The control of body orientation and center of mass location under asymmetrical loading

Effects of additional load at different heights on gait initiation: A statistical parametric mapping of center of pressure and center of mass behavior

The purpose of this study was to investigate the effects of different vertical positions of an asymmetrical load on the anticipatory postural adjustments phase of gait initiation. Sixty-eight college students (32 males, 36 females; age: 23.65 ± 3.21 years old; weight: 69.98 ± 8.15 kg; height: 1.74 ± 0.08 m) were enrolled in the study. Ground reaction forces and moments were collected using two force platforms. The participants completed three trials under each of the following random conditions: no-load (NL), waist uniformly distributed load (WUD), shoulder uniformly distributed load (SUD), waist stance foot load (WST), shoulder stance foot load (SST), waist swing foot load (WSW), and shoulder swing foot load (SSW). The paired Hotelling’s T-square test was used to compare the experimental conditions. The center of pressure (COP) time series were significantly different for the SUD vs. NL, SST vs. NL, WST vs. NL, and WSW vs. NL comparisons. Significant differences in COP time series were observed for all comparisons between waist vs. shoulder conditions. Overall, these differences were greater when the load was positioned at the shoulders. For the center of mass (COM) time series, significant differences were found for the WUD vs. NL and WSW vs. NL conditions. However, no differences were observed with the load positioned at the shoulders. In conclusion, only asymmetrical loading at the waist produced significant differences, and the higher the extra load, the greater the effects on COP behavior. By contrast, only minor changes were observed in COM behavior, suggesting that the changes in COP (the controller) behavior are adjustments to maintain the COM (controlled object) unaltered.

Important Movement Concepts: Clinical Versus Neuroscience Perspectives

Human movement is complex, presenting clinical and research challenges regarding how it is described and investigated. This paper discusses the commonalities and differences on how human movement is conceptualized from neuroscientific and clinical perspectives with respect to postural control; the limitations of linear measures; movement efficiency with respect to metabolic energy cost and selectivity; and, how muscle synergy analysis may contribute to our understanding of movement variability. We highlight the role of sensory information on motor performance with respect to the base of support and alignment, illustrating a potential disconnect between the clinical and neuroscientific perspectives. The purpose of this paper is to discuss the commonalities and differences in how movement concepts are defined and operationalized by Bobath clinicians and the neuroscientific community to facilitate a common understanding and open the dialogue on the research practice gap.

Transitions sit to stand and stand to sit in persons post-stroke: Path of centre of mass, pelvic and limb loading - A pilot study

BACKGROUND

To explore the movement patterns utilized by persons post stroke from the simultaneous perspective of pelvic and limb loading with the path of centre of mass during the movement transitions sit to stand and stand to sit.

METHODS

A descriptive pilot study where kinetic and kinematic data were collected and compared between the contribution made by the less affected versus more affected lower limb and trunk during sit to stand and stand to sit following stroke. Movement analysis was undertaken using force-plates and a 3D VICON motion capture system.

FINDINGS

Data were successfully collected on nine subjects of whom four presented with left side more affected and eight were male. Two patterns were demonstrated for pelvic loading, four patterns for limb loading and five patterns for deviation of centre of mass. There were no consistent patterns of movement demonstrated dependent upon the more or less affected side. There was no consistent relationship between pelvic and limb loading and deviation of centre of mass throughout the movement phases.

INTERPRETATION

In contrast to assumptions often made with respect to limb loading, we found large variability in movement patterns utilized by person's with a hemiparetic presentation during sit to stand and stand to sit. The findings suggest that movement problems encountered by persons post-stroke are complex and identifies limitations with respect to current measurement techniques.

