Background Due to efforts by organizations like the ASAS & EULAR, exercise therapy is nowadays considered a cornerstone treatment for the management of functional disability in ankylosing spondylitis (AS). Unfortunately, the effects yielded by RCTs on this topic are only small to moderate; perhaps due to the limited potential for effectiveness of these studies. We recently developed a scale to determine the therapeutic validity of an exercise intervention (i.e., the intervention's potential for effectiveness). Perhaps the effects of exercise therapy in AS is larger when only the therapeutically valid interventions are pooled. After all, an intervention of poor quality is less likely to be (very) effective.
Objectives The purpose of this study was to study the effectiveness of exercise therapy interventions in individuals with AS on physical functioning whilst accounting for therapeutic validity.
Methods We searched MEDLINE, EMBASE, PEDro and Cochrane (through Oct 2013) to identify RCTs on the effectiveness of structured, supervised exercise therapy on physical functioning (self-reported and observed) in adults with AS. Two reviewers independently extracted data and assessed methodological and therapeutic validity (using the PEDro and CONTENT scale  resp; scores of ≥6 reflect high validity). Studies with both methodological and therapeutic validity were included in the best evidence synthesis. In the sensitivity analysis we included all papers, regardless of their validity scores. Effects were pooled using random-effect models.
Results The search retrieved 1181 articles of which four studies – describing five interventions (207 patients) – fulfilled our inclusion criteria. No studies demonstrated therapeutic validity (median score (range) 3 (2-4)) and two demonstrated methodological validity (5 (4-7)). The latter made it impossible to perform our primary best-evidence synthesis. Sensitivity analysis demonstrated that low quality studies showed a positive association between exercise therapy self-reported functioning (SMD (95%>CI), 0.47 (0.13;0.81)) directly after the intervention compared with control participants. The effect on self-reported functioning was maintained for over three months after the intervention (0.43 (0.01;0.85). The latter could not be established for observed functioning (1.19 (-0.42;2.81)).
Conclusions The therapeutic validity of exercise programs for the management of AS, as studied in RCTs, is low. This might explain why we only found small effects of exercise therapy on self-reported functioning (and not on observed outcomes). None of the studies met our predetermined quality criteria. Even though all studies aimed to improve the functional status of people with AS, just one study specifically included individuals who were functionally impaired. Moreover, aspects like therapy monitoring, adequate dosing, and personalization and contextualization were hardly addressed in the progams. Future RCTs on the effectiveness of exercise therapy in the field of AS should invest as much time and effort on the therapeutic validity of the intervention as on the managerial aspects of the trial.
van den Berg. Rheumatology (Oxford). 2012;51(8):1388.
Dagfinrud. AC&R. 2011;63(4):597.
Hoogeboom. PLoS One. 2012;7(5):e38031.
Acknowledgements Thank you to the Dutch Arthritis Foundation for financially supporting this study.
Disclosure of Interest : None declared