Variability of Practice and its Application to Locomotor Adaptation

Jake Hinkel-Lipsker, M.S.

The concept of increasing practice difficult enhancing motor learning has been demonstrated in the learning of many different motor skills, from reaching to shooting a basketball. However, in the case of gait, the effects of increasing practice difficulty on gait training and rehabilitation are largely unknown. This is likely the case due to two reunknownasons: (1) gait is an inherently continuous task, and (2) is controlled through both spinal and supraspinal pathways. Recent research has revolved around split-belt treadmill walking, where an individual with a healthy
gait walks on a treadmill with two belts (one under each foot). When the belts are driven at different speeds, this causes an asymmetrical gait, which is novel to a healthy individual, allowing for learning to be measured over time. It has been shown that a serial blocked introduction of asymmetry is more effective on measures such as balance control and cognitive demand than a constant introduction (and considered more challenging). Thus, the purpose of this ongoing study is to collect biomechanical data to quantify learning as individuals are introduced to gait asymmetries according to either a serial, random blocked, or random protocol. This will allow for future application to rehabilitation of unilateral gait deficiencies, such as those who have suffered from limb loss or stroke.


Hinkel-Lipsker JW & Hahn ME. Novel kinetic strategies adopted in asymmetrical split-belt treadmill walking. Journal of Motor Behavior 48(3), 209-217, 2016.

Hinkel-Lipsker JW & Hahn ME. A method for automated control of belt velocity changes with an instrumented treadmill. Journal of Biomechanics 49(1), 132-134, 2015.


Lower Extremity Joint Stiffness, Energy Generation, and Transfer in Walking and Running Gait

Li Jin, M.S.                                                                                                                      

Walking and running are common daily life activities for human beings. For individuals with unilateral lower limb amputation, participation in walking and running activities pose both physical and mental challenges for them. Investigation of lower extremity gait mechanics in both able-bodied individuals and unilateral lower limb amputees would help lay a foundation to improve future prostheses development. For walking and running gait, lower extremity joint stiffness, energy generation and transfer are important parameters for speed change, gait transition and performance. Up to now little is known about the relationship between these parameters in walking and running, as well as the transition between them. The overall goal of the project is to identify the characteristics of lower extremity joints stiffness, energy generation and transfer mechanisms during walking and running gait, as well as the transition in both able-bodied individuals and lower limb amputees. The primary research question of the study is: can gait performance be enhanced when the locomotion task and speeds change?


Increasing Forefoot Function to Improve Economy in Elite Runners

Evan Day, M.S.                                                                                                  IIIIIII     

For an athlete to run faster, they have to either increase their stride rate or increase their stride length. To increase their stride length, the athlete needs to deliver more force into the ground, increasing the propulsive impulse. Current research investigating training of the toe-flexor muscles that cross the metatarsophalangeal joint of the forefoot show that these muscles do significantly hypertrophy in response to strength training protocols. The purpose of this project is to investigate if strengthening of the toe-flexors results in an increase in propulsive impulse during running at race speeds. This increase in propulsive impulse should theoretically result in an increase in stride length, resulting in less strides needed to cover a set distance, making the runner more economical. Intended future directions of this project will also examine midsole modifications to effectively improve forefoot function. Results from this research can be used by runners of all levels that desire to improve their race times.



Analysis of Unique Myoelectric Characteristics in Lower-Extremity Musculature during Locomotive State Transitions

Bryson Nakamura, Ph.D.
Research Profile - EMG Study both

Understanding the neural input to human gait has widespread ramifications in furthering rehabilitation, athletic performance, and the development of human-machine interfaces. Though mechanisms for assessing neural input are abundant, electromyography (EMG) remains the simplest. Research in EMG of gait has yielded fruitful information regarding speed, movement type, transitions, and locomotion type. In prosthetics research, these studies aim to allow amputees to ambulate with minimal complications. A specific area of need is in locomotive state transitions where amputees must transition between different locomotion types (i.e. stairs or ramps to level-ground walking). Though EMG characteristics have been established during each locomotive state, individually, research into transitions between locomotive states remains incomplete. Identification of EMG characteristics unique to locomotor transitions may aid in classification algorithm development for powered lower-extremity prostheses.

Objective Surgical Decisions & the Use of Ankle-Foot Orthotics for End-Stage Ankle Osteoarthritis

Shannon Pomeroy, M.S.
in collaboration with the Slocum Center for Orthopedics & Sports Medicine

Pomeroy_Research Profile

Ankle arthritis is most commonly triggered following trauma in the ankle, leading to altered kinematics and irreversible damage of the articular cartilage alongside worsening pain, stiffness, and quality of life. The end stages often result in surgical interventions such as ankle replacements or a fusion of the damaged articulations (Fig A). However, the immobility and instability at the ankle following a joint fusion is not ideal and detrimental compensations at surrounding joints can cause further complications long-term. Furthermore, the current surgical decisions for these patients are largely subjective and lack quantifiable parameters for such decisions. Thus, our work in this field is focused primarily on comparing the biomechanical, clinical, and anthropometric measures prior to surgery and following fusion in these patients in order to pinpoint objective measures to improve the effectiveness of both procedures. In addition, our group is introducing and observing a rigid ankle-foot orthosis on these patients (Fig B), an external bracing approach designed to restrict ankle motion, prior to their fusion to further advance our understanding of the mechanisms and etiology of ankle fusion outcomes.

Optimizing Stiffness in a Multi-Component Prosthetic Foot

Li Jin, M.S.                                                                                                                          

Lower limb amputation has been associated with secondary impairments such as knee osteoarthritis in the uninvolved limb. Greater frontal plane knee loading has been related to severity and rate of progression in knee OA. Reduced push-off work from the involved limb can increase uninvolved limb knee loading. Material stiffness and locomotion speeds can both affect uninvolved limb knee loading. The damping effect of foam or rubber cushions in prosthetic systems dissipates some of the energy that flows into the prostheses, reducing overall energy return. However, it is unknown whether this reduced energy return lead to increased uninvolved limb knee loading at similar levels of stiffness. The purpose of the study was to determine the relative effects of damping on prosthetic foot energy return and uninvolved limb knee loading.



Jin, L., Adamczyk, P.G., Roland, M., Hahn, M.E. The effect of high and low-damping prosthetic foot structures on knee loading in the uninvolved limb across different walking speeds. Journal of Applied Biomechanics, 32, 233-240, 2016.