Effects of Changing Body Weight Distribution on Mediolateral Stability Control during Gait Initiation

During gait initiation, anticipatory postural adjustments (APA) precede the execution of the first step. It is generally acknowledged that these APA contribute to forward progression but also serve to stabilize the whole body in the mediolateral direction during step execution. Although previous studies have shown that changes in the distribution of body weight between both legs influence motor performance during gait initiation, it is not known whether and how such changes affect a person's postural stability during this task. The aim of this study was to investigate the effects of changing initial body weight distribution between legs on mediolateral postural stability during gait initiation. Changes in body weight distribution were induced under experimental conditions by modifying the frontal plane distribution of an external load located at the participants' waists. Fifteen healthy adults performed a gait initiation series at a similar speed under three conditions: with the overload evenly distributed over both legs; with the overload strictly distributed over the swing-limb side; and with the overload strictly distributed over the stance-leg side. Our results showed that the mediolateral location of center-of-mass (CoM) during the initial upright posture differed between the experimental conditions, indicating modifications in the initial distribution of body weight between the legs according to the load distribution. While the parameters related to the forward progression remained unchanged, the alterations in body weight distribution elicited adaptive changes in the amplitude of APA in the mediolateral direction (i.e., maximal mediolateral shift of the center of pressure (CoP)), without variation in their duration. Specifically, it was observed that the amplitude of APA was modulated in such a way that mediolateral dynamic stability at swing foot-contact, quantified by the margin of stability (i.e., the distance between the base of support boundary and the extrapolated CoM position), did not vary between the conditions. These findings suggest that APA seem to be scaled as a function of the initial body weight distribution between both legs so as to maintain optimal conditions of stability during gait initiation.

The response of the body when carrying a handbag

BACKGROUND

Carrying a load in hand is commonly seen in daily life. There were many studies investigating the optimal weight when carrying a backpack, however, only a few studies investigated optimal weight when carrying a bag in different ways.

OBJECTIVE

To investigate the optimal weight for carrying a handbag.

METHODS

This study involved 13 healthy females, randomized into four carrying weight patterns [no load, bag weight of 5% body weight (BW), 7% BW, and 10% BW] who were walking barefoot on the platform at preferable speed. The center of pressure (COP) was collected by the platform. Spinous processes of C7, T1, T12, L1, S2 and the right tragus were attached with markers. The muscle activities of upper trapezius, erector spinae, and rectus abdominis muscles were measured. All data including discomfort scale were recorded.

RESULTS

The spinal curvature was not affected from carrying a handbag. However, the COP trend was toward the carrying side when carrying a greater load. Asymmetrical activities of the upper trapezius and erector spinae were shown (p < 0.05). The discomfort areas were the right upper trapezius and right finger flexor muscles.

CONCLUSIONS

Continuously carrying a handbag greater than 10% BW can cause musculoskeletal problems.

Association of spinal deformity and pelvic tilt with gait asymmetry in adolescent idiopathic scoliosis patients: Investigation of ground reaction force

BACKGROUND

Adolescent idiopathic scoliosis is a prevalent orthopedic problem in children ages 10 to 16years. Although genetic, physiological and biomechanical factors are considered to contribute to the onset and progression of adolescent idiopathic scoliosis, the underlying mechanisms are not yet clear. The purpose of this study was to investigate the association between spinal deformity and inter-leg ground reaction force asymmetry during walking in adolescent idiopathic scoliosis patients.

METHODS

Fourteen patients (3 males and 11 females) participated in this study. Maximum Cobb's angle, adjusted Cobb's angle, and pelvic tilt were calculated from X-ray images. Asymmetry indices between legs were also calculated from ground reaction force magnitude and time variables from their preferred speed walking. Pearson coefficients of correlation were used to investigate associations of asymmetry indices with angle variables.

FINDINGS

Asymmetry indices of ground reaction force magnitudes positively correlated with adjusted Cobb's angle and maximum Cobb's angle mainly during the peak of braking phase, average of braking phase, while asymmetry indices of ground reaction force time variables showed no significant correlation with adjusted or maximum Cobb's angle. In contrast, asymmetry indices of ground reaction force time variables positively correlated with pelvic tilt during stance phase.

