Non-pain Developers Research Articles

The effect of rest break schedule on acute low back pain development in pain and non-pain developers during seated work

A significant portion of the population (25–50%) is known to develop acute low back pain (LBP) within a bout of prolonged sitting. Previous research has supported the use of frequent rest breaks, from seated office work, in order to reduce self-reported LBP, however, there is limited consensus about the recommended frequency and duration of rest breaks. This may be due to the limited consideration of individual differences in acute LBP development. The purpose of this study was to examine the effect of three different standing rest-break conditions on a group of pain developers (PD) and non-pain developers (NPD) engaged in prolonged seated work. Twenty participants completed four one-hour-long bouts of seated typing: Condition A – no rest; Condition B – 5 min of standing rest every 30 min; Condition C – 2.5 min of standing rest every 15 min; Condition D – 50 s of standing rest every 5 min. Self-reported LBP, self-reported mental fatigue and 30-s samples of EMG were collected every 10 min throughout each session. Eight out of 20 participants (40%) reported LBP during Condition A (classified as PD). Only PD demonstrated clinically relevant increases in LBP across conditions where Conditions B, C, or D provided some relief, but did not restore pain scores to their original level, prior to sitting. PD and NPD developed mental fatigue equally, with Conditions B and D helping to reduce fatigue. No differences in productivity were observed between conditions or groups and no main effects were observed for muscle activity, median power frequency or co-contraction. These data suggests that frequent, short, standing rest breaks may help to reduce symptoms of LBP, however they are only a temporary solution as PD still developed clinically important LBP, even with frequent rest breaks.

Early static standing is associated with prolonged standing induced low back pain

Previous research points to the lack of movement during prolonged standing as a pre-disposing factor to low back pain (LBP). Such movements could be at the level of the lumbar spine or at the foot–ground interface. The primary purpose of this in vivo study was to determine if there were differences in magnitude, region, and frequency of movement patterns between non-pain developers (non-PDs) and standing induced pain developers (PDs). Thirty-two participants reported their LBP development using a visual analog scale over 2-h of prolonged standing. Time-varying lumbar spine kinematics were used to assess the magnitude and frequency of lumbar spine fidgets and shifts. Ground reaction forces were used to assess the magnitude and frequency of whole body weight transfers and anterior–posterior center of pressure movements. Fourteen of 32 participants (43.75%) were categorized as PDs. The first 15min of standing distinguished the two pain groups, as non-PD performed a higher frequency of lumbar spine flexion/extension fidgets and large body weight transfers. Both of these differences may be pre-disposing factors for transient LBP development, as they both occurred prior to PDs reaching the 10mm visual analog scale threshold for LBP classification.

Validity of a Paradigm for Low Back Pain Symptom Development During Prolonged Standing.

Examine the validity of an induced pain paradigm in which people stand while performing simulated light work tasks (standing paradigm). Initially, people with low back pain (LBP) reported the quality and location of their typical symptoms on a body pain diagram. Then, people with LBP and back-healthy people stood for 2 hours and reported the intensity, quality, and location of symptoms at baseline and every 15 minutes. Quality and location of typical symptoms of people with LBP were compared with their symptoms during standing. Back-healthy people were separated into pain developers (PDs) and nonpain developers. Symptom quality and location were compared between people with LBP and PDs. There were no differences in the quality and location of typical symptoms and symptoms during standing in people with LBP (P>0.05). Three symptom descriptors were used by >30% of people with LBP to describe typical symptoms. Only 2 people with LBP used these descriptors to describe typical symptoms but not during standing. There were no differences in the quality and location of symptoms reported in standing between people with LBP and PDs (P>0.05). Four symptom descriptors were used by >30% of participants with LBP during standing. There were no symptoms reported by PDs that were not reported by people with LBP. This study provides evidence that symptoms experienced during the standing paradigm are similar to symptoms experienced by people with LBP and, thus, provides support for the validity of the paradigm.

