Researchers show shivering can save your life

Until now, the majority of physiological studies on cold exposure involve very cold conditions where people reach hypothermia (35.0oC core temperature) within 4-6 hours. And because, ethically, researchers are not allowed to let subjects reach that point, there's a lack of data on the physiological consequences of moderate but prolonged shivering.

However, Dr. Basset and graduate student Zachery Hynes, both from the School of Human Kinetics and Recreation, are co-investigators on a recent study that intends to fill this gap. The effects a 24 hour Arctic survival simulation on human physiology and cognitive function was led by the Maritime Arctic Survival Science and Engineering Research Team (MASSERT).

Conducted at Brock University in Ontario, subjects were exposed to moderate cold (7.5 degrees Celsius) for 24 hours while wearing light, cotton coveralls. The researchers wanted the subjects to shiver, activating their cold response, without losing so much heat that they reached hypothermia. To ensure they didn't reach hypothermia, subjects ingested a telemetric radio pill that stays in the gastrointestinal tract for 30 to 40 hours, transmitting to a small logger.

The goal: to push subjects to the limit of what they could voluntarily tolerate for 24 hours and find out how shivering could be sustained during prolonged exposure. The team also looked at cognitive performance and how it would be affected by long-term cold exposure; if people would be able to perform the basic survival skills necessary to signal for help after 24 hours; how long they could maintain heat balance; and what the effects were on major physiological systems.

Dr. Basset admits the subjects were people who'd already experienced long-term cold exposure (i.e., Niagara Parks Police and Coast Guard personnel). "We knew that this subject pool may not be representative in terms of fitness and cold experience compared to the target population who might require a mass rescue from a cruise ship or aircraft," noted Dr. Basset. "But the critical need was for subjects who could psychologically push themselves through the very strenuous experimental protocol and conditions.

"Overall, six of the eight subjects tolerated the entire 24 hour exposure. All subjects reported that, psychologically and in terms of overall tolerance, the combination of environmental conditions and clothing was near or at the point of what they could voluntarily endure. But, the good news is, they were able to sufficiently thermo regulate through shivering and movement."

Dr. Basset and the rest of the team also found that cognitive responses for memory, executive control, attention, and spatial reasoning were largely unaffected. "The absence of significant changes in cognitive performance over the 24 hours of cold exposure testing is in itself an important finding, given that testing of this type and duration has not been done before," he added.

"This experiment represents the best case scenario for the average person that is, they are able to protect themselves from very cold air, splashing water, and wind which means they should be capable of surviving while waiting for a rescue team." Dr. Basset added that MASSERT would like now to determine what could happen to elderly people who are the main clientele of the cruise ship industry.