Sample size calculation
The number of participants included in this study was determined based on quadriceps muscle test data from a previously published study. According to the results of Ogut et al. the mean muscle strength before treatment was 40.6 Nm with a standard deviation of 6.5. The mean muscle strength after treatment was 44.8 Nm. The sample size calculation was based on a power of 80% (β 0.2), a dropout rate of 25% and a statistical significance (α = 0.05) of 95% (