These legs were made for propulsion: advancing the diagnosis and treatment of post-stroke propulsion deficits

Advances in medical diagnosis and treatment have facilitated the emergence of precision medicine. In contrast, locomotor rehabilitation for individuals with acquired neuromotor injuries remains limited by the dearth of (i) diagnostic approaches that can identify the specific neuromuscular, biomechanical, and clinical deficits underlying impaired locomotion and (ii) evidence-based, targeted treatments. In particular, impaired propulsion by the paretic limb is a major contributor to walking-related disability after stroke; however, few interventions have been able to target deficits in propulsion effectively and in a manner that reduces walking disability. Indeed, the weakness and impaired control that is characteristic of post-stroke hemiparesis leads to heterogeneous deficits that impair paretic propulsion and contribute to a slow, metabolically-expensive, and unstable gait. Current rehabilitation paradigms emphasize the rapid attainment of walking independence, not the restoration of normal propulsion function. Although walking independence is an important goal for stroke survivors, independence achieved via compensatory strategies may prevent the recovery of propulsion needed for the fast, economical, and stable gait that is characteristic of healthy bipedal locomotion. We posit that post-stroke rehabilitation should aim to promote independent walking, in part, through the acquisition of enhanced propulsion. In this expert review, we present the biomechanical and functional consequences of post-stroke propulsion deficits, review advances in our understanding of the nature of post-stroke propulsion impairment, and discuss emerging diagnostic and treatment approaches that have the potential to facilitate new rehabilitation paradigms targeting propulsion restoration.

Serious game for locomotor rehabilitation of hemiparetic stroke patients

Introduction: Hemiparesis post-stroke usually results in locomotor limitations. As conventional rehabilitation is monotonous, the Serious Games (SG) represents an excellent treatment strategy, allowing to perform physical training in an interesting and enjoyable way. Objective: To evaluate the effects of an exercise program using the SG developed for hemiparetic stroke patients’ locomotor rehabilitation. Method: Non-Randomized Controlled Clinical Trial. Twenty-four hemiparetic stroke patients with subacute or chronic stroke (twelve men), mean age of 57.8 ± 10.4 years (injury time of 16.8 ± 19.6 months) participated in the study. The experimental group (n = 16) participated in an exercise program with the SG for lower limb rehabilitation. The control group (n = 8) received conventional treatment (kinesiotherapy). The intervention consisted of sessions twice a week for ten weeks. The following parameters were assessed: muscle strength (dynamometry), spasticity (Modified Ashworth Scale), functional mobility (Timed Up and Go Test - TUGT), and the gait speed (GS). Results: Both groups showed improvements, but the experimental group was better in all the studied variables, the muscular strength of the lower limb paresis and of the quadriceps femoris (p = 0.002; d = 0.7); and for the hamstrings (p < 0.001; d = 1.3), TUGT (p < 0.001; d = 0.4), and GS (p = 0.001; d = 0.4). Conclusion: The exercise program with the SG was useful for the patients treated in this study. The results showed a superiority of the SG regarding the conventional treatment in all the controlled variables. This was probably because of the greater repeatability of the exercises and the increased attention and motivation.

The Impact of Cognitive Dysfunction on Locomotor Rehabilitation Potential in Multiple Sclerosis

Background: Cognitive dysfunction is a frequent manifestation of multiple sclerosis (MS) but its effect on locomotor rehabilitation is unknown. Objective: To study the impact of cognitive impairment on locomotor rehabilitation outcome in people with MS. Methods: We performed a retrospective analysis involving ambulatory patients with MS who were admitted for intensive, inpatient, multidisciplinary rehabilitation at the National Multiple Sclerosis Center of Melsbroek between the years 2012 and 2017. The Brief Repeatable Battery of Neuropsychological Tests (BRB-N) was used to determine the cognitive status of subjects as either impaired (COG–) or preserved (COG+). Locomotor outcome was compared between groups with the difference in 6-minute walk test (6MWT) measured at admission and discharge (Δ6MWT). In addition, individual test scores of the BRB-N for attention (Paced Auditory Serial Addition Test 2” and 3”), visuospatial learning/memory (7/24 Spatial Recall Test), verbal learning/memory (Selective Reminding Test) and verbal fluency (Controlled Oral Word Association Test) were correlated to the Δ6MWT. Results: A total of 318 complete and unique records were identified. Both groups showed a significant within-group Δ6MWT during hospitalization (COG+: 47.51 m; COG–: 40.97 m; P < .01). In contrast, Δ6MWT values were comparable between groups. The odds of achieving a minimal clinical important difference on the 6MWT did not differ significantly between both groups. Only attention/concentration was significantly correlated with Δ6MWT (r = 0.16, P = .013). Conclusion: Cognitive impairment based on BRB-N results appears not to impede locomotor rehabilitation in ambulatory patients with MS. Attentional deficits are correlated to the extent of locomotor rehabilitation, suggesting the presence of a subtle effect of cognition.

Learning to shape virtual patient locomotor patterns: internal representations adapt to exploit interactive dynamics

This work aimed to understand the sensorimotor processes used by humans when learning how to manipulate a virtual model of locomotor dynamics. Prior research shows that when interacting with novel dynamics humans develop internal models that map neural commands to limb motion and vice versa. Whether this can be extrapolated to locomotor rehabilitation, a continuous and rhythmic activity that involves dynamically complex interactions, is unknown. In this case, humans could default to model-free strategies. These competing hypotheses were tested with a novel interactive locomotor simulator that reproduced the dynamics of hemiparetic gait. A group of 16 healthy subjects practiced using a small robotic manipulandum to alter the gait of a virtual patient (VP) that had an asymmetric locomotor pattern modeled after stroke survivors. The point of interaction was the ankle of the VP’s affected leg, and the goal was to make the VP’s gait symmetric. Internal model formation was probed with unexpected force channels and null force fields. Generalization was assessed by changing the target locomotor pattern and comparing outcomes with a second group of 10 naive subjects who did not practice the initial symmetric target pattern. Results supported the internal model hypothesis with aftereffects and generalization of manipulation skill. Internal models demonstrated refinements that capitalized on the natural pendular dynamics of human locomotion. This work shows that despite the complex interactive dynamics involved in shaping locomotor patterns, humans nevertheless develop and use internal models that are refined with experience.NEW & NOTEWORTHY This study aimed to understand how humans manipulate the physics of locomotion, a common task for physical therapists during locomotor rehabilitation. To achieve this aim, a novel locomotor simulator was developed that allowed participants to feel like they were manipulating the leg of a miniature virtual stroke survivor walking on a treadmill. As participants practiced improving the simulated patient’s gait, they developed generalizable internal models that capitalized on the natural pendular dynamics of locomotion.