Although the serratus anterior (SA) may be relatively small in size, in terms of importance to shoulder health its stature is quite considerable. Unfortunately, dysfunction of the SA is commonplace in a large percentage of the population and is a contributing factor in a wide range of scapulohumeral (shoulder) issues. The activation and retraining of the SA is a crucial component in the rehabilitation of shoulder injuries but if strategies targeting effective SA function are implemented before such injuries occur then it may be possible to prevent them. Janda (1987) has long since established the tendency for the SA to become weak and inhibited and highlights the need to give targeted conditioning for the SA real consideration.
The SA is responsible for holding the scapula to the rib cage. This means it resists the ‘winging’ of the scapula – where the scapula protrudes from the back. It is vital for stabilising scapula position during functional tasks and providing a solid base for force production; any instability would reduce the amount of force that can be produced. If scapula positioning is compromised then this allows the humeral head to translate both anteriorly and superiorly. This increases the demand placed on the rotator cuff and often contributes to associated overuse injuries.
Concentrically, the main function of the SA is to both protract and upwardly rotate the scapula. Protraction means the scapula moving from the back towards the chest – imagine making a punching movement whilst keeping your arm completely straight and you’ve got it. Upward rotation is where the bottom portion of the scapula rotates around the top portion. To feel this place your left hand on the bottom right portion of your right shoulder blade and then lift right arm above your head. As this upward rotation is necessary to raise the arms above the head, any weakness or inhibition of the SA can cause serious problems with any overhead movements. Also, if the SA is weak and unable to upwardly rotate the scapula, an excessive downward rotation will usually occur at rest. Downward rotation of the scapula reduces acromial elevation (the space within the shoulder capsule) and can often lead to shoulder impingement.
If the SA lacks the strength to upwardly rotate the scapula then upper fibres of the trapezius will often attempt to compensate. Dominance in the upper trapezius (UT) over the SA will cause elevation of the scapula and clavicle, also contributing to a reduction in acromial elevation and overall shoulder impingement. Rehabilitation exercises attempting to emphasize the strengthening of the SA must therefore consider the relative ratio of SA/UT activity in order to condition correct motor patterning. If exercises with a tendency to display greater UT activity are selected, such as exercises performed with an upwardly rotated scapula, there is a greater likelihood that synergistic (UT) dominance will be still observed and dysfunctional motor patterns therefore reinforced.
One of the key problems with the SA is that it cannot be corrected by simply balancing conventional pushing and pulling exercises. In both pressing and pulling motions we want the scapula to be retracted and depressed to provide a solid, stable base for optimal force production. Neither type of exercise should result in protraction or upward rotation of the scapula, so we must therefore consider additional exercises to condition the SA.
The push up may often be overlooked as a basic or remedial exercise, however when performed correctly it is a fantastic exercise for conditioning SA given the protraction involved at the top of the movement. Elevating the feet is shown to further increase the SA activation. Whilst performing push ups on an unstable surface can be a useful exercise for overall shoulder health given the increased proprioceptive demand, it may not be the ideal option for targeting the dysfunctional SA. Performing exercises on an unstable surface will increase global activation of the synergistic musculature but, as reported by Martins et al. (2008), may reduce the contribution of the SA and negatively affect the SA/UT ratio.
All things considered, the two best exercises for SA targeted conditioning are the push up plus and single arm protraction (described below). The research performed by Martins et al. (2008) has demonstrated that a straight arm protraction performed on a stable surface (i.e. the single arm dumbbell protraction) was associated with the lowest SA/UT ratio.
The push up plus
The movement begins at the top position of the regular push up, Keeping the arms straight, lower your chest towards the floor – you should feel your scapula move towards your back (Figure 1a). Again keeping the arms straight, push yourself as far away from the floor as possible – you should now feel your scapula move toward your chest (Figure 1b). Remember to maintain a straight line between shoulders and feet and hold this position for a count of two.
Single arm dumbbell protraction
Set up as yourself up on the bench as if performing a regular dumbbell chest press and then extend the dumbbell to the top, or lockout, position (Figure 2a). From here press the dumbbell towards the ceiling, protracting the scapula, whilst keeping the arm fully extended (Figure 2b). Be sure to keep the opposite side of the scapula and the rest of the body flat on the bench and hold at the top position for a count of two. On the way back down think of actively pulling the dumbbell back towards the floor, retracting the scapula, whilst still keeping the arm fully extended.
Given that the makeup of the SA is predominantly slow twitch, these exercises are best performed for higher reps (12-20). Exercises must not be performed to failure given that the likelihood of synergistic dominance and improper movement patterning increases as the SA becomes fatigued. As a general guideline for individuals with poor SA function, perform either one of these exercises on three occasions a week and for two to three sets. Exercises can be included as part of a warm up or during a session but may be performed at any time.
Even for individuals with no observable SA dysfunction, I would have no hesitation in recommending these exercises. Given the potential for the SA to become weak and inhibited, regularly conditioning the muscle in a targeted manner to reinforce correct motor patterning would seem to be appropriate. As highlighted already, proper functioning of the SA significantly reduces the risk of shoulder injury. The exercises listed above can be easily implemented in the warm up as they take so little time to set up and perform. Another benefit to performing such activities in the warm up is that they will acutely enhance intramuscular coordination, reducing the potential for synergistic dominance to occur during the integrated exercises that are likely to be performed during the session. Volume can be reduced in comparison to a focused SA intervention, a single set of 8-12 reps as part of the warm-up will generally suffice.
One Piece of the Jigsaw:
SA dysfunction is not the only contributing factor to shoulder dysfunction, far from it. It may however, be the most overlooked. For a full and detailed assessment of your own scapulohumeral function please get in touch at Maloney Performance.