Abstract
Wildland firefighting requires repetitive (e.g., consecutive work shifts) physical work in dangerous conditions (e.g., heat and pollution). Workers commonly enter these environments in a nonacclimated state, leading to fatigue and heightened injury risk. Strategies to improve tolerance to these stressors are lacking. Purpose: To determine if glutamine ingestion prior to and after consecutive days of firefighting simulations in the heat attenuates subjective ratings of fatigue, and evaluate if results were supported by glutamine-induced upregulation of biological stress responses. Methods: Participants (5 male, 3 female) ingested glutamine (0.15 g/kg/day) or a placebo before and after two consecutive days (separated by 24 h) of firefighter simulations in a heated chamber (35 °C, 35% humidity). Perceived fatigue and biological stress were measured pre-, post-, and 4 h postexercise in each trial. Results: Subjective fatigue was reduced pre-exercise on Day 2 in the glutamine group (p < 0.05). Peripheral mononuclear cell expression of heat shock protein 70 (HSP70) and serum antioxidants were elevated at 4 h postexercise on Day 1 in the glutamine trial (p < 0.05). Conclusions: Ingestion of glutamine before and after repeated firefighter simulations in the heat resulted in reduced subjective fatigue on Day 2, which may be a result of the upregulation of biological stress systems (antioxidants, HSPs). This response may support recovery and improve work performance.
Highlights
IntroductionFatigue, which is a multifactorial condition, has been defined as an overwhelming and excessive whole-body tiredness that leads to reduced physical and mental performance [1]
Many labor-intensive occupations require workers to perform extreme physical tasks
We report lower ratings of on the second day of repeated bouts of wildland firefighting simulation exercises subjective fatigue on the second day of repeated bouts of wildland firefighting in the glutamine trial compared to the placebo
Summary
Fatigue, which is a multifactorial condition, has been defined as an overwhelming and excessive whole-body tiredness that leads to reduced physical and mental performance [1]. Both mental and physical fatigue, along with injury risk, are exacerbated when heavy work tasks are performed in inclement conditions [2] Factors such as hot temperatures, air pollution, and dangerous terrains are common challenges for agricultural and forest workers, military personnel, and wildland firefighters [3]. In these groups, a valid method of evaluating fatigue is through subjective evaluations [4]. In addition to the heavy physical demands and environmental stressors of outdoor occupations, another factor that heightens the injury risk of workers is the initial and repetitive exposure to Safety 2019, 5, 38; doi:10.3390/safety5020038 www.mdpi.com/journal/safety
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