Effects of Obesity on Adaptation Transfer from Treadmill to Over-Ground Walking

Discerning whether individuals with obesity transfer walking adaptation from treadmill to over-ground walking is critical to advancing our understanding of walking adaptation and its usefulness in rehabilitating obese populations. We examined whether the aftereffects following split-belt treadmill adaptation transferred to over-ground walking in adults with normal-weight body mass index (BMI) and obese BMI. Nineteen young adults with obesity and 19 age-matched adults with normal weight walked on flat ground at their preferred speed before and after walking on a treadmill with tied belts (preferred speed) and with the split-belt at their preferred speed and at a speed 50% slower than their preferred speed. The adaptation and aftereffects in step length and double-limb support time symmetry were calculated. We found that the amount of temporal adaptation was similar for adults with obesity and with normal weight (p > 0.05). However, adults with obesity showed greater asymmetry for double-limb support time following split-belt treadmill walking compared to adults with normal weight (p < 0.05). Furthermore, the transfer of asymmetry for double-limb support time from the treadmill to over-ground walking was less in adults with obesity than in adults with normal weight (p < 0.05). The transfer of adapted gait following split-belt treadmill walking provides insight into how atypical walking patterns in individuals with obesity could be remediated using long-term gait training.

Persons with essential tremor can adapt to new walking patterns

Essential tremor (ET) is a common movement disorder that causes motor deficits similar to those seen in cerebellar disorders. These include kinetic tremor, gait ataxia, and impaired motor adaptation. Previous studies of motor adaptation in ET have focused on reaching while the effects of ET on gait adaptation are currently unknown. The purpose of this study was to contrast locomotor adaptation in persons with and without ET. We hypothesized that persons with ET would show impaired gait adaptation. In a cross-sectional study, persons with ET ( n = 14) and healthy matched controls ( n = 12) walked on a split-belt treadmill. Participants walked with the belts moving at a 2:1 ratio, followed by overground walking to test transfer, followed by a readaptation period and finally a deadaptation period. Step length asymmetry was measured to assess the rate of adaptation, amount of transfer, and rates of readaptation and deadaptation. Spatial, temporal, and velocity contributions to step length asymmetry were analyzed during adaptation. There were no group by condition interactions in step length asymmetry or contributions to step length asymmetry. Regardless of condition, persons with ET walked slower and exhibited lower temporal ( P < 0.001) and velocity ( P = 0.001) contributions to step length asymmetry than controls. Persons with ET demonstrated a preserved ability to adapt to, store, and transfer a new walking pattern. Despite probable cerebellar involvement in ET, locomotor adaptation is an available mechanism to teach persons with ET new gait patterns. NEW & NOTEWORTHY This study is the first to investigate walking adaptation abilities of people with essential tremor. Despite evidence of cerebellar impairment in this population, people with essential tremor can adapt their walking patterns. However, people with essential tremor do not modulate the timing of their footsteps to meet walking demands. Therefore, this study is the first to report impairments in the temporal aspects of walking in people with essential tremor during both typical and locomotor learning.

Increased intramuscular coherence is associated with temporal gait symmetry during split-belt locomotor adaptation

When walking on a split-belt treadmill where one belt moves faster than the other, the nervous system consistently attempts to maintain symmetry between legs, quantified as deviation from double support time or step length symmetry. It is known that the cerebellum plays a critical role in locomotor adaptation. Less is known about the role of corticospinal drive in maintaining this type of proprioceptive-driven locomotor adaptation. The objective of this study was to examine the functional role of oscillatory drive in relation to changes in spatiotemporal gait parameters during split-belt walking adaptation. Eighteen healthy participants adapted and deadapted on a split-belt treadmill; 13 out of 18 participants repeated the paradigm two more times to examine the effects of reexposure. Coherence analysis was used to quantify the coupling between electromyography (EMG) from the proximal (TAprox) and distal tibialis anterior (TAdist) muscle during the swing phase of walking. EMG-EMG coherence was examined within the alpha (8–15 Hz), beta (15–30 Hz), and gamma (30–45 Hz) frequencies. Our results showed that 1) beta- and gamma-band coherence (markers of corticospinal drive) increased during early split-belt walking compared with baseline walking in the slow leg, 2) beta-band coherence decreased from early to late split-belt adaptation in the fast leg, 3) alpha-, beta-, and gamma-band coherence decreased from first to third split-belt exposure in the fast leg, and 4) there was a relationship between higher beta coherence in the slow leg TA and smaller double support asymmetry. Our results suggest that corticospinal drive may play a functional role in the temporal control of split-belt walking adaptation. NEW & NOTEWORTHY This is the first study to examine the functional role of intramuscular coherence in relation to changes in spatiotemporal gait parameters during split-belt walking adaptation. We found that the corticospinal drive measured by intramuscular coherence in tibialis anterior changes with adaptation and that the corticospinal drive is related to temporal but not spatial parameters. This study may give insight as to the specific role of the motor cortex during gait.

