When I say optimal shoulder function what do you think? My guess for many of you it is likely ‘rotator cuff function’ (yeah, for some it may be scapulohumeral rhythm). However, you would undoubtedly agree that optimal function of the rotator cuff musculature is essential in the successful rehabilitation of the majority of shoulder pathologies.
It is common in clinical practice to utilise shoulder adduction movements to guide clinical decision making, particular in subacromial impingement syndrome patients. During the physical examination it has been suggested that a positive ‘Allingham’s Test’ (or adduction maneuver) indicates a depressor cuff insufficiency. This frequently leads to the treatment choice of an adduction-based rotator cuff strengthening program to address this insufficiency (Morrison et al, 1997). However, a recent EMG study has challenged the validity of both these assessment and treatment decisions (Reed et al, 2010).
A ‘DEPRESSING’ DISCOVERY
Reed et al (2010) assessed the EMG activity in 11 shoulder muscles during adduction in the scapular plane. Fifteen healthy participants with no shoulder pain (question the implications of this freely) were randomly examined under 12 test conditions, at 30, 60 and 90 degrees of abduction under 25, 50, 75 and 100% load. The study showed some surprising results.
During shoulder adduction they found high ‘mean’ levels of activity in:
- Latissimus Dorsi
- Teres Major
- Rhomboid Major
They also found low ‘mean’ levels (<25% MVC) of activity in:
Therefore, the rotator cuff muscles are not very active in adduction activities. This new research, the authors suggest, questions the use of adduction exercises in the treatment and rehabilitation in patients with subacromial impingement syndrome.
CLINICAL IMPLICATIONS and TAKE HOME MESSAGES
- The rotator cuff muscles are active at low levels during shoulder adduction
- A positive Allingham’s Test in impingement patients is more likely due to decreased muscle activity in the deltoid (and related superior translatory force), rather than activation of the rotator cuff muscles
- There is minimal support for the use of shoulder adduction exercises to strengthen the rotator (or depressor) cuff muscles
Morrison DS, Frogameni AD, Woodworth P (1997) Non- operative treatment of subacromial impingement syndrome. Journal of Bone & Joint Surgery–American Volume 79: 732– 737.
Reed D, Halaki M, Ginn K (2010) The rotator cuff muscles are activated at low levels during shoulder adduction: an experimental study. Journal of Physiotherapy 56: 259–264