Since December 2019, Covid-19 has affected millions of people worldwide, leaving many of
them with symptoms such as fatigue, (muscle) weakness and dyspnoea, even months after
their infection (long covid). Rehabilitation centers were established to aid this new
group of patients. This study's aim is to test the reliability of 2 outcome measures for
patients with long covid. 30 seconds Sit-To-Stand and Timed Up And Go tests are not
specific to a disease but they evaluate functionality, mobility and endurance. They are
easy to perform in a clinical setting as they do not require specific equipment. The
reliability of the above tests has yet to be established in people with long covid.

A sample size of 19 people will be used. A difference in reliability of 0.9 and 0.7 at
80% power and a 5% level of significance using two ratings was set. Based on two testing
sessions, an x value of 0.05, and a power of 0.80, a minimal sample size of 19 patients
was identified (Karagiannis et al., 2020).

19 patients with long covid from the rehabilitation center will take both tests in a
single day and 3 days later they will take the tests again with no physical therapy
intervention in between the measurements.

For the statistical analysis, ICC (Intra-class correlation coefficients), SEM (standard
error of measurement) and Bland-Altman plot will be used. These tests evaluate
test-retest reliability, through the identification of the agreement of patient's scores
between the 2 measurements and they evaluate the measurement precision (Savva et al,
2014).