Background : There is lack of studies on the effects of the bag-carrying style on the shoulder muscles and body alignment in adults with rounded shoulder posture (RSP).
Objective: The purpose of this study was to investigate the effects of various bag-carrying styles on muscle tone, muscle stiffness and spinal alignment in 20 adults with RSP as they were walking on a treadmill.
Design : Crossover Study Design.
Methods: A subject performed treadmill walking for 15 minutes at a speed of 4 ㎞/ｈ while carrying three different types of bags: a backpack, a cross bag, and a shoulder bag.
Results : The results showed that the main effect of timing was observed in the muscle tone for all the variables and in muscle stiffness only for the upper and lower trapezius muscles. As for the main effect of timing, the muscle tone of the upper trapezius and the pectoralis major significantly increased in all conditions, while the muscle tone of the lower trapezius significantly decreased in all conditions. The muscle stiffness of the upper trapezius significantly increased in all conditions, while the muscle stiffness of the lower trapezius significantly decreased in all conditions. As for the spinal alignment, the dimple distance data values significantly decreased for the cross-bag style.
Conclusions : This study demonstrated that walking with a heavy bag, regardless of the bag-carrying style, increased muscle stiffness around the shoulders in adults with rounded shoulder posture, and walking with a crossbag also induced changes in spinal alignment.