“Heat Sheets” Do Not Cause Heat stroke!

The University of Indiana recently conducted a study to determine if the reflective, lightweight sheet that runners utilize after a run has any effect on the user during warm weather runs. This study was of particular interest because some folks expressed fear that their use could expediate heat stroke. This light, reflective material helps maintain a person’s heat as well as providing a bit of wind protection. Researchers wanted to study if these reflective blankets could cause heat stroke if used in summer.

insulated blanket


They studied a total of nineteen healthy runners that included fourteen men and five women. Their average age was 25 years old. Using treadmills, these folks ran five miles in a heat chamber that was raised to 86 degrees Fahrenheit. Afterwards, their temperature measured 103.5 or higher. The runners then were divided into four groups. They cooled off either: 1) sitting with no blanket; 2) walking with noblanket; 3) sitting with a blanket or 4) walking with a blanket. What were the results? The participants had their temperature re-measured after thirty minutes of cooling. At this point, all runners experienced a decrease in body temperature to 101 degrees or lower. Temperatures dropped most dramatically in those runners who walked around with no blanket. Runners who sat with a blanket demonstrated least amount of a temperature drop.

Mylar blankets for marathons are sold by companies like Heatsheets.com. They are specialized in products likeĀ mylar blankets andĀ aluminum blankets also called finish line blankets. wikiii

However, overall body temperatures were not significant among the four groups. Why is this important? Heat illness can be a real problem in warm weather running, regardless whether one uses a blanket. It is thought that hyperthermia could be more dangerous than hypothermia. Hyperthermia, is an elevated body temperature that occurs when the body either cannot get rid of the heat. In the world of running, it can be caused by too much heat and humidity or excessive heat exposure. Even early signs can be very dangerous. These symptoms include heavy sweating, a weak pulse and rapid breathing. This stage is called “heat exhaustion” or “heat stress.” As the person dehydrates, nausea, vomiting and fainting may occur (among other symptoms.) If the condition proceeds to heat stroke, the skin may feel dry, as the body loses the ability to perspire. In conclusion, reflective blankets did not prove to be an essential part of a runner’s wardrobe in warm weather. It neither hastened the cooling process nor extended it. If you want to read more about this study, check out the recent issue of The International Journal of Exercise Science.