Shawn Thistle 2015-08-14 03:58:04
Research on effects of standing to low back pain risk
Studies reviewed:
Study #1. Gallagher KM, Campbell T, Callaghan JP. “The influence of a seated break on prolonged standing induced low back pain development.” Ergonomics 2014; 57(4): 555–562 Study #2. Nelson-Wong E, Callaghan JP. “Transient low back pain development during standing predicts future clinical low back pain in previously asymptomatic individuals.” Spine 2014; 39(6): E379 - E383.
Studies of asymptomatic individuals with no lifetime history of low back pain (LBP) have indicated that 40 to 70 per cent report clinically significant LBP after a twohour standing protocol. This induced (but transient) LBP paradigm has allowed characterization of neuromuscular differences between individuals who develop LBP when standing compared with those who do not. The purpose of one study summarized here (#2 listed above) was to determine the effect of prolonged standing on the long-term rate of LBP in previously asymptomatic individuals.
This review summarizes the results of that, and an additional study from the same author group, investigating the biomechanics of LBP and the effect of standing, both during work and for prolonged periods, as causative and predictive indicators of LBP.
Study #1
Of 20 participants, 55 per cent were identified as pain developers (PD) based on their visual analog scale (VAS), demonstrating a steady increase in reported LBP over the first 45 minutes of standing. LBP decreased during a 15-minute seated break, but increased to a higher level following a second 45-minute standing period.
An interaction between time and pain Group was found for the median thoracic angle of the amplitude probability distribution function (APDF) (p = 0.0039). During standing, non-PDs demonstrated greater thoracic flexion, differing by approximately eight degrees in the first 45 minutes of standing. During sitting, Pds demonstrated an increase of the median thoracic angle of approximately 10 degrees, while non-PDs remained consistent in both sitting and standing.
A main effect of time was found for thoracic angle range. The thoracic range for both Pds and non-PDs increased during the first 45-minute standing period, continued to increase through the 15-minute rest period and remained elevated following the second standing and sitting phases.
Overall, non-PDs utilized a greater range of their lumbar spine angle compared to Pds.
Study #2
Forty-three participants aged 18 to 50 were recruited from the University of Waterloo in Ontario and surrounding communities. Seventeen participants were classified as Pds – with demonstrated 10-mm or more increase on the VAS during standing exposure – the remaining 26 were non-PDs.
For 36 months, a higher proportion of PD participants reported at least one episode of LBP severe enough to seek Medical care or that resulted in three days missed work, school or recreational activities. Three Pds and one non-PD reported more than one episode of LBP. None of these episodes were associated with trauma.
LBP developed during prolonged standing was the strongest predictor of future LBP during the first 12 months. Individuals classified as PD during prolonged standing developed LBP at a rate three times that of non-PD during the first 24 months of the study.
Although a greater proportion of Pds developed LBP as compared with non- Pds, 23.1 per cent of non-PDs nonetheless developed LBP. The resulting poor findings for negative likelihood ratios and sensitivity indicate that LBP during prolonged standing may not be a good screening tool for future pain as many individuals who did not report LBP during standing went on to experience clinical LBP.
At 36 months, a greater percentage of PD reported multiple episodes of LBP than non-PD, which may indicate Pds are more likely to transition to chronic LBP. LBP during prolonged standing may be valuable in identifying individuals prone to developing chronic LBP.
Conclusions, applications
The two studies summarized here suggest that standing in the workplace may be causative for LBP.
The combined results indicate that clinicians should consider LBP during prolonged standing as a potential screening tool to help identify “pre-clinical” LBP and caution patients from adopting a standing workstation.
DR. SHAWN THISTLE is the founder and CEO of RRS Education (rrseducation.com), which helps busy clinicians integrate current research evidence rationally into practice. He also maintains a practice in Toronto, lectures at CMCC and provides chiropractic medicolegal consulting services. Reach him at: [email protected]
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