scholarly journals Understanding patient preference in prosthetic ankle stiffness

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Tyler R. Clites ◽  
Max K. Shepherd ◽  
Kimberly A. Ingraham ◽  
Leslie Wontorcik ◽  
Elliott J. Rouse
Keyword(s):  
Patient Preference ◽  
Walking Speed ◽  
Variable Stiffness ◽  
User Preference ◽  
Physiological Factors ◽  
Knee Amputation ◽  
Ankle Stiffness ◽  
Clinical Benefits ◽  
And Performance ◽  
Walking Speeds

Abstract Background User preference has the potential to facilitate the design, control, and prescription of prostheses, but we do not yet understand which physiological factors drive preference, or if preference is associated with clinical benefits. Methods Subjects with unilateral below-knee amputation walked on a custom variable-stiffness prosthetic ankle and manipulated a dial to determine their preferred prosthetic ankle stiffness at three walking speeds. We evaluated anthropomorphic, metabolic, biomechanical, and performance-based descriptors at stiffness levels surrounding each subject’s preferred stiffness. Results Subjects preferred lower stiffness values at their self-selected treadmill walking speed, and elected to walk faster overground with ankle stiffness at or above their preferred stiffness. Preferred stiffness maximized the kinematic symmetry between prosthetic and unaffected joints, but was not significantly correlated with body mass or metabolic rate. Conclusion These results imply that some physiological factors are weighted more heavily when determining preferred stiffness, and that preference may be associated with clinically relevant improvements in gait.

A Compliant Ankle-Foot Orthoses (AFO) Based on Multi-Axial Loading of Superelastic Shape Memory Alloys

2013 ◽  
Author(s):  
Morteza GorzinMataee ◽  
Masood Taheri Andani ◽  
Mohammad Elahinia
Keyword(s):  
Experimental Data ◽  
Axial Loading ◽  
Complex Loading ◽  
Variable Stiffness ◽  
Torsional Stiffness ◽  
Human Gait ◽  
Ankle Stiffness ◽  
Walking Speeds ◽  
Tension Loading ◽  
Foot Disorder

This paper presents a novel actuation solution to address the drop foot disorder. The proposed actuator consists of a superelastic Nitinol rod with a variable torsional stiffness that is adjusted by the controlled application of an axial load. The superelastic SMA element enables the AFO to provide sufficient torque during dorsiflexion to raise the foot. The provided torque at the ankle joint assists the patient in walking more naturally and subsequently prevents further issues such as muscle atrophy. By appraising experimental data of the human gait, ankle stiffness is assessed in order to compare ankle behavior for various walking speeds during the swing phase. The adjustable compliance concept for the AFO is then explained, followed by a description of the actuation mechanism and complex loading configuration. Numerical modeling is also presented for the superelastic element of the AFO under specified multiaxial torsion-tension loading. Simulations are performed in MATLAB and variable stiffness results are compared with experimental data for verification.

scholarly journals Myofascial Release of the Hamstrings Improves Physical Performance—A Study of Young Adults

Healthcare ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 674
Author(s):  
Keisuke Itotani ◽  
Kanta Kawahata ◽  
Wakana Takashima ◽  
Wakana Mita ◽  
Hitomi Minematsu ◽  
...  
Keyword(s):  
Young Adults ◽  
Physical Performance ◽  
Walking Speed ◽  
Quadriceps Muscle ◽  
Lower Limbs ◽  
Joint Movement ◽  
Myofascial Release ◽  
Functional Reach Test ◽  
Hamstring Flexibility ◽  
Walking Speeds