Is lumbar lordosis related to low back pain development during prolonged standing?

BackgroundAn induced-pain paradigm has been used in back-healthy people to understand risk factors for developing low back pain during prolonged standing. ObjectivesThe purposes of this study were to (1) compare baseline lumbar lordosis in back-healthy participants who do (Pain Developers) and do not (Non-Pain Developers) develop low back pain during 2 h of standing, and (2) examine the relationship between lumbar lordosis and low back pain intensity. DesignCross-sectional. MethodFirst, participants stood while positions of markers placed superficial to the lumbar vertebrae were recorded using a motion capture system. Following collection of marker positions, participants stood for 2 h while performing light work tasks. At baseline and every 15 min during standing, participants rated their low back pain intensity on a visual analog scale. Lumbar lordosis was calculated using marker positions collected prior to the 2 h standing period. Lumbar lordosis was compared between pain developers and non-pain developers. In pain developers, the relationship between lumbar lordosis and maximum pain was examined. Results/findingsThere were 24 (42%) pain developers and 33 (58%) non-pain developers. Lumbar lordosis was significantly larger in pain developers compared to non-pain developers (Mean difference = 4.4°; 95% Confidence Interval = 0.9° to 7.8°, Cohen's d = 0.7). The correlation coefficient between lumbar lordosis and maximum pain was 0.46 (P = 0.02). ConclusionThe results suggest that standing in more lumbar lordosis may be a risk factor for low back pain development during prolonged periods of standing. Identifying risk factors for low back pain development can inform preventative and early intervention strategies.

Transient pain developers show increased abdominal muscle activity during prolonged sitting

BackgroundSitting is a commonly adopted posture during work and prolonged exposures may have detrimental effects. Little attention has been paid to the thoracic spine and/or multiple axes of motion during prolonged sitting. Accordingly, this study examined three-dimensional motion and muscle activity of the trunk during two hours of uninterrupted sitting. MethodsTen asymptomatic males sat during a simulated office task. Kinematics were analyzed from six segments (Neck, Upper-, Mid-, and Lower-thoracic, Lumbar, and Pelvis) and electromyography was recorded from eight muscles bilaterally. ResultsFour participants developed transient pain. These participants showed higher average muscle activations in the abdominal muscles. Additionally, the non-pain group showed less lateral bend positional change in the mid-thoracic region compared to the upper- and lower-thoracic regions. Weak-to-moderate positive correlations were also found between rated pain and low back muscle activation. DiscussionThe results provided further evidence of reduced movement in non-pain developers and altered muscle activation patterns in pain developers. Low-level, prolonged static contractions could lead to an increased risk of injury; and though the increased abdominal activity in the pain developers was not directly associated with increased rated pain scores, this could indicate a pre-disposition to, or enhancer of, transient pain development.

Investigation of trunk muscle co-contraction and its association with low back pain development during prolonged sitting

Previous work has shown muscle activation differences between chronic low back pain patients and healthy controls in sitting postures, and between asymptomatic individuals who do (PDs: pain developers) and do not (NPDs: non-pain developers) develop transient back pain during prolonged standing (as determined using a visual analog scale). The current study aimed to investigate differences in trunk muscle co-contraction between PD and NPD individuals over 2h of prolonged sitting. Ten healthy males sat continuously for 2h while performing tasks that simulated computer-aided-drafting; four were classified as PDs, and six as NPDs. Co-contraction indices were calculated from EMG data collected from eight trunk muscles bilaterally, and compared between pain groups and over time. PDs exhibited higher levels of co-contraction than NPDs. Additionally, co-contraction tended to increase over time, and was significantly correlated to pain development. The relationship between co-contraction and back pain development may actually be circular, in that it is both causal and adaptive: high co-contraction initially predisposes to pain development, following which co-contraction further increases in an attempt to alleviate the pain, and the cycle perpetuates. Further work will be required to elucidate the exact nature of this relationship, and to confirm the generalizability to other populations.

