Effects of sleeper and cross-body stretching on posterior shoulder capsule stiffness

We aimed to determine whether sleeper (SL) and cross-body (CB) stretching immediately reduce posterior capsule stiffness and to examine their differential effects on the middle and inferior posterior capsular regions. The nondominant shoulders of 15 healthy young adult men were included in this crossover study. Shear moduli of the middle and inferior posterior capsules were measured using shear-wave elastography before and 5 min after stretching. A repeated-measures two-way analysis of variance (stretching method × time) was performed for the shear modulus of each capsule, followed by post hoc Wilcoxon signed-rank tests. The significance level was set at 5 %. To assess whether the observed changes exceeded measurement error, minimal detectable change (MDC) values were calculated from pilot data. For the middle posterior capsule, a significant stretching method × time interaction was observed, and the shear modulus decreased significantly after SL stretching. All participants exhibited a decrease in shear modulus, with five exceeding the MDC. For the inferior posterior capsule, only a main effect of time was noted, indicating a significant decrease in shear modulus after both SL and CB stretching. All participants exhibited a decrease in shear modulus, with six surpassing the MDC in both SL and CB stretching. These findings indicate that SL stretching decreases the shear modulus of both regions of the posterior capsule, whereas CB stretching reduces the shear modulus of only the inferior region. These findings allow clinicians to select the most appropriate stretching techniques for the middle and inferior posterior capsules.