Weight training and shoulder pain: subacromial impingement syndrome

Shoulder pain caused by subacromial impingement can sideline a recreational weight lifter.  Research shows that weight training predisposes individuals to impingement, and that specific exercises are to blame.

If you train recreationally with weights, and have seen a physiotherapist for shoulder pain, then you’ve probably suffered from shoulder impingement (technically known as subacromial impingement syndrome).  Subacromial impingement syndrome is the most common shoulder condition causing pain and functional disability (ref 1).  It is caused by a physical compression of the tendons comprising the rotator cuff, as they pass under the coraco-acromial ligament (see MRI image in Figure 1).  This compression leads to irritation and inflammation, resulting in shoulder pain, weakness and a loss of range of motion. If left untreated, impingement can lead to partial or complete tear of the rotator cuff.  The first line of treatment for shoulder impingement is “conservative management” , which has been shown to resolve the condition in 70% to 90% of patients (ref 2,3), which includes physiotherapy (with or without subacromial steroid injections) and non-steroidal anti-inflammatory drugs (such as ibuprophen).  Unresponsive patients are good candidates for surgical intervention.

Fig 1: MRI of subacromial impingement showing partial rupture of the supraspinatus tendon (lower arrow). Picture courtesy of Wikipedia.

It has been widely suspected in the rehabilitation community that recreational weight training can predispose individuals to subacromial impingement syndrome, and physiotherapists often recommend against performing certain exercises known to exacerbate symptoms.  Past clinical reports have suggested that weight training may predispose individuals to shoulder impingement, but data from controlled studies was lacking.

A new study compared 46 individuals who participated in weight training at least 2 days per week, to 31 individuals with no history of weight training (ref 3). They had the participants fill out an exercise questionnaire detailing their training regimes, and then tested for shoulder impingement symptoms using two validated impingement tests (which in combination do a good job at identifying cases).

The authors found a significant link between weight training and testing positive for shoulder impingement symptoms, suggesting that weight training does in fact predispose patients to developing shoulder impingement syndrome.  Interestingly, they were able to go further.  They identified a significant association between impingement symptoms and the inclusion of either lateral deltoid raises or upright rows (above 90 degrees) in the participant’s weight training regime.  Conversely, impingement symptoms were significantly less likely to be observed in participants that included external rotator strengthening exercises in their exercise routines.  A larger study would be necessary to identify the full set of risky and protective exercises commonly performed in the gym (and to quantify the level of risk or protective effect), but some knowledge of exercise physiology (or advice from a physiotherapist) can help you identify the broader range of exercise do’s and dont’s.

These results suggest that weight training does in fact predispose individuals to subacromial impingement syndrome, and that participants can take a proactive approach to prevent impingement:

1. Avoid upright rows beyond 90 degrees, in other words, do not lift the bar to your chin.  Instead, raise it to mid-chest level so that your arms are parallel to the ground.
2. Avoid lateral deltoid raises.  I know for many weight lifters this is simply non-negotiable.  So if you must keep lateral deltoid raises in your routine, keep the dumbbells parallel to the ground or turned slightly up (ie, at the top of the motion your thumb should be closer to the ceiling than your pinky finger), which should lessen the risk.
3. Incorporate external rotator strengthening exercises into your routine to help strengthen the rotator cuff and as such, functionally increase the subacromial space.

References:

1. Michener L.A., McClure P.W., et al. Anatomical and biomechanical mechanisms of subacromial impingement syndrome. Clin Biomech. 2003; 18(5): 369-79.  https://doi.org/10.1016/S0268-0033(03)00047-0
2. Garofalo R., Conti M., et al. Subcoracoid impingement syndrome: a painful shoulder condition related to different pathologic factors. Musculoskelet Surg. 2011; 95(Suppl 1): S25-9.  https://doi.org/10.1007/s12306-011-0142-7
3. Castagna A., Garofalo R., et al. Posterior superior internal impingement: an evidence based review. Br J Sports Med. 2010; 44(5): 382-8. http://dx.doi.org/10.1136/bjsm.2009.059261
4. Kolber M.J., Cheatham S.W., et al. Characteristics of Shoulder Impingement in the recreational weight-training population.  J Strength Cond Res. 2013 Sep 25 [Epub ahead of print]. abstract