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Detecting gait events using ground reaction forces (i.e. kinetic detection) is the gold standard, but it is not always possible. Kinematic methods exist; however, accuracy of these methods in stroke survivors during treadmill and overground walking is unknown. Thus, this study compared the accuracy of three kinematic methods during overground and treadmill walking in stroke survivors. Heel strike and toe off were calculated bilaterally using three kinematic methods (horizontal sacral-heel distance, horizontal ankle-heel distance, and horizontal velocity) and a kinetic method for ten stroke survivors. We calculated true and absolute error for each kinematic method relative to the kinetic method to evaluate accuracy. Repeated-measures ANOVAs compared the absolute error between the different methods for each condition. There was a significant effect of method for all conditions except heel strike during treadmill walking. Post hoc tests showed ankle-heel distance detected heel strike with significantly less error than the other methods during overground walking (p < 0.05). Ankle-heel distance identified 93.0% and 77.8% of gait events within 50 ms of the kinetic event for overground and treadmill walking, respectively. Sacral-heel distance detected toe-off with significantly less error than the other methods during overground and treadmill walking (p < 0.05) and identified 87.2% and 90.3% of gait events within 50 ms of the kinetic event for overground and treadmill walking, respectively. Results suggest that ankle-heel distance and sacral-heel distance accurately detect heel strike and toe-off, respectively, in stroke survivors.

Background Kinematic coupling between the first metatarsophalangeal (MTP) and midtarsal joints is evident during gait and other movement tasks, however kinetic foot coupling during walking has not been examined. Furthermore, contributing factors to foot coupling are still unclear. Therefore, the purpose of this study was to investigate kinematic and kinetic coupling within the foot by restricting MTP motion during overground walking. We hypothesized that when the MTP joint was prevented from fully extending, the midtarsal joint would achieve less peak motion and generate less positive work compared to walking with normal MTP motion. Methods Twenty-six individuals participated in this randomized cross-over study. Using motion capture to track motion, participants walked at 1.3 m/s while wearing a brace that restricted MTP motion in a neutral (BR_NT) or extended (BR_EX) position. Additionally, participants walked while wearing the brace in a freely moveable setting (BR_UN) and with no brace (CON). A pressure/shear sensing device was used to capture forces under each foot segment. During stance, peak joint motion and work were calculated for the MTP and midtarsal joints using inverse dynamics. A series of ANOVAs and Holm post hoc tests were performed for all metrics (alpha = 0.05). Results The brace successfully decreased peak MTP motion by 19% compared to BR_UN and CON. This was coupled with 9.8% less midtarsal motion. Kinetically, the work absorbed by the MTP joint (26–51%) and generated by the midtarsal joint (30–38%) were both less in BR_EX and BR_NT compared to BR_UN. Conclusion Implications and sources of coupling between the MTP and midtarsal joints are discussed within the context of center of pressure shifts and changes to segmental foot forces. Our results suggest that interventions aimed at modulating MTP negative work (such as footwear or assistive device design) should not ignore the midtarsal joint.

Background Passive-dynamic ankle–foot orthoses (PD-AFOs) are often prescribed to address plantar flexor weakness during gait, which is commonly observed after stroke. However, limited evidence is available to inform the prescription guidelines of PD-AFO bending stiffness. This study assessed the extent to which PD-AFOs customized to match an individual’s level of plantar flexor weakness influence walking function, as compared to No AFO and their standard of care (SOC) AFO. Methods Mechanical cost-of-transport, self-selected walking speed, and key biomechanical variables were measured while individuals greater than six months post-stroke walked with No AFO, with their SOC AFO, and with a stiffness-customized PD-AFO. Outcomes were compared across these conditions using a repeated measures ANOVA or Friedman test (depending on normality) for group-level analysis and simulation modeling analysis for individual-level analysis. Results Twenty participants completed study activities. Mechanical cost-of-transport and self-selected walking speed improved with the stiffness-customized PD-AFOs compared to No AFO and SOC AFO. However, this did not result in a consistent improvement in other biomechanical variables toward typical values. In line with the heterogeneous nature of the post-stroke population, the response to the PD-AFO was highly variable. Conclusions Stiffness-customized PD-AFOs can improve the mechanical cost-of-transport and self-selected walking speed in many individuals post-stroke, as compared to No AFO and participants’ standard of care AFO. This work provides initial efficacy data for stiffness-customized PD-AFOs in individuals post-stroke and lays the foundation for future studies to enable consistently effective prescription of PD-AFOs for patients post-stroke in clinical practice. Trial Registration: NCT04619043.

