The POLM cluster randomized trial is the first large scale trial to test the purported primary prevention effects of core stabilization, alone and in combination with psychosocial education, for LBP. Trial results suggest no benefit of core stabilization exercises for preventing LBP incidence resulting in the seeking of health care in comparison to traditional lumbar exercises. In contrast, a brief psychosocial education program in combination with either of the exercise programs resulted in lower two-year incidence of health care-seeking for LBP. These results have potential importance for primary prevention strategies for Soldiers in the military given the high rates of evacuation due to musculoskeletal pain and injuries that adversely affects Soldier preparation [1, 2].
The overall decrease in LBP from brief psychosocial education might be perceived as small, but the 3.3% decrease represented the absolute risk reduction, whereas the relative risk reduction was approximately 17%. Furthermore, seeking health care for LBP is very common [30, 31], so even small decreases in LBP incidence could potentially lessen the burden on a health care system. The psychosocial education program was administered in a single, low-cost session. There is potential for similar education programs to be done in an efficient manner, such that when applied to populations they yield incremental decreases in LBP incidence. Prevention of health care seeking by education seems especially relevant when increased usage and expenditures of health care for LBP have not resulted in obvious improvements in population outcomes [32, 33].
The primary limitation of the current study is that these results may have limited direct application to civilian populations due to trial implementation in a military setting. For example, an alternate explanation for the null effects of core stabilization exercise could be that Soldiers in this trial were at high levels of general fitness and not likely to benefit from additional exercise. Another limitation is that the current study did not include a true control condition so we cannot comment on the absolute effects of the exercise programs. We did have a randomly selected group of Soldiers who received additional attention from a physical examination and ultrasound imaging . There were no differences in LBP incidence for these Soldiers, suggesting no general attention effect in this trial (Table 2).
The decision to shift from a self-report definition of LBP incidence to a definition based on seeking of health care is another limitation to consider. As previously noted, this decision was made before the planned end of the study, was not based on any interim analyses, and was not a process of choosing one outcome from multiple potential outcomes. However, the end result of this decision is that our incidence measure of LBP resulting in the seeking of health care was not based on self-report of symptoms and had close to 96% follow-up at two years. There is the potential that these findings could underestimate the effect of these interventions on mild LBP episodes that did not necessitate health care and also we were not able to further describe the utilization of health care. For example, we could not distinguish between services that were provided for care during the episode. Overall, however, we feel the shift to a LBP incidence definition that accounted for health care seeking provided an unintended positive dimension to the POLM trial. The individual differences after cluster randomization could have led to systematic effects based on the company, rather than the assigned education program. However, we had low intracluster correlations suggesting independence between clusters and outcome measure. Baseline cluster differences were also small in magnitude (Table 2) and we accounted for company as a random effect in all analyses. Therefore, we are confident that individual cluster effects are fully accounted for when presenting the results.
Another weakness of this study is that Soldiers did additional sit-ups to prepare for fitness testing and this training could have adversely affected the core stabilization exercise [12, 16]. However, the rate of additional sit-ups was equivalent across the four groups so any additive effects of extra training would likely have had an equal impact on outcomes. We took a pragmatic approach to exercise dosing and it could be argued that dosage parameters for core stabilization were not sufficient to generate a preventative effect. However, our dosing parameters were consistent with expert recommendations for core stabilization exercise . Furthermore, we did not facilitate or track exercise performance of any kind after the 12-week training period and that is another weakness to consider. Finally, we did not determine if the LBP episode resulted in medical board (disability) or evacuation for Soldiers with LBP and this outcome measure would be of importance for future prevention studies.
A strength of the POLM trial is that we recruited a large inception cohort of Soldiers not previously experiencing LBP. This factor was highlighted as a research priority for LBP prevention studies in the European Guidelines  and the application of potentially preventative interventions before deployment was consistent with recent military recommendations [1, 2]. Two-year follow-up of all LBP episodes is an additional strength of the POLM trial. Finally, use of a health care utilization database to define LBP incidence is a strength of the study because of increased utilization trends for LBP [30–33] and concerns with using self-report definitions in military samples . Readers should realize, however, that this was a specific way of determining LBP incidence and the results of the POLM trial may not generalize to other ways of determining LBP incidence (for example, survey methods).
Exercise and education for primary prevention of LBP has received mixed support from the European Guidelines  and systematic reviews of work place interventions [5, 38]. Individual trials have suggested some types of exercise may be preventative of LBP when compared to no intervention , but similar effects have been reported when exercise was compared to patient education . In the POLM trial, two different exercise approaches targeting trunk musculature were compared and there was no benefit from performing specific core stabilization as we had hypothesized. The POLM trial findings are, therefore, consistent with Guideline recommendations  that indicate no added benefit of a particular focused exercise approach for prevention of LBP. Future studies investigating primary prevention of LBP may consider different methods for delivering exercise, such as tailored individualized approaches that have demonstrated efficacy for treatment of patients with chronic LBP .
The POLM trial did provide data indicating that psychosocial education based on the FAM has potential value for decreasing incidence of LBP resulting in the seeking of health care. Similar positive effects for LBP of psychosocial patient education based on the FAM have been reported in quasi-experimental studies in Australia  and France . Although there is some evidence that FAM factors have limited prognostic value in acute stages of LBP , these educational studies provide evidence of benefit either before pain  or in the acute stage of LBP . What the previously reported education studies do not often address is processes that may account for the benefit. In the case of the POLM trial, we did perform a planned preliminary analysis to investigate the short term efficacy of our psychosocial education program for a proximal endpoint that occurred after their 12-week training but before deployment . In this preliminary analysis, Soldiers receiving the psychosocial education program reported improved beliefs related to the inevitable consequences of LBP as measured by the Back Beliefs Questionnaire . In contrast, Soldiers not receiving the psychosocial education program had a slight worsening of their beliefs of LBP. It, therefore, could be asserted that a positive shift in beliefs about LBP while an individual is pain-free may result in decreased likelihood to seek health care when LBP was later experienced during military deployment. This earlier study provides data to support a process to explain the primary findings of the POLM trial, but we did not collect LBP beliefs with the Back Beliefs Questionnaire during the episode of LBP, so we lack the long term data that would directly validate this process.
There are unanswered questions and future research directions to consider following the POLM trial. Future studies could consider testing the preventative capability of core stabilization in different populations with lower overall fitness levels. Also, determining if the psychosocial education program translates to different civilian settings would be of particular interest as there are other trials that have demonstrated positive shifts in LBP beliefs for school age children  and older nursing home residents . This particular psychosocial education program used in the POLM trial has potential to generate cost-savings for those seeking health care for LBP, especially if it prevents exposure to expensive interventions that have questionable efficacy . Finally, we used what could be considered a small dose of psychosocial education with no reinforcement after the initial session . Different dosages and reinforcement strategies for the education program could be explored in future studies to determine if larger effect sizes are observed for primary prevention of LBP.