The Neuromuscular Response to Spinal Manipulation in the Presence of Pain.

OBJECTIVE: The purpose of this study was to evaluate differences in muscle activity in participants with and without low back pain during a side-lying lumbar diversified spinal manipulation. METHODS: Surface and indwelling electromyography at eight muscle locations were recorded during lumbar side-lying manipulations in 20 asymptomatic participants and 20 participants with low back pain. The number of muscle responses and muscle activity onset delays in relation to the manipulation impulse were compared in the 2 pain groups using mixed linear regressions. Effect sizes for all comparisons were calculated using Cohen's d. RESULTS: Muscle responses occurred in 61.6% ± 23.6% of the EMG locations in the asymptomatic group and 52.8% ± 26.3% of the symptomatic group. The difference was not statistically significant but there was a small effect of pain (d = 0.350). Muscle activity onset delays were longer for the symptomatic group at every EMG location except the right side indwelling L5 electrode, and a small effect of pain was present at the left L2, quadratus lumborum and trapezius surface electrodes (d = 0.311, 0.278, and 0.265) respectively. The indwelling electrodes demonstrated greater muscle responses (P ≤ .01) and shorter muscle activity onset delays (P < .01) than the surface electrodes. CONCLUSIONS: The results revealed trends that indicate participants with low back pain have less muscle responses, and when muscle responses are present they occur with longer onset delays following the onset of a manipulation impulse.

Methods of Muscle Activation Onset Timing Recorded During Spinal Manipulation.

OBJECTIVE: The purpose of this study was to determine electromyographic threshold parameters that most reliably characterize the muscular response to spinal manipulation and compare 2 methods that detect muscle activity onset delay: the double-threshold method and cross-correlation method. METHODS: Surface and indwelling electromyography were recorded during lumbar side-lying manipulations in 17 asymptomatic participants. Muscle activity onset delays in relation to the thrusting force were compared across methods and muscles using a generalized linear model. RESULTS: The threshold combinations that resulted in the lowest Detection Failures were the "8 SD-0 milliseconds" threshold (Detection Failures = 8) and the "8 SD-10 milliseconds" threshold (Detection Failures = 9). The average muscle activity onset delay for the double-threshold method across all participants was 149 ± 152 milliseconds for the multifidus and 252 ± 204 milliseconds for the erector spinae. The average onset delay for the cross-correlation method was 26 ± 101 for the multifidus and 67 ± 116 for the erector spinae. There were no statistical interactions, and a main effect of method demonstrated that the delays were higher when using the double-threshold method compared with cross-correlation. CONCLUSIONS: The threshold parameters that best characterized activity onset delays were an 8-SD amplitude and a 10-millisecond duration threshold. The double-threshold method correlated well with visual supervision of muscle activity. The cross-correlation method provides several advantages in signal processing; however, supervision was required for some results, negating this advantage. These results help standardize methods when recording neuromuscular responses of spinal manipulation and improve comparisons within and across investigations.

Treatment and Response Factors in Muscle Activation during Spinal Manipulation.

The forces applied during a spinal manipulation produce a neuromuscular response in the paraspinal muscles. A systematic evaluation of the factors involved in producing this muscle activity provides a clinical insight. The purpose of this study is to quantify the effect of treatment factors (manipulation sequence and manipulation site) and response factors (muscle layer, muscle location, and muscle side) on the neuromuscular response to spinal manipulation. The surface and indwelling electromyographies of 8 muscle sites were recorded during lumbar side-lying manipulations in 20 asymptomatic participants. The effects of the factors on the number of muscle responses and the muscle activity onset delays were compared using mixed-model linear regressions, effect sizes, and equivalence testing. The treatment factors did not reveal statistical differences between the manipulation sequences (first or second) or manipulation sites (L3 or SI) in the number of muscle responses (p = 0.11, p = 0.28, respectively), or in muscle activity onset delays (p = 0.35 p = 0.35, respectively). There were significantly shorter muscle activity onset delays in the multifidi compared to the superficial muscles (p = 0.02). A small effect size of side (d = 0.44) was observed with significantly greater number of responses (p = 0.02) and shorter muscle activity onset delays (p < 0.001) in the muscles on the left side compared to the right. The location, layer, and side of the neuromuscular responses revealed trends of decreasing muscle response rates and increasing muscle activity onset delays as the distance from the manipulation site increased. These results build on the body of work suggesting that the specificity of manipulation site may not play a role in the neuromuscular response to spinal manipulation-at least within the lumbar spine. In addition, these results demonstrate that multiple manipulations performed in similar areas (L3 and S1) do not change the response significantly, as well as contribute to the clinical understanding that the muscle response rate is higher and with a shorter delay, the closer it is to the manipulation.

