New Paradigms in Rotator Cuff Retraining

Bahram Jam, MPhty, BScPT, FCAMT (E-mail: [email protected])

Abstract: Rotator cuff strengthening exercises are frequently prescribed to address various shoulder dysfunctions and pain syndromes. The primary function of the rotator cuff muscles is to compress, stabilize and provide fine tune control at the glenohumeral joint. Most exercise programs focus on general strengthening and not on the fine tune control function of these muscles. The purpose of this article is to introduce clinicians to new concepts in rotator cuff retraining that focus on therapeutic exercises to assist these muscles in regaining their functional role as dynamic stabilizers of the glenohumeral (GH) joint.

Key Words: Rotator cuff, Shoulder, Instability, Impingement syndrome.

Rotator cuff (RC) retraining / to produce medial rotation (MR) torque resulting in relatively poor moment arm strengthening is a routine treatment at the GH joint (Fig 1). to produce an abduction torque at the GH option for many Physical Therapists. joint (Fig. 2). It can however be Many papers and reviews hypothesize appreciated that the primary function of Fig 1: the value of RC retraining for individuals the supraspinatus is not to abduct the Force vector for Subscapularis. presenting with various shoulder shoulder, but to compress the humeral dysfunctions, including impingement head into the glenoid fossa and prevent syndromes, glenohumeral (GH) excessive superior translation of the instability and post surgical humeral head during functional activities. interventions1-2. The infraspinatus and the teres minor are The purpose of this paper is two-fold. both described as lateral rotators of the 1) To introduce and discuss four shoulder, however it can be appreciated paradigm shifts in RC retraining that the primary function of the 2) To review the techniques for infraspinatus and the teres minor is not retraining of the RC muscles only to laterally rotate the shoulder, but considering the new paradigm shifts to compress the humeral head into the glenoid fossa and prevent excessive Although clinicians are well aware of the superior and posterior translations of the value of RC retraining, it is the author’s It can however be appreciated that the humeral head during functional activities belief that most prescribed RC exercise primary function of the subscapularis (Fig. 2). regimes are not specific enough, in that muscle is not to medially rotate the they do not address the functional role of shoulder, but to compress the humeral this group of muscles as stabilizers of the head into the glenoid fossa and prevent Fig 2: GH joint. excessive anterior and superior I: Force vector for Supraspinatus translations of the humeral head during II: Force vector for Infraspinatus & The RC muscles include the functional activities (Fig. 1). Both Teres minor subscapularis, supraspinatus, anterior and superior translations of the III: Resultant vector producing infraspinatus and the teres minor humeral head are leading compression force at the GH joint muscles. The subscapularis is described biomechanical causes of RC as a medial rotator of the shoulder, impingement syndromes3. however looking at it logically it would seem that it is a relatively “insignificant” The supraspinatus muscle is most medial rotator, compared to the powerful commonly described as an abductor of pectoralis major, teres major, latissimus the shoulder. Considering its size and dorsi and the anterior deltoid muscles. If position, it is a relatively we appreciate the force-vector angle of “insignificant” abductor compared to the subscapularis muscle we can see that the powerful deltoid muscle. If we it is extremely close to the GH joint line appreciate the force-vector angle of the resulting in relatively poor moment arm supraspinatus muscle we can see that it is extremely close to the GH joint line

1 Many of the concepts outlined in this based on the findings from the studies gentle isometric supraspinatus paper are based on a single research on the lumbar multifidus following contractions held for 10 seconds. It may study by David et al “Rotator cuff muscle lumbar injury. It has been demonstrated take a few minutes to a few weeks to performances during gleno-humeral joint that patients with low back pain have achieve this goal. rotations: An Isokinetic, selective neural inhibition with Electromyographic and Ultrasonographic significant reductions in the CSA of Study”, which was presented at the their lumbar multifidus muscles5. It has Manipulative Physiotherapists also been demonstrated that specific Association of Australia Conference in multifidus retraining in isolation of the Melbourne Australia in 1997. superficial muscles can increase the The remainder of this clinical multifidus CSA6 and may dramatically commentary will focus on four paradigm reduce the risk of low back pain shifts, supportive evidence, clinical recurrences in the long term7. relevance and the clinical application for