Low back pain is a significant health issue around the world. To manage it effectively, healthcare providers need ways to predict which people are likely to have poor long-term results. Identifying these individuals early allows for more focused and timely treatment. This type of research, which seeks to find factors that can predict future health, is known as prognostic research.

The purpose of this research was to review and summarize all the existing scientific evidence on whether physical tests of a person's physical abilities can be used as "prognostic factors," or predictors, for the future outcomes of people with low back pain.

To do this, researchers conducted a "systematic review," which is a thorough and structured method for finding and analyzing all available studies on a specific topic. They followed a pre-published plan and searched multiple large scientific databases for studies published up to May 29, 2024. They also manually searched key medical journals and the reference lists of relevant articles to find any additional research.

The review included studies that followed a group of adults (age 18 or older) with low back pain over a period of time. These are called "prospective longitudinal studies." The studies had to investigate at least one physical test to see if it could predict the person's future pain or function. The review excluded cases of low back pain caused by specific serious conditions like cancer, fractures, infections, inflammatory diseases, or a serious spinal cord issue known as cauda equina syndrome. Studies that used specialized diagnostic tools like imaging, electromyography (EMG, a test of muscle and nerve function), or complex 3D motion capture systems were also excluded.

Two researchers independently screened all potential articles, extracted the relevant data, and assessed each study's "risk of bias" (RoB). Risk of bias is an evaluation of whether a study's methods might have produced flawed or unreliable results. A tool called QUIPS was used for this assessment. Because the included studies were very different from one another, their results could not be statistically combined. Instead, the findings were summarized in a descriptive report called a "narrative synthesis." The overall quality of the evidence for each finding was then graded using a system called GRADE.

The search initially found 15,889 articles, but after screening, only 42 studies met the criteria for inclusion in the review. Of these 42 studies, half were assessed as having a high risk of bias.

The review found low-quality evidence that three specific physical measures do not have the ability to predict good long-term outcomes for people with low back pain. These measures are:

• High endurance in holding a back-arched position (isometric back extension).
• High handgrip strength.
• A high score on the fingertip-to-floor test, which measures flexibility.

The review also found very low-quality evidence for the inconsistent predictive ability of three other measures. "Inconsistent" means that some studies found a predictive relationship while others did not. These measures are:

• A high range of motion when bending the lower back backwards, for predicting good short-term outcomes.
• A high range of motion in the straight leg raise test, for predicting good short-term outcomes.
• High endurance in holding a forward-curled position (isometric back flexion), for predicting good long-term outcomes.

For many other physical tests, the original studies were too varied to be summarized together. Within this group, 41 different physical measures were investigated across the studies, and 23 of them showed some potential to be useful predictors for low back pain outcomes.

This review shows that there is a lack of high-quality evidence about the ability of physical tests to predict future outcomes for people with low back pain. The existing evidence is either low-quality (for measures that show no predictive ability) or very low-quality (for measures that show inconsistent predictive ability). Because the evidence is of low or very low quality, the findings should be interpreted with caution. The low quality of the evidence was attributed to imprecision in the results, the high risk of bias in the original studies, and the failure of those studies to adequately control for other factors that could influence patient outcomes.

The review also identified some physical tests that may have potential as future predictors. The researchers suggest that a new, large, and well-designed study is needed. This future study should follow people over time, have a low risk of bias, use standardized methods for all measurements, and apply advanced statistical analysis to account for multiple influencing factors. Future research in this area should also be based on a strong scientific theory, including a plausible biological reason why a specific physical test would be expected to predict an outcome.