Optimized prediction of contact force application during side-lying lumbar manipulation.

OBJECTIVES: The purposes of this study included the following: (1) to predict L3 contact force during side-lying lumbar manipulation by combining direct and indirect measurements into a single mathematical framework and (2) to assess the accuracy and confidence of predicting L3 contact force using common least squares (CLS) and weighted least squares (WLS) methods. METHODS: Five participants with no history of lumbar pain underwent 10 high-velocity, low-amplitude lumbar spinal manipulations at L3 in a side-lying position. Data from 5 low-force criterion standard trials where the L3 contact force was directly measured were used to generate participant-specific force prediction algorithms. These algorithms were used to predict L3 contact force in 5 experimental trials performed at therapeutic levels. The accuracy and effectiveness of CLS and WLS methods were compared. RESULTS: Differences between the CLS-predicted forces and the criterion standard-measured forces were 621.0 ± 193.5 N. Differences between the WLS-predicted forces and the criterion standard-measured forces were -3.6 ± 9.1 N. The 95% limits of agreement ranged from 234.0 to 1008.0 N for the CLS and -21.9 to 14.7 N for the WLS. During both the criterion standard and experimental trials, the CLS overestimated contact forces with larger variance than the WLS. CONCLUSION: This novel method to predict spinal contact force combines direct and indirect measurements into a single framework and preserves clinically relevant practitioner-participant contacts. As advanced instrumentation becomes available, this framework will enable advancements in training and high-quality research on mechanisms of spinal manipulative therapy.

Does manual therapy affect functional and biomechanical outcomes of a sit-to-stand task in a population with low back pain? A preliminary analysis.

Introduction: Manual therapy (MT) hypothetically affects discrepant neuromuscular control and movement observed in populations with low back pain (LBP). Previous studies have demonstrated the limited influence of MT on movement, predominately during range of motion (ROM) testing. It remains unclear if MT affects neuromuscular control in mobility-based activities of daily living (ADLs). The sit-to-stand (STS) task represents a commonly-performed ADL that is used in a variety of clinical settings to assess functional and biomechanical performance. Objective: To determine whether MT affects functional performance and biomechanical performance during a STS task in a population with LBP. Methods: Kinematic data were recorded from the pelvis and thorax of participants with LBP, using an optoelectronic motion capture system as they performed a STS task before and after MT from November 2011 to August 2014. MT for each participant consisted of two high-velocity low-amplitude spinal manipulations, as well as two grade IV mobilizations of the lumbar spine and pelvis targeted toward the third lumbar vertebra and sacroiliac joint in a side-lying position; the order of these treatments was randomized. Pelvis and thorax kinematic data were used to derive the time-varying lumbar angle in the sagittal plane for each STS trial. The difference between the maximum and minimum lumbar angles during the STS trial determined the sagittal ROM that was used as the biomechanical outcome. Time to complete each STS trial was used as a functional measure of performance. Pre-MT and post-MT values for the lumbar sagittal ROM and time to completion were statistically analysed using paired samples t-tests. Results: Data were obtained from 40 participants with 35 useful datasets (NRS = 3.3 ± 1.2; 32.4 ± 9.8 years; 16 females, 19 males). After MT, lumbar sagittal ROM increased by 2.7 ± 5.5 degrees (p = 0.007). Time to complete the STS test decreased by 0.4 ± 0.4 s (p < 0.001). Discussion: These findings provide preliminary evidence that MT might influence the biomechanical and functional performance of an STS task in populations with LBP. The MT intervention in this study involved a combination of spinal manipulations and mobilizations. Future work will expand upon these data as a basis for targeted investigations on the effects of either spinal manipulation and mobilization on neuromuscular control and movement in populations with LBP.

Functional scores and subjective responses of injured workers with back or neck pain treated with chiropractic care in an integrative program: a retrospective analysis of 100 cases.

