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.

Deep Learning in Gait Parameter Prediction for OA and TKA Patients Wearing IMU Sensors.

Quantitative assessments of patient movement quality in osteoarthritis (OA), specifically spatiotemporal gait parameters (STGPs), can provide in-depth insight into gait patterns, activity types, and changes in mobility after total knee arthroplasty (TKA). A study was conducted to benchmark the ability of multiple deep neural network (DNN) architectures to predict 12 STGPs from inertial measurement unit (IMU) data and to identify an optimal sensor combination, which has yet to be studied for OA and TKA subjects. DNNs were trained using movement data from 29 subjects, walking at slow, normal, and fast paces and evaluated with cross-fold validation over the subjects. Optimal sensor locations were determined by comparing prediction accuracy with 15 IMU configurations (pelvis, thigh, shank, and feet). Percent error across the 12 STGPs ranged from 2.1% (stride time) to 73.7% (toe-out angle) and overall was more accurate in temporal parameters than spatial parameters. The most and least accurate sensor combinations were feet-thighs and singular pelvis, respectively. DNNs showed promising results in predicting STGPs for OA and TKA subjects based on signals from IMU sensors and overcomes the dependency on sensor locations that can hinder the design of patient monitoring systems for clinical application.

Lumbar Intervertebral Kinematics During an Unstable Sitting Task and Its Association With Standing-Induced Low Back Pain.

People developing transient low back pain during standing have altered control of their spine and hips during standing tasks, but the transfer of these responses to other tasks has not been assessed. This study used video fluoroscopy to assess lumbar spine intervertebral kinematics of people who do and do not develop standing-induced low back pain during a seated chair-tilting task. A total of 9 females and 8 males were categorized as pain developers (5 females and 3 males) or nonpain developers (4 females and 5 males) using a 2-hour standing exposure; pain developers reported transient low back pain and nonpain developers did not. Participants were imaged with sagittal plane fluoroscopy at 25 Hz while cyclically tilting their pelvises anteriorly and posteriorly on an unstable chair. Intervertebral angles, relative contributions, and anterior-posterior translations were measured for the L3/L4, L4/L5, and L5/S1 joints and compared between sexes, pain groups, joints, and tilting directions. Female pain developers experienced more extension in their L5/S1 joints in both tilting directions compared with female nonpain developers, a finding not present in males. The specificity in intervertebral kinematics to sex-pain group combinations suggests that these subgroups of pain developers and nonpain developers may implement different control strategies.

Assessment of Long-Term Effects of Sports-Related Concussions: Biological Mechanisms and Exosomal Biomarkers.

Concussion or mild traumatic brain injury (mTBI) in athletes can cause persistent symptoms, known as post-concussion syndrome (PCS), and repeated injuries may increase the long-term risk for an athlete to develop neurodegenerative diseases such as chronic traumatic encephalopathy (CTE), and Alzheimer's disease (AD). The Center for Disease Control estimates that up to 3.8 million sport-related mTBI are reported each year in the United States. Despite the magnitude of the phenomenon, there is a current lack of comprehensive prognostic indicators and research has shown that available monitoring tools are moderately sensitive to short-term concussion effects but less sensitive to long-term consequences. The overall aim of this review is to discuss novel, quantitative, and objective measurements that can predict long-term outcomes following repeated sports-related mTBIs. The specific objectives were (1) to provide an overview of the current clinical and biomechanical tools available to health practitioners to ensure recovery after mTBIs, (2) to synthesize potential biological mechanisms in animal models underlying the long-term adverse consequences of mTBIs, (3) to discuss the possible link between repeated mTBI and neurodegenerative diseases, and (4) to discuss the current knowledge about fluid biomarkers for mTBIs with a focus on novel exosomal biomarkers. The conclusions from this review are that current post-concussion clinical tests are not sufficiently sensitive to injury and do not accurately quantify post-concussion alterations associated with repeated mTBIs. In the current review, it is proposed that current practices should be amended to include a repeated symptom inventory, a cognitive assessment of executive function and impulse control, an instrumented assessment of balance, vestibulo-ocular assessments, and an improved panel of blood or exosome biomarkers.

A Cohort Study of the Temporal Stability of ImPACT Scores Among NCAA Division I Collegiate Athletes: Clinical Implications of Test-Retest Reliability for Enhancing Student Athlete Safety.

