Effect of a 12-week workplace interview intervention on physical activity and low back pain: a single-center, randomized controlled study


 Background Physical activity (PA) is essential in the management and rehabilitation of low back pain (LBP). However, it is not clear if workplace PA interventions can improve LBP. This study aimed to investigate the effects of workplace interview intervention on increasing PA and improving LBP among office workers. Methods We recruited 37 workers of a manufacturing company in Aichi, Japan. Participants were randomly assigned to the intervention group (n=20) or control group (n=17). We affixed waist-worn accelerometers to monitor PA in all participants, and provided face-to-face counseling with a physical therapist or nurse once a week for 12 weeks as workplace PA program to reassurance and encourage participants to keep high levels of PA. PA and LBP severity were assessed at baseline, 3 and 6 months. Results Baseline characteristics were similar in both groups, but PA was significantly higher in the intervention group than in the control group at 3 and 6 months. In the intervention group, was PA significantly increased at 3 and 6 months from baseline and LBP severity improved significantly at 6 months from baseline. We calculated the effect size of the interview intervention, and found that workplace interview intervention had a medium to large effect on PA and LBP severity. Conclusions Our data suggests that workplace PA intervention can increase PA and improve LBP among office workers. Trial registration UMIN-CTR Clinical Trial UMIN000038864 (https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000044321). Registered 12 December 2019, retrospectively registered.


Background
Physical activity (PA) is essential in the management and rehabilitation of low back pain (LBP).
However, it is not clear if workplace PA interventions can improve LBP. This study aimed to investigate the effects of workplace interview intervention on increasing PA and improving LBP among office workers.

Methods
We recruited 37 workers of a manufacturing company in Aichi, Japan. Participants were randomly assigned to the intervention group (n=20) or control group (n=17). We affixed waist-worn accelerometers to monitor PA in all participants, and provided face-to-face counseling with a physical therapist or nurse once a week for 12 weeks as workplace PA program to reassurance and encourage participants to keep high levels of PA. PA and LBP severity were assessed at baseline, 3 and 6 months.

Results
Baseline characteristics were similar in both groups, but PA was significantly higher in the intervention group than in the control group at 3 and 6 months. In the intervention group, was PA significantly increased at 3 and 6 months from baseline and LBP severity improved significantly at 6 months from baseline. We calculated the effect size of the interview intervention, and found that workplace interview intervention had a medium to large effect on PA and LBP severity.

Background
Chronic low back pain (LBP) has a high prevalence and significant social impact. In Japan, the lifetime prevalence of LBP is estimated at 83% with nearly 10% of the population suffering from LBP with a disability with a consecutive absence for ≥ 4 days. [1] The prevalence of chronic musculoskeletal pain as LBP is highest in people their 30 s to 50 s, often known as the working generation. [2] However, more than half of the people with chronic musculoskeletal pain have not received any form of treatment. [2] Many workers may suffer from LBP and thus require intervention.
Physical activity (PA) is essential in the management and rehabilitation of LBP. [3][4][5][6] Workplace health promotion programs have been shown to increase PA of workers, [7] and workplace PA interventions also reduce general musculoskeletal pain, as well as neck and shoulder pain. [8] However, it is not clear if workplace PA interventions improve LBP. [8] One advantage of workplace interventions is that workers have easy access, and additionally, workplace PA interventions may reduce social and economic loss by improving LBP in workers.
The purpose of the study was to investigate the efficacy of workplace PA program on LBP. Therefore, we assessed whether a 12-week interview intervention in the workplace given by a physical therapist and nurses increase PA and improve LBP.

Study design and participants
This was a single-center, randomized controlled study. This study was conducted at a manufacturing company in Aichi, Japan (n=471, 405 men, 86%). Eligible participants were full-time Japanese workers aged 18 or older with LBP symptoms for at least 12 weeks. Exclusion criteria included cardiac, systemic, or inflammatory disease. Workers completed a self-administered structured questionnaire for screening. We invited workers who met the criterion and assigned them to the intervention group or control group by a randomized block design. Subjects were divided into five blocks (departments in the company) in order to avoid any bias toward the kind of work performed. A lottery method of manual randomization was conducted due to the small number of blocks and participants. The randomization was carried by a nurse who is independent of the study. The intervention was provided free of charge to all participants.
This study was approved by the ethical review board of Aichi Medical University, and all participants provided written informed consent. This study was funded by the Japanese Society of Physical Therapy.

Intervention
A total of 37 workers participated in this study and were assigned either to the intervention group (n=20) or the control group (n=17). We explained the potential relationship between PA and LBP to all participants in both intervention control groups, and taught home exercises in a 60-minute session.
We supplied a handout to improve their understanding of the material. The home exercise program consists of stretching and core stability training. We lent waist-worn accelerometers (Lifecorder GS, Suzuken Co., Ltd., Japan) to all participants to monitor their PA, and we instructed participants to wear the accelerometer throughout the day except during sleep and water-related activities (e.g., bathing, swimming). Data were retrieved with physical activity analysis software (Lifelizer coach, Suzuken Co., Ltd., Japan) every week to generate reports of PA for each participant.
Participants in the intervention group received workplace PA program. This intervention aimed to increase the amount of everyday PA with adequate pacing. We visited their workplace and provided 15-minute face-to-face individual counseling sessions during working hours once a week for 12 weeks.
A physical therapist or nurses informed them of their PA in the last week and set a target PA for the next week, based on the report generated by the accelerometer and physical activity analysis software. Also, we monitored adherence to the home exercise program and provided guidance on how to exercise or new exercise whenever necessary. Moreover, we gave reassurances and encouraged participants to keep high PA.
In the control group, we gave participants reports through their company's nurse without counseling once a week for 12 weeks.

