Molly B. Johnson

Postural control in women with multiple sclerosis: effects of task, vision and symptomatic fatigue.

People with multiple sclerosis (MS) often report problems with balance, which may be most apparent during challenging postural tasks such as leaning or reaching, and when relying on non-visual sensory systems. An additional obstacle facing people with MS is a high incidence of symptomatic fatigue (>70%). The purpose of this study was to investigate the changes in balance during upright stance in individuals with mild-to-moderate disability due to MS under normal and restricted vision and different levels of self-reported fatigue. Limb loading asymmetry, sway and magnitude of postural shift in center of pressure, and time-to-contact the stability boundary of the center of mass and center of pressure were assessed during quiet standing and maximal lean and reach tasks. Compared to controls, people with MS displayed greater postural sway, greater loading asymmetry, and shorter time-to-contact during quiet standing. In the postural perturbation tasks the MS group had smaller postural shifts and reduced stability compared to controls in the direction perpendicular to the lean and reach. Limiting vision increased loading asymmetry during quiet standing and postural instability during backward lean in the MS group. Inducing additional fatigue in the MS group did affect postural control in the more challenging balance conditions but had no impact during quiet upright standing. The results of this study indicate subtle changes in postural control during standing in people with mild-to-moderate impairments due to MS.

Effect of classification-specific treatment on lumbopelvic motion during hip rotation in people with low back pain

Increased and early lumbopelvic motion during trunk and limb movements is thought to contribute to low back pain (LBP). Therefore, reducing lumbopelvic motion could be an important component of physical therapy treatment. Our purpose was to examine the effects of classification-specific physical therapy treatment (Specific) based on the Movement System Impairment (MSI) model and non-specific treatment (Non-Specific) on lumbopelvic movement patterns during hip rotation in people with chronic LBP. We hypothesized that following treatment people in the Specific group would display decreased lumbopelvic rotation and achieve more hip rotation before lumbopelvic rotation began. We hypothesized that people in the Non-Specific group would display no change in these variables. Kinematic data collected before and after treatment for hip lateral and medial rotation in prone were analyzed. The Specific group (N = 16) demonstrated significantly decreased lumbopelvic rotation and achieved greater hip rotation before the onset of lumbopelvic rotation after treatment with both hip lateral and medial rotation. The Non-Specific group (N = 16) demonstrated significantly increased lumbopelvic rotation and no change in hip rotation achieved before the onset of lumbopelvic rotation. People who received treatment specific to their MSI LBP classification displayed decreased and later lumbopelvic motion with hip rotation, whereas people who received generalized non-specific treatment did not.

Multi-segmental torso coordination during the transition from sitting to standing

BACKGROUND Research into the multi-segmental mobility of the torso could add to our understanding of the contributions of the head and torso to human movement. The purpose of this study was to determine the motion and temporal coordination of the head and multiple torso segments during the sit-to-stand task. METHODS Thirty-two young, healthy participants performed five trials of the sit-to-stand movement and 6s of sitting. Range of motion and patterns of peak flexion and extension of six segments and joints and cross correlation of pairs of the six torso segments were analyzed from 3-D kinematic data. FINDINGS Sagittal range of motion for torso joints during the sit-to-stand task was greater than during sitting trials; motion at the lumbar/pelvis joint was greater than at other torso joints. Peak flexion of torso joints occurred earlier than peak extension. Cross correlations at zero lag and time lags of maximum cross correlations varied such that there was greater temporal coordination of intermediate torso segments compared to pairs including the head and pelvis. There was greater temporal coordination of adjacent segment pairs than for pairs that were less proximal to each other. INTERPRETATION A high degree of mobility occurs within the torso during the sit-to-stand task. Varying coordination patterns suggest that there are regional differences in movement timing within the torso that may relate to segmental differences in functional roles. Employing multi-segmental torso models may indicate different movement strategies within a healthy population and could highlight differences between clinical populations.