OBJECTIVE: In this study we examined the temporal stability of the Immediate Post-Concussion Assessment and Cognitive Test (ImPACT) within NCAA Division I athletes across various timepoints using an exhaustive series of statistical models. METHODS: Within a cohort design, 48 athletes completed repeated baseline ImPACT assessments at various timepoints. Intraclass correlation coefficients (ICC) were calculated using a two-way mixed effects model with absolute agreement. RESULTS: Four ImPACT composite scores (Verbal Memory, Visual Memory, Visual Motor Speed, and Reaction Time) demonstrated moderate reliability (ICC = 0.51-0.66) across the span of a typical Division I athlete's career, which is below previous reliability recommendations (0.90) for measures used in individual decision-making. No evidence of fixed bias was detected within Verbal Memory, Visual Motor Speed, or Reaction Time composite scores, and minimal detectable change values exceeded the limits of agreement. CONCLUSIONS: The demonstrated temporal stability of the ImPACT falls below the published recommendations, and as such, fails to provide robust support for the NCAA's recommendation to obtain a single preparticipation cognitive baseline for use in sports-related concussion management throughout an athlete's career. Clinical interpretation guidelines are provided for clinicians who utilize baseline ImPACT scores for later performance comparisons.

Centre of pressure velocity shows impairments in NCAA Division I athletes six months post-concussion during standing balance.

Sport-related concussion return to play (RTP) decisions are largely based on the resolution of self-reported symptoms and neurocognitive function. Some evaluators also incorporate balance; however, an objective approach to balance that can detect effects beyond the acute condition is warranted. The purpose of this study is to examine linear measures of biomechanical balance up to 6 months post-concussion, and to present preliminary diagnostic thresholds useful for RTP. Each concussed athlete participated in instrumented standing balance tasks at 4 timepoints post-concussion. The measures from concussed athletes were compared to the sport-matched non-concussed athlete group at each timepoint. Centre of pressure (COP) mediolateral (ML) velocity in double-leg stance on a hard surface discriminated well between non-concussed and concussed athletes. COP anterior-posterior (AP) velocity in tandem stance on foam showed sensitivity to concussion. Sixty per cent of athletes at 6 months post-concussion did not recover to within the proposed COP ML velocity threshold in double-leg stance on a hard surface. Seventy-one per cent of athletes at 6 months post-concussion did not recover to within the COP AP velocity threshold in tandem stance on foam. This lack of recovery potentially indicates vestibular and motor control impairments long past the typical period of RTP.

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.

A comparison of trunk control in people with no history, standing-induced, and recurrent low back pain during trunk extension.

Objectives: This study compares people with recurrent low back pain (rLBP) and people with pre-clinical low back pain (standing-induced low back pain developers; PDs) to each other and back-healthy controls (non-pain developers; NPDs). Movement variability and muscular co-activity related to coordination are important for both rLBP and PDs, and these two groups also have altered static spine extension.Methods: Eleven participants with recurrent low back pain, and twenty-one asymptomatic participants, categorized as PDs (11) and NPDs (10) through an established standing protocol, volunteered for this study. Three phases of standing extension motion (lean, hold, and return to neutral) were analyzed. Root mean square angular jerk was calculated from trunk and pelvis kinematics, co-activation of the trunk and hip musculature were assessed in four-muscle sets.Results: Root-mean-square jerk was greater when returning to neutral than when leaning back during standing extension in all three groups. People with rLBP had reduced co-activity in their trunk extensors, people classified as PD had more co-activity in their hip extensors compared with the other groups, and anterior trunk co-activity was phase-dependent, and similar between groups.Discussion: Movement control alterations with low back pain may start as an over-protective co-activation strategy in those with standing-induced LBP and progress to an under-protective strategy in those with recurrent low back pain. Level of Evidence: 3.

Simulated hip abductor strengthening reduces peak joint contact forces in patients with total hip arthroplasty.

