High-Intensity Respiratory Muscle Training in Individuals with Parkinson's Disease

Sample size calculation: The sample size calculation was performed considering the primary outcome measures (inspiratory and expiratory muscle strength). The effect size for inspiratory muscle training was derived from a RCT with a similar population and intervention. Considering a significance level (α) of 5% and a power of 0.80, thirteen participants per group are required (a total of 26 participants). The effect size for expiratory muscle training was also derived from a RCT with a similar population and intervention. Considering a significance level (α) of 5% and a power of 0.80, fourteen participants per group are required (a total of 28 participants). Therefore, a sample size of 28 individuals (14 in each group) was defined (largest sample size calculated). Assuming an expected dropout rate of 20%, a total sample size of 34 individuals was set (17 in each group).

Statistical analyzes: All statistical analyzes will be performed by an independent examiner, blinded to the group allocation. Each participant will assigned a unique code. All analyzes will be performed using SPSS (SPSS Inc., Chicago, IL, USA). The normality of data distribution will be for all continuous numeric variables. Descriptive statistics will be calculated for all outcomes.The effects of the interventions will be analyzed from the collected data using intention-to-treat. Data from the last available assessment will be used for missed sessions. Two-way ANOVA with repeated measures (2\*3) will be used to evaluate the differences between groups, considering the time factor (considering baseline, post-intervention, and 4-week follow-up), for the variables: inspiratory and expiratory muscle strength, respiratory muscle endurance, peak cough flow and exercise capacity. The level of significance will be set at 5% and adjusted for multiple comparisons. Data distribution and equality of variance will also be analyzed, to ensure the parametric analysis has been applied correctly. The effect sizes will be calculated to determine the magnitude of the differences between the groups. The differences between the two mean values will be expressed in units of their SD, expressed as Cohen's d, or mean results for the experimental group minus the mean results for the control group, divided by the SD of the control group. Effect sizes between 0.2 and 0.5 will be considered small; between 0.5 and 0.8, medium; and above 0.8, large.