Cyril Duclos

Electrical stimulation and muscle strengthening

OBJECTIVES To identify the effects of application methods and indications of direct muscle electrostimulation on strength gain. METHODS Literature review and analysis of articles from Medline database with the following entries: muscular or neuromuscular, electromyostimulation, electrical stimulation, strengthening, strength training, immobilization, muscle dystrophy, bed-rest, bed-bound, knee or hip surgery, postoperative phase, cachexia, sarcopenia, and their French equivalent. RESULTS Because of its specific muscle recruitment order, different from that of voluntary contraction, direct muscle electrostimulation is theoretically a complementary tool for muscle strengthening. It can be used in healthy subjects and in several affections associated with muscle function loss. Its interest seems well-established for post-traumatic or postsurgery lower-limb immobilizations but too few controlled studies have clearly shown the overall benefits of its application in other indications. Whatever the indication, superimposed or combined electrostimulation techniques are generally more efficient than electrostimulation alone. CONCLUSION Even though widely used, the level of evidence for the efficiency of electromyostimulation is still low. For strength gains, it yielded no higher benefits than traditional strengthening methods. Its interest should be tested in medical affections leading to major muscle deconditioning or in sarcopenia.

Lateral Trunk Displacement and Stability During Sit-to-Stand Transfer in Relation to Foot Placement in Patients With Hemiparesis:

Background. In hemiparetic individuals, sit-to-stand (STS) transfer is characterized by asymmetric weight-bearing and altered trunk kinematics that can be improved by positioning the affected foot behind the nonaffected one. Objective. To examine the influence of frontal trunk kinematics on medio-lateral displacements of the center of pressure (CP) during STS performed with the feet placed in 2 different positions, as well as relationships between these parameters, medio-lateral stability, and clinical scores of the participants. Methods. Eighteen patients with chronic stroke and 15 control individuals were evaluated during sit-to-stand transfers either in spontaneous foot position or with their affected or dominant foot placed behind, respectively. Medio-lateral CP, pelvis, and shoulder displacement were analyzed using 3D kinematic and kinetic data recordings of the whole task. Motor and sensory impairment, spasticity, muscle strength, and equilibrium were evaluated by standard scales. The possible time during which a participant could prevent a fall (minimal time-to-contact) was used as a stability index. Results. Spontaneously, the deviation of the CP of stroke participants paralleled the tilt of the trunk toward the nonaffected side, as early as the first third of the task. With the affected foot placed behind, trunk position did not differ from those of control participants who executed the transfer spontaneously. Hemiparetic participants were less stable than control participants. Placement of the feet had no significant effect on the stability of either group. Stability was strongly associated with better motor scores on the Chedoke-McMaster Stroke Assessment. Conclusions. In hemiparetic individuals, improving STS symmetry by positioning the affected foot behind the nonaffected one did not decrease medio-lateral stability, which was associated with the level of stroke-related motor impairments.

Destabilizing and stabilizing forces to assess equilibrium during everyday activities

Postural stability is essential to functional activities. This paper presents a new model of dynamic stability which takes into account both the equilibrium associated with the body position over the base of support (destabilizing force) and the effort the subject needs to produce to keep his/her centre of mass inside the base of support (stabilizing force). The ratio between these two forces (destabilizing over stabilizing) is calculated to provide an overall index of stability for an individual. Preliminary results from data collected during walking at preferred and maximal safe speed in four older adults (aged from 64 to 84yr) showed that both forces are lower for subjects with reduced maximal gait speed. In addition, the stabilizing force increases by 2-3 times from preferred to maximal speed, while the destabilizing force barely changes with gait speed. Overall, the model through the index of stability attributes lower dynamic stability to subjects with lower maximal gait speed. These preliminary results call for larger-scale studies to pursue the development and validation of the model and its application to different functional tasks.

Guiding task-oriented gait training after stroke or spinal cord injury by means of a biomechanical gait analysis.

To recover the ability to walk is one of the most important goals of persons recovering from a stroke or spinal cord injury (SCI). While a task-oriented approach to gait training is recommended, randomized controlled trials or meta-analyses comparing different methods of delivering training have failed in general to demonstrate the superiority of one approach over the other. The large variations in the mean outcome gait measures reported in these studies reflect, at least in part, the heterogeneity of the sensorimotor impairments underlying the gait disability as well as variations in the therapeutic response. The purpose of this chapter is to demonstrate that biomechanical gait analysis can reveal information pertinent to the selection of a task-oriented approach to enhance gait training as well as the therapeutic response that clinical evaluations alone cannot provide. We first briefly review locomotor impairments underlying the gait disability after stroke and SCI as well as the effects of selected technological task-oriented gait training interventions. We then give examples that demonstrate the use of gait analysis to pinpoint underlying impairments that can guide the choice of sensorimotor therapy and then immediately identify responders to the intervention. Such an individualized approach should promote therapeutic efficacy while leading over time to the identification of clinical indices to guide therapy when gait analysis is not feasible. Given the requirements of a gait analysis laboratory and the qualified personnel to capture and interpret the data, future studies will need to demonstrate the feasibility of the technological proposed approach and assess the costs and benefits for the health care system.

