Walking Function in Diabetic Peripheral Neuropathy

A clinical evaluation occurs at the first study session. The clinical evaluation assesses walking function and mobility, lower extremity, sensation, health-related quality of life (HRQoL) and foot function. Session 2 will be a dynamometer-based evaluation of passive ankle stiffness and 3-dimensional gait analysis to evaluate baseline biomechanics. During Session 3, real-time biofeedback conditions will be used to measure the immediate effects on walking function.

Participants will be seated in a dynamometer with their trunk and thigh stabilized to the dynamometer chair, ankle joint aligned with the rotational axis of the dynamometer, and foot stabilized to the foot plate. EMG activity will be recorded from lower limb muscles (gastrocnemius, soleus, tibialis anterior) during all isolated contractions. Participants will first perform three maximum voluntary isometric contractions (MVIC) while seated in a dynamometer. Participants will then perform three isokinetic dorsiflexion tasks while using electromyographic biofeedback at a prescribed level of 50% MVIC soleus activation. The slope of the linear best fit line from the ankle moment vs. angle plot will yield total ankle joint stiffness (i.e., active + passive) at a fixed activation. In three additional trials, the dynamometer will move the ankle joint through the same motion without active subject resistance and the same analytical procedures will derive passive ankle joint stiffness.

Three-dimensional gait analysis is performed as participants walk at a self-selected speed on an instrumented treadmill. Reflective markers are attached to lower extremity segments. Elastic bands are wrapped around the thighs, calves, and pelvis to which small, thermoplastic shells containing reflective markers are attached. Additional markers are taped to the participant's shoes and on the upper back, shoulder, hip, knee, and ankle joints with adhesive skin tape. Marker data is collected using a 7-camera motion analysis system (Vicon Inc., USA). Vicon motion analysis cameras will collect the location of the retroreflective markers in Vicon Nexus software.

Audio-visual biofeedback will be provided using a screen placed in front of the treadmill and a speaker. For plantar pressure biofeedback, a visual display of a foot with a colored heat map will represent the current plantar pressure, in addition to bar graphs representing real-time movement of plantar pressure in specific areas of the foot. A target will be provided using the heat map colors of red and target line on the bar graph. For propulsion biofeedback, a visual display with a marker will represent the current propulsion (peak AGRF) and a target provided to modulate propulsion. The plantar pressure and AGRF measurements from the participant's baseline walking trials will be used to determine customized biofeedback targets.

Participants will complete a 3-dimensional gait evaluation prior to training, after a 6-minute control bout without biofeedback, and following three 6-minute biofeedback training bouts (total 18-minutes). Individualized biofeedback targets will be calculated from each participant's immediate biofeedback session to best minimize plantar pressure whilst maintaining or enhancing propulsion. Audio-visual biofeedback is provided using a screen placed in front of the treadmill and a speaker. For plantar pressure biofeedback, a visual display of a foot with a colored heat map represents the current plantar pressure, in addition to bar graphs representing real-time movement of plantar pressure in specific areas of the foot. A target is provided using the heat map colors of red and target line on the bar graph. Participants are informed that the target is a measurement of the pressure under their foot, and their goal is to decrease pressure to achieve their target.

Participants will complete a 3-dimensional gait evaluation prior to training, after a 6-minute control bout without biofeedback, and following three 6-minute biofeedback training bouts (total 18-minutes). Individualized biofeedback targets will be calculated from each participant's immediate biofeedback session to best minimize plantar pressure whilst maintaining or enhancing propulsion. Audio-visual biofeedback is provided using a screen placed in front of the treadmill and a speaker. For propulsion biofeedback, a visual display with a marker represents the current propulsion (peak AGRF) and a target provided to modulate propulsion. Participants are informed that the marker is a measurement of how hard they are pushing the ground backward, and their goal is to push-off more to achieve their target.