Inability to Load Share
The human body is highly intelligent and remarkably efficient. To protect itself from unwanted injury, the body will naturally sequence the recruitment of muscles to provide optimal load sharing across as many muscles and joints as possible. For example, when performing a bent-over row, the body will select the appropriate motor sequence to divide the load among all the pulling muscles.(1) This allows each working muscle to make its maximum contribution when most favorable with regard to optimal length/force and length/tension relationships.
An example of faulty load sharing can be witnessed in those individuals who have been taught to adduct their scapulae prior to initiating a pull with the lats and other muscles. This faulty motor sequence disrupts load sharing by first recruiting the scapular adductors — shortening them beyond the range of their optimal length/force and length/tension relationships — which then leaves the scapulohumeral musculature to perform the remainder of the work. This often leads to strain and trigger point development of the teres major, teres minor and infraspinatus muscles, or otherwise known as pattern overload.(1, 2)
The athlete who regularly performs pulling exercises in the manner described above will likely have a shortening of the scapulohumeral musculature which eventually leads to faulty scapulothoracic rhythm. The result is scapulae that rotate prematurely during all pulling or abduction movements. Over time, this results in stretch weakness of the middle and lower trapezius, and rhomboid musculature. Individuals with this type of dysfunction will present themselves clinically as experiencing pain between the shoulder blades and often demonstrate reduced range of motion in shoulder abduction, internal rotation, and shoulder flexion.
Through careful observation, you'll notice that athletes fitting the movement pattern described above chop their pulling movements into segments. The pull is usually initiated rapidly, favoring use of the now lengthened scapular adductor muscles. The pulling motion is terminated after 60-70% of the normal pulling range because the optimal working range of the short/strong scapulohumeral muscles and now lengthened scapular adductors has been reached; the scapular adductors are not weak, per say, they're just strong at the wrong time.
This pattern of overload, and many others can be seen during many exercises commonly performed in the gym. Although it may take a skilled therapist or corrective exercise specialist to identify many of them, it's safe to assume that your average gym rat or pocket calculator physical therapist with a wild new idea about how to perform an exercise isn't going to improve upon "Mother Nature." It's taken millions of years of natural development in the central nervous system (CNS) and peripheral nervous system to develop recruitment patterns that provide optimal load sharing. To test my theory, I consulted some of the oldest known experts on pulling, climbing and exercise (Figure 1). They told me, "if the body works, don't try to fix it!"