Home-based exercises are an important component of stroke rehabilitation but are seldom fully completed. Past studies of exercise perseverance in the general public have suggested the importance of early exercise frequency and schedule consistency (in terms of which days of the week exercises are performed) because they encourage habit formation. To test whether these observations apply after a stroke, we leveraged data from 2,583 users of a sensor-based system (FitMi) developed to motivate movement exercises at home. We grouped users based on their early exercise frequency (defined across the initial 6 weeks of use) and calculated the evolution of habit score (defined as exercise frequency multiplied by exercise duration) across 6 months. We found that habit score decayed exponentially over time but with a slower decay constant for individuals with higher early frequency. Only the group with an early exercise frequency of 4 days/week or more had non-zero habit score at six months. Within each frequency group, dividing individuals into higher and lower consistency subgroups revealed that the higher consistency subgroups had significantly higher habit scores. These results are consistent with previous studies on habit formation in exercise and may help in designing effective home rehabilitation programs after stroke.

Optimizing skill acquisition during novel motor tasks and (re)learning lost motor functions have been the interest of many researchers over the past few decades. One approach shown to accelerate motor learning is haptically coupling two individuals through robotic interfaces. Studies have shown that an individual’s solo performance of upper-limb tracking tasks may improve after haptically coupled training with a partner. In this study, our goal was to investigate whether these findings can be translated to lower-limb motor tasks, more specifically, during an ankle position tracking task. Using one-degree-of-freedom ankle  movements, pairs of participants (i.e., dyads) tracked target trajectories while intermittently coupled through a virtual spring rendered between two ankle rehabilitation robots. We compared changes in task performance across trials while training with and without haptic coupling. We found that dyadic haptic coupling did not lead to faster individual learning of the tracking task. Dyadic task performance (i.e., tracking performance while haptically coupled) improved during haptic coupling, likely due to averaging of errors of the dyadic pair during tracking. These results suggest that haptic coupling between unimpaired individuals may not be an effective method of training ankle movements during a simple one-degree-of-freedom task.