Sheri P. Silfies

Delayed trunk muscle reflex responses increase the risk of low back injuries

Study Design. Prospective observational study with a 2- to 3-year follow-up. Objectives. To determine whether delayed muscle reflex response to sudden trunk loading is a result of or a risk factor for sustaining a low back injury (LBI). Summary of Background Data. Differences in motor control have been identified in individuals with chronic low back pain and in athletes with a history of LBI when compared with controls. However, it is not known whether these changes are a risk for or a result of LBI. Methods. Muscle reflex latencies in response to a quick force release in trunk flexion, extension, and lateral bending were measured in 303 college athletes. Information was also obtained regarding their personal data, athletic experience, and history of LBI. The data were entered into a binary logistic regression model to identify the predictors of future LBI. Results. A total of 292 athletes were used for the final analysis (148 females and 144 males). During the follow-up period, 31 (11%) athletes sustained an LBI. The regression model, consisting of history of LBI, body weight, and the latency of muscles shutting off during flexion and lateral bending load releases, predicted correctly 74% of LBI outcomes. The odds of sustaining LBI increased 2.8-fold when a history of LBI was present and increased by 3% with each millisecond of abdominal muscle shut-off latency. On average, this latency was 14 milliseconds longer for athletes who sustained LBI in comparison to athletes who did not sustain LBI (77 [36] vs. 63 [31]). There were no significant changes in any of the muscle response latencies on retest following the injury. Conclusions. The delayed muscle reflex response significantly increases the odds of sustaining an LBI. These delayed latencies appear to be a preexisting risk factor and not the effect of an LBI.

Differences in Feedforward Trunk Muscle Activity in Subgroups of Patients With Mechanical Low Back Pain

OBJECTIVE To investigate alterations in trunk muscle timing patterns in subgroups of patients with mechanical low back pain (MLBP). Our hypothesis was that subjects with MLBP would demonstrate delayed muscle onset and have fewer muscles functioning in a feedforward manner than the control group. We further hypothesized that we would find differences between subgroups of our patients with MLBP, grouped according to diagnosis (segmental instability and noninstability). DESIGN Case-control. SETTING Laboratory. PARTICIPANTS Forty-three patients with chronic MLBP (25 instability, 18 noninstability) and 39 asymptomatic controls. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Surface electromyography was used to measure onset time of 10 trunk muscles during a self-perturbation task. Trunk muscle onset latency relative to the anterior deltoid was calculated and the number of muscles functioning in feedforward determined. RESULTS Activation timing patterns (P<.01; eta=.50; 1-beta=.99) and number of muscles functioning in feedforward (P=.02; eta=.30; 1-beta=.83) were statistically different between patients with MLBP and controls. The control group activated the external oblique, lumbar multifidus, and erector spinae muscles in a feedforward manner. The heterogeneous MLBP group did not activate the trunk musculature in feedforward, but responded with significantly delayed activations. MLBP subgroups demonstrated significantly different timing patterns. The noninstability MLBP subgroup activated trunk extensors in a feedforward manner, similar to the control group, but significantly earlier than the instability subgroup. CONCLUSIONS Lack of feedforward activation of selected trunk musculature in patients with MLBP may result in a period of inefficient muscular stabilization. Activation timing was more impaired in the instability than the noninstability MLBP subgroup. Training specifically for recruitment timing may be an important component of the rehabilitation program.

Lumbar position sense and the risk of low back injuries in college athletes: a prospective cohort study.

BackgroundImpaired proprioception in the lumbar spine has often been reported in people with low back pain. However, no prospective studies exist to assert the cause and effect of this association. We hypothesized that athletes with a history of low back injury (LBI) would demonstrate poorer lumbar position sense (PS) than athletes without a history of LBI, and that this deficit would be a risk factor for future LBI.MethodsThis was a prospective cohort study with 2–3 year follow-up. Lumbar spine PS in the transverse plane was evaluated in 292 athletes using three tests: 1) passive and 2) active trunk repositioning, and 3) motion perception threshold. Mean absolute (accuracy) and variable (precision) errors were computed.ResultsThere were no significant differences in the repositioning errors or motion perception threshold between athletes with and without a history of LBI or between those who did and did not get injured during the follow-up. Active trunk repositioning resulted in smaller errors than passive repositioning (1.6°± 0.8°) versus 2.1°± 1.0°) and 1.7°± 0.8°) versus 2.3°± 1.1°) for the absolute and relative errors, respectively).ConclusionPoor trunk PS in transverse plane is not associated with LBI in athletes, nor does it appear that poor trunk PS predisposes athletes to LBI.

