Bio-physiological responses to challenging underwater environments: insights from cave divers

Cave diving is a complex underwater activity associating multiple physiological, environmental stressors including high pressure, physical exertion, hyperoxia, cold and confined environment. We investigated the evolution of the oxidative–inflammatory stress, appetite hormones response, neurotransmitter and hydration status on a cohort of cave divers during repetitive dives (three days). Eleven male scuba-divers were divided into two groups in two Slovenian Caves. Based on the cave depth, they were classified: “Shallow” and “Deep”. Urine and saliva were collected before (T0) and after (T1) each dive. Reactive oxygen species (ROS), total antioxidant capacity (TAC), lipid peroxidation (8-iso-PGF2α), inflammatory status (Interleukin-6), cortisol, leptin, ghrelin, dopamine, creatinine, neopterin, and electrolytes balance changes were investigated. A significant post-dive decrease in body temperature was observed in “Deep” dives, with values dropping from pre- to post-dive on 2nd and 3rd day, indicating marked thermal stress during cave diving. In both groups, significant changes in oxy-inflammation were found with bigger changes in “Deep” group compared to “Shallow”. Significant hormonal changes occurred only in the “Deep” group, with increased leptin and decreased ghrelin post-dive, while cortisol remained with higher concentrations in the “Shallow” group. Dopamine levels significantly increased post-dive in both groups, with a greater rise observed in the “Deep” group. Repetitive cave dives induced a progressive change in oxidative stress, inflammation biomarker, and some hormones.