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

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.