Improving Balance and Mobility in People with Multiple Sclerosis

Impaired balance and gait function are highly prevalent and associated with reduced quality of life in those with Multiple Sclerosis (MS). Recent evidence implicates the somatosensory system as a major contributor to balance dysfunction in this population. As part of the mini-symposium entitled Advanced Computational and Technological Approaches to Mitigating Mobility Dysfunction in People with Multiple Sclerosis, this presentation will review current intervention and rehabilitation methods aimed at improving balance and mobility in people with MS. Particular focus will be on the effects of Tai Chi training, which integrates coordination, strength and flexibility in enhancing adaptive postural control and physical function

Locomotor Coordination, Visual Perception and Head Stability during Running

Perception and action are coupled such that information from the perceptual system is related to the dynamics of action in order to regulate behavior adaptively. Using running as a model of a cyclic behavior, this coupling involves a continuous, cyclic relationship between the runner’s perception of the environment and the necessary adjustments of the body that ultimately result in a stable pattern of behavior. The purpose of this paper is to illustrate how individuals relate visual perception to rhythmic locomotor coordination patterns in conditions during which foot–ground collisions and visual task demands are altered. We review the findings of studies conducted to illustrate how humans change their behavior to maintain head stability during running with and without various degrees of visual challenge from the environment. Finally, we show that the human body adapts specific segment/joint configuration and coordination patterns to maintain head stability, both in the lower extremity and upper body segments, together with an increase in coordinative variability. These results indicate that in human locomotion, under higher speed (running) and visual task demands, systematic adaptations occur in the rhythmic coupling between the perceptual and movement systems

Multiscale Entropy Identifies Postural Control Changes in Persons with Multiple Sclerosis

Multiple Sclerosis (MS) is a chronic auto-immune disorder characterized by demyelination of neurons of the central nervous system. MS-related reductions in neural activity have been associated with reductions in balance control and limitations in mobility. Multiscale entropy (MSE) analysis has been used to identify reductions in complexity of the postural control system in various disorders. The purpose of this study was to examine if center-of-pressure fluctuations, analyzed through MSE, differ between persons with MS and healthy controls. We hypothesized that MSE would be reduced in MS compared to controls in all postural tasks in both anterior-posterior (AP) and medio-lateral (ML) directions. Eight persons with MS (7 female, 1 male) and matched controls completed the testing procedures. The MS subjects had minimal functional impairment (Patient Determined Disease Steps, range 0-3). Quiet standing and fixed distance forward and backward reaches were assessed for 30 s. MSE was computed across 30 time scales (range .01-.25s). Effect size (ES) statistics were used to assess differences between MS and control groups. Quiet standing revealed moderate reductions in complexity among persons with MS compared to controls in the AP direction (ES = .71). The backward reach demonstrated moderate and strong reductions in complexity in the AP and ML direction in the MS group (ES = .74 and 1.0, respectively). Moderate reductions in ML complexity were also observed in the forward reach condition in the MS group (ES = .68). These results support the hypothesis that persons with MS display lower postural complexity compared to those without MS. MSE analysis is a promising new tool for detecting MS-related changes in postural complexity. These changes in postural complexity appear to precede locomotor impairment, as assessed by the patient determined disease steps, and may provide novel insight into MS progression

CHANGES IN COORDINATION VARIABILITY WITH SKILL DEVELOPMENT IN EXPERT PERFORMERS

The purpose of this study was to investigate the influence of skill level, in triple jumping, on the coordination variability of lower extremity intra-segmental couplings. Relative motion plots and a modified vector coding technique were utilised to quantify the coordination variability across the trials. The results suggest that coordination variability in expert performers follows a U-shape curve as skill level increases. Higher levels of coordination variability were observed in the most and least experienced performers with relatively lower levels observed in the subjects with moderate levels of experience. This study has highlighted the need for addressing the learning effect when analysing coordination variability from a dynamical systems perspective

LOWER EXTREMITY COORDINATION VARIABILITY DURING ANTICIPATED AND UNANTICIPATED SIDESTEPPING: IMPLICATIONS FOR ACL INJURY PREVENTION