each of the new paradigms. Clinical relevance: It is hypothesized that the more effective supraspinatus is Paradigm shift #1: as a stabilizer of the GH joint, the Old paradigm: Supraspinatus muscle stronger the shoulder is during LR, Fig. 3: Supraspinatus activation facilitated weakness and loss in size is due to disuse which would also increase the LR/MR by self-palpation and mental imagery. atrophy and therefore requires strength ratio. The loss of supraspinatus strengthening. Strengthening the CSA may decrease its effectiveness at supraspinatus using general resisted producing compressive forces at the Several studies have used functional MRI pulley and dumbbell exercises will GH joint, which in turn may reduce GH to compare the effects of mental imagery increase the cross sectional area (CSA) joint stiffness. Specific neural control with actual execution of simple motor and the stabilizing function of the retraining of the supraspinatus (similar tasks. These studies have demonstrated muscle. to that suggested for the deep fibers of dramatic overlapping of the motor and the lumbar multifidus6) may help pre-motor cortex activity during visualization and actual physical New paradigm: Supraspinatus muscle increase its tonic activation, neural 9-10 weakness and loss in size is due to control and eventually its CSA. This performance of an activity . The selective neural inhibition and therefore may be essential for some individuals cortical activity that occurs at the thought requires specific retraining. To restore presenting with persistent shoulder pain of a movement is very similar to the cortical activity when the movement the primary function of the supraspinatus syndromes. 11 muscle, the focus of rehabilitation must actually occurs . be on specific neural control retraining, Clinical application: To specifically and not on a generic strengthening retrain the supraspinatus in isolation of Many scientific papers have program. the superficial muscles, instruct the demonstrated that overuse, lack of use or patient to self-palpate and with open or injuries to specific musculoskeletal structures can alter cortical Evidence to support the paradigm shut eyes visualize their own 12-14 shift: Using ultrasonography, David et al supraspinatus muscle. They are then representation . It may be measured the supraspinatus muscle CSA instructed to “think about” and pull hypothesized that mentally focusing on at rest. They found a strong positive their humeral head into its socket and specific and isolated supraspinatus correlation between supraspinatus CSA simultaneously “swell up” / contract contraction, may help increase the and isokinetic lateral rotation (LR) torque the supraspinatus muscle (Fig.3). This patients’ awareness of the “existence” of productions and LR/MR strength ratios. may be performed in sitting with the the muscle and enhance its cortical In other words, the bigger the shoulder abducted 60-80 degrees in the representation. Repeated tonic supraspinatus muscle, the greater the scapular plane while the ulnar border of contractions of the supraspinatus may torque production into LR and the greater the hand rests on a table or desk. It rejuvenate the neural pathways required the LR/MR strength ratio. Other studies must be appreciated that only a subtle for its activation and fine tune control. have found the LR/MR strength ratio to contraction of the supraspinatus is This clinical hypothesis is similar to what has been demonstrated with the deep be significantly less in subjects with expected and that no scapular or GH 6- 8 fibers of the lumbar multifidus muscles shoulder pain and dysfunction . joint movement is to take place. Strong 7 contractions palpated over the . It may be hypothesized that the suprascapular region during this supraspinatus muscle may undergo exercise is most likely to be due to Paradigm shift #2: selective neural inhibition following a unwanted over activity of the upper Old paradigm: The supraspinatus shoulder injury or pain episode, which fibers of trapezius. This mental muscle should primarily be strengthened may reduce its CSA. The hypothesis of imagery exercise is performed until the by resisted GH abduction with the supraspinatus neural inhibition following therapist and the patient are able to shoulder maintained in medial rotation. shoulder pain syndromes is indirectly consistently palpate five repetitions of 2 New paradigm: The supraspinatus clinically focus on retraining the GH These findings support the hypothesis muscle may also be effectively retrained lateral rotators in their inner range or that shoulder LR may involve pre-setting with resisted GH lateral rotation with the shortened position. Compromised the supraspinatus, infraspinatus and teres shoulder maintained at various angles of stability during GH abduction and end minor before execution of the actual abduction. range LR predisposes the shoulder to movement. recurrent dislocations and to Evidence to support the paradigm developing impingement