The Combined Effect of the Trapezius Muscle Strengthening and Pectoralis Minor Muscle Stretching on Correcting the Rounded Shoulder Posture and Shoulder Flexion Range of Motion among Young Saudi Females: A Randomized Comparative Study

Background: The shortening of the pectoralis minor muscle (PMi-M) and weakening of the lower trapezius muscle (LTr-M) affect scapular movement, resulting in the development of a rounded shoulder posture and reduction in the shoulder flexion range of motion (SFROM). Objective: This study evaluated the combined effect of LTr-M strengthening and PMi-M stretching on correcting the rounded shoulder postures and SFROM among young Saudi females. Methods: This study was based on a two-arm parallel-group repeated measures randomized comparative design. A total of sixty female participants with rounded shoulder postures were recruited and randomly allocated into groups 1 and 2 (n = 30/group). Each group performed supervised PMi-M stretching; however, group 2 performed a combination of LTr-M strengthening and PMi-M stretching. The outcomes, including rounded shoulder posture and SFROM, were assessed using the pectoralis minor length test (PMLT) and universal goniometer. A repeated measure ANOVA was used to compare the differences within-group and between-group for the outcomes measures at one-week (baseline) pre-intervention, two weeks, and three -weeks post-intervention. The significance level was set at q > 2.00 and p < 0.05 for all respective statistical analyses. Results: The within-group comparison revealed significant improvements (q > 2.00) in the outcomes of PMLT and SFROM when comparing their post-intervention scores to the baseline scores. The between-group comparison revealed a significant and an insignificant (q < 2.00) difference in the outcomes of PMLT and SFROM, respectively when comparing their scores at the second- and third-week post-intervention. Furthermore, the effect size of the intervention suggests an advantage of group 2 over group 1 in increasing the resting length of the PMi-M only among young Saudi females. Conclusions: The combined effect of LTr-M strengthening and PMi-M stretching was more beneficial than PMi-M stretching alone in correcting the rounded shoulder posture among young Saudi females by increasing PMi-M resting length. However, it could not yield a differential improvement in the SFROM outcome among them.