Amount Of Body Weight Support Research Articles

Gait alterations during walking with partial body weight supported on a treadmill and over the ground

Understanding the changes induced by body weight support (BWS) systems when non-disabled adults walk can help develop appropriate rehabilitation protocols. The purpose of this study was to investigate spatial-temporal gait alterations during walking with BWS on a treadmill and over the ground. Fourteen non-disabled young adults (including seven women) walked over the ground and on a treadmill with 0%, 10%, and 20% of BWS at 80% of their self-selected comfortable walking speed (baseline). The stride length and speed, step length, and stance and double-limb support durations were calculated and compared among the different conditions. The non-disabled adults modulated their spatial-temporal gait parameters according to the surface and percentage of BWS. They walked with shorter and slower strides and shorter steps and spent more time in contact with the support surface as they walked on the treadmill than as they did over the ground. Walking on the treadmill promoted less variability and a higher rate of change than did walking over the ground. Both the surface and amount of BWS should be taken into consideration when using BWS systems for (re)learning and/or reestablishing gait.

Gait initiation and partial body weight unloading for functional improvement in post-stroke individuals

Background: To better understand gait initiation in individuals with stroke and suggest possible training strategies, we compared the gait initiation of individuals with stroke and age-matched controls, and we examined the influence of different amounts of body weight support (BWS) during the execution of gait initiation in individuals with stroke.Materials and methods: Twelve individuals with stroke and 12 age-matched controls initiated gait after a verbal command at a self-selected and comfortable speed, and individuals with stroke also initiated gait wearing a harness with 0%, 15%, and 30% of BWS. Length and velocity of the first step, distance between heels, and weight bearing in both lower limbs in the initial position were calculated. We also assessed the displacement and average velocity of the center of pressure (CoP) in the medial-lateral (ML) and anterior-posterior (AP) directions in 3 distinct sections during gait initiation, which correspond to the CoP position toward the swing limb, stance limb and progression line, respectively.Results: Individuals with stroke presented shorter and slower step, shorter and slower CoP-ML and CoP-AP toward swing limb and Cop-ML towards stance limb, and longer and faster CoP-AP toward stance limb compared to their peers. The BWS lead individuals with stroke to decrease step length and to increase CoP-ML displacement and average velocity toward stance limb.Conclusion: Individuals with stroke present impairments in executing gait initiation mainly during the preparation period and the employment of an overground BWS system promotes a better performance. These results suggest that BWS is a functional strategy that enables individuals with stroke to modulate gait initiation and it could be adopted for gait intervention.

Influence of the amount of body weight support on lower limb joints' kinematics during treadmill walking at different gait speeds: Reference data on healthy adults to define trajectories for robot assistance.

Several robotic devices have been developed for the rehabilitation of treadmill walking in patients with movement disorders due to injuries or diseases of the central nervous system. These robots induce coordinated multi-joint movements aimed at reproducing the physiological walking or stepping patterns. Control strategies developed for robotic locomotor training need a set of predefined lower limb joint angular trajectories as reference input for the control algorithm. Such trajectories are typically taken from normative database of overground unassisted walking. However, it has been demonstrated that gait speed and the amount of body weight support significantly influence joint trajectories during walking. Moreover, both the speed and the level of body weight support must be individually adjusted according to the rehabilitation phase and the residual locomotor abilities of the patient. In this work, 10 healthy participants (age range: 23-48 years) were asked to walk in movement analysis laboratory on a treadmill at five different speeds and four different levels of body weight support; besides, a trial with full body weight support, that is, with the subject suspended on air, was performed at two different cadences. The results confirm that lower limb kinematics during walking is affected by gait speed and by the amount of body weight support, and that on-air stepping is radically different from treadmill walking. Importantly, the results provide normative data in a numerical form to be used as reference trajectories for controlling robot-assisted body weight support walking training. An electronic addendum is provided to easily access to such reference data for different combinations of gait speeds and body weight support levels.

Effect of body weight support on predicted locomotive physical activity.

[Purpose] This study aimed to evaluate the effect of body weight support with an assistive device on predicted locomotive physical activity measured using triaxial accelerometers in healthy young subjects. [Subjects and Methods] Sixteen healthy subjects aged 21.9 ± 1.1 years walked on a treadmill at speeds of 45 and 55 meters/min under 0%, 10%, 20%, and 30% body weight support conditions. Predicted metabolic equivalents and number of steps were evaluated using triaxial accelerometers. Measured metabolic equivalents and number of steps were evaluated using a metabolic system and observers, respectively. Raw data of synthetic accelerations were also obtained. [Results] Predicted metabolic equivalents and number of steps and raw data of synthetic accelerations decreased with increasing amounts of body weight support. [Conclusion] These findings suggest that accelerometers may underestimate locomotive physical activity with increasing amounts of body weight support using assistive devices. Thus, it is important to consider the amount of body weight support when assessing physical activities in subjects using assistive devices for mobility.

