Trunk Lateral Bending Research Articles

Control of lateral weight-transfer initiation during sitting.

Whereas many researchers have examined the transition from quiet posture to dynamic state, study of the initiation of lateral weight-transfer during sitting has only begun recently. This action is included in many tasks performed in our daily living, i.e., reaching, dressing, looking backwards, lying down, and shuffling the buttocks. The present study was designed to describe lateral weight-transfer movements of healthy adults, kinematically and kinetically, and to clarify the strategies and speed dependency of lateral weight-transfer initiation during sitting. Seven healthy Japanese male students without orthopaedic or neurological disorders participated. Their lateral weight-transfer movements were measured during sitting, using two force platforms and a 3-dimensional analysis system. Analysis showed that there appear to be two strategies for the initiation of the task: one is the lateral bending of trunk toward the weight-transfer side, and the other is a coordinated reciprocal leg action of both legs. A combination of these strategies is used in a trade-off fashion during natural motions. These results are clinically important for the assessment and therapy of patients with sitting problems.

What is a waddling gait?

Purpose: A patient's gait can provide important diagnostic and functional information. Though ‘waddling gait’ is a long-established concept, we question whether this description is precise or clinically useful.Methods: We searched ‘waddling gait’ in all main medical specialties core textbooks, in animal locomotion books and in Medline, Healthstar and Embase. Further we obtained expert advice on the gait of ducks.Results: Many names are used for ‘waddling gait’, and its description is imprecise and inconsistent. Trendelenburg described it as a pelvic drop on the side of the swinging leg and compensatory lateral trunk bending towards the side of the standing leg. Many conditions have been described as producing a waddling gait. We accepted the gait pattern of ducks as being true waddling. This often-used comparison does not accurately reflect the gait pattern seen in humans with a range of medical disorders; nor is it the same as a Trendelenburg gait.Conclusions: As we have found no condition in which patients have a truly duck-like gait, we propose that the phrase ‘waddling gait’ should be abandoned. We suggest that for clarity and good communication, clinicians should describe the observed elements of the gait rather than using imprecise and unhelpful terms such as ‘waddling gait’.

Electromyogram and kinematic analysis of lateral bending in idiopathic scoliosis patients.

In adolescent idiopathic scoliosis (AIS), surgical planning currently relies on spinal flexibility evaluation using lateral bending radiographs. The aim was to evaluate the feasibility of non-invasive dynamic analysis of trunk kinematics and muscle activity in patients with AIS before surgical correction. During various lateral trunk bending tasks, erector spinae (18 sites) and abdominal (four sites) muscle activity was sampled using surface electrodes in ten AIS patients and in ten controls. Simultaneously, the spatial displacements of infrared emitting diodes located on the trunk were sampled. Parameters considered were the heterolateral-to-homolateral root-mean-square EMG ratios R at each site and total lateral bending and thoracic and lumbar curvature angle courses. Main alterations concerned apical muscle activity during left bending tasks. ANOVA results showed a significant effect of side (p = 2.1 x 10(-9)), EMG recording site (p = 1.9 x 10(-16)), pathology (p = 3.9 x 10(-16)) and task (p = 2.2 x 10(-11)) on R ratios. The R ratio at T10 and L1 for a simple lateral bending task during left bending averaged 4.8 (SD 4.3) and 3.0 (SD 3.1) in AIS patients, and 2.3 (SD 2.8) and 1.3 (SD 0.4) in controls (p = 6.4 x 10(-4) and 2.5 x 10(-3), LSD post hoc). This preliminary study allowed the development of a functional, non-invasive, non-irradiating dynamic tool for pre-operative evaluation in AIS.

Quantitative analysis of gait in Parkinson's disease: a pilot study on the effects of bilateral sub-thalamic stimulation.

Four patients with Parkinson's disease who had a Subthalamic Nucleus (STN) stimulator implanted and four age-matched controls underwent gait analysis using a three-dimensional system. STN stimulation substantially improved most of the key variables in the patients, without producing inefficient compensatory movements of the trunk. A reduction of ankle power production during push off was the most persistent abnormality seen when the patients were stimulated. We also found a reduction of trunk lateral bending and torsion when the patients were not stimulated when compared with controls.

