Side by side treadmill walking reduces gait asymmetry induced by unilateral ankle weight

Asymmetric gait is a hallmark of many neurological and musculoskeletal conditions. This behavior is often the result of a decrease in the stability of interlimb coordination, and synchronization to external signals such as auditory cuing or another walking individual may be helpful for altering abnormal movement patterns. The purpose of this study was to investigate the interaction between interlimb coordination and unintentional, interpersonal synchronization of gait in healthy individuals in response to unilateral ankle loading. Fifty participants completed four trials while walking on a motorized treadmill: (1) by themselves, (2) with a partner on an adjacent treadmill, (3) by themselves with additional weight applied unilaterally to their right ankle, and (4) with both a partner and unilateral weight. As expected, the addition of unilateral weight increased asymmetry according to several spatiotemporal measures of gait, but the presence of a partner on an adjacent treadmill significantly reduced this effect. Further, the amount of unintentional, interpersonal synchronization among pairings was relatively unaffected by the addition of ankle weight to one of the partners. All pairings realized a beneficial effect on asymmetrical gait but this effect was greater for pairings that consistently synchronized unintentionally. These results suggest that side by side walking might be an effective approach for influencing bilateral coordination of gait and may hold insight for understanding gait asymmetry and interlimb movement variability.     

Effects of velocity and limb loading on the coordination between limb movements during walking

The authors investigated the effects of velocity (increasing from 0.5 to 5.0 km/hr in steps of 0.5 km/hr) and limb loading on the coordination between arm and leg movements during treadmill walking in 7 participants. Both the consistency of the individual limb movements and the stability of their coordination increased with increasing velocity; the frequency coordination between arm and leg movements was 2:1 at the lower velocities and 1:1 at the higher velocities. The mass manipulation affected the individual limb movements but not their coordination, indicating that a stable walking pattern was preserved. The results differed qualitatively from those obtained in studies on bimanual interlimb coordination, implying that the dynamical principles identified therein are not readily applicable to locomotion.     

Enhanced arm swing alters interlimb coordination during overground walking in individuals with traumatic brain injury

The current study investigated interlimb coordination in individuals with traumatic brain injury (TBI) during overground walking. The study involved 10 participants with coordination, balance, and gait abnormalities post-TBI, as well as 10 sex- and age-matched healthy control individuals. Participants walked 12 m under two experimental conditions: 1) at self-selected comfortable walking speeds; and 2) with instructions to increase the amplitude and out-of-phase coordination of arm swinging. The gait was assessed with a set of spatiotemporal and kinematic parameters including the gait velocity, step length and width, double support time, lateral displacement of the center of mass, the amplitude of horizontal trunk rotation, and angular motions at shoulder and hip joints in sagittal plane. Interlimb coordination (coupling) was analyzed as the relative phase angles between the left and right shoulders, hips, and contralateral shoulders and hips, with an ideal out-of-phase coupling of 180° and ideal in-phase coupling of 0°. The TBI group showed much less interlimb coupling of the above pairs of joint motions than the control group. When participants were required to increase and synchronize arm swinging, coupling between shoulder and hip motions was significantly improved in both groups. Enhanced arm swinging was associated with greater hip and shoulder motion amplitudes, and greater step length. No other significant changes in spatiotemporal or kinematic gait characteristics were found in either group. The results suggest that arm swinging may be a gait parameter that, if controlled properly, can improve interlimb coordination during overground walking in patients with TBI.     

Coordination Between Arm and Leg Movements During Locomotion

To evaluate the contrasting dynamical and biomechanical interpretations of the 2:1 frequency coordination between arm and leg movements that occurs at low walking velocities and the 1:1 frequency coordination that occurs at higher walking velocities, the authors conducted an experiment in which they quantified the effect of walking velocity on the stability of the frequency and phase coordination between the individual limb movements. Spectral analyses revealed the presence of 2:1 frequency coordination as a consistent feature of the data in only 3 out of 8 participants at walking velocities ranging from 1.0 to 2.0 km/h, in spite of the fact that the eigenfrequencies of the arms were rather similar across participants. The degree of interlimb coupling, as indexed by weighted coherence and variability of relative phase, was lower for the arm movements and for ipsilateral and diagonal combinations of arm and leg movements than for the leg movements. Furthermore, the coupling between all pairs of limb movements was found to increase with walking velocity, whereas no clear signs were observed that the switches from 2:1 to 1:1 frequency coordination and vice versa were preceded by loss of stability. Therefore, neither a purely biomechanical nor a purely dynamical model is optimally suited to explain these results. Instead, an integrative model involving elements of both approaches seems to be required.     