Differences in end-range lumbar flexion during slumped sitting and forward bending between low back pain subgroups and genders

Patterns of lumbar posture and motion are associated with low back pain (LBP). Research suggests LBP subgroups demonstrate different patterns during common tasks. This study assessed differences in end-range lumbar flexion during two tasks between two LBP subgroups classified according to the Movement System Impairment model. Additionally, the impact of gender differences on subgroup differences was assessed. Kinematic data were collected. Subjects in the Rotation (Rot) and Rotation with Extension (RotExt) LBP subgroups were asked to sit slumped and bend forward from standing. Lumbar end-range flexion was calculated. Subjects reported symptom behaviour during each test. Compared to the RotExt subgroup, the Rot subgroup demonstrated greater end-range lumbar flexion during slumped sitting and a trend towards greater end-range lumbar flexion with forward bending. Compared to females, males demonstrated greater end-range lumbar flexion during slumped sitting and forward bending. A greater proportion of people in the Rot subgroup reported symptoms with each test compared to the RotExt subgroup. Males and females were equally likely to report symptoms with each test. Gender differences were not responsible for LBP subgroup differences. Subgrouping people with LBP provides insight into differences in lumbar motion within the LBP population. Results suggesting potential consistent differences across flexion-related tasks support the presence of stereotypical movement patterns that are related to LBP.

Sex Differences in Lumbopelvic Movement Patterns During Hip Medial Rotation in People With Chronic Low Back Pain

OBJECTIVE To examine sex differences in lumbopelvic motion and symptom behavior during hip medial rotation in people with low back pain (LBP). We hypothesized that men would demonstrate greater and earlier lumbopelvic motion and would be more likely to report increased symptoms compared with women. DESIGN Cross-sectional observational study. SETTING University musculoskeletal analysis laboratory. PARTICIPANTS Persons with chronic LBP (N=59; 30 men, 29 women) were recruited from the community and a university-based physical therapy clinic. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Lumbopelvic rotation range of motion, amount of hip rotation completed before the start of lumbopelvic motion, and provocation of LBP symptoms during the test of prone hip medial rotation were measured. RESULTS Men demonstrated significantly more lumbopelvic rotation (men, 10.0°±5.1°; women, 4.5°±3.9°; P<.001) and completed less hip rotation before the start of lumbopelvic motion (men, 5.4°±3.8°; women, 16.0°±13.2°; P<.001) compared with women. Additionally, a significantly greater percentage of men (60.0%) than women (34.5%; P=.050) reported increased symptoms with hip medial rotation. CONCLUSIONS Men could be at greater risk than women for experiencing LBP symptoms related to hip medial rotation as a result of greater and earlier lumbopelvic motion.

Gender Differences in Modifying Lumbopelvic Motion during Hip Medial Rotation in People with Low Back Pain

Reducing increased or early lumbopelvic motion during trunk or limb movements may be an important component of low back pain treatment. The ability to reduce lumbopelvic motion may be influenced by gender. The purpose of the current study was to examine the effect of gender on the ability of people with low back pain to reduce lumbopelvic motion during hip medial rotation following physical therapy treatment. Lumbopelvic rotation and hip rotation before the start of lumbopelvic rotation were assessed pre- and posttreatment for 16 females and 15 males. Both men and women decreased lumbopelvic rotation and completed more hip rotation before the start of lumbopelvic rotation post-treatment compared to pre-treatment. Men demonstrated greater lumbopelvic rotation and completed less hip rotation before the start of lumbopelvic rotation than women both pre- and post-treatment. Both men and women reduced lumbopelvic motion relative to their starting values, but, overall, men still demonstrated greater and earlier lumbopelvic motion. These results may have important implications for understanding differences in the evaluation and treatment of men and women with low back pain.

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

Objectives:Examine the validity of an induced pain paradigm in which people stand while performing simulated light work tasks (standing paradigm). Materials and Methods: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. Results: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. Discussion: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 head-on-trunk extension a proprioceptive mediator of postural control and sit-to-stand movement characteristics?

