Kinetic chain influences on upper and lower trapezius muscle activation during eight variations of a scapular retraction exercise in overhead athletes.

OBJECTIVES To describe and compare the activation levels of the upper and lower trapezius muscle and study the influence of trunk and lower extremity position or movement during eight variations of a scapular retraction exercise. DESIGN Descriptive study. Exercise performance was standardized and individualized based on height, age and body weight. METHODS Individual muscle activation was captured by surface electromyography in thirty young healthy overhead athletes. Exercises were performed in front of a pulley apparatus. RESULTS The mean values for upper trapezius and lower trapezius were 6.59% and 15.93% of maximum voluntary isometric contractions respectively. Main effects were found for "exercise" (F=2.60; p=0.037) and "muscle part" (F=25.44; p<0.001) in an ANOVA for repeated measures model showing higher lower trapezius muscle activation compared to the upper trapezius across exercises. An unipodal squat position on the contralateral leg increased trapezius muscle activation by 3.93% maximum voluntary isometric contraction (p=0.019) compared to the conventional seated performance of the exercise. No differences between phases were found and no exercise activated a particular muscle part (upper trapezius or lower trapezius) to a greater extent in comparison with other exercises since no two-way interactions were found with p<0.05. CONCLUSIONS All exercise variations may be useful in the early phases of scapular rehabilitation training because of their favorable trapezius muscle balance activation. Standing in a squat position on the contralateral leg can result in a slight increase in trapezius muscle activation. However, future comparative effectiveness studies are needed to identify the long-term training benefits of these exercises.