Kinetic chain-based shoulder exercises: effects of lower extremity contribution on scapular muscle balance in individuals with and without scapular dyskinesis

The purpose of this study was to compare the effects of kinetic chain-based forward punch plus (FPP) exercise on scapular muscle activation between individuals with scapular dyskinesis (SD) and healthy controls. A total of 30 male participants were recruited, including 15 with SD and 15 healthy individuals. Muscle activation of the upper trapezius (UT), lower trapezius (LT), serratus anterior (SA), and gluteus maximus, as well as activation ratios, were measured during FPP and FPP with contralateral leg flexion. The healthy group demonstrated decreased UT activation accompanied by increased LT and SA activation, resulting in significantly reduced UT/SA and UT/LT ratios. In contrast, the SD group showed significant increases in SA and LT; however, compensatory activation of the UT prevented improvement in muscle activation balance. These findings highlight the need for targeted neuromuscular strategies to address compensatory UT activation in individuals with SD during kinetic chain-based movements.