Transcranial Electrical Stimulation in Subacromial Pain Syndrome

The project has obtained the approval of the Ethics Committee of the University of Valencia on June 6, 2023 (Id: UV-INV\_ETICA-2701990). The intervention will take place in the laboratories of the Physiotherapy Department of the University of Valencia. All the participants, once they have signed the informed consent and, after being randomly assigned to the EG or the CG, will be evaluated before starting the treatment (T0). A post-intervention evaluation will be carried one day after the end of the 24 sessions (T1), and a follow-up evaluation 3 weeks after the intervention (T2). Subjects with unilateral shoulder pain will be recruited through social media and posters posted in primary care centers, hospitals, and other related locations. The study will be triple blind: participants, evaluators and therapists. In order to monitor the possible adverse effects derived from the application of a-TES, the Bruitoni et al. Adverse Effects Questionnaire will be completed in each session. It is a questionnaire that contains 10 possible side effects (headache, neck pain, scalp pain, tingling, itching, burning, redness of the skin, drowsiness, concentration problems, severe mood change).If any of these symptoms occurred, the stimulation would be stopped and the next day would be tried again. If these effects were repeated, especially the headache or were of severe intensity, the patient would be withdrawn from the investigation. The sample size has been calculated with the formula: n = (2 \* (Zα/2 + Zβ) / d) ² (significance level of 0.05, Zα/2 = 1.96; Zβ =0.84, d= 0.5). Total, n= 64 subjects. In addition, the sample may be increased by 15% in anticipation of possible losses throughout the study (= 10 more subjects). Classic statistical methods will be used to calculate the mean as a measure of central tendency and the standard deviation as a measure of dispersion. Before carrying out the inferential analysis, the normal distribution of the sample will be checked using the Shapiro-Wilk test, homoscedasticity using the Levene test, and sphericity using the Mauchly test. Regarding the inferential analysis, a mixed ANOVA will be used with an intra-subject factor (time), with 4 categories, corresponding to the assessments made; and a between-subjects (group) factor corresponding to the assigned intervention. For post hoc comparisons, the Bonferroni adjustment will be used. In the event that the assumptions are not met, the corresponding non-parametric tests will be applied: Wilcoxon and Mann Whitney, adjusting the type I error. In the event of losses, the intention-to-treat procedure will be used for the statistical analysis of the data. .