INTERPRETATION

We concluded that the spinal deformity of adolescent idiopathic scoliosis patients estimated using the maximum and adjusted Cobb's angles is generally associated with greater asymmetry of ground reaction force magnitudes in walking, while the pelvic tilt is associated with the greater asymmetry of ground reaction force time variables.

Adolescent idiopathic scoliosis treatment using pettibon corrective procedures: a case report

OBJECTIVE

To investigate the possible benefits of using Pettibon corrective procedures to reduce the curvature associated with idiopathic scoliosis. These procedures were tested to determine potential effectiveness in a single patient.

CLINICAL FEATURES

A patient with a 35 degrees left convex thoracolumbar scoliosis was treated using Pettibon corrective procedures. Initial and follow-up outcome measures included a Borg pain scale, a Functional Rating Index, a balance test, and radiographic analysis.

INTERVENTION AND OUTCOME

The patient was treated using a combination of manipulative and rehabilitative procedures designed to restore normal sagittal curves and reduce the severity of the coronal curvatures. After six weeks of treatment, the post treatment radiograph revealed a 20 degrees left convex thoracolumbar scoliosis, as well as decreases in the Borg pain scale from six to two, and Functional Rating Index score from 18/40 to 7/40 after the trial period. Her balance time increased from 18 seconds to 56 seconds.

CONCLUSION

Pettibon corrective procedures seemed to be effective at reducing the thoracolumbar scoliosis 15 degrees (43%) after six weeks. The subjective and objective results of this case study warrant further such investigations.

The development of a model to predict the effects of worker and task factors on foot placements in manual material handling tasks

Accurate prediction of foot placements in relation to hand locations during manual materials handling tasks is critical for prospective biomechanical analysis. To address this need, the effects of lifting task conditions and anthropometric variables on foot placements were studied in a laboratory experiment. In total, 20 men and women performed two-handed object transfers that required them to walk to a shelf, lift an object from the shelf at waist height and carry the object to a variety of locations. Five different changes in the direction of progression following the object pickup were used, ranging from 45° to 180° relative to the approach direction. Object weights of 1.0 kg, 4.5 kg, 13.6 kg were used. Whole-body motions were recorded using a 3-D optical retro-reflective marker-based camera system. A new parametric system for describing foot placements, the Quantitative Transition Classification System, was developed to facilitate the parameterisation of foot placement data. Foot placements chosen by the subjects during the transfer tasks appeared to facilitate a change in the whole-body direction of progression, in addition to aiding in performing the lift. Further analysis revealed that five different stepping behaviours accounted for 71% of the stepping patterns observed. More specifically, the most frequently observed behaviour revealed that the orientation of the lead foot during the actual lifting task was primarily affected by the amount of turn angle required after the lift (R(2) = 0.53). One surprising result was that the object mass (scaled by participant body mass) was not found to significantly affect any of the individual step placement parameters. Regression models were developed to predict the most prevalent step placements and are included in this paper to facilitate more accurate human motion simulations and ergonomics analyses of manual material lifting tasks. STATEMENT OF RELEVANCE: This study proposes a method for parameterising the steps (foot placements) associated with manual material handling tasks. The influence of task conditions and subject anthropometry on the foot placements of the most frequently observed stepping pattern during a laboratory study is discussed. For prospective postural analyses conducted using digital human models, accurate prediction of the foot placements is critical to realistic postural analyses and improved biomechanical job evaluations.

Scoliosis treatment using spinal manipulation and the Pettibon Weighting System: a summary of 3 atypical presentations

Background

Given the relative lack of treatment options for mild to moderate scoliosis, when the Cobb angle measurements fall below the 25–30° range, conservative manual therapies for scoliosis treatment have been increasingly investigated in recent years. In this case series, we present 3 specific cases of scoliosis.

