Split-belt Treadmill Training to Rehabilitate Freezing of Gait and Balance in Parkinson's Disease

Parkinson's disease (PD) related gait and balance disorders are challenging to treat because they cannot be optimized with pharmacological intervention alone. This treatment gap is important to address because gait asymmetry and incoordination are associated with increased falls in this population, which can be functionally debilitating and lead to increased morbidity and mortality. Freezing of gait (FOG) has also been associated with reduced quality of life independent of its association with impaired mobility. Gait disorders therefore represent an unmet need in the treatment of PD. A split-belt treadmill (SB-TM) can be used to adjust the speed of each leg separately and individuals can be prompted to 'adapt' to an asymmetric gait and 're-adapt' with return to symmetrical gait in a phenomenon known as 'after-effect'.

Parkinson's disease (PD) related gait and balance disorders are challenging to treat because they cannot be optimized with pharmacological intervention alone. This treatment gap is important to address because gait asymmetry and incoordination are associated with increased falls in this population, which can be functionally debilitating and lead to increased morbidity and mortality. Freezing of gait (FOG) has also been associated with reduced quality of life independent of its association with impaired mobility. Gait disorders therefore represent an unmet need in the treatment of PD.

Physiotherapy with treadmill training is a means to address the limitations of pharmacotherapy in this population. Treadmill training increases stride length, lowers cadence and improves foot clearance; long-term treadmill training results in clinically improved gait velocity and postural stability. The advent of SB-TM training can further optimize the gait instability that arises from asymmetric pathology in this population. The SB-TM has 2 belts, which can either move in unison (tied) or at different speeds (split), and it has been effective in restoring symmetrical gait in the stroke population, with gait adaptations retained for up to 3 months. The motor symptoms in PD develop asymmetrically, with the burden of symptoms often lateralizing to one side, so the SB-TM offers a unique opportunity to modulate spatial and temporal gait parameters to study gait adaptation in the PD population.

Split-belt treadmill training uses the concept of adaptive learning, which is error-driven motor leaning in response to changes in the external environment. It can be used to target specific gait deviations, and preliminary research has indicated that it can improve gait disorders in PD by decreasing limb asymmetry. Adaptive learning occurs when there is an adjustment of leg-speed perception during locomotor movement. When using a split-belt treadmill (SB-TM) to adjust the speed of each leg, the step length and double support time during gait can be manipulated. Individuals can therefore be prompted to 'adapt' to the asymmetric gait (e.g., the leg walking on a slow belt will take longer steps to accommodate to the leg walking on the faster belt) and 're-adapt' with return to symmetrical gait.

This method of rehabilitation can therefore be used to treat a range gait abnormalities and previous research has demonstrated the ability to restore symmetrical gait and reduced falls for up to 3 months in the stroke population. A preliminary study from our lab in individuals with PD and FOG demonstrated that velocity reduction by 25% on the least affected side resulted in a more symmetric and coordinated gait after 10 minutes of SB-TM training.

Eligibility Criteria:
Inclusion Criteria:

1. Idiopathic PD
2. Hoehn \& Yahr Stage 2-3, on levodopa
3. FOG, resistant to dopaminergic therapy
4. Disease duration: 5-15 years
5. Stable clinical response to medications or stimulation parameters (in case of DBS) for at least 3 months
6. MMSE \>24/30
7. Able to walk on a motor-driven treadmill

Exclusion Criteria:

1. Severe imbalance that limits ambulation (Hoehn \&Yahr score above 3)
2. Orthopedic conditions and other systemic disease affecting locomotion
3. Cardiac conditions limiting the ability to walk uninterrupted for 1 hour
4. Presence of other neurological disorder
5. Inability to be fluent in English