Effects of carbohydrate-electrolyte solutions with and without L-menthol on hydration and performance recovery following simulated firefighting exercise.

Abstract

Background: Firefighting tasks performed in full protective equipment (PPE) impose extreme thermal and physical strain, providing a model of high-intensity exercise with substantial fluid and electrolyte loss. This study compared the effects of plain water (W), a carbohydrate-electrolyte solution (CES), and a menthol-supplemented carbohydrate-electrolyte solution (MCES) on hydration and performance recovery during the first hour of post-exercise recovery.

Methods: Twenty-four male firefighters completed a standardized simulated firefighting protocol in protective clothing. Participants were randomly assigned to W, CES, or MCES (n = 8 each) and consumed 1.0 L of fluid during 60 minutes of recovery. Hydration status was evaluated using body-mass restoration, salivary osmolality, urine specific gravity, urine color, and urinary electrolytes. Renal markers, lactate clearance, cardiovascular and thermal responses, thirst ratings, and lower-limb explosive power were also assessed.

Results: Body mass restoration showed significant group effects, with MCES greater than W and CES at 60 min (p < 0.05). Rehydration rate was higher for both CES and MCES than W (p < 0.05). Salivary osmolality and urinary sodium favored electrolyte solutions over water (p < 0.05), while urine specific gravity was lower in MCES compared with W and CES (p < 0.05). Blood urea nitrogen and BUN/creatinine ratios were higher in W than both electrolyte conditions at 30 and 60 min (p < 0.05). Lactate clearance was reduced in W compared with CES and MCES (p < 0.05). Jump height declined from pre- to post-recovery in the W and CES groups but was maintained within the MCES group.

Conclusions: Carbohydrate-electrolyte solutions improved hydration compared with water. L-menthol did not enhance rehydration but maintained explosive performance, supporting its role as a perceptual adjunct to electrolyte strategies for recovery after exercise in protective clothing.