Transition versus Continuous Slope Walking: Adaptation to Change Center of Mass Velocity in Young Men

During continuous uphill walking (UW) or downhill walking, human locomotion is modified to counteract the gravitational force, aiding or impeding the body’s forward momentum, respectively. This study aimed at investigating the center of mass (COM) and center of pressure (COP) velocities and their relative distance during the transition from uphill to downhill walking (UDW) to determine whether locomotor adjustments differ between UDW and UW. Fourteen participants walked on a triangular slope and a continuous upslope of 15°. The kinematics and COPs were obtained using a force plate and a motion capture system. The vertical velocity of the COM in the propulsion phase, the horizontal distance between the COM and COP at initial contact, and the duration of the subphases significantly differed between UDW and UW (all p<0.05). Compared with the results of UW, longer durations and the deeper downward moving COM in the propulsion phase were observed during UDW (all p<0.05). Additionally, a shorter horizontal distance between the COM and COP at initial contact was associated with a slower vertical COM velocity in the propulsion phase during UDW. The reduced velocity is likely a gait alteration to decrease the forward momentum of the body during UDW.

Split-belt walking adaptation recalibrates sensorimotor estimates of leg speed but not position or force

Motor learning during reaching not only recalibrates movement but can also lead to small but consistent changes in the sense of arm position. Studies have suggested that this sensory effect may be the result of recalibration of a forward model that associates motor commands with their sensory consequences. Here we investigated whether similar perceptual changes occur in the lower limbs after learning a new walking pattern on a split-belt treadmill—a task that critically involves proprioception. Specifically, we studied how this motor learning task affects perception of leg speed during walking, perception of leg position during standing or walking, and perception of contact force during stepping. Our results show that split-belt adaptation leads to robust motor aftereffects and alters the perception of leg speed during walking. This is specific to the direction of walking that was trained during adaptation (i.e., backward or forward). The change in leg speed perception accounts for roughly half of the observed motor aftereffect. In contrast, split-belt adaptation does not alter the perception of leg position during standing or walking and does not change the perception of stepping force. Our results demonstrate that there is a recalibration of a sensory percept specific to the domain of the perturbation that was applied during walking (i.e., speed but not position or force). Furthermore, the motor and sensory consequences of locomotor adaptation may be linked, suggesting overlapping mechanisms driving changes in the motor and sensory domains.

Split-belt walking: adaptation differences between young and older adults

Human walking is highly adaptable, which allows us to walk under different circumstances. With aging, the probability of falling increases, which may partially be due to a decreased ability of older adults to adapt the gait pattern to the needs of the environment. The literature on visuomotor adaptations during reaching suggests, however, that older adults have little problems in adapting their motor behavior. Nevertheless, it may be that adaptation during a more complex task like gait is compromised by aging. In this study, we investigated the ability of young ( n = 8) and older ( n = 12) adults to adapt their gait pattern to novel constraints with a split-belt paradigm. Findings revealed that older adults adapted less and more slowly to split-belt walking and showed fewer aftereffects than young adults. While young adults showed a fast adjustment of the relative time spent in swing for each leg older adults failed to do so, but instead they were very fast in manipulating swing speed differences between the two legs. We suggest that these changes in adaptability of gait due to aging stem from a mild degradation of cortico-cerebellar pathways (reduced adaptability) and cerebral structures (decreased ability to change gait cycle timing). However, an alternative interpretation may be that the observed reduced adaptation is a compensatory strategy in view of the instability induced by the split-belt paradigm.

Prism Adaptation During Walking Generalizes to Reaching and Requires the Cerebellum

Adaptation of arm movements to laterally displacing prism glasses is usually highly specific to body part and movement type and is known to require the cerebellum. Here, we show that prism adaptation of walking trajectory generalizes to reaching (a different behavior involving a different body part) and that this adaptation requires the cerebellum. In experiment 1, healthy control subjects adapted to prisms during either reaching or walking and were tested for generalization to the other movement type. We recorded lateral deviations in finger endpoint position and walking direction to measure negative aftereffects and generalization. Results showed that generalization of prism adaptation is asymmetric: walking generalizes extensively to reaching, but reaching does not generalize to walking. In experiment 2, we compared the performance of cerebellar subjects versus healthy controls during the prism walking adaptation. We measured rates of adaptation, aftereffects, and generalization. Cerebellar subjects had reduced adaptation magnitudes, slowed adaptation rates, decreased negative aftereffects, and poor generalization. Based on these experiments, we propose that prism adaptation during whole body movements through space invokes a more general system for visuomotor remapping, involving recalibration of higher-order, effector-independent brain regions. In contrast, prism adaptation during isolated movements of the limbs is probably recalibrated by effector-specific mechanisms. The cerebellum is an essential component in the network for both types of prism adaptation.