Spatiotemporal walking performance in different settings: effects of walking speed and sex.

Background: Understanding the factors that influence walking is important as quantitative walking assessments have potential to inform health risk assessments. Wearable technology innovation has enabled quantitative walking assessments to be conducted in different settings. Understanding how different settings influence quantitative walking performance is required to better utilize the health-related potential of quantitative walking assessments. Research question: How does spatiotemporal walking performance differ during walking in different settings at different speeds for young adults? Methods: Forty-two young adults [21 male (23 ± 4 years), 21 female (24 ± 5 years)] walked in two laboratory settings (overground, treadmill) and three non-laboratory settings (hallway, indoor open, outdoor pathway) at three self-selected speeds (slow, preferred, fast) following verbal instructions. Six walking trials of each condition (10 m in laboratory overground, 20 m in other settings) were completed. Participants wore 17 inertial sensors (Xsens Awinda, Movella, Henderson, NV) and spatiotemporal parameters were computed from sensor-derived kinematics. Setting × speed × sex repeated measures analysis of variance were used for statistical analysis. Results: Regardless of the speed condition, participants walked faster overground when compared to while on the treadmill and walked faster in the indoor open and outdoor pathway settings when compared to the laboratory overground setting. At slow speeds, participants also walked faster in the hallway when compared to the laboratory overground setting. Females had greater cadence when compared to males, independent of settings and speed conditions. Significance: Particularly at slow speeds, spatiotemporal walking performance was different between the settings, suggesting that setting characteristics such as walkway boundary definition may significantly influence spatiotemporal walking performance.

The Associations Among Self-Compassion, Self-Esteem, Self-Criticism, and Concern Over Mistakes in Response to Biomechanical Feedback in Athletes.

Athletes regularly face the possibility of failing to meet expectations in training and competition, and it is essential that they are equipped with strategies to facilitate coping after receiving performance feedback. Self-compassion is a potential resource to help athletes manage the various setbacks that arise in sport over and above other psychological resources. The primary purpose of this research was to explore how athletes respond to objective biomechanical feedback given after a performance. Specifically, we investigated if levels of self-compassion, self-esteem, self-criticism, and concern over mistakes were related to one another before and after a series of sprint tests interspersed with biomechanical feedback, and whether self-compassionate athletes achieved a better sprint performance after receiving and implementing biomechanical feedback. Forty-eight athletes (20 female: M age = 19.8 years, SD = 3.1; 28 male: M age = 23.6 years, SD = 7.8) completed online measures of self-compassion, self-esteem, self-criticism and concern over mistakes before performing four sets of 40-m sprints. Participants received personalized biomechanical feedback after each sprint that compared their performance to gold standard results. Following all sprints, they then completed measures of self-criticism, and reported emotions, thoughts, and reactions. Self-compassion was positively correlated with self-esteem (r = 0.57, p < 0.01) and negatively related to both self-criticism (r = -0.52, p < 0.01) and concern over mistakes (r = -0.69, p < 0.01). We also found that athletes with higher levels of self-compassion prior to sprint performance experienced less self-critical thoughts following biomechanical feedback and subsequent sprint trials (r = -0.38, p < 0.01). Although the results of this study provide some support for the effectiveness of self-compassion in promoting healthy emotions, thoughts, and reactions in response to sprint performance-based biomechanical feedback, a moderated regression analysis between the first and fourth sprint time variables revealed that self-compassion was not a moderator for change in sprint performance (R 2 = 0.64, ΔR 2 = 0.10, p > 0.05). These findings suggest that there are likely longer-term benefits of athletes using self-compassion to cope with biomechanical feedback, but that any benefits might be limited in a short series of sprint trials.

Don't get tripped up: Haptic modalities alter gait characteristics during obstacle crossing.