Altered muscle recruitment during extension from trunk flexion in low back pain developers

BackgroundA functionally induced, transient low back pain model consisting of exposure to prolonged standing has been used to elucidate baseline neuromuscular differences between previously asymptomatic individuals classified as pain developers and non-pain developers based on their pain response during a standing exposure. Previous findings have included differences in frontal plane lumbopelvic control and altered movement strategies that are present prior to pain development. Control strategies during sagittal plane movement have not been previously investigated in this sample. The purpose of this research was to investigate neuromuscular control differences during the extension phase from trunk flexion between pain developers and non-pain developers. MethodsContinuous electromyography and kinematic data were collected during standing trunk flexion and extension on 43 participants (22 male) with an age range of 18–33years, prior to entering into the prolonged standing exposure. Participants were classified as pain developer/non-pain developer by their pain response (≥10mm increase on a 100mm visual analog scale) during standing. Relative timing and sequencing data between muscle pairs were calculated through cross-correlation analyses, and evaluated by group and gender. FindingsPain developers demonstrated a ‘top-down’ muscle recruitment strategy with lumbar extensors activated prior to gluteus maximus, while non-pain developers demonstrated a typical ‘bottom-up’ muscle recruitment strategy with gluteus maximus activated prior to lumbar extensors. InterpretationIndividuals predisposed to low back pain development during standing exhibited altered neuromuscular strategies prior to pain development. These findings may help to characterize biomechanical movement profiles that could be important for early identification of people at risk for low back pain.

Does a ‘tight’ hamstring predict low back pain reporting during prolonged standing?

The purpose of this study was to investigate the relationship between hamstring passive stiffness and extensibility in asymptomatic individuals with the reporting of low back pain during 2-h prolonged standing. Twenty healthy participants with no history of low back pain (mean±SD, age 22.6±2.7years, height 1.74±0.09m, weight 76.2±14.8kg). Low back pain (VAS score; mm) was continuously monitored during 2-h prolonged standing. Hamstring extensibility, passive stiffness, and stretch tolerance were measured before and after prolonged standing using an instrumented straight leg raise (iSLR). Ten participants reported a clinically relevant increase (Δ VAS>10mm) in low back pain during prolonged standing. Hamstring extensiblity (leg°max), passive stiffness (Nm.°−1), and stretch tolerance (VAS; mm) were no different between pain developers and non-pain developers. No changes in hamstring measures were observed following 2-h prolonged standing. No relationship was observed in this study between measures of hamstring extensibility and the reporting of low back pain during prolonged standing. There is no evidence to recommend hamstring extensibility interventions (i.e. passive stretching) as a means of reducing pain reporting in occupations requiring prolonged standing.

Do individuals who develop transient low back pain exhibit different postural changes than non-pain developers during prolonged standing?

Previous literature has shown that individuals can develop transient low back pain (LBP) during a 2-h bout of unconstrained prolonged standing. The purpose of this study was to investigate the postural changes of individuals who develop LBP during standing (PD) and those who do not (NPD). Forty-one subjects (20 male, 21 female) participated in a 2-h prolonged standing occupational simulation and recorded their ratings of perceived LBP on a visual analog scale (VAS). Center of pressure changes (shifts, drifts, and fidgets) and body weight shifts were determined for each subject. All subjects showed an increase in the BW shift frequency and a decrease in average shift duration over the 2-h protocol. All NPD and female PD were consistent for many of the variables; however, male PD did not show similar patterns to the other groups, especially for anterior–posterior (AP) shift amplitude and total body weight asymmetry. Although gender differences between the pain groups were found, PD and NPD do not use different postural changes during unconstrained standing, showing that changes to postural control may be an “adaptive”, rather than “causative” response to their LBP development. Future works should concentrate on bridging the literature seen in quiet standing before and after prolonged standing and the response of PD, as well as the effect of an exercise intervention on postural control, especially for male PD.

