Extremity cooling for heat stress mitigation in military and occupational settings

Abstract

a b s t r a c tPhysical work, high ambient temperature and wearing protective clothing can elevate body temperature and cardiovascular strain sufficiently to degrade performance and induce heat-related illnesses. We have recently developed an Arm Immersion Cooling System (AICS) for use in military training environments and this paper will review literature supporting such an approach and provide details regarding its construction. Extremity cooling in cool or cold water can accelerate body (core temperature) cooling from 0.2 to 1.0 1C/10 min vs. control conditions, depending on the size/surface area of the extremity immersed. Arm immersion up to the elbow results in greater heat loss than hand-or foot-only immersion and may reduce cardiovascular strain by lowering heart rate by 10-25 beats/min and increase work tolerance time by up to 60%. The findings from studies in this paper support the use of AICS prototypes, which have been incorporated as part of the heat stress mitigation procedures employed in US Army Ranger Training and may have great application for sports and occupational use.Published by Elsevier Ltd.

Thermal stress, human performance, and physical employment standards

“…Under uncompensable heat stress, however, sustained heat gain beyond dissipation capacity from evaporation may still persist even during recovery (McLellan et al 2013). The cooling process can be expedited through active cooling strategies, such as arm immersion cooling (DeGroot et al 2013;House et al 1997House et al , 2003 and ingestion of cold drinks (Lee et al 2013) and potentially ice slurry (Tan and Lee 2015;Yeo et al 2012). The United States military has formulated work-rest schedules for different combinations of physical workloads and weather conditions (US Army 20032003.…”

“…For instance, personnel can be pulled out from the operation immediately when their core temperature reaches a certain threshold value. At present, the ingestible thermometer pill is the most common method for real-time body core temperature monitoring in field settings (O'Brien et al 1998;Domitrovich et al 2010). However, this method has several limitations, such as its impracticality for frequent use and high cost.…”

Cryotherapy: biochemical alterations involved in reduction of damage induced by exhaustive exercise

“…Additionally, recent studies have shown that CWI is more efficient than other forms of recovery because it causes local vasoconstriction that leads to the reduction of fluid propagation in the interstitial space. Hence, this method favors the reduction of muscle damage, acute inflammation (12), muscle tissue temperature, venous O 2 saturation, plasma myoglobin concentration, and swelling (13). …”

Repeat work bouts increase thermal strain for Australian firefighters working in the heat

“…Research in military and firefighting settings has demonstrated the value of active cooling methodologies in delivering superior cooling rates compared with passive methods alone. 5,40,41 Using active cooling methodologies, specifically cold-water immersion (CWI), 42 it has been shown that core temperature rises can be attenuated through immediate cooling. Cold-water immersion also provides a precooling effect for subsequent work bouts.…”