Split-Belt Adaptation and Savings in People With Parkinson Disease

Upper extremity studies suggest that implicit adaptation is less impaired than explicit learning in persons with Parkinson disease (PD). Little work has explored implicit locomotor adaptation and savings in this population, yet implicit locomotor learning is critical for everyday function. This cross-sectional study examined adaptation and savings in individuals with PD during split-belt treadmill walking.

Fourteen participants completed the following treadmill protocol: Baseline (6 minutes belts tied), Adaptation (10 minutes split), Washout (10 minutes tied), and Readaptation (10 minutes split). Step length and step symmetry index (SSI) were calculated to determine magnitude and rate of adaptation and savings. Rate was calculated as strides to reach SSI plateau during Adaptation and Readaptation.

During Early Adaptation and Early Readaptation, SSI was perturbed from Baseline ( P < 0.001 and P = 0.002, respectively). Less perturbation in Early Readaptation ( P < 0.001) demonstrated savings. In Late Adaptation and Late Readaptation, participants returned to Baseline symmetry ( P = 0.026 and P = 0.022, respectively, with adjusted level of significance = 0.007). Adaptation was also seen in reverse asymmetry observed in Early Washout ( P = 0.003 vs Baseline). Readaptation rate was faster than in Adaptation ( P = 0.015), demonstrating savings.

Individuals with PD showed locomotor adaptation in an implicit sensorimotor adaptation task. They also demonstrated savings, with less perturbation and faster adaptation during the second split-belt exposure. However, performance was variable; some individuals showed minimal adaptation. Variations in learning, savings, and clinical presentation highlight the need to further explore characteristics of individuals with PD most likely to benefit from adaptation-based locomotor training.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A395 ).