Coordination between arm and leg movements during locomotion

To evaluate the contrasting dynamical and biomechanical interpretations of the 2:1 frequency coordination between arm and leg movements that occurs at low walking velocities and the 1:1 frequency coordination that occurs at higher walking velocities, the authors conducted an experiment in which they quantified the effect of walking velocity on the stability of the frequency and phase coordination between the individual limb movements. Spectral analyses revealed the presence of 2:1 frequency coordination as a constant feature of the data in only 3 out of 8 participants at walking velocities ranging from 1.0 to 2.0 km/h, in spite of the fact that the eigenfrequencies of the arms were rather similar across participants. The degree of interlimb coupling, as indexed by weighted coherence and variability of relative phase, was lower for the arm movements and for ipsilateral and diagonal combinations of arm and leg movements than for the leg movements. Furthermore, the coupling between all pairs of limb movements was found to increase with walking velocity, whereas no clear signs were observed that the switches from 2:1 to 1:1 frequency coordination and vice versa were preceded by loss of stability. Therefore, neither a purely biomechanical nor a purely dynamical model is optimally suited to explain these results. Instead, an integrative model involving elements of both approaches seems to be required.     

The influence of horizontal velocity on interlimb symmetry in normal walking

Changes in horizontal velocity (HV) are known to influence many biomechanical characteristics of human locomotion. The purpose of the present study was to investigate this phenomenon with respect to the interlimb symmetry of walking in a normal population. Peak and temporal ground reaction force data from both feet of 20 able-bodied males were collected at each of three relative velocity conditions (slow, normal and fast). These data were analyzed using of a series of 2 x 3 repeated measures ANOVAs, which revealed a high degree of interlimb (bilateral) symmetry across HV conditions despite significant intralimb (unilateral) changes. In contrast to this primary finding were two significant interaction effects for the stance time and peak vertical force at push-off measures respectively. These interactions indicated greater asymmetries at the slow HV condition with a trend toward improved symmetry at higher velocities. Although these results may provide some theoretical insight into the underlying nature of symmetry in gait, their overall magnitude does not seem to invalidate the current widespread use of symmetry assumptions in clinical and research settings today.     

Interlimb Coordination During Step-to-Step Transition and Gait Performance

Most energy spent in walking is due to step-to-step transitions. During this phase, the interlimb coordination assumes a crucial role to meet the demands of postural and movement control. The authors review studies that have been carried out regarding the interlimb coordination during gait, as well as the basic biomechanical and neurophysiological principles of interlimb coordination. The knowledge gathered from these studies is useful for understanding step-to-step transition during gait from a motor control perspective and for interpreting walking impairments and inefficiency related to pathologies, such as stroke. This review shows that unimpaired walking is characterized by a consistent and reciprocal interlimb influence that is supported by biomechanical models, and spinal and supraspinal mechanisms. This interlimb coordination is perturbed in subjects with stroke.     

Coordination of symmetrical and asymmetrical human gait

Most human gait forms assume symmetrical, alternating patterns of interlimb coordination (e.g., crawling, walking, running). Human galloping is a notable exception. In contrast to extensive information on galloping in animals, little is known about this gait in humans. Therefore, kinematic and topographical analyses of running and galloping were undertaken to investigate the manner in which the lower limbs are uncoupled to produce this asymmetrical gait. Seven adult females were filmed while running and galloping at their preferred speed. Analysis of the gaits revealed differences in the following: (a) preferred speed, (b) coupling between upper- and lower-limb girdles, and (c) point of foot fall (end-point trajectories). In contrast to clear differences in interlimb coordination, intralimb coordination was remarkably similar across gaits, although when galloping was adopted, the rear leg did show more variable change than the front leg.     

