Design: The design of this study is an assessor-blinded randomized controlled trial. Prior to evaluation, participants will be randomly allocated to either the experimental or control group by means of concealed envelopes. The number of patients required for this study was calculated a priori to ensure sufficient statistical power. Analysis showed that a sample size of 30 patients in each group was necessary to detect a difference (ES1) with 80 % using a two-tailed hypothesis (with significance of p=0.05).