Screening procedures will be performed as part of this study. In order to be eligible to participate in this study, an individual must meet all of the following criteria: - Male or female, aged 18 to 80 years - Previous infection with SARS-CoV2 at least 4 weeks prior to enrollment, confirmed by laboratory or a healthcare provider. Participants with a documented positive home antigen test will need confirmation of positive COVID-19 antibodies (positive anti-Nucleocapsid antibody test, OR positive anti-Spike antibody test if unvaccinated at the time of the antibody test) to be considered. - Presence of physical limitations or significant fatigue since COVID-19 as demonstrated by: - Total score <= 19 on the PROMIS short form for physical function or total score >= 9 on the PROMIS short form for fatigue, AND - Score >= 1 on the Patient Global Rating of Flu Severity and Patient Global Assessment of Interference with Daily Activities - Absence of post-exertional malaise (PEM) as identified on the DSQ-PEM where: - Items 1 to 5 has no score >= 2 for frequency and no score >= 2 for severity, occurring in the same row, AND - Item 7 or 8 is No , AND - Item 9 is <= 13 hours - Able to read, speak and understand English or Spanish - Able to understand and willing to sign a written informed consent document - Willing and able to complete study procedures

An individual who meets any of the following criteria will be excluded from participation in this study: - Above normal performance (i.e, >=100% predicted) in the 6MWT based on normative data for gender and age - History or cardiac condition as determined by NIH cardiology to be unsafe for exercise participation (e.g. ischemic heart disease, right- or left-sided heart failure, cor pulmonale or pulmonary hypertension, dilated or hypertrophic cardiomyopathy or non-idiopathic cardiomyopathy) - Significant hepatic or renal dysfunction - Cancer diagnosis with evidence of metastasis or a life expectancy of less than one year - History of stroke resulting in impairments in functional mobility that limits safe participation - Active substance abuse including EtOH - Severe psychiatric disease, not responsive to treatment or medication - History of diabetes and on insulin pump therapy, or uncontrolled diabetes with HbA1c > 9.0% - Pregnancy - Acceptance onto a lung transplant waiting list - Extreme obesity with BMI > 40 kg/m2 - On medications that would influence exercise performance such as beta blockers or antiretroviral therapy - Ongoing tobacco and/or nicotine product use - Enrolled in another interventional clinical research trial - Any other medical or health condition(s) that unduly increases the risk of exercise testing or training, affects the normal physiologic response to exercise testing or training, and/or would otherwise interfere with the ability to interpret the data as determined by the PI