OBJECTIVE: The purpose of this study is to report on integrative care for the treatment of injured workers with neck or back pain referred to a doctor of chiropractic from a medical or osteopathic provider. METHODS: This retrospective case series study evaluated data on 100 patients referred for chiropractic care of work-related spinal injuries involving workers' compensation claims. Deidentified data included age, sex, visual analog scale scores for pain, pre- and posttreatment Functional Rating Index (FRI) scores, and subjective response to chiropractic care. Based on date of injury to first chiropractic treatment, patients were subdivided as acute, subacute, or chronic injured workers. Cases were analyzed for differences in pretreatment FRI scores, posttreatment FRI scores, FRI change scores (posttreatment FRI minus pretreatment FRI score), and subjective percentage improvement using a 1-way analysis of variance. Treatment included manual therapy techniques and exercise. RESULTS: Injured workers with either an acute or subacute injury had significantly lower posttreatment FRI scores compared with individuals with a chronic injury. The FRI change scores were significantly greater in the acute group compared with either the subacute or chronic injured workers. Workers in all categories showed improved posttreatment tolerance for work-related activities and significantly lower posttreatment subjective pain scores. CONCLUSIONS: The study identified positive effects of chiropractic management included in integrative care when treating work-related neck or back pain. Improvement in both functional scores and subjective response was noted in all 3 time-based phases of patient status (acute, subacute, and chronic).

Comparison of a targeted and general massage protocol on strength, function, and symptoms associated with carpal tunnel syndrome: a randomized pilot study.

OBJECTIVE: Carpal tunnel syndrome (CTS) is a major, costly public health issue that could be dramatically affected by the identification of additional conservative care treatment options. Our study aimed to evaluate the effectiveness of two distinct massage therapy protocols on strength, function, and symptoms associated with CTS. DESIGN: This was a randomized pilot study design with double pre-tests and subjects blinded to treatment group assignment. SETTING/LOCATION: The setting for this study was a wellness clinic at a teaching institution in the United States. SUBJECTS: Twenty-seven (27) subjects with a clinical diagnosis of CTS were included in the study. INTERVENTIONS: Subjects were randomly assigned to receive 6 weeks of twice-weekly massage consisting of either a general (GM) or CTS-targeted (TM) massage treatment program. OUTCOME MEASURES: Dependent variables included hand grip and key pinch dynamometers, Levine Symptom and Function evaluations, and the Grooved Pegboard test. Evaluations were conducted twice during baseline, 2 days after the 7th and 11th massages, and at a follow-up visit 4 weeks after the 12th massage treatment. RESULTS: A main effect of time was noted on all outcome measures across the study time frame (p < 0.001); improvements persist at least 4 weeks post-treatment. Comparatively, TM resulted in greater gains in grip strength than GM (p = 0.04), with a 17.3% increase over baseline (p < 0.001), but only a 4.8% gain for the GM group (p = 0.21). Significant improvement in grip strength was observed following the 7th massage. No other comparisons between treatment groups attained statistical significance. CONCLUSIONS: Both GM and TM treatments resulted in an improvement of subjective measures associated with CTS, but improvement in grip strength was only detected with the TM protocol. Massage therapy may be a practical conservative intervention for compression neuropathies, such as CTS, although additional research is needed.

Experience and practice organization in learning a simulated high-velocity low-amplitude task.

OBJECTIVE: To evaluate the effect of practice schedule, type of feedback, and experience level on simulated force production accuracy in chiropractic students. METHODS: Thirty-three chiropractic students simulated a high-velocity low-amplitude prone thoracic spine manipulation. Three force goals based on percent of maximum thrusting ability were used in blocked and random variable practice. Participants received either visual feedback or knowledge of performance feedback regarding their force-time history. Serial retention tests without feedback followed blocked and random variable practice. Peak and average rates of thrust development, as well as the constant error, absolute constant error, and variable error of peak force production, were calculated. CONCLUSION: Familiarity and practice of high-velocity low-amplitude spinal manipulation resulted in greater accuracy of peak force production. Lower error scores were observed in acquisition with blocked variable practice. However, short-term accuracy was enhanced in retention when participants had used random variable practice. Random variable practice combined with visual feedback improved force production accuracy in retention. The variability of peak force production increased to 61% of maximum thrusting ability and then decreased. The greatest accuracy with least variability of peak force production was seen near 75% of maximum thrusting ability.