Lower extremity muscle strength training is a focus of rehabilitation following total hip arthroplasty (THA). Strength of the hip abductor muscle group is a predictor of overall function following THA. The purpose of this study was to investigate the effects of hip abductor strengthening following rehabilitation on joint contact forces (JCFs) in the lower extremity and low back during a high demand step down task. Five THA patients performed lower extremity maximum isometric strength tests and a stair descent task. Patient-specific musculoskeletal models were created in OpenSim and maximum isometric strength parameters were scaled to reproduce measured pre-operative joint torques. A pre-operative forward dynamic simulation of each patient performing the stair descent was constructed using their corresponding patient-specific model to predict JCFs at the ankle, knee, hip, and low back. The hip abductor muscles were strengthened with clinically supported increases (0-30%) above pre-operative values in a probabilistic framework to predict the effects on peak JCFs (99% confidence bounds). Simulated hip abductor strengthening resulted in lower peak JCFs relative to pre-operative for all five patients at the hip (18.9-23.8 ±â€¯16.5%) and knee (20.5-23.8 ±â€¯11.2%). Four of the five patients had reductions at the ankle (7.1-8.5 ±â€¯11.3%) and low back (3.5-7.0 ±â€¯5.3%) with one patient demonstrating no change. The reduction in JCF at the hip joint and at joints other than the hip with hip abductor strengthening demonstrates the dynamic and mechanical interdependencies of the knee, hip and spine that can be targeted in early THA rehabilitation to improve overall patient function.

Design and Pilot Evaluation of a Reconfigurable Spinal Exoskeleton.

Low back pain is a leading cause of disability, and there is a tremendous need for nonsurgical, nonpharmaceutical interventions to manage it. Versatile spinal exoskeletons have been proposed as a method of supporting or augmenting the wearer, but experimental data from human subjects are limited, and the effects of such exoskeletons remain poorly understood. We thus present a prototype of a reconfigurable spinal exoskeleton that features easily adjustable resistance and compression at multiple spinal levels, allowing us to study the effect of different exoskeleton configurations on the body. In a pilot evaluation with a single subject, both thoracic and abdominal compression were found to affect trunk angle, low back moment and the electromyogram of the erector spinae, though different exoskeleton configurations had different effects during different tasks. This supports the premise that intelligent mechanical adjustments of a spinal exoskeleton are necessary for optimal support or augmentation of the wearer, though the results need to be examined in a larger, varied sample of subjects.

Use of high speed stereo radiography to assess the foot orthoses effectiveness in controlling midfoot posture during walking: A pilot study.

BACKGROUND: The intent of this pilot study was to determine the feasibility of using high-speed stereo radiography (HSSR) to assess the effectiveness of footwear and foot orthoses in controlling the change in the position of the midfoot during walking in individuals with a flexible pes planus foot type. METHODS: Four individuals (1 female; 3 male) with a mean age of 25 years (range 22-29) and a bilateral flexible pes planus foot type participated in the study. The HSSR system was used to measure 3-dimensional changes in the longitudinal arch angle (LAA) with each participant walking barefoot, shoe only and shoes with orthoses. RESULTS: The HSSR system was found to be highly effective in measuring the change in the position of the midfoot, as measured using the LAA, when wearing footwear with or without foot orthoses. Based on an assessment of mean values, three out of the four participants demonstrated a change in the LAA as a result of using either shoes only or shoes with orthoses. The methodology used in this pilot study for assessing the effect of footwear and foot orthoses on the posture of the midfoot was highly effective with no side-effects noted by any of the study participants. CONCLUSIONS: Future studies using the HSSR will require modifications to participant inclusion criteria as well as alterations to the data collection methodology. The HSSR system used in this study is feasible for use in larger cohort studies assessing footwear and foot orthosis effectiveness with the described modifications.

Trunk movement compensations and corresponding core muscle demand during step ambulation in people with unilateral transtibial amputation.

The objective of this investigation was to identify demands from core muscles that corresponded with trunk movement compensations during bilateral step ambulation in people with unilateral transtibial amputation (TTA). Trunk rotational angular momentum (RAM) was measured using motion capture and bilateral surface EMG was measured from four bilateral core muscles during step ascent and descent tasks in people with TTA and healthy controls. During step ascent, the TTA group generated larger mediolateral (P = 0.01) and axial (P = 0.01) trunk RAM toward the leading limb when stepping onto the intact limb than the control group, which corresponded with high demand from the bilateral erector spinae and oblique muscles. During step descent, the TTA group generated larger trunk RAM in the sagittal (P < 0.01), frontal (P < 0.01), and transverse planes (P = 0.01) than the control group, which was an effect of falling onto the intact limb. To maintain balance and arrest trunk RAM, core muscle demand was larger throughout the loading period of step descent in the TTA group. However, asymmetric trunk movement compensations did not correspond to asymmetric core muscle demand during either task, indicating a difference in motor control compensations dependent on the leading limb.

