Investigation of respiratory muscle strength, exercise capacity and sleep quality level in post-COVID-19 Individuals: case-control study

Introduction
COVID-19 patients may arrive at the hospital with a variety of symptoms, from severe pneumonia and multiple organ failure to moderate upper respiratory symptoms, or no symptoms at all. The aim of the was to evaluate the respiratory muscle strength, exercise capacity and sleep quality of young individuals who had COVID-19 infection and recovered without the need for hospitalization, and to compare them with asymptomatic individuals.

Material and methods
Fifty-five sedentary people aged 18 to 45 were recruited: 30 post-COVID-19, and 22 who had not contracted COVID. All COVID-19 patients had achieved a negative PCR test three months after infection, were not hospitalized during the disease, did not smoke and were not involved in any exercise program. A spirometer was used to measure pulmonary function, an electronic mouth pressure monitor was used to measure respiratory muscle strength, the six-minute walk test (6MWT) was used to measure exercise capacity, and the Pittsburgh Sleep Quality Scale was used to measure sleep quality.

Results
The individuals with COVID-19 infection had significantly lower measured and maximal inspiratory pressure, maximal expiratory pressure, and 6MWT distances compared to the healthy individuals (respectively; p=0.001, p=0.001, p=0.002). They also had lower sleep quality (p=0.003). Pulmonary function values (FEV1, FVC, FEV1/FVC, PEF) of both groups were similar (p>0.05).

Conclusions
Our study indicated that young individuals with a history of COVID-19 who had not required hospitalization during the period of infection had lower respiratory muscle strength and exercise capacity, as well as poorer sleep quality in the post-disease period compared to those without a history of COVID.