Physical performance is mainly assessed in terms of gait speed, chair rise capacity, and balance skills, and assessments are often carried out on the lower limbs. Such physical performance is largely influenced by the strength of the quadriceps and hamstrings muscles. Flexibility of the hamstrings is important because quadriceps muscle activity influences the hip flexion angle. Therefore, hamstring flexibility is essential to improve physical performance. In this study, Myofascial Release (MFR) was applied to the hamstrings to evaluate its effects. MFR on the hamstrings was performed on 17 young adults. Physical function and physical performance were measured before, immediately after, and 5 days after the MFR intervention: finger floor distance (FFD), range of motion (ROM) of the straight leg raising test (SLR), standing long jump (SLJ), squat jump (SJ), functional reach test (FRT), comfortable walking speeds (C-walking speed), and maximum walking speeds (M-walking speed). The results of the analysis show a significant increase in FFD (−2.6 ± 8.9 vs. 0.4 ± 9.4 vs. 2.4 ± 8.9, p < 0.01), SLJ (185.6 ± 44.5 vs. 185.0 ± 41.8 vs. 196.6 ± 40.1, p < 0.01), and M-walking speed (2.9 ± 0.6 vs. 3.0 ± 0.6 vs. 3.3 ± 0.6, p < 0.01). This study has shown that MFR for hamstrings not only improves flexibility but also increases M-walking speed and physical performance of the SLJ. As MFR is safe and does not involve joint movement, it may be useful for maintaining and improving performance and flexibility during inactivity and for stretching before exercise.

Pedestrian Behavior at Signalized Intersection Crosswalks: Observational Study of Factors Associated with Distracted Walking, Pedestrian Violations, and Walking Speed

2018 ◽  
Vol 2672 (35) ◽  
pp. 1-12 ◽  
Author(s):  
Brendan J. Russo ◽  
Emmanuel James ◽  
Cristopher Y. Aguilar ◽  
Edward J. Smaglik
Keyword(s):  
Traffic Safety ◽  
Walking Speed ◽  
The United States ◽  
Ordinary Least Squares ◽  
Signalized Intersections ◽  
Video Data ◽  
High Definition ◽  
Pedestrian Behavior ◽  
Factors Associated ◽  
Walking Speeds

In the past two decades, cell phone and smartphone use in the United States has increased substantially. Although mobile phones provide a convenient way for people to communicate, the distraction caused by the use of these devices has led to unintended traffic safety and operational consequences. Although it is well recognized that distracted driving is extremely dangerous for all road users (including pedestrians), the potential impacts of distracted walking have not been as comprehensively studied. Although practitioners should design facilities with the safety, efficiency, and comfort of pedestrians in mind, it is still important to investigate certain pedestrian behaviors at existing facilities to minimize the risk of pedestrian–vehicle crashes, and to reduce behaviors that may unnecessarily increase delay at signalized intersections. To gain new insights into factors associated with distracted walking, pedestrian violations, and walking speed, 3,038 pedestrians were observed across four signalized intersections in New York and Arizona using high-definition video cameras. The video data were reduced and summarized, and an ordinary least squares (OLS) regression model was estimated to analyze factors affecting walking speeds. In addition, binary logit models were estimated to analyze both pedestrian distraction and pedestrian violations. Ultimately, several site- and pedestrian-specific variables were found to be significantly associated with pedestrian distraction, violation behavior, and walking speeds. The results provide important information for researchers, practitioners, and legislators, and may be useful in planning strategies to reduce or mitigate the impacts of pedestrian behavior that may be considered unsafe or potentially inefficient.

Online Assortment Optimization with Reusable Resources

2021 ◽  
Author(s):  
Xiao-Yue Gong ◽  
Vineet Goyal ◽  
Garud N. Iyengar ◽  
David Simchi-Levi ◽  
Rajan Udwani ◽  
...  
Keyword(s):  
Optimization Problem ◽  
Online Algorithm ◽  
Random Number ◽  
Optimal Algorithm ◽  
User Preference ◽  
Substitutable Products ◽  
Assortment Optimization ◽  
Myopic Policy ◽  
Expected Revenue ◽  
And Performance

