About

Matthew J Major is an Associate Professor at the Feinberg School of Medicine in the Department of Physical Medicine and Rehabilitation. He is also an Associate Professor at the McCormick School of Engineering. His research is associated with the Major Lab - Prosthetics and Orthotics Rehabilitation Assessment Laboratory (PORTAL), which focuses on advancements in prosthetics and orthotics, aiming to improve rehabilitation outcomes. He is affiliated with the Northwestern University Clinical and Translational Sciences Institute (NUCATS).

Research topics

• Medicine
• Physical medicine and rehabilitation
• Surgery
• Physics
• Computer Science
• Physical therapy
• Engineering
• Structural engineering
• Orthodontics
• Nursing
• Anatomy

Selected publications

• Estimation of Recommended Damping Coefficient Range to Achieve Target Peak Knee Flexion in a Passive Prosthetic Knee

  Annals of Biomedical Engineering · 2026-02-16

  article
  PublisherDOI

• State of the art of lower limb prosthesis simulators: A literature review

  RWTH Publications (RWTH Aachen) · 2026-01-01

  articleOpen access
  PublisherDOI

• Effects of ankle-foot prosthesis design on gait and standing performance in transfemoral prosthesis users: A scoping review

  Wearable Technologies · 2026-01-01 · 1 citations

  articleOpen accessSenior authorCorresponding

  Ankle-foot mechanisms are designed to substitute for missing anatomical behavior of lower-limb prosthesis users. Historically, the majority of ankle-foot mechanism research has been focused on transtibial prosthesis users despite evidence that current knowledge is not directly translated to transfemoral prosthesis users, such as the influence of single-axis knee alignment during gait and the differences in standing balance management. This review attempts to characterize the current state of published knowledge about the effects of ankle-foot prosthesis design on standing and walking performance in transfemoral prosthesis users. The databases of PubMed, Embase, Cochrane Library, CINAHL, and IEEE Xplore were searched on January 6, 2025. Data from the selected articles were extracted and reported following the PRISMA extension for scoping reviews. Thirty-five articles were included that reported on seven different types of feet, ranging from simple designs like a solid ankle-cushioned heel (SACH) foot to more complex ones such as a microprocessor foot. The range of reported study tasks extended from standing and level walking to more complex tasks like incline/decline slopes and parcourse walking. The results suggest some parallels between transfemoral and transtibial prosthesis users, such as improvements with the incorporation of roll-over-shape (ROS) features and adaptation of a hydraulic ankle. The literature also emphasized how ankle-foot components affect ground force vector position and direction, influencing prosthetic knee control, highlighting the importance of considering the interaction between the prosthetic ankle-foot and knee mechanisms. Understanding these interactions will support the development of clinical practice guidelines by identifying the pair of prosthetic components that maximizes performance.

  PublisherOA PDFDOI

• State of the art of lower limb prosthesis simulators: A literature review

  Wearable Technologies · 2026-01-01

  articleOpen access

  Individuals with limb loss present significant challenges to testing and evaluating prosthetic devices, such as medical approval processes and participant availability. Prosthesis simulators, designed for mimicking prosthesis use with able-bodied individuals, offer an alternative to conducting controlled experiments and enhancing the development of prosthetic technologies. This review examines the design features, applications, and limitations of lower limb prosthesis simulators. A literature search identified 73 studies that have used lower limb prosthesis simulators. Most studies have focused on transfemoral prosthesis simulators (TFsims) and testing prosthetic designs and control mechanisms. The most frequently assessed movement was walking, while other movements, were explored only sporadically. The findings reveal significant variability in simulator configurations, training protocols, and the range of movements assessed. Additionally, a notable research gap exists in evaluations of the effect of transtibial prosthesis simulators (TTsims) and hip disarticulation prosthesis simulators (HDsims) on gait. Despite these challenges, prosthesis simulators offer promising potential for accelerating and improving prosthesis development while putting less stress on the relatively small target group of individuals with limb loss. Further research is needed to standardize methodologies and better understand the effects of simulator design and training on gait performance to facilitate advancements in prosthetic research.

