Effect of Aging and Cortical Stroke on Motor Adaptation to Overground Gait-Slips: Quantifying Differences in Adaptation Rate and Adaptation Plateau.

We examined the effect of aging and cortical stroke on the rate of motor adaptation (adaptation rate) and amount of performance gains (adaptation plateau) in balance skills. Fourteen older (≥60 years) and fifteen younger (<60 years) adults with chronic stroke, and thirteen healthy older adults (≥60 years) participated. Participants experienced 8 consecutive gait-slips (≤45 cm) to their non-paretic/dominant limb. Slip outcome (backward/no balance loss) was compared using generalized estimating equations (GEE). Proactive (pre-slip stability) and reactive adjustments (post-slip stability, slip displacement and velocity, and compensatory step length) were compared using non-linear regression models. GEE showed the main effect of group, trial, and group × trial interaction for slip outcome (p < 0.05). There were no differences in the adaptation rate for proactive and reactive variables and plateau for proactive variables (p > 0.05). However, both stroke groups demonstrated a smaller adaptation plateau for the majority of reactive variables compared to healthy older adults (p < 0.05). The rate of adaptation to gait-slips does not slow with aging and cortical stroke; however, cortical stroke, age notwithstanding, may reduce performance gains in reactive balance skills, possibly hindering retention and transfer to real-life scenarios. People with stroke may need adjunctive therapies/supplemental agents to apply laboratory-acquired balance skills to daily life.