An Energetic Comparison of Symmetrical and Asymmetrical Human Gait

This article contrasts the mechanical energy profiles of asymmetrical galloping with those of symmetrical running in adult humans. Seven female subjects were filmed while performing overground running and galloping at their preferred velocities. A previous study (Whitall & Caldwell, 1992) showed that kinematic differences between these gait modes included higher preferred velocity for running than galloping, with distinct differences in interlimb coordination but surprisingly similar intralimb patterns. Energetically, in the present study the whole body center of mass during galloping was found to behave much as it does in walking; kinetic and potential energy profiles were out of phase, as compared with running, which exhibited in-phase fluctuations of kinetic and potential energies. The primary reason for these center of mass differences was found in the energetics of the back leg of galloping, which demonstrated alterations in timing of its energy fluctuations and less energy generation than the front leg. Analysis of the power sources underlying the segmental energies during swing phase showed that the back leg's energy changes were accomplished mainly through reduced use of the hip muscles and less interlimb energy transfer. The back leg's energetics during swing also displayed a shift toward greater reliance on nonmuscular energy sources. A pattern of energy inflow during early swing and energy outflow during late swing was common to both running and galloping, although the galloping legs both demonstrated more abrupt transitions between these phases. The possibility is raised that the 67/33 interlimb phasing ratio used in galloping is selected to reduce mechanical energy variations of the total body center of mass. These data suggest that models of asymmetric gait in humans must account for more than merely phase alteration.     

Attentional loads associated with interlimb interactions underlying rhythmic bimanual coordination

Studies of rhythmic bimanual coordination under dual-task conditions revealed (1) a dependence of secondary task performance on the stability of coordinative tasks, in that secondary task performance was better during in-phase than antiphase coordination, and (2) a shift in the mean relative phasing between the limbs compared to single-task conditions. The present study aimed to account for these phenomena by dissociating three qualitatively different interactions between the limbs that govern this motor behavior, related to movement planning, error correction, and interlimb reflex activity. The experiment probed the cognitive demands associated with each interlimb interaction by examining the attentional load under dual-task conditions, indexed by reaction times of the secondary task and kinematic changes in the coordinative tasks relative to single-task conditions. First, only in the condition that involved interlimb interactions at the level of movement planning reaction times were shorter for in-phase than for antiphase coordination, highlighting an intimate relation between movement planning and attentional processes. Second, under dual-task conditions a shift in the mean relative phase was observed relative to single-task conditions, but only for the interlimb interactions that depend directly on sensory feedback (error correction and interlimb reflex activity). These observations qualified the effects of attentional load reported in previous studies. Third, reaction times varied systematically over the movement cycle. These variations revealed a dynamical signature of the attentional load that differed between the three interlimb interactions.     

Stability and variability may respond differently to changes in walking speed

In gait research it has often been assumed that variability and stability are negatively correlated, where increases in variability are assumed to equate with increases in instability. The purpose of this paper is to illustrate that variability does not always equate with stability. To proof this point, a method was developed to directly assess stability and variability during the application of a visual perturbation at different walking speeds. Walking variability was measured by using the average standard deviation of the knee joint angle across the gait cycle. Walking stability was measured by the recovery time of the knee joint angle trajectory from the distortion induced by a visual perturbation that was delivered at the beginning of the stance phase. Five participants were required to walk at six different velocities on a treadmill (0.67, 0.80, 0.94, 1.07, 1.21, and 1.34 m/s). The coefficients of intraclass correlations for the experiment were 83% and 80% for the calculated stability and variability, respectively. The calculated stabilities were not sensitive to changes in walking speed (p>0.98). The calculated variability however decreased with increases in walking speed (p=0.004). No significant correlation between variability and stability was observed (r=-0.002). We suggest that gait stability is independent of variability during locomotion and should thus be measured independently.     

The effects of forearm movements on human gait during walking with various self-selected speeds

The forearms significantly contribute to the upper extremity movements and, consequently, whole-body responses during locomotion. The purpose of this study is to provide a more in-depth understanding of the mechanism controlling forearm movements during walking by comprehensively investigating the effects of the forearms on the lower and upper limb movements. Such an understanding can provide critical information for the design and control of robotic upper-limb prostheses. Twelve healthy young participants were recruited to compare their gait during (1) natural walking, (2) walking while wearing a pair of artificial passive forearms and having their actual forearms restrained by orthopedic braces, and (3) walking with only having their forearms restrained by the braces (i.e., no artificial forearms). While the passive forearms in condition 2 were to determine if the forearm movements were passively or actively controlled, condition 3 was to account for the effects of restraining the forearms in condition 2. The participants' lower-limb joint angles and spatiotemporal parameters remained unchanged across the three conditions while walking at their normal and fast self-selected gait speeds. However, significant decreases were observed in the shoulder and trunk angles, the interlimb coordination, and the shoulder-trunk correlations when walking with the artificial forearms. These observations were in tandem with the increased muscle activity of the biceps, trapeziuses, and posterior deltoids, which controlled the shoulder motion and trunk rotation during walking with the artificial forearms across both normal and fast self-selected speeds. Although not significant, the metabolic energy analysis of five participants revealed an increase during walking with artificial forearms. The results support the idea that the body actively controls the forearm movements through the shoulder and trunk rotations to mitigate the undesired disturbances induced by the passive forearm movements during locomotion.     

