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EFFECT OF POST RUNNING HOT WATER IMMERSION ON WILDLAND FIREFIGHTERS WEARING PROTECTIVE CLOTHING DURING EXERCISE

Abstract

Wildland Firefighting (WFF) is a physically demanding job that can require manual work for 8 or more consecutive hours in hot conditions while wearing personal protective equipment (PPE). Early season work and training can pose additional risk because firefighters may not be acclimatized to working in hot conditions. Previous studies have demonstrated that heat acclimatization occurs in response to post-exercise hot water immersion (HWI). However, to our knowledge, the effect of exercise + HWI on exercise efficiency in WFF wearing PPE has not been examined. PURPOSE: Our study aimed to measure the effect of 5 consecutive days of post exercise HWI on heart rate (HR), blood lactate, and rate of perceived exertion in WFF during graded exercise testing while wearing PPE. METHODS: Male WFF (n=4) completed a baseline graded exercise test at room temperature where each stage was 3 min and speed increased after each stage while wearing gym clothes (GC). Next, they completed the same test at room temp while wearing PPE (PPE1). Subjects then completed 40 min of moderate jogging followed by 25 minutes in a hot bath (38-40C) each day for five days. Two to three days after finishing their final exercise + HWI session subjects returned to the lab for a final graded exercise test at room temp while wearing PPE (PPE2). Heart rate, blood lactate, and rate of perceived exertion (RPE) were measured at the end of each stage during all exercise tests. RESULTS: For the GC condition, mean RPE was 6.25±2.44, lactate was 3.6±2.50 mmol/L, and mean HR was 167.09±20.59 BPM. For the PPE1 condition mean RPE was 6.17±2.59 out of 10, mean lactate was 3.78±2.58 mmol/L, and mean HR was 164.75±21.65 BPM. For the PPE2 condition mean RPE was 6.09±2.4 out of 10, mean lactate was 3.78±2.50 mmol/L, and mean HR was 156.06±20.59. Comparison of blood lactate between PPE1 and PPE2 conditions showed no statistical difference. Likewise, there was no difference in RPE between PPE1 and PPE2. Mean HR was significantly lower in PPE2 compared to PPE1 (p<0.05). CONCLUSION: This preliminary study showed that 5 days of 40 min exercise at room temp followed by 25 min of HWI lead to an average HR reduction of 8.69 BPM during a graded exercise test in PPE at room temp. This finding suggests that exercise + HWI increases exercise efficiency and may help WFF acclimatize to heat prior to fire season.

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