Case presentation

Patient presentation, examination, intervention and outcomes are detailed for each case. The types of scoliosis presented here are left thoracic, idiopathic scoliosis after Harrington rod instrumentation, and a left thoracic scoliosis secondary to Scheuermann's Kyphosis.

Each case carries its own clinical significance, in relation to clinical presentation. The first patient presented for chiropractic treatment with a 35° thoracic dextroscoliosis 18 years following Harrington Rod instrumentation and fusion. The second patient presented with a 22° thoracic levoscoliosis and concomitant Scheuermann's Disease. Finally, the third case summarizes the treatment of a patient with a primary 37° idiopathic thoracic levoscoliosis. Each patient was treated with a novel active rehabilitation program for varying lengths of time, including spinal manipulation and a patented external head and body weighting system. Following a course of treatment, consisting of clinic and home care treatments, post-treatment radiographs and examinations were conducted. Improvement in symptoms and daily function was obtained in all 3 cases. Concerning Cobb angle measurements, there was an apparent reduction in Cobb angle of 13°, 8°, and 16° over a maximum of 12 weeks of treatment.

Conclusion

Although mild to moderate reductions in Cobb angle measurements were achieved in these cases, these improvements may not be related to the symptomatic and functional improvements. The lack of a control also includes the possibility of a placebo effect. However, this study adds to the growing body of literature investigating methods by which mild to moderate cases of scoliosis can be treated conservatively. Further investigation is necessary to determine whether curve reduction and/or manipulation and/or placebo was responsible for the symptomatic and functional improvements noted in these cases.

The Effect of a Repetitive, Fatiguing Lifting Task on Horizontal Ground Reaction Forces

There are many outdoor work environments that involve the combination of repetitive, fatiguing lifting tasks and less-than-optimal footing (muddy/slippery ground surfaces). The focus of the current research was to evaluate the effects of lifting-induced fatigue of the low back extensors on lifting kinematics and ground reaction forces. Ten participants performed a repetitive lifting task over a period of 8 minutes. As they performed this task, the ground reaction forces and whole body kinematics were captured using a force platform and magnetic motion tracking system, respectively. Fatigue was verified in this experiment by documenting a decrease in the median frequency of the bilateral erector spinae muscles (pretest-posttest). Results indicate significant (p< 0.05) increases in the magnitude of the peak anterior/posterior (increased by an average of 18.3%) and peak lateral shear forces (increased by an average of 24.3%) with increasing time into the lifting bout. These results have implications for work environments such as agriculture and construction, where poor footing conditions and requirements for considerable manual materials handling may interact to create an occupational scenario with an exceptionally high risk of a slip and fall.

Scoliosis treatment using a combination of manipulative and rehabilitative therapy: a retrospective case series

Background

The combination of spinal manipulation and various physiotherapeutic procedures used to correct the curvatures associated with scoliosis have been largely unsuccessful. Typically, the goals of these procedures are often to relax, strengthen, or stretch musculotendinous and/or ligamentous structures. In this study, we investigate the possible benefits of combining spinal manipulation, positional traction, and neuromuscular reeducation in the treatment of idiopathic scoliosis.

Methods

A total of 22 patient files were selected to participate in the protocol. Of these, 19 met the study criterion required for analysis of treatment benefits. Anteroposterior radiographs were taken of each subject prior to treatment intervention and 4–6 weeks following the intervention. A Cobb angle was drawn and analyzed on each radiograph, so pre and post comparisons could be made.

Results

After 4–6 weeks of treatment, the treatment group averaged a 17° reduction in their Cobb angle measurements. None of the patients' Cobb angles increased. A total of 3 subjects were dismissed from the study for noncompliance relating to home care instructions, leaving 19 subjects to be evaluated post-intervention.

Conclusions

The combined use of spinal manipulation and postural therapy appeared to significantly reduce the severity of the Cobb angle in all 19 subjects. These results warrant further testing of this protocol.