The attentional capacity required of haptic modalities while obstacle crossing may limit their effectiveness. Therefore, this study examined the attentional demands of haptic modalities during obstacle crossing. Nineteen healthy young adults walked across a 10 m laboratory floor within two modality blocks using either: 1) light touch on a railing, or 2) pulling haptic anchors. Randomly dispersed within these blocks were trials without added haptic input and verbal reaction time (VRT) tasks. VRT was compared across the three walking conditions. Gait characteristics, obstacle crossing stability, and obstacle toe clearance were compared across the three walking conditions (normal walking, light touch walking, anchored walking) and 2 VRT conditions (absence vs. presence). VRTs did not differ according to walking conditions (p > .05). Step length variability for the normal walking condition was significantly greater than for both the light touch and anchored walking conditions (p = .026). Toe clearance for the trail leg was less during light touch than normal walking (p = .020). The presence of the VRT resulted in greater toe clearance for both lead (p = .018) and trail limbs (F(2,34) = 8.053, p = .011). Neither haptic modality required significantly increased attentional demand; however, light touch walking results in less obstacle toe clearance. Haptic modalities likely provide greater benefit than risk to users during obstacle crossing.

The measurement properties of the Lean-and-Release test in people with incomplete spinal cord injury or disease.

OBJECTIVE: To evaluate test-retest reliability, agreement, and convergent validity of the Lean-and-Release test for the assessment of reactive stepping among individuals with incomplete spinal cord injury or disease (iSCI/D). DESIGN: Multi-center cross-sectional multiple test design. SETTING: SCI/D rehabilitation hospital and biomechanics laboratory. PARTICIPANTS: Individuals with motor incomplete SCI/D (iSCI/D). INTERVENTIONS: None. OUTCOME MEASURES: Twenty-six participants attended two sessions to complete the Lean-and-Release test and a battery of clinical tests. Behavioral (i.e. one-step, multi-step, loss of balance) and temporal (i.e. timing of foot off, foot contact, swing of reactive step) parameters were measured. Test-retest reliability was determined with intraclass correlation coefficients, and agreement was evaluated with Bland-Altman plots. Convergent validity was assessed through correlations with clinical tests. RESULTS: The behavioral responses were reliable for the Lean-and-Release test (ICC = 0.76), but foot contact was the only reliable temporal parameter using data from a single site (ICC = 0.79). All variables showed agreement according to the Bland-Altman plots. The behavioral responses correlated with scores of lower extremity strength (0.54, P<0.01) and balance confidence (0.55, P < 0.01). Swing time of reactive stepping correlated with step time (0.73, P < 0.01) and cadence (-0.73 P < 0.01) of over ground walking. CONCLUSIONS: The behavioral response of the Lean-and-Release test is a reliable and valid measure for people with iSCI/D. Our findings support the use of the behavioral responses to evaluate reactive stepping for research and clinical purposes. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02960178.

Ipsilesional Motor Cortex Activation with High-force Unimanual Handgrip Contractions of the Less-affected Limb in Participants with Stroke.

Stroke is a leading cause of severe disability that often presents with unilateral motor impairment. Conventional rehabilitation approaches focus on motor practice of the affected limb and aim to suppress brain activity in the contralesional hemisphere. Conversely, exercise of the less-affected limb promotes contralesional brain activity which is typically viewed as contraindicated in stroke recovery due to the interhemispheric inhibitory influence onto the ipsilesional hemisphere. Yet, high-force unimanual handgrip contractions are known to increase ipsilateral brain activation in control participants, and it remains to be determined if high-force contractions with the less-affected limb would promote ipsilateral brain activation in participants with stroke (i.e., the ipsilesional hemisphere). Therefore, this study aimed to determine how parametric increases in handgrip force during repeated contractions with the less-affected limb impacts brain activity bilaterally in participants with stroke and in a cohort of neurologically intact controls. Participants performed repeated submaximal contractions at 25%, 50%, and 75% of their maximum voluntary contraction during separate functional magnetic resonance imaging brain scans. Brain activation during the tasks was quantified as the percent change from resting levels. In this study, higher force contractions were found to increase brain activation in the ipsilesional (stroke)/ipsilateral (controls) hemisphere in both groups (p = .002), but no between group differences were observed. These data suggest that high-force exercise with the less-affected limb may promote ipsilesional cortical plasticity to promote motor recovery of the affected-limb in participants with stroke.