Dynamic stability requirements during gait and standing exergames on the wii fit® system in the elderly

BackgroundIn rehabilitation, training intensity is usually adapted to optimize the trained system to attain better performance (overload principle). However, in balance rehabilitation, the level of intensity required during training exercises to optimize improvement in balance has rarely been studied, probably due to the difficulty in quantifying the stability level during these exercises. The goal of the present study was to test whether the stabilizing/destabilizing forces model could be used to analyze how stability is challenged during several exergames, that are more and more used in balance rehabilitation, and a dynamic functional task, such as gait.MethodsSeven healthy older adults were evaluated with three-dimensional motion analysis during gait at natural and fast speed, and during three balance exergames (50/50 Challenge, Ski Slalom and Soccer). Mean and extreme values for stabilizing force, destabilizing force and the ratio of the two forces (stability index) were computed from kinematic and kinetic data to determine the mean and least level of dynamic, postural and overall balance stability, respectively.ResultsMean postural stability was lower (lower mean destabilizing force) during the 50/50 Challenge game than during all the other tasks, but peak postural instability moments were less challenging during this game than during any of the other tasks, as shown by the minimum destabilizing force values. Dynamic stability was progressively more challenged (higher mean and maximum stabilizing force) from the 50/50 Challenge to the Soccer and Slalom games, to the natural gait speed task and to the fast gait speed task, increasing the overall stability difficulty (mean and minimum stability index) in the same manner.ConclusionsThe stabilizing/destabilizing forces model can be used to rate the level of balance requirements during different tasks such as gait or exergames. The results of our study showed that postural stability did not differ much between the evaluated tasks (except for the 50/50 Challenge), compared to dynamic stability, which was significantly less challenged during the games than during the functional tasks. Games with greater centre of mass displacements and changes in the base of support are likely to stimulate balance control enough to see improvements in balance during dynamic functional tasks, and could be tested in pathological populations with the approach used here.

Influence of visual inputs on quasi-static standing postural steadiness in individuals with spinal cord injury.

Postural steadiness while standing is impaired in individuals with spinal cord injury (SCI) and could be potentially associated with increased reliance on visual inputs. The purpose of this study was to compare individuals with SCI and able-bodied participants on their use of visual inputs to maintain standing postural steadiness. Another aim was to quantify the association between visual contribution to achieve postural steadiness and a clinical balance scale. Individuals with SCI (n = 15) and able-bodied controls (n = 14) performed quasi-static stance, with eyes open or closed, on force plates for two 45 s trials. Measurements of the centre of pressure (COP) included the mean value of the root mean square (RMS), mean COP velocity (MV) and COP sway area (SA). Individuals with SCI were also evaluated with the Mini-Balance Evaluation Systems Test (Mini BESTest), a clinical outcome measure of postural steadiness. Individuals with SCI were significantly less stable than able-bodied controls in both conditions. The Romberg ratios (eyes open/eyes closed) for COP MV and SA were significantly higher for individuals with SCI, indicating a higher contribution of visual inputs for postural steadiness in that population. Romberg ratios for RMS and SA were significantly associated with the Mini-BESTest. This study highlights the contribution of visual inputs in individuals with SCI when maintaining quasi-static standing posture.

Perception threshold of locomotor symmetry while walking on a split-belt treadmill in healthy elderly individuals.

Some hemiparetic patients walk asymmetrically. To better understand the mechanisms of this deficiency, the perception of locomotor symmetry was investigated in healthy elderly individuals. 16 participants (6 women, 10 men; M age = 70.9 yr., SD = 4.1) walked on a split-belt treadmill either at a self-selected or imposed gait speed. The speed of the two belts was initially similar (or different) and then gradually differed (or matched), so participants had to detect the point of perceived asymmetry (or symmetry). The results revealed that thresholds occurred when the belt speed ratios were .88 and .85. Initial gait speed did not affect the threshold. The parameter that correlated the most with belt speed asymmetry was stance time of the parameters measured. Future studies will investigate whether stroke affects gait symmetry judgments.

