Susan S. Smith

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.

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.

Paradoxical Findings in the Treatment of Predominant Stress and Urge Incontinence: A Pilot Study With Exercise and Electrical Stimulation

Objective:To determine whether women with predominantly urge urinary incontinence (UI) would show greater gains from adding 12.5-Hz electrical stimulation to a progressive exercise program whereas those with predominantly stress UI would show similar gains from progressive exercise alone. Study Design:Randomized block design with participants assigned to exercise alone, exercise with electrical stimulation, or control group, blocked on diagnosis (urge UI or stress UI). Background:Further research needed to address exercise parameters, the role of electrical stimulation, and urinary incontinence type. Methods and Measures:Sixty-four women, 38 with stress UI and 26 with urge UI, were randomized into groups; 42 completed the study. Outcome measures were quality of life, pelvic muscle strength, leaks, and urination frequency. Exercise group performed 6 pelvic floor and abdominal exercises progressed over 8 weeks. Electrical stimulation was added to the progressive exercises for the exercise with electrical stimulation group. Percent change in pretreatment and posttreatment outcome measures were calculated for each treatment group by diagnosis. Results:For women with either stress UI or urge UI, controls worsened and treatment groups improved. For women with stress UI, the greatest gains (57.8%–119.8%) were made by the exercise with electrical stimulation group (P < .001). For women with urge UI, the greatest gains (78.7%-155.1%) were made by the exercise-alone group (P < .01). Conclusions:Our exercise protocol appears to be of sufficient frequency, duration, intensity, and mode to be effective in improving outcomes and may inhibit the detrusor muscle in persons with urge UI. The addition of electrical stimulation appears most useful for muscle reeducation in women with weak pelvic floor muscles.

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.

Effects of Weight-Bearing and Resistance Exercises on Lower Extremity Strength, Postural Stability, and Quality of Life in Postmenopausal Women With Low Bone Mass

Objective:To determine the effects of weight-bearing aerobic (WBA) exercise, resistance strengthening (RS) exercise, and no exercise on strength, postural stability, and quality of life (QOL), and to determine exercise adherence of 2 different exercise programs in postmenopausal women with low bone mass. Study Design:Randomized controlled trial. Background:Three risk factors for fall-related fractures in women with low bone mass are decreased strength, poor balance, and low bone mineral density. Investigators have not demonstrated the specific type, intensity, or duration of exercise most beneficial for improving lower extremity strength, postural stability, and QOL in postmenopausal women with low bone mass. Method and Measures:Twenty-six sedentary post- menopausal women with low bone mass were randomly allocated to 3 groups: WBA (n = 8), RS (n = 9), or control (n = 9). The WBA group performed walking/stepping exercises and the RS group performed 7 lower extremity resistance exercises for 24 sessions over 8 to 12 weeks. The control group participants continued their usual activity for 8 weeks. Lower extremity strength, postural stability, and QOL were measured prior to and at completion of the study. Results:Statistical tests revealed significantly greater postin- tervention hip extension (P = .001) and flexion (P = .009) strength in the RS group compared with the control group. Conclusions:Hip extensor strength is important for postural stability and prevention of falls. The current study demonstrated that RS exercises improve hip extension strength, which is important for postural stability.

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.