syndromes1. These findings are very similar to the shift: Using electromyography (EMG), findings from the EMG studies on the David et al studied infraspinatus, lumbar spine. It has been demonstrated supraspinatus and subscapularis activities that during limb movement, the during isokinetic LR and MR at 45° of transversus abdominis (TrA) muscle also abduction. Surprisingly, EMG activity activates 30-110 milliseconds prior to the was very high in both the infraspinatus other superficial abdominal muscles16, 18. and supraspinatus muscles during LR. Since TrA activation also consistently Clinical relevance: Clinicians frequently preceded the activation of the muscle prescribe resisted shoulder abduction in responsible for limb movement, it is medial rotation in order to strengthen the hypothesized that TrA must be pre- supraspinatus muscle. However, since programmed by the central nervous this exercise is often painful and may system to stabilize the spine prior to further contribute to an impingement Fig. 4: Supraspinatus retraining with movement initiation15-16. In patients with syndrome, exercises focusing on LR may isometric lateral rotation facilitated by low back pain, the activation of the TrA be more comfortable, functional and self-palpation and mental imagery. was significantly delayed and failed to 17 effective. occur in the pre-movement period . It is also imperative to avoid aberrant Clinical application: Many individuals scapular movement when training the Many studies now support the concept with persistent shoulder pain syndromes RC muscles, as scapular motion tends that the TrA and the deep lumbar need to begin their RC retraining using to substitute for “pure” GH rotation multifidus muscles are controlled only isometric exercises, irrespective of when there is poor control of the RC independently of other trunk muscles and their age or physical fitness level. Lateral should be trained separately from the muscles. 18-19 rotation may be resisted isometrically at other trunk muscles . 20-30° of shoulder abduction (Fig. 4). Paradigm shift #3: The slight degree of abduction may be Old paradigm: All resisted lateral Now let us relate the studies on the achieved by placing a folded pillow rotation exercises will strengthen the lumbar spine to the glenohumeral joint. It between the humerus and the body, infraspinatus and teres minor muscles, may be hypothesized that the RC which often increases comfort during the which may help improve GH joint muscles are also controlled exercise. Once the isometric exercises stability. independently of the other shoulder are performed correctly, they can be girdle muscles and should therefore be progressed into resisted LR at various New paradigm: Resisted lateral trained separately from the other angles of abduction, using elastic tubing rotation without deltoid muscle shoulder muscles. or pulley resistance. It is essential to contraction is required for retraining focus on performing the lateral rotation the infraspinatus and the teres minor Clinical relevance: During RC exercises very slowly, especially during muscles. Strengthening is not the focus exercises, clinicians frequently do not the eccentric phases. Each eccentric of the exercises, as the timing and the monitor for excessive compensation by phase of contraction should ideally take ability of the RC muscles to contract in the superficial muscles. In fact many approximately 5-10 seconds to complete; isolation of the deltoids is the key to clinically prescribed RC strengthening therefore the patient must be instructed improving GH joint stability. programs strengthen the deltoid and the not to simply “snap back”, but to slowly pectoral muscles far more than RC control the return from the end range of Evidence to support the paradigm muscles. LR. shift: Using EMG, David et al demonstrated that during isokinetic Clinical application: The key to Many functional and recreational lateral rotation, supraspinatus, achieving isolated activation of the RC activities such as swimming, tennis, infraspinatus and teres minor were muscles is learning to avoid unwanted baseball and weight training require active 80-190 milliseconds prior to the contractions of the deltoid muscle. In shoulder abduction with end range LR. initiation of actual movement and 10- order to monitor over-activity of the Although stability is most essential in 120 milliseconds prior to the activation deltoid muscle, an EMG biofeedback this position, ironically the lateral of the delto-pectoral muscle groups4. unit or a simple deltoid palpation rotators are often weak / insufficient in technique may be used (Fig. 5). end range LR. It is therefore crucial to 3 Encouraging gentle shoulder adduction the subscapularis was active 10-120 head back into its socket. The Therapist during the lateral rotation exercises may milliseconds prior to the other delto- may facilitate this exercise by providing minimize deltoid contractions. Placing a pectoral muscles during isokinetic a feedback