Evaluating Intrinsic Fall Risk Factors After Incomplete Spinal Cord Injury: Distinguishing Fallers From Nonfallers.

OBJECTIVE: To determine whether performance on measures of lower extremity muscle strength, sensory function, postural control, gait speed, and balance self-efficacy could distinguish fallers from nonfallers among ambulatory individuals with spinal cord injury or disease (SCI/D). DESIGN: Prospective cohort study. SETTING: Community. PARTICIPANTS: Individuals (N=26; 6 female, aged 58.9±18.2y) with motor incomplete SCI/D (American Spinal Injury Association Impairment Scale rating C [n=5] or D [n=21]) participated. Participants were 7.5±9.1 years post injury. Seventeen participants experienced traumatic causes of spinal cord injury. MAIN OUTCOME MEASURES: Participants completed laboratory-based and clinical measures of postural control, gait speed, balance self-efficacy, and lower extremity strength, as well as proprioception and cutaneous pressure sensitivity. Participants were then followed for up to 1 year to track falls using a survey. The survey queried the circumstances and consequences of each fall. If a participant's number of falls equaled or exceeded the median number of falls experience by all participants, they were classified a faller. RESULTS: Median follow-up duration was 362 days and median time to first fall was 60.5 days. Fifteen participants were classified as fallers. Most falls occurred during the morning or afternoon (81%), at home (75%), and while walking (47%). The following laboratory-based and clinical measures distinguished fallers from nonfallers (P<.05): measures of lower extremity strength, cutaneous pressure sensitivity, walking speed, and center of pressure velocity in the mediolateral direction. CONCLUSIONS: There are laboratory-based and clinical measures that can prospectively distinguish fallers from nonfallers among ambulatory individuals with spinal cord injury. These findings may assist clinicians when evaluating their patients' fall risk.

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.

Design characteristics and inclusion of evidence-based exercise recommendation in fall prevention community exercise programs for older adults in Canada: a national descriptive self-report study.

BACKGROUND: Training balance through exercise is an effective strategy to reduce falls in community-dwelling older adults. Evidence-based fall prevention exercise recommendations have been proposed, specifying that exercise programs should: (1) provide a high challenge to balance, (2) be offered for a least three hours per week, (3) be provided on an ongoing basis. Community exercise programs have the potential to deliver effective fall prevention exercise; however, current design characteristics and whether they include the recommendations is not known. This study described design characteristics of fall prevention community exercise programs for older adults (50 years and older) across Canada, and explored whether these programs included the three evidence-based exercise recommendations. METHODS: Instructors of fall prevention community exercise programs completed electronic self-report questionnaires following a modified Dillman recruitment approach. Questions explored program characteristics, exercise content, target population, and program and instructor demographic information. Using a previously developed coding scheme based on recommendations, exercises were coded for balance challenge. RESULTS: One hundred fourty completed eligible questionnaires were analyzed (74% response rate). One hundred thirty-three programs (95%) included the challenge recommendation by prescribing mostly moderate or high challenge balance exercises, 16 programs (11%) included at least three hours of exercise a week, and 59 programs (42%) were offered on an ongoing basis. Eight programs (6%) included all three recommendations. CONCLUSIONS: Most programs included at least one recommendation for effective fall prevention exercise. Future studies should examine organizational barriers and facilitators to incorporating evidence-based exercise recommendations and explore the use of mixed home/in-class strategies to include the recommendations.

Haptic input and balance control: An exploratory study examining normative messaging.

This study examined the effect of descriptive norm messaging information on the relationship between haptic input and balance control. Participants were randomly assigned to either a message group where they balanced with haptic input after receiving a descriptive norm message about the positive effect of haptic input or a control group. Findings from an analysis of covariance revealed a significant difference between the two groups. Those in the descriptive norm message group had better balance control than those in the control group. These findings suggest that efforts designed to improve balance control through haptic input may be enhanced through normative messaging.

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, MOSML, MOSML_SD, MOSAP, and MOSAP_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 MOSML_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.

