There was no funding for the device to be used in the study.

Some individuals with Parkinson disease experience "freezing" during walking which results in their inability to move their feet. They often have difficulty starting to move once they have stopped. Freezing often results in loss of balance and falling. Oral medications for Parkinson disease aren't as effective in treating freezing as it is in reducing other symptoms. Another treatment for freezing is instruction in walking using visual targets or auditory cues (thinking of a rhythm or beat). These cues can be initially effective for some individuals, but the effects do not last. Other types of cues have not been studied. We want to examine the effects of two other cues, tactile (touch) or motor (muscle contraction), on the effects of freezing.

We will use a device (TENS unit) that provides electrical stimulation to a nerve in the lower legs. Electrodes will be placed on the skin of your lower legs and a box that delivers electrical current will cause a tingling feeling in the legs. Subjects will be asked to perform three gait tasks with the device on and off to compare the effects of the sensory cue on the speed/time to complete gait tasks and the frequency and duration of any freezing events. This use of the device (TENS unit) is investigational. While it has been approved by the Food and Drug Administration for the treatment of pain, it has not been approved for the treatment of freezing. Because the TENS unit can provide a sensory cue, it may help to prevent or reduce freezing. If it is found that this cue works, it could lead to new treatments for the treatment of freezing.

Inclusion Criteria:

1. PD diagnostic criteria include those used for clinically defined "definite PD", as previously outlined22 based upon established criteria.22, 23
2. history of consistent freezing with ambulation in a straight line and/or when turning.
3. normal central and peripheral neurological function
4. at least grade 4 strength and normal joint ranges of motion in both legs
5. normal somatosensory function in the feet (joint position sense), except for their neurological diagnosis and use of levodopa.
6. Each must have had clear benefit from levodopa for at least some of his/her PD symptoms
7. All subjects with PD must be able to walk independently for 10 feet.

Exclusion Criteria:

1. serious medical problem that would impair the ability to undergo testing.
2. use of neuroleptic or other dopamine-blocking drug
3. use of drugs that might affect balance
4. history or evidence of other neurological deficit that could interfere, such as previous stroke or muscle disease
5. participants who are unable to provide informed consent