Collaborative robotic biomechanical interactions and gait adjustments in young, non-impaired individuals

A Graded Exposure, Locomotion-Enabled Virtual Reality App During Walking and Reaching for Individuals With Chronic Low Back Pain: Cohort Gaming Design

BACKGROUND

Chronic low back pain (cLBP) can interfere with daily activities, and individuals with elevated pain-related fear (also known as kinesiophobia or the fear of injury due to movement) can develop worse long-term disability. Graded exposure (GEXP) protocols use successive participation in avoided activities to help individuals overcome fearful movement appraisals and encourage activity. We sought to develop a series of GEXP virtual reality (VR) walking and reaching scenarios to increase the exposure and engagement of people with high kinesiophobia and cLBP.

OBJECTIVE

This study aims to (1) determine GEXP content validity of the VR application and (2) determine the feasibility of individuals with cLBP performing locomotion-enabled physical activities.

METHODS

We recruited 13 individuals with cLBP and high pain-related fear to experience six VR modules, which provide progressive movement exposure over three sessions in a 1 week period. At session 1, participants ranked each module by likelihood to avoid and assigned an expected pain and concern for harming their back rating to each module. Participants provided a rating of perceived exertion (RPE) after experiencing each module. To test feasibility, we administered the system usability scale (SUS) and treatment evaluation inventory (TEI) following the final session. In addition, we measured pain and pain-related fear at baseline and follow-up.

RESULTS

The 12 participants who completed the study period assigned higher avoidance (P=.002), expected pain (P=.002), and expected concern (P=.002) for session 3 modules compared with session 1 modules. RPE significantly increased from session 1 (mean 14.8, SD 2.3) to session 3 (mean 16.8, SD 2.2; P=.009). The VR application showed positive feasibility for individuals with cLBP through acceptable SUS (mean 76.7, SD 13.0) and TEI (mean 32.5, SD 4.9) scores. Neither pain (P=.20) nor pain-related fear (P=.58) changed significantly across sessions.

CONCLUSIONS

The GEXP VR modules provided progressive exposure to physical challenges, and participants found the VR application acceptable and usable as a potential treatment option. Furthermore, the lack of significant change for pain and pain-related fear reflects that participants were able to complete the modules safely.

Fore-aft resistance applied at the center of mass using a novel robotic interface proportionately increases propulsive force generation in healthy nonimpaired individuals walking at a constant speed

Background

Past studies have utilized external interfaces like resistive bands and motor-generated pulling systems to increase limb propulsion during walking on a motorized treadmill. However, assessing changes in limb propulsion against increasing resistance demands during self-controlled walking has not been undertaken.

Purpose

We assessed limb propulsion against increasing fore-aft loading demands by applying graded fore-aft (FA) resistance at the center of mass during walking in a novel, intent-driven treadmill environment that allowed participants to control their walking speeds. We hypothesized that to maintain a target speed against progressively increasing resistance, participants would proportionately increase their limb propulsion without increasing vertical force production, with accompanying increases in trailing limb angle and positive joint work.

Methods

Seventeen healthy-nonimpaired participants (mean age 52 yrs., SD = 11) walked at a target, self-controlled speed of 1.0 m/s against 10, 15, 20, and 25% (% body weight) FA resistance levels. We primarily assessed linear slope values across FA resistance levels for mean propulsive force and impulse and vertical impulse of the dominant limb using one-sample t-tests. We further assessed changes in trailing and leading limb angles and joint work using one-way ANOVAs.

Results

Participants maintained their target velocity within an a priori defined acceptable range of 1.0 m/s ± 0.2. They significantly increased propulsion proportional to FA resistance (propulsive force mean slope = 2.45, SD = 0.7, t (16) =14.44, p < 0.01; and propulsive impulse mean slope = 0.7, SD = 0.25, t (16) = 11.84, p < 0.01), but had no changes in vertical impulse (mean slope = − 0.04, SD =0.17, p > 0.05) across FA resistance levels. Mean trailing limb angle increased from 24.3° at 10% resistance to 27.4° at 25% (p < 0.05); leading limb angle decreased from − 18.4° to − 12.6° (p < 0.05). We also observed increases in total positive limb work (F (1.7, 26) = 16.88, p ≤ 0.001, η² = 0.5), primarily attributed to the hip and ankle joints.

Conclusions

FA resistance applied during self-driven walking resulted in increased propulsive-force output of healthy-nonimpaired individuals with accompanying biomechanical changes that facilitated greater limb propulsion. Future rehabilitation interventions for neurological populations may be able to utilize this principle to design task-specific interventions like progressive strength training and workload manipulation during aerobic training for improving walking function.

Electronic supplementary material

The online version of this article (10.1186/s12984-019-0577-x) contains supplementary material, which is available to authorized users.

Walking and balance outcomes for stroke survivors: a randomized clinical trial comparing body-weight-supported treadmill training with versus without challenging mobility skills

Background

Treadmill training, with or without body-weight support (BWSTT), typically involves high step count, faster walking speed, and higher heart-rate intensity than overground walking training. The addition of challenging mobility skill practice may offer increased opportunities to improve walking and balance skills. Here we compare walking and balance outcomes of chronic stroke survivors performing BWSTT with BWSTT including challenging mobility skills.

