Abstract Body (Do not enter title and authors here): Background: Persistent cardiorespiratory impairment after COVID-19 has raised concerns about long-term recovery. This study examines the impact of regular exercise on functional improvement using two physiological assessments.

Hypothesis: Regular physical activity accelerates recovery of cardiorespiratory parameters in individuals recovering from COVID-19.

Objective: To compare recovery in resting oxygen saturation (SpO₂), exertional desaturation (ΔSpO₂), and cardiopulmonary efficiency between individuals who exercise regularly and those leading sedentary lifestyles, using non-invasive measurement tools.

Methods: A cross-sectional study was conducted with 91 COVID-19 survivors, aged 20-68 years. Participants were grouped into those who exercised (n=28) and those who were sedentary (n=35). Modified 6-minute walk tests (6MWT) were performed at 1, 2, and 3 months post-discharge. Harvard Step Tests (HST) were conducted at 1 and 2 months post-discharge. Primary endpoints included resting SpO₂, ΔSpO₂, SpO₂ recovery index, total distance walked, and cardiopulmonary efficiency index. Analysis used Friedman, Mann-Whitney U, and Kruskal-Wallis tests. A Generalized Estimating Equations model compared trends.

Results: Baseline SpO₂ levels were significantly higher in individuals who engaged in physical exercise (mean 96.18%) compared to those who were sedentary (mean 95.51%, p<0.001). After three months, SpO₂ levels improved to 97.91% and 97.81% in the exercising and sedentary groups, respectively. The change in SpO₂ (ΔSpO₂) was more pronounced in sedentary participants (−1.40) than in those who exercised (+0.73), although this difference was not statistically significant (p=0.582). The total distance walked increased from 409.8 meters to 454.8 meters in the exercising group and from 289.8 meters to 436.4 meters in the sedentary group, with the sedentary group showing a significantly greater improvement due to a lower baseline (p=0.004). At two months, the CP efficiency index was significantly higher in the exercising group (mean 69.4) compared to the sedentary group (mean 64.3, p<0.001).

Conclusion: Regular physical exercise significantly enhances cardiorespiratory recovery following COVID-19. Both the 6MWT and the HST are straightforward and effective tools for monitoring this recovery process. The findings advocate for the integration of structured physical activity into post-COVID rehabilitation pathways.