  PublisherOA PDFDOI

• Mixed methods analysis of an interdisciplinary intervention to promote balance confidence in lower limb prosthesis users

  Frontiers in Rehabilitation Sciences · 2025-09-01 · 1 citations

  articleOpen accessSenior author

  Introduction: Low balance confidence, i.e., low self-perception in ones' ability to maintain balance while performing activities, is prevalent among lower limb prostheses users (LLPUs) and can affect community participation and quality of life (QoL). Although low balance confidence can manifest from poor function, it also depends on one's beliefs in their abilities to engage in activities, which need not reflect actual abilities. Increasing low balance confidence and associated participation limitations requires approaches that address its' physical and psychological underpinnings. Methods: A randomized controlled trial was conducted to evaluate the initial effectiveness of a multicomponent intervention to target balance confidence in LLPU. Nineteen adults with ≥6-months experience using a prosthesis for unilateral, transtibial amputation, and with low balance confidence (Activities-specific Balance Confidence (ABC) scale scores ≤ 80) completed up to eight intervention sessions following an established protocol, which integrated physical therapy exercises (primarily virtual reality active gaming) and cognitive behavioral therapy strategies, or eight weeks of at home-seated exercises. Outcome measures, collected before randomization, and 0- and 16- weeks after completing the intervention/at-home exercises, addressed four domains: (i) balance confidence-the ABC scale, modified Gait Self Efficacy scale and the Fear of Falling Avoidance Behavior Questionnaire; (ii) community participation-sections of the 36-Item Short Form Survey, sections of the Community Reintegration of Injured Servicemembers scale, the Frenchay Activity Index and step counts; (iii) QoL-the wellbeing scale of the Prosthetic Evaluation Questionnaire; and (iv) function-the Berge Balance Sale and the L-Test of walking. Statistical tests compared baseline and post-training assessment scores between groups, and individual responsiveness was evaluated by comparing change scores to minimum detectable change (MDC). Results: Overall, results support the initial efficacy of the intervention, with at least one outcome in 3-of-4 domains (balance confidence, community participation and functional mobility) showing strong, significant group-level effects, or individual-level effects (>30% of participants having changes > MDC). Moreover, semi-structured exit interviews suggest participants perceived benefit from the intervention. Discussion: Integrating physical therapy exercises with cognitive behavioral therapy strategies to simultaneously address physical underpinnings and maladaptive cognitions around low balance confidence can meaningfully improve balance and walking confidence, as well as community participation. To the best of our knowledge the current study is the first to evaluate an intervention to specifically target balance confidence in LLPUs. Clinical Trial Registration: clinicaltrials.gov, identifier NCT03411148.

  PublisherOA PDFDOI

• An Open-Source Wearable System for Real-Time Human Biomechanical Analysis

  Sensors · 2025-05-06 · 1 citations

  articleOpen accessSenior authorCorresponding

  The advancement of inertial measurement unit (IMU) technology has opened new opportunities for motion analysis, yet its widespread adoption in clinical practice remains constrained by the high costs of proprietary systems, lengthy setup procedures, and the need for specialized expertise. To address these challenges, we present a multi-IMU system designed with streamlined calibration, efficient data processing, and a focus on accessibility for patient-facing applications. Although initially developed for human gait analysis, the modular design of this system enables adaptability across diverse motion tracking scenarios. This work outlines the system's technical framework, including protocols for data acquisition, derivation of gait variables, and considerations for user-friendly software deployment. We further illustrate its utility by measuring lower-limb gait kinematics in near-real time and providing stride-to-stride biofeedback using a single sensor. These initial results underscore the potential of this system for both laboratory-based gait assessment and rehabilitation interventions in clinical environments and future work will assess validation against traditional optical motion capture methods.

  PublisherOA PDFDOI

• Estimating the Replicability of Sports and Exercise Science Research

  Sports Medicine · 2025-06-16 · 21 citations

  articleOpen access

  BACKGROUND: The replicability of sports and exercise research has not been assessed previously despite concerns about scientific practices within the field. AIM: This study aims to provide an initial estimate of the replicability of applied sports and exercise science research published in quartile 1 journals (SCImago journal ranking for 2019 in the Sports Science subject category; www.scimagojr.com ) between 2016 and 2021. METHODS: A formalised selection protocol for this replication project was previously published. Voluntary collaborators were recruited, and studies were allocated in a stratified and randomised manner on the basis of equipment and expertise. Original authors were contacted to provide deidentified raw data, to review preregistrations and to provide methodological clarifications. A multiple inferential strategy was employed to analyse the replication data. The same analysis (i.e. F test or t test) was used to determine whether the replication effect size was statistically significant and in the same direction as the original effect size. Z-tests were used to determine whether the original and replication effect size estimates were compatible or significantly different in magnitude. RESULTS: In total, 25 replication studies were included for analysis. Of the 25, 10 replications used paired t tests, 1 used an independent t test and 14 used an analysis of variance (ANOVA) for the statistical analyses. In all, 7 (28%) studies demonstrated robust replicability, meeting all three validation criteria: achieving statistical significance (p < 0.05) in the same direction as the original study and showing compatible effect size magnitudes as per the Z test (p > 0.05). CONCLUSION: There was a substantial decrease in the published effect size estimate magnitudes when replicated; therefore, sports and exercise science researchers should consider effect size uncertainty when conducting subsequent power analyses. Additionally, there were many barriers to conducting the replication studies, e.g., original author communication and poor data and reporting transparency.