Methods

Single-blind randomized clinical trial comparing two BWSTT interventions performed in a rehabilitation research laboratory facility over 6 weeks. Participants were 18+ years of age with chronic (≥5 months) poststroke hemiparesis due to a cortical or subcortical ischemic or hemorrhagic stroke and walking speeds < 1.1 m/s at baseline. A hands-free group (HF; n = 15) performed BWSTT without assistance from handrails or assistive devices, and a hands-free plus challenge group (HF + C; n = 14) performed the same protocol while additionally practicing challenging mobility skills. The primary outcome was change in comfortable walking speed (CWS), with secondary outcomes of fast walk speed (FWS), six-minute walk distance, Berg Balance Scale (BBS) scores, and Activities Specific Balance Confidence (ABC) scores.

Results

Significant pre-post improvement of CWS (Z = − 4.2, p ≤ 0.0001) from a median of 0.35 m/s (range 0.10 to 1.09) to a median of 0.54 m/s (range 0.1 to 1.17), but no difference observed between groups (U = 96.0, p = 0.69). Pre-post improvements across all participants resulted in reclassified baseline ambulation status from sixteen to ten household ambulators, three to seven limited community ambulators, and ten to twelve community ambulators. Secondary outcomes showed similar pre-post improvements with no between-group differences.

Conclusions

The addition of challenging mobility skills to a hands-free BWSTT protocol did not lead to greater improvements in CWS following 6 weeks of training. One reason for lack of group differences may be that both groups were adequately challenged by walking in an active, self-driven treadmill environment without use of handrails or assistive devices.

Trial registration

NCT02787759 Falls-based Training for Walking Post-Stroke (FBT); retrospectively registered June 1st, 2016.

Effect of forward-directed aiding force on gait mechanics in healthy young adults while walking faster

BACKGROUND

Forces can be applied to people while they are walking on a treadmill in different ways that aid individuals to walk at faster walking speeds with potentially less effort. Forward-directed aiding forces (FAF) are a special class of aiding forces where "push" or "pull" forces are mechanically applied to the person's pelvis in the forward direction.

OBJECTIVE

To determine if FAF, applied by a robotic interface, can be effective in providing assistance to walk at a faster walking speed with reduced kinetic requirements.

METHODS

Twenty non-neurologically impaired physical active young adults were recruited and biomechanical gait mechanics were measured during walking at two constant treadmill belt speeds (1.0 m/s and 1.6 m/s), with the robotic device in aiding mode to provide FAF (FAF), and also outside of the robotic device (no-FAF). The spatiotemporal gait parameters, anterior-posterior force, sagittal impulse, and hip, knee and ankle power and net work were calculated from kinematic and kinetic data, comparing changes in parameters from slower to faster speeds within each mode, and then, comparing values between each mode.

RESULTS

The spatiotemporal gait parameters were not different between conditions, but in FAF condition, the propulsive force impulse change was not increased, there was smaller propulsion increase, and smaller maximal power generation and ankle work done at the faster speed, whereas all of these parameters were appropriately increased in the no-FAF condition.

CONCLUSIONS

These results indicate that providing FAF at the pelvis is an effective means for reducing the amount of mechanical effort required to walk faster and thus could be used as a training tool to improve walking ability.

A Challenge-Based Approach to Body Weight-Supported Treadmill Training Poststroke: Protocol for a Randomized Controlled Trial

Background

Body weight support treadmill training protocols in conjunction with other modalities are commonly used to improve poststroke balance and walking function. However, typical body weight support paradigms tend to use consistently stable balance conditions, often with handrail support and or manual assistance.

Objective

In this paper, we describe our study protocol, which involved 2 unique body weight support treadmill training paradigms of similar training intensity that integrated dynamic balance challenges to help improve ambulatory function post stroke. The first paradigm emphasized walking without any handrails or manual assistance, that is, hands-free walking, and served as the control group, whereas the second paradigm incorporated practicing 9 essential challenging mobility skills, akin to environmental barriers encountered during community ambulation along with hands-free walking (ie hands-free + challenge walking).

Methods

We recruited individuals with chronic poststroke hemiparesis and randomized them to either group. Participants trained for 6 weeks on a self-driven, robotic treadmill interface that provided body weight support and a safe gait-training environment. We assessed participants at pre-, mid- and post 6 weeks of intervention-training, with a 6-month follow-up. We hypothesized greater walking improvements in the hands-free + challenge walking group following training because of increased practice opportunity of essential mobility skills along with hands-free walking.

Results

We assessed 77 individuals with chronic hemiparesis, and enrolled and randomized 30 individuals poststroke for our study (hands-free group=19 and hands-free + challenge walking group=20) from June 2012 to January 2015. Data collection along with 6-month follow-up continued until January 2016. Our primary outcome measure is change in comfortable walking speed from pre to post intervention for each group. We will also assess feasibility, adherence, postintervention efficacy, and changes in various exploratory secondary outcome measures. Additionally, we will also assess participant responses to a study survey, conducted at the end of training week, to gauge each group's training experiences.