Spinal cord modularity: evolution, development, and optimization and the possible relevance to low back pain in man

The words of Hughlings Jackson in 1884 were inspired by a consideration of what was then the recent work of Darwin on evolution. In the quoted article he applied this perspective to CNS evolution, development and subsequent neurological damage. His overall framework likely remains relevant today. Our paper’s goal is to review current perspectives on motor modularity and its mechanisms, especially at the spinal level (for Jackson ‘well-organized’, ‘simpler’ and ‘more automatic’), but also beyond. Modularity can be defined as the use of designs employing standardized components or units, allowing easy assembly, repair and flexible arrangements of the components. The simplest modules in a system, from which other larger modules might be made, can be termed primitives. This term derives from a combination of the biological definition of primitive as ‘occurring in or characteristic of an early stage of development or evolution’, the definition of primitive as an element assumed as a basis, and the computer science definition of ‘a basic or fundamental unit of machine instruction’. Like Jackson, we will argue that these modules and primitives are in significant part already organized at birth. At the end of this review, we discuss how these issues in spinal modularity and protective reflex structure may relate to trunk control and low back pain mechanisms in humans.

Altered Trunk Motor Planning in Patients with Nonspecific Low Back Pain

ABSTRACT The authors investigated differences in trunk muscle activation timing between patients with chronic nonspecific low back pain (NSLBP) and asymptomatic controls during a self-initiated postural challenge. The authors compared 30 participants with NSLBP to 30 controls. Surface electromyographic data were collected from bilateral trunk muscles. Dependent variables were trunk muscle onset and offset relative to extremity muscle activation and duration of the trunk muscle burst and abdominal–extensor cocontraction. Patients with NSLBP demonstrated significantly delayed trunk muscle onset latency (p < .01), and shorter burst (p = .02) and cocontraction durations (p < .01). Results suggest that patients with NSLBP may be inefficient in regulating trunk posture during voluntary extremity movements. These alterations could also represent a compensatory control pattern imposed by the CNS to avoid pain.

Clinical Observation of Standing Trunk Movements: What Do the Aberrant Movement Patterns Tell Us?

STUDY DESIGN Clinical measurement, cross-sectional study. OBJECTIVE To investigate the reliability of observation of aberrant movement patterns (altered lumbopelvic rhythm, deviation from sagittal plane, instability catch or judder, and painful arc of motion) and to determine whether each pattern is associated with current low back pain (LBP). BACKGROUND Identification of aberrant movement patterns during trunk motion is an important component of subclassifying patients with LBP and prescribing evidence-based interventions. However, reported reliability for observation of specific aberrant patterns is low, and observation of any aberrant pattern (clinical definition of positive test) has ranged from poor to moderate. In addition, the validity of the association of clinical observations of aberrant movements during forward bending with LBP or dysfunction has yet to be determined. METHODS Experienced physical therapists simultaneously observed trunk movements of 102 subjects with no LBP, current LBP, or history of LBP. Kappa statistics were used to evaluate interrater agreement in identifying different types of aberrant patterns. Associations were used to determine the validity of the hypothesized relationship between aberrant patterns and LBP. RESULTS Interrater reliability of identifying the different types of aberrant patterns in subjects with LBP ranged from fair (κ = 0.35; 95% confidence interval: 0.00, 0.71) to excellent (κ = 0.89; 95% confidence interval: 0.69, 1.00). Using the clinical definition of 1 observation of any aberrant motion, interrater agreement was substantial (κ = 0.65; 95% confidence interval: 0.00, 1.00). Significant association was found between judder, deviation, and LBP. The frequency of observed aberrant patterns was significantly associated with LBP. CONCLUSION Simultaneous observation for specific aberrant movement patterns suggests that identification can be performed with at least fair interrater agreement, and observation of any pattern with substantial agreement. Aberrant patterns are more frequently observed in patients with current complaints of LBP; however, they also appear in individuals with a history of LBP and no LBP.

The evolving role of physical therapists in the long-term management of chronic low back pain: longitudinal care using assisted self-management strategies