Speed-accuracy tradeoffs in rapid bimanual aiming movements.

Two experiments reported the effect of movement time and knowledge of results on overall spatial errors in rapid simultaneous bimanual aiming movements. In Exps. 1 (n=32) and 2 (n=32), participants used light, aluminum levers oriented vertically in the sagittal plane to make reversal movements over the same distance (20 degrees - 20 degrees or 60 degrees - 60 degrees) or different distances (20 degrees - 60 degrees) in each arm in 250, 350, or 450 msec. to the reversal point. The participants in Exp. 1 were given knowledge of results on the spatial and temporal accuracy for both arms, while in Exp. 2 knowledge of results was provided for one arm only. Strong speed-accuracy tradeoffs were shown for all groups in both experiments, but errors were larger in the different distance movements compared to the same distance groups. Spatial errors were also elevated in Exp. 2 when knowledge of results was not available compared to those conditions where knowledge of results was available. Overall, bimanual speed-accuracy tradeoffs are similar to single arm movements when one moves the same distance in each arm and when knowledge of results is available.

Colorado workers' compensation: medical vs chiropractic costs for the treatment of low back pain.

OBJECTIVE: Low back disorders (LBDs) are the most common complaint among workers; therefore, many questions arise about cost-effective treatment approaches. This investigation evaluated the differences in cost-related factors among a population of patients selecting chiropractic vs allopathic care for the treatment of nonspecific LBDs. The study hypothesis was that chiropractic care would be more cost-effective or equivalent to allopathic care for the noncomplicated LBDs. METHODS: Cases were extracted from an insurance company database of patients reporting work-related low back injuries who were treated with either chiropractic or allopathic approaches. Cases were matched using the International Classification of Diseases, Ninth Revision, codes 722 (intervertebral disk disorders), 724 (other and unspecified disorders of the back), and 847 (sprains and strains of other and unspecified parts). The data set included 76 chiropractic cases and 2386 medical cases. RESULTS: The total amount paid by the insurance company was 1.7 times higher for patients treated by doctors of chiropractic (DCs) compared with those treated by medical doctors (MDs), and the cost of clinical treatment was 3.3 times higher for the DCs than MDs. CONCLUSION: The cost for treatment by DCs was greater than that of MDs for similarly classified conditions affecting the low back. The amount paid by the insurance company was primarily related to the number of services given by each provider.

Trial-by-trial analysis or averaging: implications for electromyographic models of rapid limb control.

The control of human limb movement has been the focus of research for more than a century. A major issue to emerge from this work is the manner in which the central nervous system regulates electromyographic (EMG) activity to produce movements that differ in distance, velocity, and movement time. However the different methods of analysis often used to analyze EMG data could result in different kinematic-EMG relationships. In this study, participants performed an elbow flexion task to one of five distance goals (between 5 degrees and 50 degrees) using three movement speeds. EMG data from the right elbow flexors were compared using a trial-by-trial analysis and one based on averaged data. Averaging across trials underestimated biceps EMG amplitude at all movement distances and speeds compared to a trial-by-trial analysis. Averaging overestimated EMG burst duration compared to the trial-by-trial analysis. Peak agonist EMG amplitude was positively related to distance and inversely related to movement time. Agonist EMG duration was constant for movement distances less than 30 degrees but increased in the 50 degrees condition. The results support the view that peak EMG amplitude and duration can be controlled independently, but EMG duration changes only for longer distance movements when additional force is required.

Low back pain in Hispanic residential carpenters.

OBJECTIVE: Low back pain (LBP) is a leading cause of lost work time and has been recognized as America's number one workplace safety challenge. Low back pain is occurring at epidemic proportions among construction workers, and minority populations have been underinvestigated for risk of back injury. This project investigated the multiple potential risk factors for occupational LBP among Hispanic residential carpenters. METHODS: This investigation evaluated 241 Hispanic residential framing carpenters. Data for this study were collected using a 91-question survey. End points of interest included point, annual, and lifetime prevalence of LBP. RESULTS: Nineteen percent of respondents reported they had an episode of LBP in their lifetime. CONCLUSIONS: Hispanic residential carpenters reported less than expected prevalence of LBP compared with non-Hispanic counterparts in the same trade and location. Job tasks and personal and workplace risk factors, including psychological and morphological characteristics, affect the prevalence of LBP among Hispanic framing carpenters.