Page 74 - Journal of Special Operations Medicine - Summer 2016

SOF may be exposed to harsh environmental condi- warranted to determine the passive cooling shirt’s ability
tions such as hot, humid austere climates. The cool- to cool while completely covered (e.g., under ABUs and
19
ing shirt is a practical device for SOF during SUSOPS. body armor).
Hence, testing this product’s effectiveness in maintain-
ing or reducing core body temperature and enhancing Funding
human performance fulfilled an Air Force Special Op-
erations Command research gap related to exertional This work was supported by the US Air Force School of
heat illness. Aerospace Medicine.

The independent variable for this study was the cooling Disclaimer
shirt technology and the dependent variables included
core body temperature, exercise heart rate, physical The views expressed in this article are those of the au-
work capacity test, capillary blood lactate level, and thors and do not necessarily reflect the official policy or
subjective ratings of perceived exertion. position of the Air Force, the Department of Defense, or
the US Government.
There were two statistically significant differences with
respect to core body temperature during the 70-minute Disclosure
weighted-vest walking test. Peak and core body tem- The authors have no financial relationships relevant to
peratures were 0.26˚F and 0.27˚F less when the subjects this article to disclose.
were exercising in the loaded state, respectively (p <
.05). No statistically significant differences were found References
in blood lactate level, number of sandbag shuttles com-
pleted in 10 minutes, or participants’ subjective ratings 1. Cheung SS, McLellan TM. Heat acclimation, aerobic fitness,
of perceived exertion. and hydration effects on tolerance during uncompensable
heat stress. J Appl Physiol (1985). 1998;84:1731–1739.
2. Nybo L, Secher NH, Nielsen B. Inadequate heat release from
Discussion the human brain during prolonged exercise with hyperther-
mia. J Physiol. 2002;545:697–704.
The primary aim of this study was to determine the ef- 3. González-Alonso J, Calbet JA. Reductions in systemic and
fects of a cooling shirt with passive cooling inserts on skeletal muscle blood flow and oxygen delivery limit maximal
aerobic capacity in humans. Circulation. 2003;107:824–830.
core body temperature during high-intensity physical 4. Maughan RJ, Watson P, Shirreffs SM. Heat and cold: what
activity on a treadmill. A secondary interest was to de- does the environment do to the marathon runner? Sports
termine the effects of a cooling shirt on physical work Med. 2007;37:396–399.
capacity (e.g., sandbag shuttle) and various other physi- 5. Kerstein MD, Wright D, Connelly J, et al. Heat illness in hot/
humid environment. Mil Med. 1986;151:308–311.
ological parameters related to physical performance. 6. Lee SM, Williams WJ, Fortney Schneider SM. Core tempera-
Examination of the effects of this cooling technology ture measurement during supine exercise: esophageal, rectal,
substantiated its role in mitigating heat-related illnesses and intestinal temperatures. Aviat Space Environ Med. 2000;
and improving physical performance in a like group of 71:939–945.
SOF in a controlled laboratory environment. 7. Brooks GA, Fahey TD, Baldwin KM. Exercise physiology:
human bioenergetics and its applications. 4th ed. Mountain
View, CA: McGraw Hill; 2004:515–521.
Most cooling technologies must either be frozen or 8. Geor RJ, McCutcheon LJ. Thermoregulatory adaptations as-
contain a form of cooling crystals or gel packs that are sociated with training and heat acclimation. Vet Clin North
enclosed within fabric and are activated by soaking in Am Equine Pract. 1998;14:97–120.
water or by pressing a sensor attached to a cooling vest. 9. Sawka MN, Wengor CB, Pandolf KB. Thermoregulatory re-
The cooling effects provided are minimal and are not sponses to acute exercise-heat stress and heat acclimation. In:
Fregly MJ, Blatties CM, eds. Handbook of physiology. Sec-
sustained, especially when SOF are exposed to hot, hu- tion 4: Environment physiology. New York, NY: Oxford Uni-
mid conditions during SUSOPS missions. versity Press; 1996:157–158.
10. Zhu L. Theoretical evaluation of contributions of heat con-
duction and countercurrent heat exchange in selective brain
Conclusion cooling in humans. Ann Biomed Eng. 2000;28:269–277.
11. Smith JA, Yates K, Lee H, et al. Pre-cooling improves cycling
The results from this investigation showed reduced performance in hot/humid conditions [abstract]. Med Sci
core and peak core body temperatures while using the Sports Exerc. 1997;29(5 suppl):S263.
“loaded” shirt with the cooling inserts. Future research 12. Nybo L, Secher NH. Cerebral perturbations provoked by
will focus on additional field studies and test the ef- prolonged exercise. Prog Neurobiol. 2004;72:223–261.
fectiveness of the cooling shirt on flight maintenance, 13. Palmer CD, Sleivert GG, Cotter JD. The effects of head and
neck cooling thermoregulation, pace selection, and perfor-
air crew, and emergency flight surgeons in non–air- mance. Proc Aust Physiol Pharmcol Soc. 2001;32(2 suppl 1):
conditioned rooms overseas. Additional field studies are 122P.

60 Journal of Special Operations Medicine Volume 16, Edition 2/Summer 2016