## 2 Aims
### Secondary Outcome Measures  
1. QuickDASH: A self-reported questionnaire measuring physical function in individuals with upper limb disorders [20; 21]. Valid and reliable for individuals with shoulder pain [20; 21; 22; 23].
2. Fear-Avoidance Beliefs Questionnaire (FABQ): An 11-item psychological questionnaire evaluating the influence of fear on behavior, including work (FABQ-W) and physical activity (FABQ-PA) sections. Valid and reliable for RCRSP [24; 25].
3. Shoulder pain intensity was measured using a 10 cm VAS for each shoulder, ranging from no pain (0) to worst imaginable pain (10). The VAS was found to be valid and reliable for shoulder pain intensity measurement [26]. The VAS minimal clinical importance difference for people with RCRSP was found to be 1.4 [27; 28].
4. Grip strength: Measured using the \"JAMAR\" Hydraulic Hand Dynamometer (5030)[1], Preston Corporation, NJ, USA) to estimate upper extremity strength [16]. Measurements were taken in a seated position with a neutral shoulder, 90\({}^{\circ}\) elbow flexion, and a neutral wrist [17]. The average of three 5 s hold repetitions was used in the analysis [17].
5. Active shoulder flexion range of motion (AROM) was measured using the smartphone application 'Clinometer-level and slope finder' (version 2.0, Plaincode Software Solutions, Stephanskirchen, Germany) [29]. This application has been found to be reliable compared to a double-armed goniometer (ICC = 1-0.98) [30].  
Statistical Analysis  
Sample size was calculated a priori using G*power software version 3.1.9.4 [31], with a medium-large effect size of 0.75, power of 0.8, and alpha of 0.05, using a \(t\)-test between means [32]. This resulted in a required sample size of 58 participants.  
Data normality was assessed using the Shapiro-Wilk test. Abnormally distributed measures underwent monotonic transformation. Univariate analysis was conducted to identify demographic differences between the RCRSP and control groups. BMI was found to be significantly different and was controlled for in further analyses. Due to known strength differences, dominance was also used as a covariate [18].  
Pearson correlations were calculated between all measures within each group. For the RCRSP group, correlations with unilateral measures were investigated within the painful side.  
For unilateral measures (ULSP, grip, and ROM), two control groups were used: control group 1 (the asymptomatic side of participants with unilateral RCRSP) and control group 2 (participants with no shoulder symptoms). This allowed for the comparison of symptomatic and asymptomatic sides in participants with unilateral RCRSP and the generation of normative data.  
A two-way 3 (painful side groups: control, RCRSP-non painful side, RCRSP-painful side) * 2 (dominance: yes, no) mixed-model repeated-measures analysis of variance (ANOVA) was conducted to examine the effect of painful side and dominance on the outcome measures. All models were controlled for BMI and considered the same subject measurements autocorrelation. When an interaction was established, simple mean analysis was used to reveal the source of significance. The Studentized Maximum Modulus post hoc adjustment method was used to reveal significance between pairs of painful side groups.  
A _p_-value of \(\leq\)0.05 was considered significant. Statistical analysis was performed using SAS for Windows version 9.4.