Author(s): SELLERI, V., D'ALISERA, R., SINIGAGLIA, G., ZANINI, G., MICHELONI, G., SAVINO, G., TRENTI, T., FASANO, T., MATTIOLI, A.V., PINTI, M., NASI, M., Institution: UNIVERSITY OF MODENA AND REGGIO EMILIA, Country: ITALY, Abstract-ID: 1967

INTRODUCTION:
Intermittent hypoxic training (IHT) alternates normoxia and hypoxia to reproduce key features of altitude acclimatization and enhance sea-level performance. According to the principle of hormesis, controlled hypoxia induces vascular, hematological, and metabolic adaptations that improve oxygen utilization and stress resilience, whereas excessive exposure may be detrimental. IHT may stimulate erythropoietin release, increase erythrocyte mass, and promote structural and biochemical adaptations in skeletal muscle favoring oxidative metabolism; improvements in anaerobic performance have also been described. Hypoxia modulates mitochondrial dynamics, optimizing electron transport and ATP production while influencing inflammatory and antioxidant pathways. Monocytes, central regulators of innate immunity, undergo bioenergetic and functional reprogramming under hypoxia, potentially affecting their inflammatory phenotype. Although IHT is increasingly adopted by athletes, particularly through hypoxic masks, limited data are available regarding its systemic safety and mitochondrial impact. This study aimed to investigate these aspects in non-professional athletes.
METHODS:
Ten non-professional athletes performed three 50-minute spinning sessions following an IHT protocol once weekly for three consecutive weeks wearing the training mask with three airflow levels. Evaluations were conducted at baseline (T0), immediately after the first session (T1), after the third session (T2), and one month post-intervention (T3). At each time point, five vital signs were recorded using a certified medical device. Venous blood samples were collected for the assessment of fifty-two hematochemical parameters (complete blood count and comprehensive metabolic, lipid, iron, and endocrine panel). Monocyte subsets (classical, intermediate, non-classical) were quantified, and their mitochondrial morphology and function were analyzed, including mitochondrial respiration and reactive oxygen species (ROS) production. Circulating cell-free mtDNA and proinflammatory cytokines (IL-6, IL-8, TNF-α) were also measured in plasma.
RESULTS:
In Group 1, systolic and diastolic blood pressure remained stable throughout the study. As expected, heart rate and respiratory rate increased acutely at T1 and T2 and returned toward baseline at T3. A similar transient pattern was observed for ROS production and circulating mtDNA levels. No significant differences were detected across time points for hematochemical parameters, including blood oxygen levels.
CONCLUSION:
Under the study controlled experimental conditions, this IHT protocol did not induce significant alterations in blood oxygenation or hematochemical parameters. Although limited by the small sample size, these preliminary findings suggest that mask-based IHT appears safe in healthy athletes. The inclusion of two additional comparison groups (training without mask and mask use at rest) will enable a more comprehensive evaluation of mask-specific and exercise-related effects.