The Effect of Hyper-Hydration on Perceptual and Physiological Heat Strain in Personal Protective Equipment

Abstract

Firefighters and pre-hospital providers use personal protective equipment (PPE) in response to hazardous materials emergencies. PPE has been reported to be physiologically taxing increasing the risk for hyperthermia. A possible method for monitoring the risk of heat-related injury may involve the use of ratings of thermal sensation (RTS; modified Gagge) and ratings of perceived exertion (RPE; OMNI). PURPOSE: To examine the perceptual and physiological heat strain associated with treadmill exercise performed wearing level C chemical-resistant PPE with and without pre-participation intravenous saline. METHODS: RTS, RPE, heart rate (HR), and core temperature (TC) were assessed for seven male (29.3 ± 5.6 yrs) and two female (22.5 ± 2.1 yrs) pre-hospital providers (6 firefighters, 3 EMS). Subjects alternated between carrying an 8.2 kg bar (6.8 kg bar for females) at 4.8 kph and a 5% treadmill grade for 10 min followed by an active recovery of 3.2 kph and a 0% treadmill grade for 5 min. RESULTS: Two-way analyses of variance indicated that perceptual (PeSI) was generally significantly higher than physiological (PhSI) heat strain indices for both the control and experimental conditions during Time Point 1 (min 8), Time Point 2 (min 23), and Time Point 3 (termination). There were no significant differences between the control and experimental conditions for both PeSI and PhSI.Table: Caption not availableCONCLUSIONS: Hyper-hydration does not influence the perceptual awareness of heat strain nor the physiological response to heat strain. The mismatch between perceptual and physiological heat strain indices when wearing PPE suggests factors other than core temperature and heart rate may contribute to perceived thermal strain.