Bending stiffness of passive-dynamic ankle–foot orthoses (PD-AFOs) is a functional characteristic thought to restore lost ankle function due to weakened plantar flexors. However, lower extremity impairment profiles of patients are seldom limited to plantar flexion weakness, and PD-AFO characteristics often influence gait in other ways. Combined, all PD-AFO characteristics and patient impairments likely mask the main effect of PD-AFO bending stiffness and complicate the PD-AFO bending stiffness prescription process. In this study, we propose a biomechanical probing paradigm, where customized PD-AFOs with a range of precise stiffness values are worn by healthy subjects, to experimentally test a PD-AFO strength substitution hypothesis while simultaneously documenting gait adaptations to PD-AFO use. Two healthy subjects walked at a scaled velocity while wearing a series of three PD-AFOs that ranged in bending stiffness levels. Supporting the strength substitution hypothesis, peak ankle plantar flexion moments remained unchanged across PD-AFO stiffness conditions. Further biomechanical analyses documented a complex series of ankle related kinematic and kinetic adaptive movement strategies due to PD-AFO use. This study demonstrated the utility of the biomechanical probing paradigm to help understand the contribution of PD-AFO stiffness to ankle strength and its secondary effects on ankle biomechanics.

Background Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study’s purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. Methods After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. Results Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. Conclusions Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.

Stiffness-customized passive-dynamic ankle–foot orthoses (PD-AFOs) have been shown to reduce the mechanical cost of transport (COT) of individuals post-stroke. However, the mechanisms underlying this reduced COT are unknown. Therefore, this study aimed to identify the factors driving COT reduction with PD-AFO use for individuals post-stroke. Results showed that changes in limb work were strongly correlated to changes in COT with the PD-AFO compared to No AFO in the paretic (tau = 0.637, p < 0.001) and non-paretic (tau = 0.621, p < 0.001) limbs. There was also a strong correlation between changes in limb work and changes in COT compared to SOC AFO in the paretic (tau = 0.569, p < 0.001) and non-paretic (tau = 0.503, p = 0.003) limbs. Conversely, changes in stride length and changes in COT were not correlated. Changes in COT between No AFO and PD-AFO were moderately correlated to the number of constituents that performed less mechanical work for both the paretic (tau = −0.462, p = 0.009) and non-paretic (tau = −0.402, p = 0.025) limbs. Compared to walking with SOC AFOs, there was a moderate correlation between COT and the number of constituents in the paretic limb (tau = −0.458, p = 0.011) but not the non-paretic limb (tau = −0.247, p = 0.173). These findings indicate that PD-AFOs reduce COT primarily through small changes in work across many lower limb constituents. Understanding how COT reduction occurs can help optimize PD-AFO design and possibly other rehabilitation interventions for individuals post-stroke.

Purpose of Review Dynamic ankle-foot orthoses (AFOs) are assistive devices that can be prescribed to individuals with mobility limitations to support and align joints. Dynamic AFOs are a category of passive AFOs that can control ankle motion to address both ankle joint range of motion limitations and ankle muscle weakness. This control of motion is achieved through the dynamic AFO’s functional characteristics, namely bending stiffness, which need to be customized to each individual’s needs. However, current conventions for customizing dynamic AFOs for each individual are variable and often not clearly documented. The purpose of this review was to synthesize the current state of customizing functional characteristics of dynamic AFOs to provide a foundation for ultimately optimizing the prescription of AFOs. Recent Findings Dynamic AFO bending stiffness, bending axis, alignment, and footplate design were identified as key functional characteristics that can be customized. Studies showed that customizing these dynamic AFO functional characteristics has the ability to alter gait, and customizing multiple functional characteristics at once is key to improving individual outcomes. Summary Researchers have continued to expand their knowledge on how dynamic AFO functional characteristics can impact individual outcomes. Continued research should work towards developing guidelines for prescribing dynamic AFO functional characteristics based on individuals’ level of needs. Additionally, researchers and clinicians need to work together to ultimately translate these scientific findings into clinical practice.

