The current COVID-19 pandemic is the most severe health crisis of the 21st century. This is not only due to the deaths caused by the disease. People that were affected by COVID-19 and supposedly recovered may suffer from long lasting sequelae. The presence of symptoms longer than 3 months after the infection with SARS-CoV-2 is referred to as Post-COVID-19 Syndrome or Long COVID-19. It is estimated that 10-20 percent of all infected people are affected. The most common symptoms include persistent fatigue, reduced physical capacity, dyspnoea, ageusia, anosmia, musculoskeletal pain and neuropsychological complaints such as depression, anxiety, insomnia and a loss of concentration.

Considering the novelty of the pathology, evidence on the successful treatment of Post-COVID/Long-COVID is scarce. Physical activity has been established as a treatment option for chronic diseases that have similar symptomatic manifestations to those of Post-COVID/Long-COVID. For example, exercise therapy has shown positive effects on the health status of patients with lung disease, depression, anxiety, insomnia and cognitive impairment. However, there has been controversy whether so-called Graded Exercise Therapy (GET) is a safe treatment strategy for patients with Chronic Fatigue Syndrome (CFS). This population may experience Post Exertional Malaise (PEM), a worsening of symptoms after physical, cognitive or emotional exertion. Since COVID-19 might be an infectious trigger for CFS, particular caution has to be taken when recruiting participants and when screening them for adverse events and worsening of symptoms during an exercise intervention.

It can be hypothesized that patients suffering from Post-COVID/Long-COVID can benefit from exercise in various ways, guaranteed that there is sufficient screening for PEM before and during the intervention and training volume and intensity are increased slowly and progressively.

The current study investigates the effects of two different training modalities, endurance training and a combination of endurance training and resistance training, on various parameters in people affected by Post-COVID/Long-COVID.

Inclusion Criteria:

• laboratory-confirmed infection with SARS-CoV-2 via PCR a minimum of 12 weeks ago
• presence of at least one or more of persistent symptoms that can be attributed to Post-COVID/Long-COVID or a manifestation of reduced physical performance capacity since the infection with SARS-CoV-2

Exclusion Criteria:

• previous or current hospitalization due to the COVID-19 disease
• regular engagement in endurance or strength training (more than once per week) in the six months prior to enrollment
• contraindications for physical endurance and resistance exercise according to the guidelines of the American College of Sports Medicine (ACSM)
• clinical diagnosis of depression
• clinical diagnosis of anxiety
• clinical diagnosis of a sleep disorder
• clinical diagnosis of a cognitive deficit disorder
• a grade of 3 or higher on the Post-COVID-19 Functional Status Scale (PCFS)
• presence of post exertional malaise (PEM)