Pendular energy transduction within the step during human walking on slopes at different speeds

J NeuroEngineering Rehabil

2020

Background: Promising studies have shown that the gait symmetry of individuals with hemiparesis due to brain lesions, such as stroke, can improve through motor adaptation protocols forcing patients to use their affected limb more. However, little is known about how to facilitate this process. Here we asked if increasing propulsion demands during split-belt walking (i.e., legs moving at different speeds) leads to more motor adaptation and more symmetric gait in survivors of a stroke, as we previously observed in subjects without neurological disorders. Methods: We investigated the effect of propulsion forces on locomotor adaptation during and after split-belt walking in the asymmetric motor system post-stroke. To test this, 12 subjects in the chronic phase post-stroke experienced a split-belt protocol in a flat and incline session so as to contrast the effects of two different propulsion demands. Step length asymmetry and propulsion forces were used to compare the motor behavior between the two sessions because these are clinically relevant measures that are altered by split-belt walking. Results: The incline session resulted in more symmetric step lengths during late split-belt walking and larger aftereffects following split-belt walking. In both testing sessions, subjects who have had a stroke adapted to regain speed and slope-specific leg orientations similarly to young, intact adults. Importantly, leg orientations, which were set by kinetic demands, during baseline walking were predictive of those achieved during split-belt walking, which in turn predicted each individual's post-adaptation behavior. These results are relevant because they provide evidence that survivors of a stroke can generate the leg-specific forces to walk more symmetrically, but also because we provide insight into factors underlying the therapeutic effect of split-belt walking. Conclusions: Individuals post-stroke at a chronic stage can adapt more during split-belt walking and have greater after-effects when propulsion demands are augmented by inclining the treadmill surface. Our results are promising since they suggest that increasing propulsion demands during paradigms that force patients to use their paretic side more could correct gait asymmetries post-stroke more effectively.

Section: General Paradigmmentioning

confidence: 99%

Augmenting propulsion demands during split-belt walking increases locomotor adaptation of asymmetric step lengths

J NeuroEngineering Rehabil

2020

“…Each step length was also decomposed into anterior and posterior components relative 153 to the hip position ( Figure 1B) as in previous work (Finley et al, 2015). This was done because 154 inclination is known to affect these measures Dewolf et al, 2017). The 155 anterior component, 'α', was defined as the distance in millimeters between the leading leg's 156 ankle and the hip at heel strike; similarly, the posterior component, 'X', was defined as the 157 distance in millimeters between the trailing leg's ankle and the hip.…”

Section: Kinematic Data Analysis: 142mentioning

confidence: 99%

“…into leading (α) and trailing (X) leg positions with respect to the body are illustrated. This 170 decomposition was done because it is known that inclination affects these aspects of step 171 length differently Dewolf et al 2017). Also note that when taking a step, the 172 step length will depend on the position of the leading and trailing leg, which are generating a 173 braking and propulsion force, respectively.…”

Section: Kinematic Data Analysis: 142mentioning

confidence: 99%

Large propulsion demands increase locomotor learning at the expense of step length symmetry

Calvert

2018

Preprint

There is a clinical interest in increasing the extent of locomotor learning induced by split-belt treadmills that move each leg at different speeds. However, factors facilitating locomotor learning are poorly understood. We hypothesized that augmenting the braking forces, rather than propulsion forces, experienced at the feet would increase locomotor adaptation and learning. To test this, forces were modulated during split-belt walking with distinct slopes:inclined (larger propulsion than braking), declined (larger braking than propulsion), and flat (similar propulsion and braking). These groups were compared using step length asymmetry, which is a clinically relevant measure robustly adapted on split-belt treadmills. Unexpectedly, the group with larger propulsion demands (i.e., the incline group) adapted faster and more, and had larger after-effects when the split-belt perturbation was removed. We also found that subjects who propelled more during baseline and experienced larger disruptions of propulsion forces in early adaptation exhibited greater after-effects, which further highlights the catalytic role of propulsion on locomotor learning. The relevance of mechanical demands on shaping our movements was also indicated by the steady state split-belt behavior, during which each group recovered their baseline leg orientation to meet leg-specific force demands at the expense of step length symmetry. Notably, the flat group was nearly symmetric, whereas the incline and decline group overshot and undershot symmetry, respectively. Taken together, our results indicate that forces propelling the body facilitate gait adaptation during split-belt walking.Therefore, interventions that increase propulsion demands may be a viable strategy for augmenting locomotor learning in individuals with hemiparesis. 1999), reducing walking speed (Balasubramanian et al., 2007), compromising balance (Lewek et 47 al., 2014), and if not corrected, step length asymmetry leads to other comorbidities such as 48 musculoskeletal injuries (Jørgensen et al., 2000) and joint pain (Patterson et al., 2012). 49Promising studies have shown that walking with the legs moving at different speeds (i.e., split-50 belt walking) results in long-lasting reduction of step length asymmetry post-stroke when 51 walking overground (Reisman et al., 2009(Reisman et al., , 2013. However, split-belt walking is not always 52 effective even after repeated exposure to the split-belt experience (Reisman et al., 2013; Lewek 53 et al., 2017) and it is still unclear why some stroke survivors re-learn to walk symmetrically but 54 others do not. Thus, it is fundamental to identify factors facilitating split-belt adaptation to 55 augment them for increasing motor learning in all individuals. 56The increased mechanical work (Selgrade et al., 2017), step length asymmetry (Reisman 57 et al., 2005), and hence metabolic effort (Finley et al., 2013), upon introducing the split-belt 58 environment are thought to drive locomotor adaptation. Notably, these three factors are l...

“…169 170 Each step length was also decomposed into anterior and posterior foot distances relative 171 to the hip position ( Figure 1B) as in previous work (Finley et al 2015). This was done to quantify 172 the leading and trailing legs' positions relative to the body when taking a step because inclination 173 is known to affect these measures (Leroux et al 2002;Dewolf et al 2017). The leading leg's 174 position ('α') was computed as the distance in millimeters between the leading leg's ankle and 175 the hip at heel strike; similarly, the trailing leg's position ('X') was computed as the distance in 176 millimeters between the trailing leg's ankle and the hip at heel strike.…”

Section: Data Collection 137 138mentioning

confidence: 99%

“…(B) The decomposition of step length into leading (α) and 494trailing (X) leg positions with respect to the body is illustrated for each sloped condition. This 495 decomposition was done because it is known that inclination affects these aspects of step length 496 differently(Leroux et al 2002;Dewolf et al 2017Dewolf et al , 2018. Also note that when taking a step, the 497 step length will depend on the position of the leading and trailing leg, which are generating a 498 braking and propulsion force, respectively.…”

mentioning

confidence: 99%

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

2019

Preprint

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 ...