Core muscle activation during dynamic upper limb exercises in women.

Although several everyday functions and sporting activities demand controlled use of the abdominal and back muscles while working with the upper limbs, the activity of core muscles during dynamic upper limb exercises in the standing position has not been studied extensively. The purpose of this cross-sectional study was to examine abdominal and back muscle activity during dynamic upper limb exercises while standing and to evaluate whether dynamic exercises are appropriate for strengthening muscles. The activation of the rectus abdominis, obliquus externus abdominis, longissimus, and multifidus muscles during dynamic bilateral or unilateral shoulder exercises with or without fixation of the pelvis was measured in 20 healthy women using surface electromyography. Trunk muscle activation during isometric maximum contraction was used as a comparative reference. With bilateral shoulder extension and unilateral shoulder horizontal adduction, abdominal muscle activity was >60% of activity during reference exercises. With unilateral shoulder horizontal abduction and shoulder extension exercises, back muscle activity was >60% of the activity level reference exercise. Muscle activation levels were 35-64% lower during shoulder horizontal adduction and abduction without fixation compared with exercises with fixation. The results indicate that upper limb exercises performed in the standing position are effective for activating core muscles. Bilateral and unilateral shoulder extension and unilateral shoulder horizontal abduction and adduction with the pelvis fixed elicited the greatest activity of the core muscles.

Effect of isometric upper-extremity exercises on the activation of core stabilizing muscles.

OBJECTIVE: To evaluate whether isometric exercises for the upper extremities could sufficiently activate core stabilizing muscles to increase muscle strength. DESIGN: Cross-sectional study. SETTING: Department of physical medicine and rehabilitation at a Finnish hospital. PARTICIPANTS: Healthy adult women (N=20). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Peak isometric strength of the back and abdominal muscles was measured and relative loading in 5 test exercises was evaluated by surface electromyography. RESULTS: The rectus abdominis and obliquus externus abdominis were activated to the greatest degree in a bilateral shoulder extension exercise and the average surface electromyographic activity was 114% and 101% compared with the amplitude elicited during the maximal isometric trunk flexion exercise. Horizontal shoulder extension elicited the greatest activation of the longissimus and multifidus muscles. In this exercise, the activity levels of the left side multifidus and longissimus muscles were 84% and 69%, respectively, compared with the level of activity elicited during trunk extension. CONCLUSIONS: Of all the exercises studied, bilaterally performed isometric shoulder extension and unilaterally performed horizontal shoulder extension elicited the greatest levels of activation of the trunk musculature. Thus, it can be assumed that these exercises elicit sufficient levels of contraction of the trunk muscles for the development of their endurance and strength characteristics in rehabilitation.