Trunk balance control during beam walking improves with the haptic anchors without the interference of an auditory-cognitive task in older adults.

BACKGROUND: Prior studies have shown that older adults reduced trunk acceleration when walking on a balance beam with haptic inputs provided by anchors; however, it is unknown whether these benefits would remain in the presence of a concurrent cognitive task. RESEARCH QUESTION: This study aimed to evaluate the effect of a cognitive task on balance control when using the anchors while walking on a balance beam in older adults. METHODS: Thirty older adults participated in this study. They walked on a balance beam under four conditions combining haptic inputs (with and without anchors) and a cognitive task (present and absent). The anchors consisted of a flexible cable with a small load (125 g) attached at the end contacting the ground. Participants held one anchor in each hand and dragged the loads over the ground while walking. In the cognitive task, participants silently counted the number of times they heard a target number within a series of random numbers and provided their response at the end of each trial. Trunk acceleration and normalized step speed were assessed. RESULTS: The anchors reduced the normalized step speed and the trunk acceleration amplitude in the frontal plane when walking on the beam. The cognitive task also diminished the normalized step speed in the beam walking. The use of the anchors did not influence the cognitive task performance. SIGNIFICANCE: Even on a balance beam in the presence of a cognitive task, haptic anchors were able to reduce trunk acceleration in older adults to improve balance control. The cognitive task did not affect the use of haptic anchors.

Reactive balance responses to an unexpected slip perturbation in individuals with incomplete spinal cord injury.

BACKGROUND: Frequent falls while walking among individuals with incomplete spinal cord injury may suggest impairments in reactive balance control; however, reactive balance control during walking has not been studied in this population. The objective was to compare reactive balance control with respect to changes in margin of stability, onset of arm and heel responses, and onset and magnitude of muscle activity following an unexpected slip perturbation in individuals with incomplete spinal cord injury and able-bodied individuals. METHODS: Kinematic and electromyography data were obtained during normal walking and one unexpected slip. Changes in margin of stability following a compensatory or aborted step, onset of arms and trail heel responses, and onset and magnitude of activation of the tibialis anterior, soleus and gluteus medius were calculated. Multivariate analyses compared responses between incomplete spinal cord injury and able-bodied groups. FINDINGS: Data from 16 participants with incomplete spinal cord injury (all American Spinal Injury Association Impairment Scale Grade D, 8 with tetraplegia) and 13 age-and-sex matched able-bodied individuals were included. Individuals with incomplete spinal cord injury demonstrated limited ability to increase margin of stability in the lateral direction during a compensatory or aborted step, and a smaller magnitude of soleus activity compared to able-bodied individuals. INTERPRETATION: There are limitations in reactive balance control of individuals with incomplete spinal cord injury, which may be a reason for the high frequency of falls in this population. Reactive balance assessment should be included as a component of routine balance assessment and fall avoidance strategies in this population.

Adding Light Touch While Walking in Older Adults: Biomechanical and Neuromotor Effects.

Adding haptic input may improve balance control and help prevent falls in older adults. This study examined the effects of added haptic input via light touch on a railing while walking. Participants (N = 53, 75.9 ± 7.9 years) walked normally or in tandem (heel to toe) with and without haptic input. During normal walking, adding haptic input resulted in a more cautious and variable gait pattern, reduced variability of center of mass acceleration and margin of stability, and increased muscle activity. During tandem walking, haptic input had minimal effect on step parameters, decreased lower limb muscle activity, and increased cocontraction at the ankle closest to the railing. Age was correlated with step width variability, stride length variability, stride velocity, variability of medial-lateral center of mass acceleration, and margin of stability for tandem walking. This complex picture of sensorimotor integration in older adults warrants further exploration into added haptic input during walking.

Current state of balance assessment during transferring, sitting, standing and walking activities for the spinal cord injured population: A systematic review.