Non-contact anterior cruciate ligament (ACL) injuries commonly occur during sidestepping, particularly under time constraints. This study investigated the differences in lower limb coordination variability (CV) of five male team sport athletes during anticipated and unanticipated sidestepping. Intra-limb couplings associated with ACL injury mechanisms were investigated. Athletes demonstrated 21% greater thigh rot/leg rot CV; 31% greater thigh abd-add/leg abd-add CV; 22% greater knee flex-ext/hip rot CV and 14% greater hip rot/knee abd-add CV during unanticipated sidestepping. These results suggest that CV increases as a function of task complexity. Consequently, injury prevention programs must incorporate perceptual components in order to optimise planning time and coordinate appropriate postural adjustments to counter external loads

TASK CONSTRAINTS MODIFY INTRISIC HEAD-TRUNK DYNAMICS DURING RUNNING AND SIDESTEPPING

The purpose of this study was to examine head movement control during running and sidestepping tasks. Fourteen collegiate male athletes performed running and sidestepping tasks. Sagittal and transverse head and trunk angles, vertical trunk displacement and head-trunk coordination were assessed during the flight and stance phases. The sidestepping task resulted in greater transverse and sagittal plane head and trunk range of motion. During stance, transverse plane head-trunk coordination was more in-phase, with reduced vertical trunk-sagittal head anti-phase coordination during sidestepping tasks. During sidestepping tasks, visual field reorientation required greater contributions from the head in the transverse plane, but with reduced sagittal plane compensation, reduced perceptual awareness may be observed, with negative implications on sport performance and injury risk

COORDINATIVE VARIABILITY IN FOREFOOT RUNNERS DURING AN EXHAUSTIVE RUN

The purpose of this study was to investigate the effects of a prolonged run on coordinative variability and how it relates to impact dynamics in forefoot runners during an exhaustive run. Thirteen individuals ran on an instrumented treadmill and were instructed to select a pace they can maintain for at least 15 minutes but no longer than 20 minutes. A post hoc analysis revealed two subgroups emerged. Eight individuals were able to maintain a forefoot striking pattern throughout the run (NCG: no change group), while the remaining five moved to a more rearfoot strike (CG: change group). The results demonstrated that the impact characteristics changed for the CG only. This was accompanied by changes in CV, suggesting that individuals reorganize their degrees of freedom as they fatigue. The reorganization of footfall patterns may represent an adaptation to meet energy requirements to complete the task

COORDINATION BETWEEN LOCOMOTION AND BREATHING DURING RUNNING

This study investigated the coupling between locomotory and breathing rhythms based on speed, and running experience level. Findings in the current literature are inconclusive because of the wide variety of techniques used as well as their insensitivity to half-integer couplings and/or changes from one coupling to another. Male subjects (5 runners, 5 non-runners) ran at three treadmill speeds. The relative phase between heel strike and end-inspiration allowed for the assessment of the strength and variability of frequency coupling. Results indicate strong individual differences that are masked by grouping subjects. The difference between runners and non-runners may not lie in the coupling strength but in the stability of the dominant coupling across running speeds

USING COORDIN'ATlON MEASURES FOR MOVEMENT ANALYSIS

Traditionally, in biomechanics we have investigated the actions of single joints or segments without taking into account the interactions of these structures. A dynamical systems approach has been increasingly used in biomechanics to give a different perspective on the interaction of specific structures in human movement. That is, the study of coordination has become more prominent in the biomechanics literature based on the work of Bernstein (1967). Coordination is defined as overcoming excessive degrees of freedom thereby turning individual movement elements into a controllable system. In this paper, we will' describe a theoretical framework for analyzing coordination, present examples in the literature and discuss future developments for this type of analysis

OVERUSE INJURIES IN RUNNING: DO COMPLEX ANALYSES HELP OUR UNDERSTANDING?

The purpose of this paper is to discuss the change in focus in biomechanics from relatively simple analysis techniques to more complex techniques. Overuse injuries, linked to rearfoot motion, will be used as an example. In the early development of biomechanical techniques, the angle magnitudes were presented to suggest the mechanisms of overuse injuries. Later, coupling rearfoot motion with actions of the knee became commonplace. In these analyses, the timing and ratios of the angular movements were expressed. However, none of these measures provided a sufficient explanation for injury mechanisms. New techniques, derived from dynamical systems theory, have provided a more salient explanation of the overuse injury mechanism through assessing the role of variability in movement coordination