The critical limiting temperature and selective brain cooling: neuroprotection during exercise?

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Neuroscience

Background:

• Exercise in hot conditions is known to impair performance.
• Critical limiting core temperature (CLT) and reduced central nervous system (CNS) drive are commonly observed.
• Selective brain cooling (SBC) is proposed to offer neuroprotection during heat stress.

Purpose of the Study:

• To examine the postulates of the CLT and SBC hypotheses.
• To investigate the relationship between CLT, SBC, and neuroprotection during exercise heat stress.
• To evaluate the theoretical compatibility of CLT and SBC in preventing a 'hot brain'.

Main Methods:

• Literature review and theoretical analysis.
• Examination of existing hypotheses on exercise in heat.
• Discussion of the physiological implications of CLT and SBC.

Main Results:

• The CLT hypothesis suggests rising brain temperature reduces CNS drive.
• SBC aims to attenuate brain temperature, potentially conflicting with CLT's mechanism.
• The theoretical incompatibility challenges neuroprotection as the primary outcome of SBC.

Conclusions:

• The CLT and SBC hypotheses present a potentially circular model regarding brain temperature and CNS drive.
• The concept of neuroprotection via SBC appears counter-intuitive if CLT relies on elevated brain temperature.
• This review argues against neuroprotection being the key strategy in exercise-induced hyperthermia based on current theoretical frameworks.