Augmenting propulsion demands during split-belt walking increases locomotor adaptation in the asymmetric motor system

Abstract

15 16 Background: 17Promising studies have shown that the mobility of individuals with hemiparesis due to 18 brain lesions, such as stroke, can improve through motor adaptation protocols forcing patients to 19 use their affected limb more. However, little is known about how to facilitate this process. Here 20 we asked if increasing propulsion demands during split-belt walking (i.e., legs moving at 21 different speeds) leads to more motor adaptation and more symmetric gait in survivors of a 22 stroke, as we previously observed in subjects without neurological disorders. 23 24 Methods: 25We investigated the effect of propulsion forces on locomotor adaptation during and after 26 split-belt walking in the asymmetric motor system post-stroke. To test this, 12 subjects in the 27 chronic phase post-stroke experienced a split-belt protocol in a flat and incline session so as to 28 contrast the effects of two different propulsion demands.Step length asymmetry and propulsion 29 forces were used to compare the motor behavior between the two sessions because these are 30 clinically relevant measures that are altered by split-belt walking. 31 32 Results: 33The incline session resulted in more symmetric step lengths during late split-belt walking 34 and larger after-effects following split-belt walking. In both testing sessions, subjects who have 35 had a stroke adapted to regain speed and slope-specific leg orientations similarly to young, intact 36 adults. Importantly, leg orientations during baseline walking were predictive of those achieved 37 during split-belt walking, which in turn predicted each individual's post-adaptation behavior. 38 3 39 Conclusion: 40These results indicated that survivors of a stroke can adapt their movements to meet leg-41 specific kinetic demands. This promising finding suggests that augmenting propulsion demands 42 during split-belt walking could favor symmetric walking in individuals who had a stroke, 43 possibly making split-belt interventions a more effective gait rehabilitation strategy. 44 45 Key Words 46 47 Stroke, motor learning, hemiparesisOur previous work indicates that locomotor adaptation in young, unimpaired subjects 61 increases by augmenting propulsion demands during split-belt walking. More specifically, we 62 found that baseline kinetic demands were predictive of step lengths at steady state and after-63 effects, such that greater propulsion demands led to more adaptation and larger after-effects in 64 every individual (Sombric et al. 2019). It is unclear if the same could be observed post-stroke 65given their known propulsion deficits (Bowden et al. 2006; Balasubramanian et al. 2007). This 66 might be possible since there is evidence that survivors of a stroke can augment their propulsion 67 forces when required by the task (Kesar et al. 2011;Awad et al. 2014; Hsiao 68 et al. 2015 Hsiao 68 et al. , 2016b Hsiao 68 et al. , 2016a). Thus, we tested whether locomotor adaptation in survivors of a stroke 69 could be augmented by increasing propulsion demands with inclined ...

The Effect of Split-Belt Treadmill Interventions on Step Length Asymmetry in Individuals Poststroke: A Systematic Review With Meta-Analysis

“…All symmetry ratios were converted to standardized mean differences (Hedge's g). Data from 4 studies 8,10,15,22 were obtained from the original research articles, whereas data from 6 studies 7,9,11,[16][17][18] were obtained from the authors through electronic correspondence. Data from 7 studies [12][13][14][23][24][25][26] were not obtained after reaching out to the corresponding authors.…”

“…Out of these 20 studies, 9 calculated the fast belt speed as the fastest comfortable walking speed and the slow belt speed as half of that speed, 7,9,11,13,16,[23][24][25][26] 6 calculated the slow belt speed as the participant's self-selected speed and the fast belt as twice the self-selected speed, 8,10,22,27,28,30 3 studies had the fast belt move at 1.0 m/s and the slow belt move at 0.5 m/s, 12,14,17 and 2 studies calculated each participant's self-selected speed and the fast belt was 133% of that speed and the slow belt was 66% of that speed. 18,29 One study 25 had a group complete the training at 3 different speed ratios, 1.5:1, 2:1, and 2.5:1. Last, one study controlled the ratio of the belt speeds based on the degree of the patient's asymmetry and it changed on a step-by-step basis.…”

“…These studies were combined into one analysis and the heterogeneity statistic (I 2 ) for this analysis was very low, indicating minimal variation between study outcomes (I 2 = 0%, P = .50, Figure 2). Four individual effect sizes 8,10,17,18 were used to calculate the pooled effect of baseline to posttraining after a single session. Five individual effect sizes from 3 studies 11,15,22 were used to calculate the pooled effect of baseline to posttraining after multiple training sessions, and 5 individual effect sizes from 3 studies 11,15,22 were used to calculate the pooled effect of baseline to follow-up.…”

“…The lack of significant differences between baseline and late adaptation indicate that individuals poststroke overcame the error induced by the treadmill and returned to their baseline walking pattern while walking on the treadmill. 7,9,10,16,18 Several studies suggest that the treadmill protocol has little impact on the participants' ability to adapt back to baseline walking during treadmill training. 10,17,30 Contradictory to these claims, Tyrell and colleagues reported that participants returned to baseline asymmetry during an error augmentation protocol but failed to do so when the split-belt minimized the error in the participants' gait.…”

“…For example, some studies place the paretic limb on the slow belt regardless of step length. 8,17,18 Other studies focus on comparing participants' biomechanical characteristics, such as baseline asymmetry or muscle strength, to how an individual is able to adapt to the protocol. 8,17 Because not all studies utilizing a split-belt training paradigm aim to reduce gait asymmetry posttraining, it is important to consider study objectives when evaluating results and determining which protocol is best for improving step length symmetry.…”