Exercise Intolerance

COPD: A Leading Cause of Respiratory Disability COPD, primarily linked to smoking, affects 3.5 million people in France and causes 15,000 deaths each year. It is a major source of disability, particularly due to dyspnoea, which affects one in three patients. Around 400,000 patients are registered under long-term conditions (ALD), and 200,000 receive home-based respiratory support. The most severe cases fall under the category of chronic respiratory failure-a term also applicable to other respiratory or neuromuscular diseases. Walking Exposes Physical Limitations In patients with respiratory failure, walking rapidly induces disabling dyspnoea, as it may represent their maximal effort. This severely limits autonomy and quality of life. To improve exercise tolerance, clinicians rely on pulmonary rehabilitation (exercise reconditioning, bronchodilators, oxygen therapy). When these measures are insufficient, mobility aids such as scooters or electric scooters may help, although they have limitations (cost, bulkiness, muscular deconditioning). The Six-Minute Walk Test (6MWT): A Key Tool The 6MWT is a standardised test that assesses walking distance, dyspnoea, heart rate, and oxygenation. It is used to evaluate the severity and prognosis of respiratory failure and to measure response to treatment. It is integrated into prognostic indices and criteria for assessing the effectiveness of rehabilitation. The only non-standardised parameter remains the type of footwear worn. Research Hypothesis Some so-called "active" sports shoes enhance walking by design-through cushioning, rocker soles, and rigid inserts-which store and return impact energy to assist propulsion. We hypothesise that wearing such shoes could improve walking performance in COPD patients, as reflected by a greater distance on the 6MWT. If confirmed, this simple and low-cost solution could meaningfully improve the daily lives of many patients.

Exercise intolerance, measured as peak oxygen consumption (VO₂peak) during exercise in patients with heart failure with reduced ejection fraction (HFrEF). Change in VO₂peak (ΔVO₂peak), which serves as a prognostic marker for HFrEF engaged in exercise based cardiac rehabilitation program (ExCR). Responders to ExCR generally show improved cardiac function but some patients with HFrEF do not respond to ExCR. VO₂peak depends on three major components of oxygen transport: Pulmonary (lungs), circulatory (heart and vessels) and skeletal muscle (oxygen utilization) functions. These physiological responses to ExCR may be influenced by epigenetic regulation, specifically the expression of circulating microRNAs (c-miRNAs). Linking non-invasive measurements and epigenetic markers could 1) identify which component of the oxygen transport chain is most impaired and 2) allow personalized interventions to maximize VO₂peak improvements. The primary objective of this stidy is to assess the association between changes in VO₂peak during exercise training and circulating microRNA expression (miR-146a, miR-191, miR-23a, miR-140, miR-1, miR-21, miR-133a, miR-17-5p, miR-3200-3p). The secondary objective is to examine the relationship between pulmonary, cardiovascular, and neuromuscular adaptations to exercise and circulating microRNA expression.

This study investigates whether respiratory muscle training (RMT) and dietary nitrate supplementation can improve exercise tolerance under simulated moderate altitude conditions. Exposure to reduced oxygen availability at altitude places additional strain on the cardiovascular and respiratory systems, which may limit endurance performance. By combining RMT-designed to strengthen the muscles involved in breathing-with nitrate therapy, which enhances nitric oxide availability and vascular function, this study aims to determine whether these interventions independently or synergistically improve oxygen delivery, reduce physiological strain, and enhance exercise performance. The findings will help identify non-pharmacological strategies to improve physical performance and tolerance to hypoxia in both clinical and operational environments.