Dietary habits and self-reported hypoxic events in competitive freedivers: an observational study

Competitive freediving involves repeated voluntary breath-holding, during which hypoxic events such as loss of motor control (LMC) or blackout (BO) may occur. Although nutrition may influence metabolic responses to hypoxia, evidence in competitive freedivers remains limited. This study aimed to investigate the relationship between dietary habits and self-reported hypoxic events in Spanish competitive freedivers.

A cross-sectional study was conducted in 71 competitive freedivers (19 women: 39.4 ± 9.3 years; 52 men: 41.9 ± 8.6 years). Participants completed a questionnaire on training characteristics and hypoxic events. Events were classified as LMC or BO, and participants were categorized according to the most severe event experienced. Dietary habits were assessed using a validated food frequency questionnaire (PREDIMED). Associations were examined using chi-square or Fisher's exact tests, and significant variables were included in a binomial logistic regression adjusted for age, sex, and years of practice.

Overall, participants showed moderate consumption across dietary groups, with higher intake of fruits, vegetables, and protein-rich foods; and low intake of ultra-processed foods and alcohol. Male divers consumed moderate amounts of protein-rich foods, whereas female counterparts reported lower intake [χ² (2) = 8.53, p = 0.014; Fisher's exact test, p = 0.010]. Overall, 21 freedivers (29.6%) reported at least one hypoxic event. The occurrence of hypoxic events were associated with years of practice (p = 0.003) and consumption of stimulant beverages (p = 0.013). Beginners experienced fewer events than expected, whereas divers with >4 to 10 years of practice were overrepresented. In the adjusted model, years of practice remained significantly associated with hypoxic events [OR = 3.06, 95% CI (1.43, 6.53), p = 0.004]. Moderate stimulant beverage consumption emerged as a potential associated factor [OR = 12.54, 95% CI (1.27, 123.9), p = 0.031].

Hypoxic events in competitive freedivers were primarily associated with years of practice, suggesting that cumulative exposure may be a relevant risk factor. Overall dietary habits showed no clear relationship with hypoxic events, although stimulant beverage consumption may warrant further investigation.