ABSTRACT During stance, head extension increases postural sway, possibly due to interference with sensory feedback. The sit-to-stand movement is potentially destabilizing due to the development of momentum as the trunk flexes forward and the body transitions to a smaller base of support. It is unclear what role head orientation plays in the postural and movement characteristics of the sit-to-stand transition. The authors assessed how moving from sitting to standing with head-on-trunk extension compared with moving with the head neutral or flexed, or with moving with the head facing forward in space (which would involve head-on-trunk extension, but not head-in-space extension) in healthy, young participants. Head-on-trunk extension increased center of pressure variability, but decreased movement velocities, movement duration, and trunk flexion compared with flexed and neutral head-on-trunk orientations. Similarities in movement characteristics between head-on-trunk extension and the forward head-in-space orientation suggest that stabilizing the head in space does not fully counteract the postural and movement changes due to head-on-trunk extension. Findings suggest that proprioceptive feedback from the neck muscles contributes to the regulation of posture and movement, and therefore should not be overlooked in research on the role of sensory feedback in postural control.

The Impact of Head Orientation on Multi-segmental Torso Coordination during the Transition from Sitting to Standing

Objective: The aim of this research was to assess how changing the orientation of the head to the trunk would impact the mobility and coordination of multiple torso segments during a common postural transition. Background: The dynamic relationship of the head to the trunk has a major impact on vestibular, visual, and neck muscle stretch receptor sensory feedback. Integration of sensory feedback is necessary to regulate postural control, which is necessary for the performance of daily and occupational activities. During upright stance, head extension induces postural sway (Vuillerme & Rougier, 2005); however, postural control within the torso may also be impacted. Methods: Eleven male and thirteen female, healthy, young subjects performed the sit-to-stand movement starting from standardized sitting conditions. Each subject performed four sit-to-stand trials with each of three different head orientations: extended, flexed, and neutral. 3-D kinematic data were analyzed for six torso segments: head, cervical, upper-thoracic, mid-thoracic, lumbar, and pelvis. Sagittal range of motion was calculated for torso joints composed of adjacent segment pairs. Cross correlations and time lag to maximum cross correlation were analyzed for all possible pairs of torso segments for normalized sit-to-stand trials. Results: Moving from sitting to standing elicited greater range of motion of most torso joints with the head extended compared to with the head flexed or neutral. Cross correlations at zero lag and maximum cross correlations for most torso segment pairs were lower with the head extended compared to flexed or neutral. The lag to maximum cross correlation was higher for all non-adjacent torso segments with the head extended compared to flexed or neutral. Conclusion: Extending the head on the trunk increased mobility within the trunk and decreased temporal coordination between multiple torso segments. These findings suggest that changing the relationship of the head to the trunk induces postural instability within the torso in a healthy population during a postural transition. Application: Increased mobility and reduced stability within the torso during postural transitions could increase occupational risk for falls and injuries, such as low back pain. Avoiding unnecessary head extension could decrease the likelihood of postural instability and subsequent injury risk.

Asymmetry of lumbopelvic movement patterns during active hip abduction is a risk factor for low back pain development during standing

An induced-pain paradigm has been used in back-healthy people to understand risk factors for developing low back pain (LBP) during prolonged standing. We examined asymmetry of lumbopelvic movement timing during a clinical test of active hip abduction in back-healthy people who developed LBP symptoms during standing (Pain Developers; PDs) compared to back-healthy people who did not develop LBP symptoms during standing (Non Pain Developers, NPDs). Participants completed the hip abduction test while movement was recorded with a motion capture system. Difference in time between start of hip and lumbopelvic movement was calculated (startdiff). PDs moved the lumbopelvic region earlier during left hip abduction than right hip abduction. There was no difference between sides in NPDs. In PDs, the amount of asymmetry was related to average symptom intensity during standing. Asymmetric lumbopelvic movement patterns may be a risk factor for LBP development during prolonged standing.