Outcomes
Assessments were performed for all participants 2-4 weeks prior to their first scheduled intervention (baseline time point), 1-3 weeks, and 3 months after the last day of the intervention (3, 6-month time point). Fig.1 shows a flow diagram of the study design.
Physical activity PA was measured with waist-worn accelerometers (Lifecorder GS, Suzuken Co., Ltd., Japan) which assessed number of steps and motor activity (kcal) a day on average for a week. LBP severity LBP severity was assessed using a visual analog scale (VAS) scoring of max low-back-specific pain during the last week. The participants were instructed to indicate, using an arrow, the intensity of pain in each of these positions on a 100 mm line, with 100 representing the worst pain and zero representing no pain. LBP-related disabilities on lifestyle were assessed using the Roland-Morris Disability Questionnaire (RDQ), which is a self-administered disability measure on a 24-point scale; greater levels of disability are reflected by higher numbers. [9] The RDQ was conducted using Japanese translations. [10] Physical function The physical function assessment measured endurance (6-min walking distance [6MD]); flexibility (seated forward bends). For 6MD, the participants walked as far as possible a flat, 50 m course, and the distance walked in 6 minutes was measured. [11] Seated forward bends were analyzed by measuring the distance from the fingertips to the toes with the knees fully extended using a seated forward-bend measurement instrument (Takei Scientific Instruments, Japan). Results were expressed as positive numbers when the fingertips passed the toes and as negative numbers when the fingertips did not reach the toes.

Statistical analysis
Demographics data were expressed means and standard deviations (SD). Median and range were calculated for all parameters without demographic data because our data did not meet the requirements of a parametric test. The data at baseline, 3-month and 6-month time points were first analyzed by Friedman test (p<0.05). A posthoc procedure was performed to identify significant differences between baseline, 3-month, and 6-month time points by Wilcoxon signed-rank test (p<0.025). Differences among intervention and control group at each time point were evaluated using the Mann-Whitney U test (p<0.016). A significance level of p<0.05 was used for each outcome.
However, for multiple outcome measures, the Bonferroni-adjusted significance level was calculated to account for the increased possibility of a type-1 error (α=0.05). We also used "r" as calculated by Z translation to evaluate the magnitude of the effect size (r = Z/√N), where an r value from 0.1 to 0.3 = small effect size, 0.3 to 0.5 = medium effect size, and r > 0.5 = large effect size based on Cohen's effect size. [12] Results The demographic data of participants are shown in Table 1. There was no significant difference in demographic characteristic between the intervention or control group. Only men participated because women did not reply to our invitation.  Table 2 shows the outcomes at each time point. At baseline, none of the outcomes were significantly different between the intervention and control group. In the intervention group, PA and physical function significantly improved at 3 and 6 months from baseline. LBP severity significantly improved at 6 months from baseline. In the control group, 6MD was significantly increased at 3 and 6 months from baseline. PA was significantly higher in the intervention group than in the control group at 3 and 6 months. The effect size of workplace PA intervention is presented in Table 3. The within-group comparison showed that workplace PA intervention had medium to large effect on PA, LBP severity, and physical function. The between-group comparison showed that workplace PA intervention had medium to large effect on PA.

Discussion
This study investigated the efficacy of a workplace PA program on LBP and PA. Administration of a 12- week interview intervention at the workplace by a physical therapist and nurses improved PA, LBP severity, and physical function. Moreover, PA improved significantly in the intervention group compared to the control group. The effect size of improvement in outcomes was medium to large.

Interview intervention as workplace PA program
We provided face-to-face counseling with a physical therapist or nurse for about 15 minutes per session as a workplace PA program. Participants also wore an accelerometer and we set a target PA level based on a report of current PA generated by the accelerometer and physical activity analysis software. The interview intervention significantly increased workers PA. In contrast the control group received only the report, and this did not increase their PA levels. A previous meta-analysis study showed that individually delivered face-to-face interventions are superior to other interventions in improving PA. [13] Owing to the constant interview, it was probable that the reassurance and encouragement to the workers helped to increase their PA.
A few studies have shown that workplace PA intervention improves LBP. Our study suggests that interview intervention by physical therapists or/and nurses at a workplace reduces LBP. In previous studies, [14][15][16]

Conclusion
In summary, we conducted a 12-week interview intervention of 15-minute face-to-face sessions in the workplace a physical therapist and nurses to improve LBP and PA. Our results show that a workplace PA intervention can improve PA, LBP severity, and physical function.