Intermittent Hypoxia: Physiological and Biomedical Perspectives

Dear Colleagues,

Intermittent hypoxia (IH) refers to repeated episodes of reduced oxygen availability, alternating with periods of normoxia. This phenomenon can occur naturally, such as during altitude training, or pathologically, as in respiratory disorders like obstructive sleep apnea. In recent decades, intermittent hypoxia has become a relevant field of study in both physiology and pathophysiology due to its ability to induce cellular and systemic adaptations that may be beneficial or, conversely, contribute to disease progression when dysregulated.

The molecular mechanisms involved in the response to hypoxia include activation of hypoxia-inducible factors (HIFs), oxidative stress, inflammation, and vascular remodeling.

In sports, IH has been used as a strategy to enhance aerobic performance and physiological adaptability. Hypoxic training has been shown to achieve the following:

• Elevate erythropoietin (EPO) levels, enhancing erythropoiesis and oxygen transport;
• Improve mitochondrial efficiency and muscular oxidative capacity;
• Promote vasodilation and tissue perfusion via nitric oxide pathways;
• Increase tolerance to metabolic stress, supporting endurance in high-intensity disciplines.

Such adaptations are particularly advantageous in endurance-based sports such as cycling, long-distance running, and team-based athletics.

Beyond its applications in sports, IH has emerged as a promising therapeutic modality with notable clinical relevance. When employed as a preconditioning strategy prior to ischemia–reperfusion events—commonly encountered during cardiac surgery and organ transplantation—IH preconditioning has demonstrated the ability to foster tissue and organ resistance or tolerance to subsequent injury.

However, IH can also have adverse effects, especially in the context of chronic respiratory diseases. In individuals with conditions like sleep apnea, chronic obstructive pulmonary disease (COPD), or pulmonary fibrosis, IH has been implicated in the following:

• Sustained oxidative stress and systemic inflammation;
• Impaired cardiovascular regulation, elevating the risk of hypertension and cardiac dysfunction;
• Neurocognitive decline due to recurrent cerebral hypoxia;
• Pathological vascular remodeling, contributing to pulmonary hypertension.

These negative effects highlight the importance of understanding the differential mechanisms of intermittent hypoxia, whether it occurs in a physiological or pathological context.

We are pleased to announce a forthcoming Special Issue dedicated to the exploration of intermittent hypoxia from both physiological and biomedical perspectives. We invite researchers and clinicians to submit high-quality contributions that advance our understanding of this multifaceted phenomenon.

We welcome original research articles and comprehensive reviews addressing (but not limited to) the following:

• Mechanisms of adaptation to intermittent hypoxia;
• Applications in sports science and performance enhancement;
• Pathophysiological effects in chronic respiratory and cardiovascular diseases;
• Therapeutic strategies and clinical implications of IH exposure.

This Special Issue offers a unique platform to showcase cutting-edge research and foster interdisciplinary dialogue. We seek contributions that will shape the future of IH research and its applications in health and disease and look forward to hearing from you.

Dr. Teresa Carbonell Camós
Dr. Olga Tura-Ceide
Dr. Norma Alva
Guest Editors

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