The first SExSI trial publication left a lot to be desired. This study assessed whether adding a large resistance exercise dose to usual care using a time-contingent approach (similar to graded activity) is superior to usual care alone for improving pain perception and pain catastrophizing, in patients with chronic subacromial pain at 16 weeks follow-up. Exercise effects may be influenced by abnormal pain mechanisms (increased activity of top-down pain modulatory pathways and impaired descending inhibitory mechanisms and enhanced temporal summation of pain) and negative pain cognitions. Previous research suggests exercise can normalize these pathways through a time-contingent approach (exercises are not stopped based on immediate pain response). By pairing a time-contingent approach with pain education (to address negative pain cognition, the authors aimed to improve should pain and pain catastrophizing
The study included participants aged 18-65 years with persistent subacromial impingement (>3 months). 200 participants were randomly assigned to the intervention (IG) or control group (CG). Both groups received usual care. The IG group completed an add-on intervention of progressive, high-volume resistance exercise split into three phases of 5-6 weeks each. The exercise load was increased and a new exercise was added at each phase. All exercises were performed unilaterally, targeted the rotator cuff, and were performed to contraction failure (muscular exhaustion). Each exercise was performed for three sets daily. The participants were taught pain during the exercises did not indicate danger or damage and that they should continue exercises, provided it was tolerable. They were instructed to stop the exercises if a flare-up lasted longer than 24 hours. Once the flare-up resolved, they resumed the exercises at a light load.
When pooling all of the patients, the authors found no difference in pain mechanism outcomes, pain catastrophizing, or strength between the groups at 4-month follow-up. There was a difference when dividing the groups by pain catastrophizing levels. The group with low baseline pain catastrophizing (PCS < 16) experienced significantly greater improvements in SPADI score than the CG and moderate to high pain catastrophizing participants in the IG. There was a dose relationship as well. The low-pain catastrophizing participants completed more additional exercises (1.7 hours additional) than the other participants in the IG.
These results are not surprising when we consider exercise physiology research. Training to failure is a strategy to enhance hypertrophy and endurance, not strength. Low levels of pain and catastrophizing are unlikely to impede force output, so we wouldn’t expect strength to increase strictly due to a further reduction in pain. If someone has moderate or high levels of pain catastrophizing, more exercise may worsen symptoms as they are fearful the exercises are causing harm. If your patient has a low level of catastrophizing, they will likely benefit from a high dose of resistance training. If you want to improve strength, the interventions need to focus on maximal force output (high velocity with moderate to high loads).