Biomechanical compensations of the trunk and lower extremities during stepping tasks after unilateral transtibial amputation.

BACKGROUND: Lower extremity movement compensations following transtibial amputation are well-documented and are likely influenced by trunk posture and movement. However, the biomechanical compensations of the trunk and lower extremities, especially during high-demand tasks such as step ascent and descent, remain unclear. METHODS: Kinematic and kinetic data were collected during step ascent and descent tasks for three groups of individuals: diabetic/transtibial amputation, diabetic, and healthy. An ANCOVA was used to compare peak trunk, hip and knee joint angles and moments in the sagittal and frontal planes between groups. Paired t-tests were used to compare peak joint angles and moments between amputated and intact limbs of the diabetic/transtibial amputation group. FINDINGS: During step ascent and descent, the transtibial amputation group exhibited greater trunk forward flexion and lateral flexion compared to the other two groups (P<0.016), which resulted in greater low back moments and asymmetric loading patterns in the lower extremity joints. The diabetic group exhibited similar knee joint loading patterns compared to the amputation group (P<0.016), during step descent. INTERPRETATION: This study highlights the biomechanical compensations of the trunk and lower extremities in individuals with dysvascular transtibial amputation, by identifying low back, hip, and knee joint moment patterns unique to transtibial amputation during stepping tasks. In addition, the results suggest that some movement compensations may be confounded by the presence of diabetes and precede limb amputation. The increased and asymmetrical loading patterns identified may predispose individuals with transtibial amputation to the development of secondary pain conditions, such as low back pain or osteoarthritis.

Trunk kinetic effort during step ascent and descent in patients with transtibial amputation using angular momentum separation.

BACKGROUND: Patients with transtibial amputation adopt trunk movement compensations that alter effort and increase the risk of developing low back pain. However, the effort required to achieve high-demand tasks, such as step ascent and descent, remains unknown. METHODS: Kinematics were collected during bilateral step ascent and descent tasks from two groups: 1) seven patients with unilateral transtibial amputation and 2) seven healthy control subjects. Trunk kinetic effort was quantified using translational and rotational segmental moments (time rate of change of segmental angular momentum). Peak moments during the loading period were compared across limbs and across groups. FINDINGS: During step ascent, patients with transtibial amputation generated larger sagittal trunk translational moments when leading with the amputated limb compared to the intact limb (P=0.01). The amputation group also generated larger trunk rotational moments in the frontal and transverse planes when leading with either limb compared to the healthy group (P=0.01, P<0.01, respectively). During step descent, the amputation group generated larger trunk translational and rotational moments in all three planes when leading with the intact limb compared to the healthy group (P<0.017). INTERPRETATION: This investigation identifies how differing trunk movement compensations, identified using the separation of angular momentum, require higher kinetic effort during stepping tasks in patients with transtibial amputation compared to healthy individuals. Compensations that produce identified increased and asymmetric trunk segmental moments, may increase the risk of the development of low back pain in patients with amputation.

Assessment of Knee Kinematics in Older Adults Using High-Speed Stereo Radiography.

PURPOSE: Quantification of knee motion is essential for assessment of pathologic joint function, such as tracking osteoarthritis progression and evaluating outcomes after conservative or surgical treatment, including total knee arthroplasty. Our purpose was to establish a useful baseline for the kinematic envelope of knee motion in healthy older adults performing movements of daily living. METHODS: A high-speed stereo radiography system was used to measure the three-dimensional tibiofemoral kinematics of eight healthy people over 55 yr of age (4 women/4 men; age, 61.7 ± 5.4 yr; body mass, 74.6 ± 7.7 kg; body mass index, 26.7 ± 4.4 kg·m; height, 168.2 ± 13.7 cm) during seated knee extension, level walking, pivoting, and step descent. RESULTS: Internal-external and varus-valgus rotation and anterior-posterior range of motion through stance in normal walking averaged 3.6° ± 1.1°, 2.3° ± 0.6°, and 3.4 ± 1.57 mm, respectively. Average range of motion across subjects was greater during the step-down in both internal-external rotation (average, 6.5° ± 3.1°) and anterior-posterior translation (average, 4.5 ± 1.1). Average internal-external range of motion increased to 13.5° ± 3.6° during pivoting. Range of motion of the knee in varus-valgus rotation was nearly the same for each subject across activities, rarely exceeding 6°. CONCLUSIONS: Pivoting and step descending during walking had greater internal-external rotation and anterior-posterior translation than normal gait. Internal-external rotation and anterior-posterior translation were shown to have greater activity dependence, whereas varus-valgus rotation was consistent across activities. These results were similar to prior measurements in younger cohorts, though a trend toward reduced range of motion in the older adults was observed.