Preserved gait kinematics during controlled body unloading

BackgroundBody weight supported locomotor training was shown to improve walking function in neurological patients and is often performed on a treadmill. However, walking on a treadmill does not mimic natural walking for several reasons: absent self-initiation, less active retraction of leg required and altered afferent input. The superiority of overground training has been suggested in humans and was shown in rats demonstrating greater plasticity especially in descending pathways compared to treadmill training. We therefore developed a body weight support system allowing unrestricted overground walking with minimal interfering forces to train neurological patients. The present study investigated the influence of different amounts of body weight support on gait in healthy individuals.MethodsKinematic and electromyographic data of 19 healthy individuals were recorded during overground walking at different levels of body weight support (0, 10, 20, 30, 40, and 50%). Upper body inclination, lower body joint angles and multi-joint coordination as well as time-distance parameters were calculated. Continuous data were analyzed with regard to distinct changes within a gait cycle across all unloading conditions.ResultsTemporal gait parameters were most sensitive to changes in body unloading while spatial variables (step length, joint angles) showed modest responses when unloaded by as much as 50% body weight. The activation of the gastrocnemius muscle showed a gradual decrease with increasing unloading while the biceps femoris muscle showed increased activity levels at 50% unloading. These changes occurred during stance phase while swing phase activity remained unaltered.ConclusionsHealthy individuals were able to keep their walking kinematics strikingly constant even when unloaded by half of their body weight, suggesting that the weight support system permits a physiological gait pattern. However, maintaining a given walking speed using close-to-normal kinematics while being unloaded was achieved by adapting muscle activity patterns. Interestingly, the required propulsion to maintain speed was not achieved by means of increased gastrocnemius activity at push-off, but rather through elevated biceps femoris activity while retracting the leg during stance phase. It remains to be investigated to what extent neurological patients with gait disorders are able to adapt their gait pattern in response to body unloading.

Enhancement of brain plasticity and recovery of locomotive function after lumbar spinal cord stimulation in combination with gait training with partial weight support in rats with cerebral ischemia

Lumbar spinal cord stimulation (LSCS) is reportedly effective for the recovery of locomotive intraspinal neural network, motor cortex and basal ganglia in animals with complete spinal cord injury and parkinsonism. We evaluated the effect of LSCS in combination with gait training on the recovery of locomotive function and brain plasticity using a rat model of brain ischemia. Adult male Sprague Dawley rats with ischemia were randomly assigned into one of four groups: sham treatment (group 1), LSCS only (group 2), LSCS with gait training and 50% (group 3) and 80% (group 4) of body weight support. Evaluations before randomization and 4weeks after intervention included motor scoring index, real-time PCR and Western blot. Motor scoring index was significantly improved after the intervention in groups 2 and 3. The ratio of phospho-protein kinase C (PKC) to PKC measured in the infarcted area tended to be higher in groups 3 and 4. Protein expression of mGluR2 and mRNA expression of mGluR1 measured in the contralateral cortex were lower in groups 3 and 4. The ratio of phospho-Akt to Akt and mRNA expression of vascular endothelial growth factor measured in the ischemic border zone were higher in group 2. The mRNA expression of MAP1b measured in the infarcted area was significantly higher in group 2. The findings suggest that LSCS and gait training with an adequate amount of body weight support may promote brain plasticity and facilitate the functional recovery.

Body weight support during robot-assisted walking: influence on the trunk and pelvis kinematics.

Efficacy studies concerning robot assisted gait rehabilitation showed limited clinical benefits. A changed kinematic pattern might be responsible for this. Little is known about the kinematics of the trunk and pelvis during robot assisted treadmill walking (RATW). The aim of this study was to assess the trunk and pelvis kinematics of healthy subjects during RATW, with different amounts of body weight support (BWS) compared to regular treadmill walking (TW). Eighteen healthy participants walked on a treadmill, while kinematics were registered by an electromagnetic tracking device. Hereafter, the kinematics of pelvis and trunk were registered during RATW (guidance force 30%) with 0%, 30% and 50% BWS. Compared to TW, RATW showed a decrease in the following trunk movements: axial rotation, anteroposterior flexion, lateral and anteroposterior translation. Besides, a decrease in lateral tilting and all translation of the pelvis was found when comparing RATW with TW. Furthermore, the anteroposterior tilting of the pelvis increased during RATW. In general, there was a decrease in trunk and pelvis movement amplitude during RATW compared with regular TW. Though, it is not known if these changes are responsible for the limited efficacy of robot assisted gait rehabilitation. Further research is indicated.

