Participants will complete testing on the 3 meter backward test (3MBWT) for 3 trials (pretest). Participants will perform mid-squats on a whole body vibration (WBV) platform. The participant will complete the WBV with the platform next to a wall so they can use the wall for balance if needed. Additionally, supervision or hand held assist will be provided if needed for balance by a licensed physical therapist. After the completion of the WBV session, the participant will complete testing 3MBWT for 3 trials (posttest). All participants will have a gait belt donned the entire time and be closely guarded during every test by a licensed physical therapist. At any point the participant appears unsafe to continue, the protocol will stop immediately. Participants will be given the option to stop and rest when needed.

Participants will complete testing on the 3 meter backward test (3MBWT) for 3 trials (pretest). Participants will perform 5 sets of 60 seconds of mid-squats on level ground. There will be a 1 minute rest in between each set. The participant will complete the mid-squats next to a wall so they can use the wall for balance if needed. Additionally, supervision or hand held assist will be provided if needed for balance by a licensed physical therapist. After the completion of the the mid-squats, the participant will complete testing 3MBWT for 3 trials (posttest). All participants will have a gait belt donned the entire time and be closely guarded during every test by a licensed physical therapist. At any point the participant appears unsafe to continue, the protocol will stop immediately. Participants will be given the option to stop and rest when needed.

WBV is a platform that vibrates while a person stands or sits and performs exercises. The WBV session will consist of 5 sets of 60 seconds set at 6 Hertz (frequency), 3 mm (amplitude) while performing mid-squats. There will be a 1 minute rest in between each set. These parameters were chosen as commonly used parameters in previous studies of WBV in people with PD.

The 3MBWT has excellent intrarater reliability as a backward walking velocity assessment. This standardized measure demonstrates diagnostic accuracy for predicting falls within a year in healthy older adults and people with Parkinson disease. Participants stand with their heel touching a line of tape on the floor and are instructed to initiate backward walking at the verbal cue "start" and to continue until instructed to stop (3 meters) by the tester guarding. The average of 3 trials is the score.