CONTEXT: Comprehensive balance measures with high clinical utility and sound psychometric properties are needed to inform the rehabilitation of individuals with spinal cord injury (SCI). OBJECTIVE: To identify the balance measures used in the SCI population, and to evaluate their clinical utility, psychometric properties and comprehensiveness. METHODS: Medline, PubMed, Embase, Scopus, Web of Science, and the Allied and Complementary Medicine Database were searched from the earliest record to October 19/16. Two researchers independently screened abstracts for articles including a balance measure and adults with SCI. Extracted data included participant characteristics and descriptions of balance measures. Quality was evaluated by considering study design, sampling method and adequacy of description of research participants. Clinical utility of all balance measures was evaluated. Comprehensiveness was evaluated using the modified Systems Framework for Postural Control. RESULTS: 2820 abstracts were returned and 127 articles included. Thirty-one balance measures were identified; 11 evaluated a biomechanical construct and 20 were balance scales. All balance scales had high clinical utility. The Berg Balance Scale and Functional Reach Test were valid and reliable, while the mini-BESTest was the most comprehensive. CONCLUSION: No single measure had high clinical utility, strong psychometric properties and comprehensiveness. The mini-BESTest and/or Activity-based Balance Level Evaluation may fill this gap with further testing of their psychometric properties.

Modulation of the Hoffmann reflex in the tibialis anterior with a change in posture.

Hoffmann (H-) reflex amplitudes in plantar flexor soleus muscle are modulated by posture, yet dorsiflexor tibialis anterior (TA) H-reflex parameters have sparingly been studied. The purpose was to investigate modulation of the TA H-reflex when postural demands are increased from sitting to standing. In this study, data from 18 participants (Age: 25 ± 4 years, Height: 170.9 ± 9.5 cm, Weight: 75.9 ± 17.2 kg) allowed comparison of two experimental conditions involving different postures (i.e. sitting and standing). Maximal amplitude of the TA H-reflex (Hmax ) as a percent of the maximal M-wave amplitude (Mmax ) (Hmax (% Mmax )) during sitting and standing was compared using ANOVA. Modulation of TA H-reflex amplitude was found: Eleven participants showed facilitation and seven showed no change of reflex amplitudes. Only participants in the facilitation group showed modulation related to changes in posture (sitting: 8.7 ± 2.9%; standing: 14.8 ± 6.7%, P = 0.005). These data provide evidence of the sensitivity to posture of TA H-reflexes. As with task-dependent changes in soleus H-reflexes, presynaptic regulation of Ia afferent transmission is a possible mechanism. Further investigations into causes of modulation are warranted.

To what extent do older adult community exercise programs in Winnipeg, Canada address balance and include effective fall prevention exercise? A descriptive self-report study.

BACKGROUND: Effective fall prevention exercise for community-dwelling older adults requires (i) challenging balance exercise, (ii) offered at least 3 hrs/ week, and (iii) on an ongoing basis, to reduce falls. Community exercise programs are a potential implementation strategy for fall prevention exercise; however, the extent to which they address balance and include effective fall prevention exercise is unknown. Study objectives were to describe program delivery, exercise design, and assessment characteristics of older adult community exercise programs in Winnipeg, Canada; determine if they included effective fall prevention exercise; determine the balance challenge and components of postural control addressed in the most- and least-frequently reported exercises. METHODS: A public inventory of older adult community exercise programs served as the sampling frame for cross-sectional telephone questionnaires exploring program, exercise, and assessment characteristics. Exercises were coded independently by two investigators for balance challenge level and components of postural control. Programs were categorized by number of effective fall prevention exercise components established by evidence-based recommendations. Descriptive statistics were calculated. RESULTS: Thirty-three eligible programs were identified and nine individuals participated. Most programs (n = 5, 56%) identified as general exercise, and two (22%) as fall prevention exercise. Most programs (n = 5, 56%) were offered two or more times/ week and reported exercise intensity as somewhat challenging. Exercise time offered ranged between 1 and 3 h/ week. Assessments were conducted in two programs (22%). Only one program (general exercise) included all components of effective fall prevention exercise. Two programs (22%) included the component of being offered at least 3 hrs/ week. Three programs (33%) included the component of being offered on an ongoing basis. Seven programs (78%) prescribed mostly moderate challenge balance exercise, and one program (11%) prescribed mostly high challenge exercise. Most of the 19 most-frequently prescribed exercises (n = 17, 89%) targeted static stability and none targeted reactive postural control. CONCLUSIONS: Most of the older adult community exercise programs participating in this study did not focus on fall prevention, and did not include all components of effective fall prevention exercise. Future studies should focus on fall prevention programs and explore factors influencing implementation of effective fall prevention exercise components to facilitate planning.