EMG activity during positive-pressure treadmill running

Success has been demonstrated in rehabilitation from certain injuries while using positive-pressure treadmills. However, certain injuries progress even with the lighter vertical loads. Our purpose was to investigate changes in muscle activation for various lower limb muscles while running on a positive-pressure treadmill at different amounts of body weight support. We hypothesized that some muscles would show decreases in activation with greater body weight support while others would not.Eleven collegiate distance runners were recruited. EMG amplitude was measured over 12 lower limb muscles. After a short warm-up, subjects ran at 100%, 80%, 60%, and 40% of their body weight for two minutes each. EMG amplitudes were recorded during the final 30s of each stage.Most muscles demonstrated lower amplitudes as body weight was supported. For the hip adductors during the swing phase and the hamstrings during stance, no significant trend appeared.Positive-pressure treadmills may be useful interventions for certain injuries. However, some injuries, such as hip adductor and hamstring tendonitis or strains may require alternative cross-training to relieve stress on those areas. Runners should be careful in determining how much body weight should be supported for various injuries to return to normal activity in the shortest possible time.

Patterns of muscle coordination vary with stride frequency during weight assisted treadmill walking

Partial body weight-supported treadmill training is an approach for gait rehabilitation. Variables such as stepping frequency and the amount of body weight support are key parameters manipulated during training. The purpose of this study was to quantify the extent to which body weight support and stride frequency contribute and interact to produce the coordination patterns of the leg muscles. Principal components analysis was used to provide insight into the interaction effects of these factors on electromyographical (EMG) activity during treadmill locomotion. Eight healthy subjects walked on a treadmill at 15 different combinations of weight support (0%, 20%, 40%, 60%, 100%), and stride frequency (0.40, 0.49, 0.57 Hz). Treadmill walking was performed with the Lokomat robotic gait orthosis to constrain leg kinematics. Surface EMG data were collected from several lower limb muscles. Results indicate that much of the variance in EMG activity during treadmill locomotion can be attributed to the mechanics of the locomotor task imposed by the level of body weight support and stride frequency. We also showed that body weight support and stride frequency interact in different ways to affect muscle coordination patterns. EMG coordination patterns are similar between conditions of high levels of body weight support and faster stride frequencies vs. lower levels of body weight support and slower stride frequency. Our data suggest that the interaction of body weight support and stride frequency should be taken into consideration for optimizing motor output during locomotor training.

Walkaround: Mobile Balance Support for Therapy of Walking

We describe here the Walkaround, a new rehabilitation device that allows walking without hand support of individuals with limited ability to control posture. The design of this device was motivated by the recent development of functional electrical therapy of walking in individuals with hemiplegia, who in many cases need postural and body weight assistance while walking. The Walkaround assists humans with a compromised posture, inability to fully support the body weight on one leg, and prevents their falls. These three features are accomplished by an ergonomic lumbar belt being attached to a rigid wheeled frame by a suspensor system. The height of the frame which interfaces the ground by three telescopic bars, the size of the belt, and the pretension of the suspension system, can all be adjusted to complement the size and the needs of the potential user. The amount of body weight support can be adjusted by setting the lengths of telescopic bars and the pretension of the springs in the suspensors. The prototype device was tested on five individuals with hemiplegia. The walking assisted by the Walkaround was significantly faster (Deltav = 0.13 m/s p 0.05) in comparison to walking assisted by a therapist. The symmetry index between paretic and non affected leg was decreased (Delta R(stance) = -7.4% p 0.05, Delta R (swing) =-9.2%, p 0.05, symmetry improved) when walking assisted by the Walkaround. The users and therapists were positive about the performance of the Walkaround. The users felt safer and the therapists were relieved from the physical effort allowing them to concentrate more on assisting - a nearly normal walking pattern.

The human spinal cord interprets velocity-dependent afferent input during stepping.

We studied the motor response to modifying the rate of application of sensory input to the human spinal cord during stepping. We measured the electromyographic (EMG), kinematic and kinetic patterns of the legs during manually assisted or unassisted stepping using body weight support on a treadmill (BWST) in eight individuals with spinal cord injury (SCI). At various treadmill speeds (0.27-1.52 m/s), we measured the EMG activity of the soleus (SOL), medial gastrocnemius (MG), tibialis anterior (TA), medial hamstrings (MH), vastus lateralis (VL), rectus femoris (RF) and iliopsoas (ILIO); the hip, knee and ankle joint angles; the amount of body weight support (BWS); and lower limb loading. The EMG amplitude and burst duration of the SOL, MG, TA, MH, VL, RF and ILIO were related to the step cycle duration during stepping using BWST. EMG mean amplitudes increased at faster treadmill speeds, and EMG burst durations shortened with decreased step cycle durations. Muscle stretch of an individual muscle could not account for the EMG amplitude modulation in response to stepping speed. The effects on the EMG amplitude and burst duration were similar in subjects with partial and no detectable supraspinal input. We propose that the human spinal cord can interpret complex step-related, velocity-dependent afferent information to contribute to the neural control of stepping.