We consider an online assortment optimization problem where we have n substitutable products with fixed reusable capacities [Formula: see text]. In each period t, a user with some preferences (potentially adversarially chosen) who offers a subset of products, St, from the set of available products arrives at the seller’s platform. The user selects product [Formula: see text] with probability given by the preference model and uses it for a random number of periods, [Formula: see text], that is distributed i.i.d. according to some distribution that depends only on j generating a revenue [Formula: see text] for the seller. The goal of the seller is to find a policy that maximizes the expected cumulative revenue over a finite horizon T. Our main contribution is to show that a simple myopic policy (where we offer the myopically optimal assortment from the available products to each user) provides a good approximation for the problem. In particular, we show that the myopic policy is 1/2-competitive, that is, the expected cumulative revenue of the myopic policy is at least half the expected revenue of the optimal policy with full information about the sequence of user preference models and the distribution of random usage times of all the products. In contrast, the myopic policy does not require any information about future arrivals or the distribution of random usage times. The analysis is based on a coupling argument that allows us to bound the expected revenue of the optimal algorithm in terms of the expected revenue of the myopic policy. We also consider the setting where usage time distributions can depend on the type of each user and show that in this more general case there is no online algorithm with a nontrivial competitive ratio guarantee. Finally, we perform numerical experiments to compare the robustness and performance of myopic policy with other natural policies. This paper was accepted by Gabriel Weintraub, revenue management and analytics.

Effects of Varying Overground Walking Speeds on Lower-Extremity Muscle Synergies in Healthy Individuals

Motor Control ◽  
2020 ◽  
pp. 1-18
Author(s):  
Manuel J. Escalona ◽  
Daniel Bourbonnais ◽  
Michel Goyette ◽  
Damien Le Flem ◽  
Cyril Duclos ◽  
...  
Keyword(s):  
Lower Extremity ◽  
Nonnegative Matrix Factorization ◽  
Walking Speed ◽  
Nonnegative Matrix ◽  
Gait Training ◽  
Muscle Synergies ◽  
Training Strategy ◽  
Lower Extremity Muscle ◽  
Walking Speeds ◽  
Weight Acceptance

The effects of walking speeds on lower-extremity muscle synergies (MSs) were investigated among 20 adults who walked 20 m at SLOW (0.6 ± 0.2 m/s), natural (NAT; 1.4 ± 0.1 m/s), and FAST (1.9 ± 0.1 m/s) speeds. Surface electromyography of eight lower-extremity muscles was recorded before extracting MSs using a nonnegative matrix factorization algorithm. Increasing walking speed tended to merge MSs associated with weight acceptance and limb deceleration, whereas reducing walking speed does not change the number and composition of MSs. Varying gait speed, particularly decreasing speed, may represent a gait training strategy needing additional attention given its effects on MSs.

Gait worsening and the microlesion effect following deep brain stimulation for essential tremor

2019 ◽  
Vol 90 (8) ◽  
pp. 913-919 ◽  
Author(s):  
Ryan Roemmich ◽  
Jaimie A Roper ◽  
Robert S Eisinger ◽  
Jackson N Cagle ◽  
Lauren Maine ◽  
...  
Keyword(s):  
Deep Brain Stimulation ◽  
Essential Tremor ◽  
Brain Stimulation ◽  
Repeated Measures ◽  
Walking Speed ◽  
Stimulation Parameters ◽  
Gait Parameters ◽  
Before And After ◽  
Walking Speeds ◽  
Deep Brain

ObjectiveTo investigate the effects of unilateral thalamic deep brain stimulation (DBS) on walking in persons with medication-refractory essential tremor (ET).MethodsWe performed laboratory-based gait analyses on 24 persons with medication-refractory ET before and after unilateral thalamic DBS implantation. Normal and tandem walking parameters were analysed across sessions (PRE-DBS/DBS OFF/DBS ON) by repeated measures analyses of variance. Pearson’s correlations assessed whether changes in walking after DBS were global (ie, related across gait parameters). Baseline characteristics, lead locations and stimulation parameters were analysed as possible contributors to gait effects.ResultsDBS minimally affected gait at the cohort level. However, 25% of participants experienced clinically meaningful gait worsening. Walking speed decreased by >30% in two participants and by >10% in four others. Decreased walking speed correlated with increased gait variability, indicating global gait worsening in affected participants. The worsening persisted even after the stimulation was turned off. Participants with worse baseline tandem walking performance may be more likely to experience post-DBS gait worsening; the percentage of tandem missteps at baseline was nearly three times higher and tandem walking speeds were approximately 30% slower in participants who experienced gait worsening. However, these differences in tandem walking in persons with gait worsening as compared with those without worsening were not statistically significant. Lead locations and stimulation parameters were similar in participants with and without gait worsening.ConclusionGlobal gait worsening occurred in 25% of participants with unilateral DBS for medication-refractory ET. The effect was present on and off stimulation, likely indicating a microlesion effect.

