The relationship between low back pain and leisure time physical activity in a working population of cleaners--a study with weekly follow-ups for 1 year

Abstract

Background: Low back pain (LBP) and leisure time physical activity (LTPA) are considered to be closely related, and clinical guidelines for the treatment of acute LBP recommend patients stay physically active. However, the documentation for this recommendation is sparse and based on studies involving patient populations. The purpose of the study was (1) to investigate the correlation between LBP and LTPA on a weekly basis over the course of a year in a high-risk group of cleaners; and (2) to investigate if maintaining LTPA during an episode of acute LBP has a positive effect on LBP intensity in the subsequent 4 weeks.

Methods: 188 cleaners consented to participate in a 52-week text message survey about hours of LTPA and intensity of LBP (from 0 to 9) over the previous 7 days. The correlation between LBP and LTPA was calculated by Pearson correlation coefficient. During an episode of acute LBP, a mixed effect logistic regression model was used to investigate whether cleaners who maintain LTPA have a lower pain intensity and higher probability of returning to initial pain intensity within the following four weeks compared with cleaners who decrease LTPA during acute LBP.

Results: The correlation between weekly LTPA and LBP data was negative, but numerically low (r = -0.069) and statistically insignificant (p = 0.08). Among the 82 cleaners experiencing at least one episode of acute LBP, those maintaining LTPA during an episode of acute LBP did not have a lower pain intensity (average LBP intensity difference between groups of 0.06; 95% confidence interval (95% CI) of -0.417 to 0.539) or higher probability of returning to initial pain level (Odds ratio 1,02; 95% CI of 0.50 to 2.09) in the following four weeks compared with cleaners decreasing LTPA during acute LBP.

Conclusions: Hours of LTPA and intensity of LBP measured on a weekly basis throughout a year showed no close correlation. Maintaining LTPA during an episode of acute LBP did not result in a positive effect on LBP in the following 4 weeks. Documentation of LTPA recommendations for acute LBP in working populations is still needed.

Figure 1

A model illustration of hours per week of LTPA and weekly LBP intensity over 9 weeks. An increase in LBP intensity by 2 or more from one week to the next is defined as an acute LBP episode (Period A). The following 4 weeks after the acute LBP episode is defined as the follow-up period (Period B). Initial LBP intensity is the pain intensity before the acute LBP episode.

Figure 2

Flow chart on text message survey participation. Participation in text message survey was offered to 238 cleaners and 188 consented to participate. Among the 188, 48 never responded, leaving 140 participants, who responded to both questions at least once and 95 still responded in week 12. In the last week (week 52) 46 participants still responded.

Figure 3

Weekly mean low back pain intensity (scale from 0 to 9, with 0 as no pain within the last 7 days and 9 as worst pain imaginable) and mean hours of leisure time physical activity (time spent on activities like aerobics, running, bicycling, swimming and active transport) during the previous 7 days for the high responders, (those who responded more than 80%, n = 49). Time period was from Week 46 (November) 2008 to Week 45 (November) 2009 and each weekly dot covers 48 to 49 responses.

Figure 4

a) Example of a cleaner who reported constant low to moderate LBP intensity (Black line) throughout the year and the simultaneous LTPA (Grey line), b) Example of a cleaner who reported a larger variation in LBP intensity (Black line) and the simultaneous LTPA (Grey line).

Figure 5

Average Pearson correlation coefficients with 95% confidence intervals (CI) between hours of leisure time physical activity and low back pain intensity over the 52 weeks for cleaners answering more than 80% of the text messages (n = 49). When time lag (week) = 0, the correlation coefficient is between leisure time physical activity and low back pain reported in the same week (e.g. leisure time physical activity in Week 3 vs. low back pain intensity in Week 3). Lag = -1 when leisure time physical activity is correlated with low back pain intensity in the previous week (e.g. leisure time physical activity Week 3 vs. low back pain intensity Week 2).). Lag = +1 when leisure time physical activity is correlated with low back pain intensity in the following week (e.g. leisure time physical activity Week 3 vs. low back pain intensity Week 4).