Instruction and feedback for conscious contraction of the abdominal muscles increases the scapular muscles activation during shoulder exercises

The study aimed to investigate the effect of the instruction for conscious contraction of the abdominal muscles on the scapulothoracic muscles activation during shoulder exercises.

Repeated measures design in a single group, pre-post instruction.

Sixty healthy male and female subjects (mean age 23.5 ± 3 years) volunteered for this study. Two isometric and three dynamic exercises for the scapulothoracic muscles, focusing on the serratus anterior muscle were assessed before and after familiarization training, standardized verbal, and tactile feedback applied to encourage abdominal muscle contraction. Repeated measures ANOVA and Bonferroni post-hoc test were used to compare normalized EMG amplitudes.

Instruction increased EMG amplitude only for serratus anterior muscle during isometric exercises (Inferior Glide and Isometric Low Row). Conscious contraction of the abdominal muscles resulted in significant increase (p < 0.05) in the serratus anterior, upper, middle and lower trapezius EMG amplitude, during dynamic exercises (Wall Slide, Wall Press, and Knee Push-Up).

Conscious contraction of the abdominal muscle increased the activation of the serratus anterior e the three parts of the trapezius during dynamic shoulder exercises with moderate to minimal levels of EMG activation. In the other hand, abdominal muscles contraction was effective to increase the activation of the serratus anterior during isometric exercises but did not increase the trapezius activation. So, Inferior Glide and Isometric Low Row performed along with encouraged abdominal muscle contraction are compatible to initial phases of the serratus anterior strengthening with low levels of upper trapezius muscle activation.