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.

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.

Walking Stability During Normal Walking and Its Association with Slip Intensity Among Individuals with Incomplete Spinal Cord Injury.

BACKGROUND: Ambulatory individuals with incomplete spinal cord injury (iSCI) experience frequent falls suggesting impairments in their balance control. Individuals with iSCI are more stable during normal walking as compared to able-bodied (AB) individuals; however, it is not known whether this increased stability helps prevent hazardous slips. OBJECTIVE: To compare walking stability during normal walking between iSCI and AB individuals, and to study the association between stability during normal walking and the intensity of an unexpected slip perturbation. DESIGN: Cross-sectional. SETTING: Biomechanics of Balance and Movement lab, University of Saskatchewan, Saskatoon. PARTICIPANTS: Twenty iSCI (15 men; age: M = 60.05, SD = 17.77 years) and 16 (12 men; age: M = 58.92, SD = 17.10 years) AB individuals. METHODS: Stability measures during unperturbed walking at a self-selected speed were collected from all the participants. Additionally, stability measures were also collected from 10 of the AB participants walking at a slower speed. An unexpected slip perturbation was recorded in all participants during a self-selected speed trial and peak-slip heel velocity post slip was recorded. MAIN OUTCOME MEASUREMENTS: Measures of stability: ankle co-contraction, required coefficient of friction, walking velocity, foot angle, anteroposterior margin of stability, percentage double support, step length, and step width were compared between iSCI, AB-self selected, and AB-slow walking groups. Associations between slip intensity, indicated by peak post-slip heel velocity, and stability measures were also examined through correlation analysis. RESULTS: Individuals with iSCI walked slower, took shorter steps, and spent a greater percentage of time in double support compared with AB individuals walking at a self-selected pace (P < .01). Slower walking velocity was correlated with slower post-slip velocity in participants with iSCI (P = .01) only. CONCLUSIONS: Individuals with iSCI walk with greater stability than AB individuals during unperturbed walking because of a lower self-selected speed, which appears to reduce the intensity of an unexpected slip perturbation. LEVEL OF EVIDENCE: III.

Haptic information provided by anchors and the presence of cognitive tasks contribute separately to reducing postural sway in young adults.

BACKGROUND: Haptic information provided by the anchors reduces postural sway while standing upright. It is unclear whether this benefit would remain in the presence of cognitive tasks combined with a more challenging postural task. RESEARCH QUESTION: Our aim was to investigate the effects of the anchors and visual and auditory cognitive tasks on postural control in young adults in a challenging balancing task. METHODS: Twenty young adults stood upright on a balance beam with the central portion of each foot placed over the beam and feet at shoulder width without and with the use of the anchors in three cognitive conditions: control, visual Stroop task, and auditory digit-monitoring task. Each anchor consisted of a flexible cable with a light load (125 g) attached at one end of the cable. With the anchors, the participants held the flexible cable in each hand with the light load resting on the ground while keeping tension in the cable. RESULTS: Both visual and auditory cognitive tasks reduced the center of pressure (COP) ellipse area, the root mean square of the margin of dynamic stability (based on the extrapolated center of mass, COM) and increased the COM time-to-contact relative to the boundaries of the base of support in the AP direction. The anchors reduced the COP ellipse area. SIGNIFICANCE: There is a functional integration between postural control and cognitive tasks, such that postural sway was reduced to facilitate the execution of the cognitive tasks. Anchors were effective in reducing postural sway, suggesting that haptic information was able to benefit postural control in a challenging balancing task regardless of the cognitive task.