Center-of-pressure total trajectory length is a complementary measure to maximum excursion to better differentiate multidirectional standing limits of stability between individuals with incomplete spinal cord injury and able-bodied individuals

BackgroundSensorimotor impairments secondary to a spinal cord injury affect standing postural balance. While quasi-static postural balance impairments have been documented, little information is known about dynamic postural balance in this population. The aim of this study was to quantify and characterize dynamic postural balance while standing among individuals with a spinal cord injury using the comfortable multidirectional limits of stability test and to explore its association with the quasi-static standing postural balance test.MethodsSixteen individuals with an incomplete spinal cord injury and sixteen able-bodied individuals participated in this study. For the comfortable multidirectional limits of stability test, participants were instructed to lean as far as possible in 8 directions, separated by 45° while standing with each foot on a forceplate and real-time COP visual feedback provided. Measures computed using the center of pressure (COP), such as the absolute maximal distance reached (COPmax) and the total length travelled by the COP to reach the maximal distance (COPlength), were used to characterize performance in each direction. Quasi-static standing postural balance with eyes open was evaluated using time-domain measures of the COP. The difference between the groups and the association between the dynamic and quasi-static test were analyzed.ResultsThe COPlength of individuals with SCI was significantly greater (p ≤ 0.001) than that of able-bodied individuals in all tested directions except in the anterior and posterior directions (p ≤ 0.039), indicating an increased COP trajectory while progressing towards their maximal distance. The COPmax in the anterior direction was significantly smaller for individuals with SCI. Little association was found between the comfortable multidirectional limits of stability test and the quasi-static postural balance test (r ≥ −0.658).ConclusionStanding dynamic postural balance performance in individuals with an incomplete spinal cord injury can be differentiated from that of able-bodied individuals with the comfortable limits of stability test. Performance among individuals with an incomplete spinal cord injury is characterized by lack of precision when reaching. The comfortable limits of stability test provides supplementary information and could serve as an adjunct to the quasi-static test when evaluating postural balance in an incomplete spinal cord injury population.

Postural and dynamic balance while walking in adults with incomplete spinal cord injury

The purpose of this study was to characterize balance in individuals with and without an incomplete spinal cord injury (ISCI) during the single support phase of gait. Thirty-four individuals (17 with a ISCI, 17 able-bodied) walked at their self-selected walking speed. Among those, eighteen individuals (9 with ISCI, 9 able-bodied) with a similar walking speed were also analyzed. Stabilizing and destabilizing forces quantified balance during the single support phase of gait. The biomechanical factors included in the equation of the stabilizing and destabilizing forces served as explanatory factors. Individuals with ISCI had a lower stabilizing force and a higher destabilizing force compared to able-bodied individuals. The main explanatory factors of the forces extracted from the equations were the speed of the center of mass (maximal stabilizing force) and the distance between the center of pressure and the base of support (minimal destabilizing force). Only the minimal destabilizing force was significantly different among subgroups with a similar walking speed. The stabilizing and destabilizing forces suggest that individuals with ISCI were more stable than able-bodied, which was achieved by walking more slowly - which decrease the speed of the center of mass - and keeping the center of pressure away from the margin of the base of support in order to maintain balance within their range of physical ability.

PlANTARflExION MOMENT IS A CONTRIbUTOR TO STEP lENgTh AfTER-EffECT fOllOWINg WAlkINg ON A SPlIT-bElT TREADMIll IN INDIvIDUAlS WITh STROkE AND hEAlThy INDIvIDUAlS*

OBJECTIVE To assess plantarflexion moment and hip joint moment after-effects following walking on a split-belt treadmill in healthy individuals and individuals post-stroke. DESIGN Cross-sectional study. SUBJECTS Ten healthy individuals (mean age 57.6 years (standard deviation; SD 17.2)) and twenty individuals post-stroke (mean age 49.3 years (SD 13.2)). METHODS Participants walked on an instrumented split-belt treadmill under 3 gait periods: i) baseline (tied-belt); ii) adaptation (split-belt); and iii) post-adaptation (tied-belt). Participants post-stroke performed the protocol with the paretic and nonparetic leg on the faster belt when belts were split. Kinematic data were recorded with the Optotrak system and ground reaction forces were collected via the instrumented split-belt treadmill. RESULTS In both groups, the fast plantarflexion moment was reduced and the slow plantarflexion moment was increased from mid-stance to toe-off in the post-adaptation period. Significant relationships were found between the plantarflexion moment and contralateral step length. CONCLUSION Split-belt treadmills could be useful for restoring step length symmetry in individuals post-stroke who present with a longer paretic step length because the use of this type of intervention increases paretic plantarflexion moments. This intervention might be less recommended for individuals post-stroke with a shorter paretic step length because it reduces the paretic plantarflexion moment.