This work in progress focuses on bringing unmet clinical needs identified in one course into a capstone design course. The goal is to develop working prototypes and applicable research solutions to solve the unmet clinical needs and offer an active biomedical engineering learning opportunity. Clinical Immersion for Engineers is taught over Winter Session (5 week session, Jan-Feb). The students are paired with clinicians in a range of local sites, including hospitals (typically in one specialty area), physical therapy clinics and prosthetic/orthotic practitioners. The students shadow the clinicians, and identify unmet clinical needs. At the end of the term the students present a proposed solution to one of the unmet needs, but the process stops there. One down is that there is no mechanism to easily transition the unmet clinical needs into a design project to address the unmet need. During Senior Design, biomedical engineering (BME) students have the opportunity to work in BME only teams or in interdisciplinary engineering teams (biomedical, civil & environment, computer & electrical, and mechanical engineering). The composition of the teams depends of the project need. The capstone design course is a 6-credit, one-semester engineering design focused course. Traditionally, industrial partners and university researchers sponsored the design projects. The 2014 offering of Senior Design had two projects that came out of the Clinical Immersion course. However there is a prohibiting factor that has kept more clinicians from sponsoring project. The sponsors are required to pay a sponsorship fee to cover administration and maintenance cost of design space. The sponsor is also required to pay prototyping fees. The majority of the clinical collaborators do not have the financial resources to cover these fees. To alleviate this issue the authors applied for and received an NIH R25 Educational Grant. Facilitated by the R25, the 2015 offering of Senior Design has three design projects that are products of the unmet needs identified during the prior offering of Clinical Immersion (anesthesiology, otolaryngology, and sports medicine). During Senior Design the students and clinicians have weekly meeting (phone call or in person) to identify the wants and constraints of the projects, discuss prior art, preliminary design or research concepts, and design iterations. The students shadow the clinician in their respective clinical setting, to gain a better understanding of the complexity of the environment and interview end users. At the end of the course the students present the sponsors with a report that is a full synopsis of their design, a working prototype or research plan, and paths forward. To assess the success of the bridging the unmet clinical needs from Clinical Immersion to Senior Design, the students will be given pre and post surveys and the sponsors will be interviewed. The primary goal of is to evaluate the success of clinical and nonclinical projects in senior design in terms of student preparation, the student’s technical skills, and communication with the clinical community. Technical confidence and strong communication skills with clinical partners are keys to success in the biomedical field.

Purpose – Individuals showing high consumer ethnocentrism (CE) prefer domestic over foreign-made products and their preferences may contribute to barriers to international market entry. Therefore, how to identify such consumers is an important question. Shankarmahesh’s (2006) review reveals inconsistencies in the literature with regard to CE and its antecedents. To shed theoretical and empirical light on these inconsistencies, the purpose of this paper is to contribute two new perspectives on CE: first, a typology that classifies ethnocentric consumers by the extent to which they support government-controlled protectionism and consumer-controlled protectionism; and second, a configurational (recipe) perspective on the antecedents. Design/methodology/approach – The study applies fuzzy-set qualitative comparative analysis of survey data from 3,859 consumers. The study contrasts the findings with findings using traditional statistical hypotheses testing via multiple regression analysis. Findings – The results reveal several configurations of antecedents that are sufficient for consistently explaining three distinct types of CE. No single antecedent condition is necessary for high CE to occur. Practical implications – The findings help global business strategists in their market entry decisions and in their targeting and segmentation efforts. Originality/value – The authors show the value of asymmetrical thinking about the relationship between CE and its antecedents. The results expand understanding of CE and challenge conventional net-effects thinking about its antecedents.