The effect of light touch on balance control during overground walking in healthy young adults

Dynamic gait stability and stability symmetry for people with transfemoral amputation: A case-series of 19 individuals with bone-anchored limbs

For some individuals with severe socket-related problems, prosthesis osseointegration directly connects a prosthesis to the residual limb creating a bone-anchored limb (BAL). We compared dynamic gait stability and between-limb stability symmetry, as measured by the Margin of Stability (MoS) and the Normalized Symmetry Index (NSI), for people with unilateral transfemoral amputation before and one-year after BAL implantation. The MoS provides a mechanical construct to assess dynamic gait stability and infer center of mass and limb control by relating the center of mass and velocity to the base of support. Before and one-year after BAL implantation, 19 participants walked overground at self-selected speeds. We quantified dynamic gait stability anteriorly and laterally at foot strike and at the minimum lateral MoS value. After implantation, we observed decreased lateral MoS at foot strike for the amputated (MoS mean(SD) %height; pre: 6.6(2.3), post: 5.9(1.3), d = 0.45) and intact limb (pre: 6.2(1.2), post: 5.8(1.0), d = 0.38) and increased between-limb MoS symmetry at foot strike (NSI mean(SD) %; anterior-pre: 10.3(7.3), post: 8.4(3.6), d = 0.23; lateral-pre: 18.8(12.4), post: 12.4(4.9), d = 0.47) and at minimum lateral stability (pre: 28.1(18.1), post: 19.2(6.8), d = 0.50). Center of mass control using a BAL resulted in dynamic gait stability more similar between limbs and may have reduced the adoption of functional asymmetries. We suggest that improved between-limb MoS symmetry after BAL implantation is likely due to subtle changes in individual limb MoS values at self-selected walking speeds resulting in an overall positive impact on fall risk through improved center of mass and prosthetic limb control.

Rollator usage lets young individuals switch movement strategies in sit-to-stand and stand-to-sit tasks

The transitions between sitting and standing have a high physical and coordination demand, frequently causing falls in older individuals. Rollators, or four-wheeled walkers, are often prescribed to reduce lower-limb load and to improve balance but have been found a fall risk. This study investigated how rollator support affects sit-to-stand and stand-to-sit movements. Twenty young participants stood up and sat down under three handle support conditions (unassisted, light touch, and full support). As increasing task demands may affect coordination, a challenging floor condition (balance pads) was included. Full-body kinematics and ground reaction forces were recorded, reduced in dimensionality by principal component analyses, and clustered by k-means into movement strategies. Rollator support caused the participants to switch strategies, especially when their balance was challenged, but did not lead to support-specific strategies, i.e., clusters that only comprise light touch or full support trials. Three strategies for sit-to-stand were found: forward leaning, hybrid, and vertical rise; two in the challenging condition (exaggerated forward and forward leaning). For stand-to-sit, three strategies were found: backward lowering, hybrid, and vertical lowering; two in the challenging condition (exaggerated forward and forward leaning). Hence, young individuals adjust their strategy selection to different conditions. Future studies may apply this methodology to older individuals to recommend safe strategies and ultimately reduce falls.

