The effects of caffeine during exercise in fire protective ensemble

Area of Science:

• Exercise Physiology
• Occupational Health
• Environmental Heat Stress

Background:

• Firefighters wear fire protective ensembles (FPE) during strenuous activity.
• Heat strain and reduced work tolerance are concerns for firefighters.

Purpose of the Study:

• To investigate caffeine's effects on physiological and psycho-physical responses during exercise in FPE.
• To assess caffeine's impact on body temperature and physiological strain in a simulated firefighting scenario.

Main Methods:

• Ten healthy males performed treadmill exercise in FPE on two separate occasions.
• Participants ingested either caffeine (6 mg/kg) or a placebo 60 minutes before exercise in a double-blind, randomized manner.
• Core body temperature, ventilation, and perceived exertion were measured.

Main Results:

• Caffeine ingestion significantly increased end-exercise gastrointestinal temperature (T(gi)) compared to placebo.
• Ventilation (V(E)) and tidal volume (V(t)) were higher with caffeine, increasing air consumption from breathing apparatus.
• Perceived exertion decreased with caffeine, but the elevated T(gi) resulted in a higher calculated physiological strain index.

Conclusions:

• Caffeine alters physiological and psycho-physical responses during exercise in FPE.
• Increased core body temperature and physiological strain suggest a heightened risk of heat-related illness for caffeine-consuming workers in hot environments.
• This study is the first to demonstrate caffeine-induced increases in human core body temperature during exercise in FPE.