Effect of CO₂ and H₂ gas mixture in cold water immersion on recovery after eccentric loading

The findings of previous studies support the efficacy of cold water immersion (CWI) with carbon dioxide (CO₂) in enhancing muscle blood flow and maintaining aerobic performance efficiency. We hypothesize that the addition of hydrogen gas (H₂), known for its antioxidant properties and role in inflammation regulation, to C-CWI can enhance recovery after eccentric exercise.

and Methods: Thirty-four healthy subjects performed a knee-extensor eccentric exercise. They were randomly allocated into four groups: control, CWI, CO₂-rich CWI (C-CWI), and CO₂ + H₂ gas mixture CWI (CH-CWI). In the three CWI groups, all subjects were immersed in the appropriate bath at 20 °C for 20 min immediately after 60 repetitions of eccentric exercise. Before exercise and after 48 h of recovery, the subjects' maximal voluntary isometric contraction torque (MVC-ISO), maximal voluntary concentric (MVC-CON) contraction torque, countermovement jump (CMJ) height, knee flexion range of motion (ROM), muscle soreness, and muscle thickness were measured.

In the CH-CWI group only, the MVC-ISO, CMJ height, and ROM did not decrease significantly post-exercise, whereas all of these decreased in the other three groups. Muscle soreness at palpation, contraction, and stretching significantly increased post-exercise in all groups. Echo intensity and tissue hardness did not increase significantly in the CH-CWI group.

CH-CWI stimulated recovery from impairments in MVC-ISO torque, CMJ height, knee-flexion ROM, tissue hardness, and echo intensity. These findings indicate that CH-CWI can promote recovery after eccentric exercise.