Conclusions

Our treadmill training paradigms, and study protocol represent advances in standardized approaches to selecting body weight support levels without the necessity for using handrails or manual assistance, while progressively providing dynamic challenges for improving poststroke ambulatory function during rehabilitation.

Trial Registration

ClinicalTrials.gov NCT02787759; https://clinicaltrials.gov/ct2/show/NCT02787759 (Archived by Webcite at http://www.webcitation.org/6yJZCrIea)

Minimizing Postural Demands of Walking While Still Emphasizing Locomotor Force Generation for Nonimpaired Individuals

In motor control studies, the interdependent nature of the neural controllers for posture and locomotion makes it difficult to separate components of stepping control from postural maintenance functions. To better understand the separate influences of postural versus locomotor control during walking, we fabricated a novel postural support apparatus. This apparatus was intended to minimize the postural demands of walking but allow for matched locomotor force generation, thus isolating the control of stepping. We tested the ability of this support apparatus to minimize the postural demands of walking tasks for nonimpaired participants ( ) and characterized the behavior of these participants when walking in this environment. We demonstrated that the apparatus reduced trunk motion in flexion/extension, lateral flexion, and transverse rotation, minimized peak vertical ground reaction forces to 15.8% body weight, and reduced total positive and negative work compared to walking with typical postural demands. In addition, using visual feedback, participants were able to successfully match vertical forces during supported walking to those of walking with typical postural demands. We plan to use this apparatus to design future experiments exploring mechanisms underlying postural and locomotor control in both nonimpaired walking and of individuals with impaired coordination of posture and stepping.

Step-by-step variability of swing phase trajectory area during steady state walking at a range of speeds

BACKGROUND

Step kinematic variability has been characterized during gait using spatial and temporal kinematic characteristics. However, people can adopt different trajectory paths both between individuals and even within individuals at different speeds. Single point measures such as minimum toe clearance (MTC) and step length (SL) do not necessarily account for the multiple paths that the foot may take during the swing phase to reach the same foot fall endpoint. The purpose of this study was to test a step-by-step foot trajectory area (SBS-FTA) variability measure that is able to characterize sagittal plane foot trajectories of varying areas, and compare this measure against MTC and SL variability at different speeds. We hypothesize that the SBS-FTA variability would demonstrate increased variability with speed. Second, we hypothesize that SBS-FTA would have a stronger curvilinear fit compared with the CV and SD of SL and MTC. Third, we hypothesize SBS-FTA would be more responsive to change in the foot trajectory at a given speed compared to SL and MTC. Fourth, SBS-FTA variability would not strongly co-vary with SL and MTC variability measures since it represents a different construct related to foot trajectory area variability.

METHODS

We studied 15 nonimpaired individuals during walking at progressively faster speeds. We calculated SL, MTC, and SBS-FTA area.

RESULTS

SBS-FTA variability increased with speed, had a stronger curvilinear fit compared with the CV and SD of SL and MTC, was more responsive at a given speed, and did not strongly co-vary with SL and MTC variability measures.

CONCLUSION

SBS foot trajectory area variability was sensitive to change with faster speeds, captured a relationship that the majority of the other measures did not demonstrate, and did not co-vary strongly with other measures that are also components of the trajectory.

Comparison of Resistance-Based Walking Cardiorespiratory Test to the Bruce Protocol

Hurt, CP, Bamman, M, Naidu, A, and Brown, DA. Comparison of resistance-based walking cardiorespiratory test to the Bruce Protocol. J Strength Cond Res 34(12): 3569-3576, 2020-Cardiorespiratory fitness is assessed through graded exercise tests that determine the maximum amount of sustained mechanical work that an individual can perform while also providing health- and fitness-related information. This article describes a novel method to perform graded exercise tests that use posteriorly directed resistive forces. The purpose of this investigation was to validate a novel resistance-based test (RBT) in comparison with a traditional speed- and incline-based test (SIBT) in a cohort of nonimpaired individuals. Twenty nonimpaired individuals, 8 men and 20 women age 28.4 ± 9.6, range 20-54 years old performed 2 maximal exercise tests. The SIBT used the Bruce Protocol and increased treadmill incline and speed every 3 minutes. The RBT used a robotic device interfaced with the treadmill that provided specified horizontal resistive forces at the center of mass calculated to match each Bruce Protocol stage while individuals walked at 1.1 m·s. Subjects obtained ∼3% higher maximum V[Combining Dot Above]O2 measure using the speed- and incline-based method (dependent t-test p = 0.08). V[Combining Dot Above]O2peaks between tests were strongly correlated (r = 0.93, p < 0.001). Peak values of secondary physiologic measures (i.e., max heart rate and respiratory exchange ratio) were within 3% between tests. We found a significant linear relationship between mass-specific work rate and measured V[Combining Dot Above]O2 stage by stage for both tests, but no significant difference between each linear fit (p = 0.84). These data suggest that horizontal resistive forces, while walking on a treadmill, can be used to increase aerobic effort in a way that closely simulates work rates of the Bruce Protocol.