Strength Testing

[gcoe]

Hi Natty1905

When you were studying the SA did you go back and look at any research articles?

Kendall’s book is interesting and the latest one gives lots of detailed testing and examples of paralysis. However none of it is supported by research. I think there is quite a lot out there on the SA in the normal and in pathology. Robert Donatelli’s: Book Physical therapy of the Shoulder gives an excellent account of the Serratus anterior in scapular movement.

I understood that serratus anterior as a whole works in pure protraction of the scapular so is tested with a shoulder protraction test. What Kendall is getting at in their preferred test but don't really state, is that the lower fibres of SA that originate on the lower medial border and the inferior angle and run to the 3rd 4th and 5th ribs work as a force couple with upper trapezius and lower trapezius to rotate the scapular up during shoulder elevation. In this force coupling the lower border of of the scapular is pulled forward and upward, the upper trapezius pulls the lateral part of the acromion upwards in medially, and the lower trapezius pulls the medial part of the acromion downwards in inwards. Each muslce counters the unwanted action of the other two so you get a relatively pure upward rotation..

So clinically in:
1. frank paralysis of the long thoracic nerve the patient can’t protract the scapular at all and you get the classic winging of the scapular.

2. Whereas a common muscle imbalance problem where the scapular fails to get the proper scapula-humeral rhythm during shoulder elevation, you often get weakness of these lower fibres of SA along with weakness of the lower trapezius ending up with excessive upper trapezius activity and a failure to sufficiently upwardly rotate the scapular

[natty1905]

Yes I have been reading that in Movement Impairment Syndromes however I still struggle to understand the test. Is it merely a case of observing the scapular humeral rhythm from behind or is there some way to test the lower fibres of trapezius and lower digitations of serratus during upward rotation of the scapular. I am not just being lazy here but have read various authors and cant get to the bottom of it!