Long COVID is characterized by persistent symptoms and physiological impairments beyond acute infection. Oxygen consumption (VO₂) and ventilatory efficiency, key indicators of cardiorespiratory fitness, are commonly diminished in this population, contributing to exercise intolerance. This study compared cardiorespiratory patterns and exercise capacity among individuals with Long COVID (LCG), those with resolved symptoms (Short COVID; SCG), and healthy controls (CG). The secondary objective was to assess longitudinal changes over six months. Cross-sectional comparisons at baseline addressed the primary objective, while the longitudinal component explored on changes over time. Participants included 94 in the LCG, 100 in the SCG, and 70 in the CG. All performed a 6-minute walk test (6MWT) during which peak oxygen uptake (VO₂), minute ventilation (VE), and VE/VCO₂ (ratio of VE to carbon dioxide output, reflecting ventilatory efficiency) were continuously measured using the Metamax 3B system. Baseline differences were assessed by one-way ANOVA, and longitudinal changes by generalized estimating equations. At baseline, VO₂was significantly reduced in the LCG (70.1 % predicted) versus SCG (80.6 %) and CG (84.6 %) (p = 0.001). VE/VCO₂ was elevated in the LCG (30.2 ± 4.2) compared to SCG (27.9 ± 2.8) and CG (28.7 ± 3.3) (p < .001). The 6MWT distance was also lower in the LCG (484 ± 127 m) than SCG (607 ± 69.1 m) and CG (571 ± 89.6 m) (p < .001). No statistically significant Group × Time interaction emerged between the groups. Individuals with Long COVID exhibited persistent ventilatory inefficiency and reduced exercise capacity, with impairments persisting over six months, underscoring the need for targeted rehabilitation. SHORT ABSTRACT: Individuals with Long COVID exhibit reduced exercise capacity and persistent ventilatory inefficiency compared to Short COVID and control groups. At baseline and over six months, VO₂, VE/VCO₂, and 6MWT distances were significantly impaired, highlighting the need for targeted rehabilitation strategies to address ongoing physiological limitations in this population. peak peak
Long Covid