Validity of fixed-interval observations for postural assessment in construction work

While observing six simulated construction tasks in the field, trained analysts recorded arm, trunk and leg postures categorically with two fixed-interval observational protocols. Observations were compared to measurements obtained with an electronic postural assessment system coupled with video analysis. The electronic postural assessment system consisted of electronic inclinometers to measure upper arm posture, knee flexion and trunk flexion, coveralls to house the inclinometer wiring, and an eletrogoniometric system to measure trunk lateral bending and twisting. Video analysis included frozen-frame analysis that corresponded to the moment of observation and simulated real-time analysis. Measurements were made on five male participants who each performed three tasks representative of construction laborers’ work. Agreement among the observational and reference methods was generally high, although significant differences in measured frequency of exposure existed for knee flexion, trunk lateral bending and trunk twisting. The results suggest that, under appropriate conditions, discrete observations can be used to obtain reasonably accurate estimates of exposure frequency for broad categories of certain body postures.

A Validity Study of Fixed-Interval Observations for the Assessment of Body Postures during Construction Work

Categories of body posture recorded with two observational methods were compared to measurements obtained with an electronic postural assessment system and video analysis during simulated construction tasks. The electronic postural assessment system consisted of electronic inclinometers to measure upper arm posture, knee flexion and trunk flexion, coveralls to house the inclinometer wiring, and an electro-goniometric system to measure trunk lateral bending and torsion. Video analysis included frozen-frame analysis that corresponded to the moment of observation and simulated real-time analysis. Measurements were made on five male participants who performed three of six simulated construction tasks. Overall, agreement among the observational and reference methods was high, although significant differences among the methods were found in the measured frequency of some leg and trunk postures, particularly for knee flexion, trunk lateral bending and trunk torsion. These results suggest that discrete observations can be used to obtain accurate estimates of exposure frequency for arm postures at or above shoulder height, kneeling, climbing and gross categories of trunk flexion.

Spine loading during trunk lateral bending motions

Increases in lateral trunk velocities have been identified as a mechanism for increasing the risk of low-back disorder. Previous studies have identified an increase in coactivation of the trunk musculature during lateral bends, but no studies have evaluated how spine loading changes as lateral trunk velocity increases. Twelve subjects were asked to lift loads laterally at one static and three dynamic velocities. Ten trunk muscle activities and trunk kinematics were documented and used as input parameters to an EMG-assisted model to evaluate spine loading. Muscle coactivation was observed in all lateral bends. Coactivation significantly increased during dynamic trials compared to the static trials. Coactivity increased spinal loads by as much as 25% compared to values predicted by models that did not consider coactivity. Movements to the right significantly increased spine loadings (252 N increase in compression) compared to movements to the left. Spine compression, A-P shear, and lateral shear all increased in the dynamic trials compared to the static conditions. Peak compression increased by an average of 525 N at 45° s −1 compared to static loading. Compression and lateral shear increased monotonically as trunk velocity increased. It is expected that this combined (compression and lateral shear) loading is the mechanism for increased risk observed in industry.