ABSTRACT Background Longitudinal studies have shown that the symptoms of chronic low back pain (CLBP) will follow an episodic trajectory characterized by periods of high and low pain intensity that can persist for many years. There is a growing belief that the contemporary approach of limiting physical therapy to short, but intense courses of treatment for (CLBP) may be sub-optimal because these limited “windows” of clinical care are not congruent with the natural history of this condition. Recent research has suggested that people with CLBP undergo substantial, and individualized long-term variations in the neural processing of nociception over time. This has led to the concept of a “unique biosignature of pain” that may explain much of the variation in a person’s clinical picture. These and other findings have led to the reconceptualization of CLBP as an individualized, and continually evolving condition that may be more suitably managed by empowering the patient toward self-management strategies that can be modified as needed over time by the PT. Objectives The purpose of this Master Class Paper is to describe an emerging approach for the treatment of CLBP that emphasizes the formation of a long-term therapeutic alliance between the patient and the PT with an emphasis on individualized, patient-preferred approaches for activity-based self-management as an alternative to the contemporary approach of short, intense episodes of care directed toward pain reduction. Conclusion Longitudinal care using assisted self-management strategies is more congruent with the natural history of CLBP than are traditional approaches for PT intervention. This approach may empower patients to undergo lifestyle changes that will favorably influence long-term outcomes; however additional research is needed.

Critical review of the impact of core stability on upper extremity athletic injury and performance

BACKGROUND: Programs designed to prevent or rehabilitate athletic injuries or improve athletic performance frequently focus on core stability. This approach is based upon the theory that poor core stability increases the risk of poor performance and/or injury. Despite the widespread use of core stability training amongst athletes, the question of whether or not sufficient evidence exists to support this practice remains to be answered. OBJECTIVES: 1) Open a dialogue on the definition and components of core stability. 2) Provide an overview of current science linking core stability to musculoskeletal injuries of the upper extremity. 3) Provide an overview of evidence for the association between core stability and athletic performance. DISCUSSION: Core stability is the ability to control the position and movement of the trunk for optimal production, transfer, and control of forces to and from the upper and lower extremities during functional activities. Muscle capacity and neuromuscular control are critical components of core stability. A limited body of evidence provides some support for a link between core stability and upper extremity injuries amongst athletes who participate in baseball, football, or swimming. Likewise, few studies exist to support a relationship between core stability and athletic performance. CONCLUSIONS: A limited body of evidence exists to support the use of core stability training in injury prevention or performance enhancement programs for athletes. Clearly more research is needed to inform decision making when it comes to inclusion or emphasis of core training when designing injury prevention and rehabilitation programs for athletes.

Trunk Postural Muscle Timing Is Not Compromised In Low Back Pain Patients Clinically Diagnosed With Movement Coordination Impairments

Trunk muscle timing impairment has been associated with nonspecific low back pain (NSLBP), but this finding has not been consistent. This study investigated trunk muscle timing in a subgroup of patients with NSLBP attributed to movement coordination impairment (MCI) and matched asymptomatic controls in response to a rapid arm-raising task. Twenty-one NSLBP subjects and 21 matched controls had arm motion and surface EMG data collected from seven bilateral trunk muscles. Muscle onset and offset relative to deltoid muscle activation and arm motion, duration of muscle burst and abdominal-extensor co-contraction time were derived. Trunk muscle onset and offset latencies, and burst and co-contraction durations were not different (p > .05) between groups. Patterns of trunk muscle activation and deactivation relative to arm motion were not different. Task performance was similar between groups. Trunk muscle timing does not appear to be an underlying impairment in the subgroup of NSLBP with MCI.

Kinematic characterization of clinically observed aberrant movement patterns in patients with non-specific low back pain: a cross-sectional study

BackgroundClinical observation of aberrant movement patterns during active forward bending is one criterion used to identify patients with non-specific low back pain suspected to have movement coordination impairment. The purpose of this study was to describe and quantify kinematic patterns of the pelvis and trunk using a dynamics systems approach, and determine agreement between clinical observation and kinematic classification.MethodNinety-eight subjects performed repeated forward bending with clinical observation and kinematic data simultaneously collected. Kinematic data were plotted using angle-angle, coupling-angle, and phase-plane diagrams. Accuracy statistics in conjunction with receiver operating characteristic curves were used to determine agreement between clinical observation and kinematic patterns.ResultsKinematic patterns were consistent with clinical observation and definitions of typical and aberrant movement patterns with moderate agreement (kappa = 0.46–0.50; PABAK = 0.49–0.73). Early pelvic motion dominance in lumbopelvic coupling-angle diagram ≥59° within the first 38% of the movement represent observed altered lumbopelvic rhythm. Frequent disruptions in lumbar spine velocity represented by phase-plane diagrams with local minimum occurrences ≥6 and sudden decoupling in lumbopelvic coupling-angle diagrams with sum of local minimum and maximum occurrences ≥15 represent observed judder.ConclusionThese findings further define observations of movement coordination between the pelvis and lumbar spine for the presence of altered lumbopelvic rhythm and judder. Movement quality of the lumbar spine segment is key to identifying judder. This information will help clinicians better understand and identify aberrant movement patterns in patients with non-specific low back pain.