The Effects of Prosthesis Inertial Parameters on Inverse Dynamics: A Probabilistic Analysis.

Joint kinetic measurement is a fundamental tool used to quantify compensatory movement patterns in participants with transtibial amputation (TTA). Joint kinetics are calculated through inverse dynamics (ID) and depend on segment kinematics, external forces, and both segment and prosthetic inertial parameters (PIPS); yet the individual influence of PIPs on ID is unknown. The objective of this investigation was to assess the importance of parameterizing PIPs when calculating ID using a probabilistic analysis. A series of Monte Carlo simulations were performed to assess the influence of uncertainty in PIPs on ID. Multivariate input distributions were generated from experimentally measured PIPs (foot/shank: mass, center of mass (COM), moment of inertia) of ten prostheses and output distributions were hip and knee joint kinetics. Confidence bounds (2.5-97.5%) and sensitivity of outputs to model input parameters were calculated throughout one gait cycle. Results demonstrated that PIPs had a larger influence on joint kinetics during the swing period than the stance period (e.g., maximum hip flexion/extension moment confidence bound size: stance = 5.6 N·m, swing: 11.4 N·m). Joint kinetics were most sensitive to shank mass during both the stance and swing periods. Accurate measurement of prosthesis shank mass is necessary to calculate joint kinetics with ID in participants with TTA with passive prostheses consisting of total contact carbon fiber sockets and dynamic elastic response feet during walking.

Separation of rotational and translational segmental momentum to assess movement coordination during walking.

This investigation presents an analysis of segmental angular momentum to describe segmental coordination during walking. Generating and arresting momentum is an intuitive concept, and also forms the foundation of Newton-Euler dynamics. Total segmental angular momentum is separated into separate components, translational angular momentum (TAM) and rotational angular momentum (RAM), which provide different but complementary perspectives of the segmental dynamics needed to achieve forward progression during walking. TAM was referenced to the stance foot, which provides insight into the mechanisms behind how forward progression is achieved through coordinated segmental motion relative to the foot. Translational and rotational segmental moments were calculated directly from TAM and RAM, via Euler's 1st and 2nd laws in angular momentum form, respectively, and are composed of the effects of intersegmental forces and joint moments. Using data from 14 healthy participants, the effort required to generate and arrest momentum were assessed by linking the features of segmental angular momentum and the associated segmental moments to well-known spatiotemporal and kinetic features of the gait cycle. Segmental momentum provides an opportunity to explore and understand system-wide dynamics of coordination from an alternative perspective that is rooted in fundamentals of dynamics, and can be estimated using only segmental kinematic measurements.

Long-Term Task- and Dopamine-Dependent Dynamics of Subthalamic Local Field Potentials in Parkinson's Disease.

Subthalamic nucleus (STN) local field potentials (LFP) are neural signals that have been shown to reveal motor and language behavior, as well as pathological parkinsonian states. We use a research-grade implantable neurostimulator (INS) with data collection capabilities to record STN-LFP outside the operating room to determine the reliability of the signals over time and assess their dynamics with respect to behavior and dopaminergic medication. Seven subjects were implanted with the recording augmented deep brain stimulation (DBS) system, and bilateral STN-LFP recordings were collected in the clinic over twelve months. Subjects were cued to perform voluntary motor and language behaviors in on and off medication states. The STN-LFP recorded with the INS demonstrated behavior-modulated desynchronization of beta frequency (13-30 Hz) and synchronization of low gamma frequency (35-70 Hz) oscillations. Dopaminergic medication did not diminish the relative beta frequency oscillatory desynchronization with movement. However, movement-related gamma frequency oscillatory synchronization was only observed in the medication on state. We observed significant inter-subject variability, but observed consistent STN-LFP activity across recording systems and over a one-year period for each subject. These findings demonstrate that an INS system can provide robust STN-LFP recordings in ambulatory patients, allowing for these signals to be recorded in settings that better represent natural environments in which patients are in a variety of medication states.

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.