Validity of visually recorded temporal-distance measures at selected walking velocities for gait analysis

The purpose of this study was to examine the validity of measures of temporal distance in a clinical analysis of gait. Data were collected from 15 normal subjects by one examiner. Equipment consisted of a 10-meter laminated walking track, dictaphone, metronome, and ink markers. The number of errors at four walking speeds were examined using a standardized analysis of gait. Analysis of variance showed a significant number of errors between the first and last halves of the measurement distance and among the four walking velocities. Post hoc analysis using the Scheffé test indicated significant differences in the mean number of errors at the velocities of 60 and 75 versus 25 and 40 m.min-1. An F test for simple effects indicated a significant number of errors occurred during the second half of the measured distance and at walking velocities of 60 and 75 m.min-1. These results indicate that the gait analysis is valid for measurements taken at all of the walking velocities only when recorded over a three-meter distance and only at the velocities of 25 and 40 m.min-1 over a six-meter distance.     

Topological assessment of gait synchronisation in overground walking groups

Walking is one of the fundamental forms of human gross motor activity in which spatiotemporal movement coordination can occur. While considerable body of evidence already exists on pedestrian movement coordination while walking in pairs, little is known about gait control while walking in more complex topological arrangements. To this end, this study provides some of the first evidence of spontaneous gait synchronisation while walking in a group. Nine subjects covered the total distance of 40 km at different speeds while assembled in a three-by-three formation. Two experimental protocols were applied in which the subjects were either not specifically asked to or specifically asked to synchronise their gait. To obtain results representative from the point of view of gait control, the movement coordination was quantified using the indirectly measured vertical component of ground reaction force, based on output from a network of wireless motion monitors. Bivariate phase difference analysis was conducted using wavelet transform, synchronisation strength measures derived from Shannon entropy, and circular statistics. A fundamental relationship describing the influence of the group walking speed on individuals’ pacing frequency was established, showing a positive correlation different from that previously reported for walking in solitude. A positive correlation was found between the average synchronisation strength within a group and group’s walking speed. The most persistent coordination patterns were identified for pedestrians walking front-to-back and side-by-side. Overall, the spontaneous gait synchronisation while walking in a group is relatively weak, well below the levels reported for walking in pairs.     

Walking perception by walking observers

People frequently analyze the actions of other people for the purpose of action coordination. To understand whether such self-relative action perception differs from other-relative action perception, the authors had observers either compare their own walking speed with that of a point-light walker or compare the walking speeds of 2 point-light walkers. In Experiment 1, observers walked, bicycled, or stood while performing a gait-speed discrimination task. Walking observers demonstrated the poorest sensitivity to walking speed, suggesting that perception and performance of the same action alters visual-motion processes. Experiments 2-6 demonstrated that the processes used during self-relative and other-relative action perception differ significantly in their dependence on observers' previous motor experience, current motor effort, and potential for action coordination. These results suggest that the visual analysis of human motion during traditional laboratory studies can differ substantially from the visual analysis of human movement under more realistic conditions.     

Person identification from biological motion: effects of structural and kinematic cues

Human observers are able to identify a person based on his or her gait. However, little is known about the underlying mechanisms and the kind of information used to accomplish such a task. In this study, participants learned to discriminate seven male walkers shown as point-light displays from frontal, half-profile, or profile view. The displays were gradually normalized with respect to size, shape, and walking frequency, and identification performance was measured. All observers quickly learned to discriminate the walkers, but there was an overall advantage in favor of the frontal view. No effect of size normalization was found, but performance deteriorated when shape or walking frequency was normalized. Presenting the walkers from novel viewpoints resulted in a further decrease in performance. However, even after applying all normalization steps and rotating the walker by 90 degrees, recognition performance was still nearly three times higher than chance level.     