Changes in the Dynamic Stability of Walking in Active Healthy Older Adults Independent of Changes in Walking Speed

2008 ◽  
Author(s):  
Hyun Gu Kang ◽  
Jonathan B. Dingwell
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Dynamic Stability ◽  
Walking Speed ◽  
Age Groups ◽  
Leg Strength ◽  
Age Related ◽  
Increased Risk ◽  
Risk Of Falls ◽  
Walking Speeds

Older adults commonly walk slower, which many believe helps improve their walking stability. However, they remain at increased risk of falls. We investigated how differences in age and walking speed independently affect dynamic stability during walking, and how age-related changes in leg strength and ROM affected this relationship. Eighteen active healthy older and 17 younger adults walked on a treadmill for 5 minutes each at each of 5 speeds (80–120% of preferred). Local divergence exponents and maximum Floquet multipliers (FM) were calculated to quantify each subject’s responses to small inherent perturbations during walking. These older adults exhibited the same preferred walking speeds as the younger subjects (p = 0.860). However, these older adults still exhibited greater local divergence exponents (p&lt;0.0001) and higher maximum FM (p&lt;0.007) than young adults at all walking speeds. These older adults remained more unstable (p&lt;0.04) even after adjusting for declines in both strength and ROM. In both age groups, local divergence exponents decreased at slower speeds and increased at faster speeds (p&lt;0.0001). Maximum FM showed similar changes with speed (p&lt;0.02). The older adults in this study were healthy enough to walk at normal speeds. However, these adults were still more unstable than the young adults, independent of walking speed. This greater instability was not explained by loss of leg strength and ROM. Slower speeds led to decreased instability in both groups.

scholarly journals Control Reference Parameter for Stance Assistance Using a Passive Controlled Ankle Foot Orthosis—A Preliminary Study

2019 ◽  
Vol 9 (20) ◽  
pp. 4416 ◽  
Author(s):  
Dimas Adiputra ◽  
Mohd Azizi Abdul Rahman ◽  
Ubaidillah ◽  
Saiful Amri Mazlan ◽  
Nurhazimah Nazmi ◽  
...  
Keyword(s):  
Body Mass Index ◽  
Body Mass ◽  
Standard Error ◽  
Walking Speed ◽  
Parameters Estimation ◽  
Ankle Foot Orthosis ◽  
Preliminary Study ◽  
Reference Parameters ◽  
Walking Speeds ◽  
Foot Orthosis

This paper aims to present a preliminary study of control reference parameters for stance assistance among different subjects and walking speeds using a passive-controlled ankle foot orthosis. Four young male able-bodied subjects with varying body mass indexes (23.842 ± 4.827) walked in three walking speeds of 1, 3, and 5 km/h. Two control references, average ankle torque (aMa), and ankle angular velocity (aω), which can be implemented using a magnetorheological brake, were measured. Regression analysis was conducted to identify suitable control references in the three different phases of the stance. The results showed that aω has greater correlation (p) with body mass index and walking speed compared to aMa in the whole stance phase (p1(aω) = 0.666 > p1(aMa) = 0.560, p2(aω) = 0.837 > p2(aMa) = 0.277, and p3(aω) = 0.839 > p3(aMa) = 0.369). The estimation standard error (Se) of the aMa was found to be generally higher than of aω (Se1(aMa) = 2.251 > Se1(aω) = 0.786, Se2(aMa) = 1.236 > Se2(aω) = 0.231, Se3(aMa) = 0.696 < Se3(aω) = 0.755). Future studies should perform aω estimation based on body mass index and walking speed, as suggested by the higher correlation and lower standard error as compared to aMa. The number of subjects and walking speed scenarios should also be increased to reduce the standard error of control reference parameters estimation.

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