Coactivation of the shoulder and arm muscles during closed kinetic chain exercises on an unstable surface

Andrade R, Araújo RC, Tucci HT, Martins J, Oliveira AS
Correspondence: Prof Rodrigo Cappato de Araújo, rodrigocappato@yahoo.com.br

ABSTRACT
Introduction The purpose of this study was to compare the electromyography index of muscle coactivation of the following muscle pairs: posterior deltoid and pectoralis major (PD/PM); triceps brachii and biceps brachii (TB/BB); and serratus anterior and upper trapezius (SA/UT) during three different closed kinetic chain exercises (wall-press, bench-press and push-up) on an unstable surface at the maximal load.
Methods A total of 20 healthy sedentary men participated in the study. Integral linear values were obtained from three sustained contractions of six seconds each for the three proposed exercises. Mean coactivation index values were compared using the mixed-effects linear model, with a five percent significance level.
Results Electromyography indexes of muscle coactivation showed significant differences for the PD/PM and TB/BB muscle pairs. No differences were found between exercises for the SA/UT muscle pair.
Conclusion Our results seem to differ from those of previous studies, which reported that the similarity in exercises performed is responsible for the comparable muscle activation levels.

Keywords: coactivation, closed kinetic chain, electromyography, shoulder
Singapore Med J 2011; 52(1): 35-41