Changes in interlimb coordination during walking and grasping task in older adult fallers and non-fallers

The aim of this study was to investigate interlimb coordination in young and older adults with and without a history of falls during the combined task of walking and prehension with different levels of manual task difficulty. Participants walked on a pathway and grasped a dowel. A vector coding technique evaluated coordination patterns. The coordination pattern was not affected by the difficulty level of the manual task. Older adults seemed to prioritize the movement of the right shoulder to grasp the dowel and then ‘froze’ the movement of the other joint (left shoulder) not directly involved in the grasping task. The preference to pick up the dowel in the double support phase and the increase in right shoulder phase made by older adults with a history of falls suggests an even greater decoupling between walking and prehension.     

The step cycle organization of infant walkers

To walk independently, the human infant must coordinate its multisegmented body to achieve both postural stability and forward mobility. In this experiment, we sought evidence of the form this coordination takes in infants who have been walking 3 to 10 months. Using the Philippson phases to represent the step cycle, we analyzed film records of infants and adults walking at speeds from 2 to 4 km/hr. Our results reveal a clear relationship between walking speed and the F and E(3) Philippson phases of the step cycle in both the young walkers and the adults. Indeed, across all four phases of the step cycle, the infants exhibited an organization that was almost identical to that of the mature walkers.     

Age and walking conditions differently affect domains of gait

IntroductionAnalysing gait in controlled conditions that resemble daily life walking could overcome the limitations associated with gait analysis in uncontrolled real-world conditions. Such analyses could potentially aid the identification of a walking condition that magnifies age-differences in gait. Therefore, the aim of the current study was to determine the effects of age and walking conditions on gait performance.MethodsTrunk accelerations of young (n = 27, age: 21.6) and older adults (n = 26, age: 68.9) were recorded for 3 min in four conditions: walking up and down a university hallway on a track of 10 m; walking on a specified path, including turns, in a university hallway; walking outside on a specified path on a pavement including turns; and walking on a treadmill. Factor analysis was used to reduce 27 computed gait measures to five independent gait domains. A multivariate analysis of variance was used to examine the effects of age and walking condition on these gait domains.ResultsFactor analysis yielded 5 gait domains: variability, pace, stability, time & frequency, complexity, explaining 64% of the variance in 27 gait outcomes. Walking conditions affected all gait domains (p < 0.01) but age only affected the time & frequency domain (p < 0.05). Age and walking conditions differently affected the domains variability, stability, time & frequency. The largest age-differences occurred mainly during straight walking in a hallway (variability: 31% higher in older adults), or during treadmill walking (stability: 224% higher, time&frequency: 120% lower in older adults).ConclusionWalking conditions affect all domains of gait independent of age. Treadmill walking and walking on a straight path in a hallway, were the most constrained walking conditions in terms of limited possibilities to adjust step characteristics. The age by condition interaction suggests that for the gait domains variability, stability, and time & frequency, the most constrained walking conditions seem to magnify the age-differences in gait.     

Effects of passive interpersonal light touch during walking on postural control responses: An exploratory study

The effects of passive interpersonal light touch (PILT) on postural stability can be observed through improved postural coordination through haptic feedback from the contact provider to the contact receiver while walking. It is unclear, however, whether PILT affects the contact receiver's detailed physical responses, such as muscle activity, body sway, and joint movements. In this study, surface electromyography and an inertial measurement unit were used simultaneously to explore changes in walking speed and control responses induced by PILT. We evaluated fourteen healthy participants for their walking speed and physical responses under two walking conditions: no-touch (NT) and PILT. As a physical response during walking, we measured muscle activity (rectus femoris, semitendinosus, tibialis anterior, and soleus muscles), body sway (pelvis and neck), and joint angles (direction of hip, knee, and ankle joint movements). In PILT condition, fingertip contact force was measured while the contact provider touched the third level of the recipient's lumbar spine. In comparison with the NT condition, PILT condition increased walking speed and decreased body sway on neck position. There were significant correlations between walking speed and neck sway regarding NT and PILT change values. Passive haptic information to the contact receiver may assist in the smooth shift of the center of gravity position during gait through interpersonal postural coordination. These findings suggest that PILT may provide an efficient and stable gait.