Human-Human Hand Interactions Aid Balance During Walking by Haptic Communication

Principles from human-human physical interaction may be necessary to design more intuitive and seamless robotic devices to aid human movement. Previous studies have shown that light touch can aid balance and that haptic communication can improve performance of physical tasks, but the effects of touch between two humans on walking balance has not been previously characterized. This study examines physical interaction between two persons when one person aids another in performing a beam-walking task. 12 pairs of healthy young adults held a force sensor with one hand while one person walked on a narrow balance beam (2 cm wide x 3.7 m long) and the other person walked overground by their side. We compare balance performance during partnered vs. solo beam-walking to examine the effects of haptic interaction, and we compare hand interaction mechanics during partnered beam-walking vs. overground walking to examine how the interaction aided balance. While holding the hand of a partner, participants were able to walk further on the beam without falling, reduce lateral sway, and decrease angular momentum in the frontal plane. We measured small hand force magnitudes (mean of 2.2 N laterally and 3.4 N vertically) that created opposing torque components about the beam axis and calculated the interaction torque, the overlapping opposing torque that does not contribute to motion of the beam-walker’s body. We found higher interaction torque magnitudes during partnered beam-walking vs. partnered overground walking, and correlation between interaction torque magnitude and reductions in lateral sway. To gain insight into feasible controller designs to emulate human-human physical interactions for aiding walking balance, we modeled the relationship between each torque component and motion of the beam-walker’s body as a mass-spring-damper system. Our model results show opposite types of mechanical elements (active vs. passive) for the two torque components. Our results demonstrate that hand interactions aid balance during partnered beam-walking by creating opposing torques that primarily serve haptic communication, and our model of the torques suggest control parameters for implementing human-human balance aid in human-robot interactions.

Incremental Visual Occlusion During Split-Belt Treadmill Walking Has No Gradient Effect on Adaptation or Retention

Split-belt treadmills have become an increasingly popular means of quantifying ambulation adaptability. Multiple sensory feedback mechanisms, including vision, contribute to task execution and adaptation success. No studies have yet explored visual feedback effects on locomotor adaptability across a spectrum of available visual information. In this study, we sought to better understand the effects of visual information on locomotor adaptation and retention by directly comparing incremental levels of visual occlusion. Sixty healthy young adults completed a split-belt adaptation protocol, including a baseline, asymmetric walking condition (adapt), a symmetric walking condition (de-adapt), and another asymmetric walking condition (re-adapt). We randomly assigned participants into conditions with varied visual occlusion (i.e., complete and lower visual field occlusion, or normal vision). We captured kinematic data, and outcome measures included magnitude of asymmetry, spatial and temporal contributions to step length asymmetry, variability of the final adapted pattern, and magnitude of adaptation. We used repeated measures and four-way MANOVAs to examine the influence of visual occlusion and walking condition. Participants with complete, compared to lower visual field visual occlusion displayed less consistency in their walking pattern, evident via increased step length standard deviation (p = .007, d = 0.89), and compared to normal vision groups (p = .003 d = 0.81). We found no other group differences, indicating that varying levels of visual occlusion did not significantly affect locomotor adaptation or retention. This study offers insight into the role vision plays in locomotor adaptation and retention with clinical utility for improving variability in step control.

Investigating proactive balance control in individuals with incomplete spinal cord injury while walking on a known slippery surface

BACKGROUND

Up to 83 % of individuals with incomplete spinal cord injury (iSCI) experience ≥ 1 fall/year. Individuals with iSCI employ more cautious walking strategies than able-bodied (AB) individuals during normal walking. Whether individuals with iSCI can use proactive balance strategies to adapt to expected slip perturbations/reduce slip severity while walking has not been previously assessed.

METHODS

19 individuals with iSCI (AIS D; 14 males; 61 ± 18 years) and 17 AB individuals (13 males; 61 ± 18 years) completed 3 walking conditions: normal walking trials, an unexpected slip trial, and expected slip trials. Steel rollers induced a slip in the antero-posterior (AP) direction. Outcome variables included step length, center of mass velocity, foot-floor angle, AP margin of stability, and maximum post-slip velocity (PSV).

RESULTS

The iSCI group used a greater magnitude of cautious strategies (i.e. walking slower with shorter, flatter steps) than AB individuals in all conditions. However, the lack of significant interaction effects indicate that the proactive adaptations compared to normal walking (i.e. walking slower with shorter, flatter steps, and a more anterior xCOM-position) were similar between the two groups (AB & iSCI). Both groups showed a similar rate of adaptation (after just 1 slip) and these feedforward changes were maintained throughout the remaining slip trials which was effective at reducing maximum PSV.

