Lower Leg Submersion Viable for Cooling Suited Responders
A study in the August issue of JOEH found this method increased volunteers' work tolerance by 24 percent over forearm submersion.
A new study suggests lower leg submersion may be a better way than forearm submersion to cool firefighters effectively and prevent hyperthermia during training exercises and emergency incidents. Charles P. Katica of the University of Alabama's Department of Kinesiology and five colleagues from there or Central Washington University (Ellensburg, Wash.) published their results in the August issue of the Journal of Occupational and Environmental Hygiene.
They outfitted 10 healthy, male firefighter volunteers in NFPA-approved fire fighting apparel (jacket, pants, gloves, Nomex flash hood, rubber steel-toed boots, helmet, and a full SCBA to keep the tank weight consistent -- the participants breathed room air during the tests) and had them walk on an 0 percent inclined treadmill at 3.5 mph until they became exhausted or reached a core temperature of 38.5 degrees C. After doffing their apparel and equipment, they underwent 20 minutes of either forearm submersion or lower leg submersion, then went through a second "work tolerance phase" of walking the treadmill. The researchers then compared how long the volunteers from each cooling group walked.
The tests took place in a chamber with the temperature controlled to 32.8 degrees C. The subjects were not acclimatized to the heat prior to testing, the authors wrote.
While the work tolerance time difference between the two was not significant, volunteers who had experienced lower leg submersion walked 5.1 minutes (plus or minus 0.3 minutes), or 24 percent, longer than the forearm submersion group, they found. The authors point out that this could mean a firefighter could spend 10 more minutes during 45 minutes of combating a fire. The authors say lower leg submersion's effect on work tolerance time and physiological variables has not been studied up to now. They theorized that the larger leg muscles might increase heat storage for active firefighters and conducted this study to test the hypothesis. For information, contact Katica at cpkatica@crimson.ua.edu.
Eight Canadian researchers are the authors of a second article in the same issue of the ACGIH/AIHA magazine (Vol. 8, No. 8) concluding that ice vests are effective at reducing the level of thermal and cardiovascular strain in individuals doing prolonged, continuous work in heat stress conditions.