Self-acknowledged limitations in exercise therapy trials for low back pain

Despite the widespread recommendation to engage in therapeutic exercise for the treatment of low back pain (LBP), there is conflicting evidence regarding clinical outcomes and effectiveness. Poor methodological quality may be to blame for reducing the overall strength of evidence for this intervention, yet little is known about the difficulties researchers encounter when designing and implementing their study methods.

The aim of this study was to characterize the extent and type of self-acknowledged limitations (SALs) in exercise therapy trials for LBP to gain a better understanding of challenges encountered when conducting this research.

This is a methodological review of clinical trials in which SALs were extracted, categorized by theme and subcategorized within each theme. Counts and prevalence rates were tabulated for the number of SALs in each category and subcategory.

There were 914 SALs among the 312 included trials, with a mean of 2.93 (95% confidence interval [CI], 2.77-3.09) per trial. Analysis of the data resulted in the development of 13 distinct categories of limitations, among which were 37 subcategories. The top three categories pertained to statistical power (14.3% of total SALs), study length and/or follow-up (14.3%) and inclusion criteria (14.2%). The top three subcategories were lack of long-term follow-up (13.8% of total SALs), inadequate sample size (13.3%) and inclusion of specific populations (12.3%).

Statistical power, study length and/or follow-up, and inclusion criteria were the three most commonly reported categories of SALs in exercise trials for LBP. Lack of long-term follow-up, inadequate sample size and inclusion of specific populations were the most common subcategories. Research protocols recognizing and avoiding these limitations will enhance the overall quality of evidence of exercise therapy trials for LBP.