Muscle activated during side laterals.

How many times have we heard and read about the idea that during shoulder abduction, the Supraspinatus is the muscle that initiates the movement, yet, while this claim is generally assumed to be true… it actually is not. 🤷🏻‍♂️

In fact, Reed and colleagues investigated this very question, and concluded that – contrary to most people’s (and Anatomy Books) beliefs – “All muscles tested were activated prior to movement onset. Subscapularis was activated signif- icantly later than supraspinatus, infraspinatus, deltoid and upper trapezius, while supraspinatus, infraspinatus, upper trapezius, lower trapezius, serratus anterior and deltoid all had similar initial activation times. The effects of load or plane of movement were not significant.

“Supraspinatus is recruited prior to movement of the humerus into abduction but not earlier than many other shoulder muscles, including infraspinatus, deltoid and axioscapular muscles. The com- mon statement that supraspinatus initiates abduction is therefore, misleading.”

Reference:

Reed D, Cathers I, Halaki M, Ginn K. Does supraspinatus initiate shoulder abduction? J Electromyogr Kinesiol. 2013 Apr;23(2):425-9. doi: 10.1016/j.jelekin.2012.11.008. Epub 2012 Dec 21. PMID: 23265661.