CONCLUSIONS

Individuals with iSCI use proactive balance strategies to adapt to a known slippery surface in a similar manner to AB individuals both in terms of the proportion and timing of adaptation.

Mediolateral damping of an overhead body weight support system assists stability during treadmill walking

BACKGROUND

Body weight support systems with three or more degrees of freedom (3-DoF) are permissive and safe environments that provide unloading and allow unrestricted movement in any direction. This enables training of walking and balance control at an early stage in rehabilitation. Transparent systems generate a support force vector that is near vertical at all positions in the workspace to only minimally interfere with natural movement patterns. Patients with impaired balance, however, may benefit from additional mediolateral support that can be adjusted according to their capacity. An elegant solution for providing balance support might be by rendering viscous damping along the mediolateral axis via the software controller. Before use with patients, we evaluated if control-rendered mediolateral damping evokes the desired stability enhancement in able-bodied individuals.

METHODS

A transparent, cable-driven robotic body weight support system (FLOAT) was used to provide transparent body weight support with and without mediolateral damping to 21 able-bodied volunteers while walking at preferred gait velocity on a treadmill. Stability metrics reflecting resistance to small and large perturbations were derived from walking kinematics and compared between conditions and to free walking.

RESULTS

Compared to free walking, the application of body weight support per-se resulted in gait alterations typically associated with body weight support, namely increased step length and swing phase. Frontal plane dynamic stability, measured by kinematic variability and nonlinear dynamics of the center of mass, was increased under body weight support, indicating reduced balance requirements in both damped and undamped support conditions. Adding damping to the body weight support resulted in a greater increase of frontal plane stability.

CONCLUSION

Adding mediolateral damping to 3-DoF body weight support systems is an effective method of increasing frontal plane stability during walking in able-bodied participants. Building on these results, adjustable mediolateral damping could enable therapists to select combinations of unloading and stability specifically for each patient and to adapt this in a task specific manner. This could extend the impact of transparent 3-DoF body weight support systems, enabling training of gait and active balance from an early time point onwards in the rehabilitation process for a wide range of mobility activities of daily life.

The effects of light touch on gait and dynamic balance during normal and tandem walking in individuals with an incomplete spinal cord injury

STUDY DESIGN

Prospective cross-sectional study OBJECTIVES: To investigate the effect of adding haptic input during walking in individuals with incomplete spinal cord injury (iSCI).

SETTING

Research laboratory.

METHODS

Participants with iSCI and age- and sex-matched able-bodied (AB) individuals walked normally (SCI n = 18, AB n = 17) and in tandem (SCI n = 12, AB n = 17). Haptic input was added through light touch on a railing. Step parameters, and mediolateral and anterior-posterior margins of stability (means and standard deviations) were calculated. Surface electromyography data were collected bilaterally from the tibialis anterior (TA), soleus (SOL), and gluteus medius (GMED) and integrated over a stride. Repeated measures ANOVAs examined within- and between-group differences (α = 0.05). Cutaneous and proprioceptive sensation of individuals with iSCI were correlated to changes in outcome measures that were affected by haptic input.

RESULTS

When walking normally, adding haptic input decreased stride velocity, step width, stride length, MOS_ML, MOS_ML_SD, MOS_AP, and MOS_AP_SD, and increased GMED activity on the limb opposite the railing. During tandem walking, haptic input had no effect; however, individuals with iSCI had a larger step width SD and MOS_ML_SD compared with the AB group. Sensory abilities of individuals with iSCI were not correlated to any of the outcome measures that significantly changed with added haptic input.

CONCLUSIONS

Added haptic input improved balance control during normal but not in tandem walking. Sensory abilities did not impact the use of added haptic input during walking.

