Heat transfer during Hiking

Heat transfer during Hiking - Thermoregulation: An Overview...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Cart Already a member? Log in SIGN UP! View other Techniques » Techniques Thermoregulation: An Overview of Heat Loss Mechanisms and Practical Guidelines for Staying Warm with Lightweight Gear Share | Print by Ryan Jordan | 2003-10-24 03:00:00-06 Excerpted From: “Lightweight Backpacking: A Field Guide to Wilderness Hiking Equipment, Technique, and Style,” Ryan Jordan (Ed.). Beartooth Mountain Press 2004. http://www.backpackinglight.com/cgi-bin/backpackinglight/00070.html . Overview The literature on physiological thermoregulation and clothing’s effect upon it is already vast. If you’re interested in a comprehensive review of thermoregulation in an outdoor context, refer to the excellent Secrets of Warmth (Hal Weiss, The Mountaineers, 1992). This article focuses primarily on specific classes of apparel, shelter, and sleep systems for cold, wet conditions. We’ll cover clothing systems for hot and dry weather elsewhere. Specifically, this article covers three major topics: mechanisms of heat generation, mechanisms of heat loss, and the design of equipment to minimize heat loss. Mechanisms of Heat Generation Even in cold conditions, heat generation can be a problem:excess heat generation resulting from vigorous activity can result in sweating that leads in turn to rapid evaporative cooling and the eventual breakdown of the body’s thermoregulatory capacity. We’ll consider this problem later. For now, let’s assume that conservation of every bit of the body’s heat is a desirable condition, and address the primary means by which the body gains heat in cold conditions. Metabolism Your best source of heat is generated internally by your body’s metabolic engine, fueled by calories gained from the metabolism of food. When you reduce caloric intake, you can reduce your body’s ability to produce heat. In a recent alpine climb in Wyoming’s Teton Range, Alan Dixon and I spent 38 hours without sleep and with only enough calories for a twelve-hour climb as we engaged in a difficult descent out of a summit snow and ice storm. By the end of the route, as we were approaching our car on a sun-warmed trail in sixty-degree temperatures at the valley floor, we were still shivering – while wearing our PolarGuard 3D-insulated belay parkas. Our metabolic engines, which had been fueled by more than 300 calories per hour for the first twelve hours of the climb, had slowed to a crawl. Trying to calculate the proper number of calories needed for a given level of exertion while simultaneously accounting for environmental factors such as temperature, wind, and precipitation, is a futile exercise. The National Outdoor Leadership School (NOLS) has devised elegant predictive models for caloric consumption that significantly overestimate the amount of food required for most individuals. This results in extra comfort, but not necessarily extra safety. Consider that the two to five pounds of extra food could be better spent on warmer insulation, or dropped from a pack altogether to reduce the energy expended to carry the extra weight: such
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 5

Heat transfer during Hiking - Thermoregulation: An Overview...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online