Characterization and Clinical Trial of a Variable Friction Shoe

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Shirley Ryan AbilityLab


Not yet enrolling




Device: Ankle Foot Orthosis (AFO) Training
Device: Variable Friction Shoe Training

Study type


Funder types



1R01HD112475-01 (U.S. NIH Grant/Contract)

Details and patient eligibility


More than one million Americans present with foot drop after stroke. As the aging population grows in the United States and across the world, incidence of stroke will grow as age is a key risk factor, thus there will be a need for low-cost, easy-to-use, and scalable solutions to administer proper therapy to promote recovery. This study will evaluate a Variable Friction shoe (VF shoe), a new low-cost medical device, for foot drop in an at-home setting.

Full description

The investigators propose an alternative strategy that addresses the hazard of tripping even while allowing full volitional control of the ankle: an inexpensive Variable Friction (VF) shoe. Its outsole is high-friction during the stance phase of gait and low friction during swing; further, it produces a "click" when a scuff occurs. The investigator's central hypothesis is that allowing volitional motion of the ankle while mitigating the hazard of tripping coupled with gait-phased auditory biofeedback will result in improved gait for subjects with drop foot. Specifically, the investigators hypothesize that the VF shoe will show significantly greater therapeutic effects than an AFO, yet maintain the desirable orthotic effect of the AFO. The study is arranged in two Aims. Specific Aim 1: Characterize the scuff-force reduction of the VF shoe over the lifetime of use. Critical to understanding the effects of the VF shoe is a characterization of the level of scuff-force reduction. Specific Aim 2: Evaluate the effects of the VF shoe on gait in individuals with chronic stroke and drop foot. During each 12-week phase of an AB-BA clinical trial, participants will walk for at least 30-45 minutes per day for at least 5 days per week at home.


50 estimated patients




18+ years old


No Healthy Volunteers

Inclusion criteria

  1. 3 months - 1-year poststroke (the period in which patients would typically be fitted with a device for foot drop)
  2. Age 18 or older
  3. Possess a prescribed AFO or be a potential candidate for use of an AFO
  4. Can ambulate at least 10m with or without an assistive device such as a cane or walker
  5. Medically stable as determined by physician medical clearance
  6. No expected change in medications for at least 3 months
  7. Adequate stability at the ankle during stance
  8. Ability to hear clicking noise made by the VF shoe
  9. Physician approval
  10. Ability to give informed consent
  11. Able to sit unsupported and be able to follow a three-step command
  12. No unhealed/unresolved orthopedic injury to either upper or lower extremity and no history of severe back pain
  13. English speaking
  14. Willing to follow an exercise program with both devices for at least 30 minutes per day, at least 5 days per week for the full length of the program (6 months)

Exclusion criteria

  1. History of falling more than once a week prior to the stroke
  2. Gait speed: self-selected velocity (SSV) greater than 1.2 m/s
  3. Inability to operate in the devices safely and no caregiver assistance available
  4. Morbid obesity (body mass index >40 kg/m2)
  5. Preexisting conditions such as serious cardiac conditions, myocardial infarction, congestive heart failure, demand pacemaker, seizures, excessive dysesthetic pain, and severe lower extremity pathology that would interfere with fit or use of the shoe.
  6. Severe deficits in cognition or communication
  7. Pregnant women (status determined by self-reporting).
  8. Co-morbidity that interferes with the study (e.g. significant arthritis or joint problems, history of back injury, neuromuscular disorders, epilepsy, etc.).
  9. Severe Osteoporosis (status determined by self-reporting).
  10. Prisoners

Trial design

Primary purpose




Interventional model

Crossover Assignment


Single Blind

50 participants in 2 patient groups

Arm AB: Variable Friction Shoe Training, AFO Training
Experimental group
Baseline (T0), 12 weeks Variable Friction Shoe Training, Follow-up (T1), 2-week washout, Follow-up (T2), 12 weeks AFO Training, Follow-up (T3)
Device: Variable Friction Shoe Training
Device: Ankle Foot Orthosis (AFO) Training
Arm BA: Ankle Foot Orthosis (AFO) Training, Variable Friction Shoe Training
Experimental group
Baseline (T0), 12 weeks AFO Training, Follow-up (T1), 2-week washout, Follow-up (T2), 12 weeks Variable Friction Shoe Training, Follow-up (T3)
Device: Variable Friction Shoe Training
Device: Ankle Foot Orthosis (AFO) Training

Trial contacts and locations



Central trial contact

Joe Harris, DPT; Sara Prokup, DPT

Data sourced from

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