil Nielsen
1Department of Human Physiology, Institute of Exercise and Sport Sciences, University of Copenhagen, Denmark. lnnielsen@aki.ku.dk
The Journal of Physiology
|November 29, 2002
Summary
During prolonged exercise, brain temperature increases. Reduced cerebral blood flow during hyperthermia impairs heat removal, leading to brain heat storage and elevated brain temperatures.
Area of Science:
- Physiology
- Neuroscience
- Exercise Science
Background:
- Brain temperature is crucial for motor activity.
- The extent of brain temperature rise during prolonged human exercise is not well understood.
Purpose of the Study:
- To evaluate cerebral heat exchange during exercise.
- To investigate the impact of hyperthermia on brain temperature regulation during exercise.
Main Methods:
- Monitored middle cerebral artery mean blood velocity (MCA V(mean)).
- Determined global cerebral blood flow (CBF) and cerebral energy turnover.
- Measured arterial to venous temperature difference across the brain (v-aD(temp)) using thermocouples.
Main Results:
- Heat was released via cerebral blood flow during both normothermic and hyperthermic exercise.
- Heat removal was 30% lower during hyperthermia due to a 20% reduction in CBF.
- Brain heat storage increased during hyperthermia, with brain temperature at least 0.2°C higher than core body temperature.
Conclusions:
- Hyperthermia impairs cerebral heat loss during exercise.
- Reduced cerebral blood flow is the primary mechanism for impaired heat removal.
- Elevated brain temperature during exercise, particularly with hyperthermia, is a significant physiological response.