The impact of a sloped surface on low back pain during prolonged standing work: A biomechanical analysis

Background Occupations that require prolonged periods of standing have been associated with increased reports of musculoskeletal disorders including low back pain. Previous work has utilized a prospective design of functionally inducing low back pain in previously asymptomatic individuals during a prolonged standing task. Increased trunk and gluteus medius muscle co-activation has been found in previously asymptomatic individuals who developed pain during standing compared with individuals who did not develop pain. Purpose The purpose of this study was to investigate the subjective and biomechanical responses of known pain developers and non-pain developers (previously determined during level standing) when exposed to the same prolonged standing task protocol completed while standing on a ±16° sloped surface. Results Overall low back pain scores were reduced by 59.4% for the pain development group, identified in level standing, when using the sloped surface. There was a marked decrease in the co-activation of the bilateral gluteus medius muscles in the known pain developers when standing on the sloped surface compared with level standing. However the non-pain developer group responded in the opposite direction by having an increase in the co-activation of these muscles, although they did not have a commensurate increase in low back pain. There were changes in both the postural and joint-loading variables examined. These changes were minimal and in most cases the sloped surface produced responses that bracketed the postures and loading magnitudes found in level standing depending on whether the participant was standing on the +16° or −16° surface. Conclusions The sloped surface resulted in decreased subjective low back pain during prolonged standing. There were also associated biomechanical changes resulting from using a sloped surface during prolonged standing. These positive findings were supported in an exit survey satisfaction rating with 87.5% indicating that they would use the sloped surface if they were in an occupational setting that required prolonged standing work.

Development of Active Hip Abduction as a Screening Test for Identifying Occupational Low Back Pain

Analytic observational prospective study performed in a controlled laboratory setting. To assess the ability of a new screening tool, the active hip abduction test, to predict low back pain development during prolonged standing in previously asymptomatic individuals. Most screening tools used for a patient with low back pain do not assess the patient's ability to maintain postural control in the frontal plane, when placed in an unstable position. Postural-control differences in pain developers, as compared to non-pain developers, during standing have been found previously. An attempt was made to predict pain development with a simple screening test. Forty-three previously asymptomatic volunteers underwent a clinical assessment prior to a 2-hour standing protocol designed to induce low back pain. Participants rated low back pain with a visual analog scale and were classified into pain developers or non-pain developers. Forty percent of participants developed low back pain. The active hip abduction test was the only test that discriminated between pain-developer groups. When the examiner scored the test, the odds ratio was 3.85 (95% confidence interval [CI]: 1.05-19.07), and when the test was self-rated, the odds ratio was 6.55 (95% CI: 1.14-37.75) for pain development during standing. The active hip abduction test appears to show promise for predicting individuals who are at risk for low back pain development during prolonged standing. More work is required to validate the test in clinical populations, and to assess interrater and intrarater reliability.

Is muscle co-activation a predisposing factor for low back pain development during standing? A multifactorial approach for early identification of at-risk individuals

Purpose and scope Low back pain development has been associated with static standing postures in occupational settings. Previous work has demonstrated gluteus muscle co-activation as a predominant pattern in previously asymptomatic individuals who develop low back pain when exposed to 2-h of standing. The purpose of this work was to investigate muscle co-activation as a predisposing factor in low back pain development while including a multifactorial approach of clinical assessment tools and psychosocial assessments to identify individuals who are at risk for pain development during standing. Results Forty percent of participants developed low back pain during the 2-h of standing. Pain developers demonstrated bilateral gluteus medius and trunk flexor–extensor muscle co-activation prior to reports of pain development. Pain developers and non-pain developers demonstrated markedly different patterns of muscle activation during the 2-h of standing. A novel screening test of active hip abduction was the only clinical assessment tool that predicted pain development. Conclusions Gluteus medius and trunk muscle co-activation appears to be a predisposing rather than adaptive factor in low back pain development during standing. A combination of a positive active hip abduction test and presence of muscle co-activation during standing may be useful for early identification of at-risk individuals.