  PublisherOA PDFDOI

• Bone Health Deterioration in Transfemoral Prosthetic Users: An Analytical Biomechanical Explanation

  International Journal for Numerical Methods in Biomedical Engineering · 2025-02-01 · 3 citations

  articleOpen access

  There is a five-decade recorded history indicating that persons with transfemoral amputation experience bone loss in their amputated femur at levels seen in bedridden and post-menopausal individuals, irrespective of age or mobility levels. We used computer simulation to recreate the mechanical environment created by the mechanical design of a prosthetic device in the surviving femur of individuals with transfemoral amputations. Finite element models of gait instances were developed from the hip joint computerized tomography scan of a subject along with a coupled ischial containment prosthetic socket fitted as per standard clinical guidelines. Accompanying mirror models, assembled similarly but without the prosthetic socket were used for stimulus comparison. Simulation showed that more than 90% of the trabecular bone volume in the amputated femur with an ischial containment socket registered compressive strain magnitudes below 300με. These strain magnitudes are below the threshold for bone maintenance as per mechanotransduction theory (i.e., they lie within the disuse window). Only 50% of the bone was in the disuse window for the mirror model for the gait instances considered. These results are consistent with reported in vivo evidence which shows that transfemoral prosthesis users may lose bone mass irrespective of age or mobility levels when using traditional socket designs. Clinically, this study shows that prosthetic sockets that support load through the ischium alter the kinetic chain and preclude application of mechanical stimulus that sustains healthy levels of bone mass in the proximal femur. The study also shows that femur length, prosthetic alignment and tissue tone influence this stimulus.

  PublisherOA PDFDOI

• Day-To-Day User Adaptation to a Robotic Ankle-Foot Prosthesis

  2025-05-12

  article

  Adaptation in locomotion of lower limb amputees is essential for effective interaction with assistive devices such as robotic ankle-foot prostheses (AFP), which can provide personalized assistance. Bayesian Optimization (BO) and Human-in-the-Loop (HIL) optimization frameworks have been utilized to personalize device parameters based on user feedback; however, these methods may not always fully consider the dynamic nature of human adaptation. This study investigates day-to-day adaptation to a robotic ankle-foot prosthesis by modeling socket pressure distributions across different AFP stiffness conditions using Gaussian processes. We performed a secondary analysis on data from three unilateral transtibial amputees who participated in a four-day experimental protocol involving discrete parameter sweeps and HIL optimization using BO. Gaussian process models were constructed from data collected on the discrete sweep day and the HIL optimization day. Comparative analyses using Kullback-Leibler (KL) divergence and a mean absolute error (MAE) loss metric revealed subject-specific shifts in optimal stiffness values and changes in the pressure landscape between the two days. The average KL divergence was 1.15, and the MAE loss was 0.59, suggesting adaptations in gait and limb dynamics. These findings suggest the importance of using adaptation in a short time period and personalization methods may need to not only optimize device parameters based on static performance snapshots but also accommodate the dynamic shifts that occur as users adapt over time.

  PublisherDOI

• Koopman Modeling of Human Gait Dynamics for Global Modal Analysis Using Periodic Motion Regularization

  2025-07-08

  article

  This paper presents a data driven global linear model of steady state walking dynamics. Instantaneous whole body angular momentum is a physics informed aggregate quantity used as a marker for dynamic balance during locomotion. Gait dynamics are often modeled as hybrid and nonlinear. We propose using Koopman Operators to model the gait stability dynamics with a global, linear model. This is achieved by augmenting the whole body angular momentum state variables with learned observables, or basis functions, such that the dynamics look linear in the lifted dimension. Considering that the gait dynamics are periodic, a regularization term that encourages the state transition matrix to be orthonormal is added to the loss term when learning the observables. This forces a periodic model to be learned and prevents the likelihood of unstable poles. A low average MSE was obtained over 2 gait cycles for different population types, each with slightly differing gait dynamics. Furthermore, this linear representation enables the use of linear analysis tools that could have clinical implications for assessing the gait of different patient groups.

  PublisherDOI

Recent grants

• Sensory-Motor Mechanisms Underlying Fall Risk in Transtibial Amputees

  NIH · 2014–2020

Frequent coauthors

• Steven A. Gard

  Northwestern University

  82 shared

• Rebecca Stine

  Jesse Brown VA Medical Center

  51 shared

• John T. Brinkmann

  Northwestern University

  39 shared

• Kiley Armstrong

  United States Department of Veterans Affairs

  36 shared

• Martina Lukin

  30 shared

• Stefania Fatone

  University of Washington

  27 shared

• Ryan Caldwell

  Aneurin Bevan University Health Board

  26 shared

• Elizabeth Russell Esposito

  Uniformed Services University of the Health Sciences

  25 shared