Axial muscle function during lizard locomotion

It was recently reported that the epaxial muscles of a lizard, Varanus salvator, function to stabilize the trunk during locomotion, and it was suggested that this stabilizing role may be a shared derived feature of amniotes. This result was unexpected because it had previously been assumed that the epaxial muscles of lizards function to produce lateral bending during locomotion and that only in mammals and birds were the epaxial muscles active in stabilizing the trunk. These results and the inferences made from them lead to two questions. (1) Is the pattern of epaxial muscle activity observed in V. salvator representative of a basal lizard condition or is it a derived condition that evolved within lizards? (2) If the epaxial muscles do not produce lateral bending, which muscles do carry out this function? These questions were addressed by collecting synchronous electromyographic (EMG) and kinematic data from two lizard species during walking and running. EMG data were collected from the epaxial muscles of a lizard species from a basal clade, Iguana iguana, in order to address the first question. EMG data were collected from the hypaxial muscles of both Iguana iguana and Varanus salvator to address the second question. The timing of epaxial muscle activity in Iguana iguana relative to the kinematics of limb support and lateral trunk bending is similar to that observed in Varanus salvator, a finding that supports the hypothesis that the epaxial muscles stabilize the trunk during locomotion in lizards and that this stabilizing role is a basal feature of lizards. Therefore, a stabilizing function of the epaxial muscles is most parsimoniously interpreted as a basal amniote feature. In both Iguana iguana and Varanus salvator, the activity of two of the hypaxial muscles, the external oblique and rectus abdominis, is appropriately timed for the production of lateral bending. This indicates that elements of the hypaxial musculature, not the epaxial musculature, are the primary lateral bending muscles of lizards.

Epaxial muscle function during locomotion in a lizard (Varanus salvator) and the proposal of a key innovation in the vertebrate axial musculoskeletal system

The pattern of electromyographic activity in the epaxial muscles of walking and running lizards (water monitors, Varanus salvator) was quantified with high-speed video and synchronized electromyography. Muscle denervation experiments were performed and ground reaction forces were recorded to evaluate hypotheses of muscle function. Water monitors exhibit unilateral, uniphasic activation of the epaxial muscles ipsilateral to rear limb support. The iliocostalis and longissimus dorsi muscles are active throughout the support phase of the rear limb, while the transversospinalis is active only during the second half of the support phase. The timing of muscle activity does not support the presumed locomotor function of the epaxial muscles of lizards (lateral bending of the trunk). Bilateral denervation of the two most lateral epaxial muscles (iliocostalis and longissimus dorsi) caused no significant change in the amplitude of lateral trunk bending. These two epaxial muscles do not appear to be necessary for lateral bending of the trunk, nor do they appear to be involved in resisting lateral bending of the trunk. On the basis of the data reported in this study, as well as a re-evaluation of previously existing data, it is proposed that the locomotor function of the epaxial muscles of lizards is to stabilize the trunk against the vertical component of the ground reaction forces; i.e. the epaxial muscles function in a postural role during locomotion in lizards, as they do in other amniotes. This proposed postural role of the epaxial muscles may represent a key innovation of amniotes, made possible by the loss of an aquatic larval stage in their common ancestor.

The effects of lateral trunk bending on muscle recruitments when resisting nonsagittally symmetric bending moments.

Surface electromyographic activities were measured in 15 subjects as they maintained a static laterally bent trunk posture and resisted sagittally symmetric and asymmetric moments applied to their torsos. The moment magnitudes were 20 and 40 Nm and had transverse plane directional components in 30 degrees increments surrounding the subjects' torsos. To quantify the myoelectric responses from eight trunk muscles as asymmetric loads were applied to the laterally bent torso. Asymmetric material handling frequently results in lateral bending of the torso. Each of these factors have been linked via epidemiologic investigations to the incidence of low back disorders. Little information is available that describes the response of the trunk muscles when the trunk is bent to the side. Subjects stood in a reference frame and adjusted their trunk posture to marks on a video display that indicated when a 20 degrees lateral bend to the right had been achieved. Moments were applied to the torso by connecting weights via cables and pulleys to a chest harness. Electromyographic activities were recorded bilaterally from the erector spinae, latissimus dorsi rectus abdominis, and external oblique muscles. The electromyographic data indicated that the muscles showed the greatest activity when they were in opposition to the applied sagittal and frontal plane moments. The left external oblique showed the greatest response and was sensitive to the widest range of moment direction conditions. All of the muscles, except for the left latissimus dorsi, at times contributed antagonistic moments in the sagittal plane or the frontal plane, or in both planes. These data were compared with previously obtained data from an upright neutral posture. Statistical analyses indicated that the responses of both external obliques and the left erector spinae to the moment direction conditions were significantly different between the laterally bent and neutral postures.