The influence of abdominal muscles on shoulder isometric muscular strength

Abstract

It has been known that core stabilization is associated with the trunk stability and the mobility of limbs. However, studies on the relationships between the core stabilization and the muscle strength of limbs were very rare. Also, the Valsalva maneuver reportedly had an optimal breathing condition that created the maximal muscle strength. However, there has not been any comparative study of the maximal muscle strength by the Valsalva maneuver with that upon the core contraction. Thus, this study aimed to compare the impacts of the core contraction and the Valsalva maneuver on the isometric maximal muscle strengths at the internal rotation of a shoulder. The participants composed of 11 male and 24 female adults (age 21 ± 1.8). The measurement was performed 3 times with the single group. The experiment was carried out to measure the isometric maximal muscle strengths upon the internal rotation of a shoulder in the three groups consisting of the control group, the core stabilization group contracting transverses abdominal muscle and the Valsalva maneuver group using intra-abdominal pressure. A significant difference (p<0.05) was shown between the core stabilization group (10.27±7.06) and the Valsalva maneuver group (16.39±9.09). As a result, it was found that the core stabilization group and the Valsalva maneuver group had impacts on the maximal muscle strength at the isometric internal rotation of a shoulder. If compared with the control group, the core stabilization group displayed the reduced maximal muscle strength while the Valsalva maneuver group showed the increased maximal muscle strength in comparison with the core stabilization group. Since there were no overlapping conditions between the core contraction and the measurement of muscle strength, which comprised the dual task, the concentration of the participation on the task was lowered and thus the maximal muscle strength of the core stabilization group was reduced. It has been known that the Valsalva maneuver enhanced the trunk stability and provided the additional muscle tension along with the increased intraperitoneal and intrathoracic pressures, leading to the improved power generation of the proximal and limb muscles. Consistent with this, the Valsalva maneuver group displayed the highest maximal muscle strength.