Effects of tandem walk and cognitive and motor dual- tasks on gait speed in individuals with chronic idiopathic neck pain: a preliminary study

Introduction: Gait impairment has been associated with neck pain. It is relevant to understand the possible influence of narrow-based walk and an attention-demanding secondary task on gait performance in neck pain.Purpose: To investigate the effects of tandem walk and cognitive and motor dual-tasks on gait speed in persons with chronic idiopathic neck pain (CINP) compared with controls.Methods: A cross-sectional study. Thirty participants with CINP and 30 asymptomatic controls participated in the study. Gait speed was assessed using a timed 10-m walk test at a comfortable pace under four conditions: (1) comfortable walk (as reference); (2) tandem walk (single task); (3) cognitive dual-task walking; and (4) motor dual-task walking. Dual-task interference was calculated.Results: There was no difference in comfortable gait speed between groups (p= 0.40). The CINP group had slower gait speed during the tandem walk than controls (p= 0.02). The dual-task interference on gait speed was not different between groups (p = 0.67 for cognitive, p = 0.93 for motor).Conclusion: Participants with CINP had impaired gait stability during tandem walk. An attention-demanding secondary task did not influence gait speed in individuals with CINP compared to controls. The study suggests that tandem walk could be considered as an assessment tool and part of rehabilitation for neck pain.

Are there attentional demands associated with haptic modalities while walking in young, healthy adults?

STUDY DESIGN

A prospective, observational study.

OBJECTIVES

To assess the attentional demands of using haptic modalities during walking using a multi-task paradigm in young, healthy adults.

SETTING

Biomechanics of Balance and Movement (BBAM) Lab, University of Saskatchewan.

METHODS

Twenty-two (12 male) young, healthy adults performed walking trials with and without a verbal reaction time (VRT) task, as well as with and without the use of haptic anchors and light touch on a railing. Walking performance was evaluated using normalized stride velocity and step width, and dynamic stability was evaluated using step width variability and medial-lateral margin of stability (ML MOS) and its variability.

RESULTS

There were no significant differences in VRT when walking with and without added haptic input and no interactions between the added VRT task and added haptic input. Step width increased and variability of the ML MOS increased during trials with the VRT task compared to trials without the VRT task. The ML MOS decreased when using both haptic tools with a greater decrease when using light touch on the railing compared to when using the haptic anchors. Normalized stride velocity and step width decreased when using light touch on the railing only.

CONCLUSION

Both haptic tools affected stability during walking. Using the railing to add haptic input had a greater effect on walking stability and was the only haptic tool to affect walking performance. Attentional demands should be considered in future research and applications of adding haptic input during walking.

Comparing the effect of haptic modalities on walking balance control: Is using one or two arms better?

BACKGROUND

Adding haptic input by lightly touching a railing or using haptic anchors may improve walking balance control. Typical use of the railing(s) and haptic anchors requires the use of one and two arms in an extended position, respectively. It is unclear whether it is arm configuration and/or the number of arms used or the addition of sensory input that affects walking balance control.

RESEARCH QUESTION

This study examined whether using one arm or two arms to add haptic input through light touch on a railing or using the haptic anchors affects walking balance control.

METHODS

In this study, young adults (n = 24) walked while using (actual use) or pretending to use (pretend use) the railing(s) and haptic anchors with one or two arms. Inertial-based sensors (Mobility Lab, APDM) were used to measure stride velocity, relative time spent in double support (%DS), and peak normalized medio-lateral trunk velocity (pnMLTV).

RESULTS

Using two arms lead to a decrease in pnMLTV compared to using one arm and pnMLTV was lower in the actual use trials compared to the pretend use trials for the anchors only. Stride velocity and %DS did not change between trials when one or two arms were used or when participants actually or pretended to use the haptic tools. Participants walked slower when using the railing compared to the anchors.

SIGNIFICANCE

The importance of considering the number of arms is highlighted in the improved balance control when using two arms with either tool. The augmented sensory input adds to the stabilizing effect of arm configuration for the anchors but not the railings. These results have implications for future research and rehabilitation efforts emphasizing sensorimotor integration to improve walking balance control.