using a gentle manual folded pillow or a towel roll between the medial rotation4. posterior glide of the humeral head (Fig. arm and the body may encourage this 6). adduction. These findings support the hypothesis that shoulder medial rotation involves Clinical example: Instruct a patient with The therapist must instruct the patient to pre-setting the subscapularis before GH instability or RC impingement visualize or “think about” pulling the execution of the actual movement and related to an anteriorly translated humeral head into its socket throughout activation of the superficial muscles. humeral head to… the exercise. It is essential to palpate for Step #1: Actively abduct their arm (note any posterior deltoid contractions during Clinical relevance: Subscapularis level of pain & ROM) and bring the arm this exercise. Over-activity of the deltoid strengthening exercises typically back down muscle may indicate poor isolated involve some form of resisted medial Step #2: This time prior to abducting, control of the supraspinatus and rotation, however these exercises visualize taking the shoulder (humeral infraspinatus muscles. If this exercise is primarily engage the dominating head) back into it's socket performed correctly with each eccentric latissimus dorsi, pectoralis major, teres Step #3: Hold that position, and contraction phase lasting 5-10 seconds, major and anterior deltoid muscles, reattempt the abduction most individuals will fatigue within 5-10 which do not have significant “fine Step #4: Try to keep the "joint back" and repetitions with only 1-3 Kg of tune” control over the GH joint. slowly bring the arm down from the resistance. Resisted medial rotation exercises abducted position focus on the function of the subscapularis as a medial rotator, when Many patients with symptoms related to in fact focus needs to be on the excessive anterior translation of the function of the subscapularis as a humeral head respond favourably to this preventor of excessive anterior simple test and potential treatment translation of the humeral head. An technique. alternative method of retraining the subscapularis is therefore essential. Summary The four paradigm shifts introduced in Clinical application: An effective this paper include: method of retraining the subscapularis as a posterior translator of the humeral 1) Supraspinatus muscle insufficiency head is by "thinking about it"! may be due to selective neural Fig. 5: Resisted lateral rotation in inhibition, hence exercises should maximum lateral rotation range with With the arm simply resting on the arm initially focus on specific neural palpation of the posterior fibers of the deltoids monitoring for over-activity. of a chair, or while performing the control retraining, not strengthening. lateral rotation exercises, the patient can be instructed to visualize and 2) The supraspinatus muscle may be Paradigm shift #4: "think about" pulling his/her humeral more functionally and effectively Old paradigm: Resisted medial rotation retrained with resisted GH lateral will strengthen the subscapularis muscle, rotation at varying angles of which is important for improving GH abduction instead of with resisted joint stability. A strong subscapularis GH abduction in medial rotation. muscle helps resist excessive anterior translation of the humeral head. 3) The infraspinatus and teres minor muscles may be more effectively New paradigm: Resisted medial rotation retrained with resisted outer range without delto-pectoral muscle contraction lateral rotation with focus on slow is required for retraining the eccentric contractions and in subscapularis muscle. The ideal isolation of the deltoid muscle. subscapularis exercise program should not focus on strengthening it as a medial 4) The subscapularis muscle may be rotator, but retraining it independently of more effectively retrained with focus the superficial muscles as a posterior Fig. 6: Resisted lateral rotation with on its function as a posterior subscapularis activation facilitated by translator of the humeral head. translator of the humeral head, rather manual feedback into posterior translation than its function as a medial rotator and mental imagery. This is a high-level of the shoulder. Evidence to support the paradigm rotator cuff exercise. shift: David et al also demonstrated that 4 It is crucial to keep in mind that all RC therapy techniques, acupuncture and The concepts reviewed in this article are retraining exercises must be pain-free other modalities were not discussed in primarily based on direct clinical which may be achieved by modifying the this paper, they are often required for experience and further studies and degree of GH abduction, the amount of reducing symptoms before the RC clinical trials are essential to either resistance and the number of repetitions. exercises can be commenced. support or negate the new paradigms Although scapular stabilization, manual presented in this paper.

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