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Background: Aging and pathology result in changes in the dynamics of several physiological subsystems. Often, these changes are concurrent, altering the dynamics between subsystems. Cardiac and gait rhythms are one example in which patterns change during physical activity., Aims: The purpose of this research is to simultaneously monitor changes in cardiac and gait rhythms when participants complete various treadmill walking tasks-normal speed, fast speed, and while synchronizing steps with a blinking metronome., Methods: The cardiac and gait rhythms of younger and older healthy adults were examined in this study during treadmill walking tasks. Pre-test and post-test walking at a preferred walking speed were compared to fast walking and walking with a gait synchronization test. Cardiac and gait rhythms were observed to calculate the mean, standard deviation, coefficient of variation, detrended fluctuation analysis scaling exponent alpha (DFA α), and sample entropy from each 15-min trial. Separate MANOVAs were used to examine the two experimental conditions for cardiac and gait rhythm variability., Results: During the gait synchronization experiment, main effects for phase were exhibited for all gait variables, but none were shown during the fast walking task. Meanwhile, the cardiac rhythms demonstrated decreased mean and increased DFA α only during the synchronization condition., Discussion: Participants, regardless of age, exhibited similar patterns of change in their cardiac and locomotor rhythms during the treadmill walking tasks. Cardiac rhythms were only altered during the gait synchronization task, suggesting it may be possible to simultaneously influence the variability and structure of cardiac and gait rhythms.

The assessment of gait variability using stochastic signal processing techniques such as detrended fluctuation analysis (DFA) has been shown to be a sensitive tool for evaluation of gait alterations due to aging and neuromuscular disease. However, previous studies have suggested that the application of DFA requires relatively long recordings (600 strides), which is difficult when working with clinical populations or older adults. In this paper we propose a model for predicting DFA variance in experimental data and conduct a Monte Carlo simulation to estimate the sample size and number of trials required to detect a change in DFA scaling exponent. We illustrate the model in a simulation to detect a difference of 0.1 (medium effect) between two groups of subjects when using short gait time series (100 to 200 strides) in the context of between- and within-subject designs. We assumed that the variance of DFA scaling exponent arises due to individual differences, time series length, and experimental error. Results showed that sample sizes required to achieve acceptable power of 80% are practically feasible, especially when using within-subject designs. For example, to detect a group difference in the DFA scaling exponent of 0.1, it would require either 25 subjects and 2 trials per subject or 12 subjects and 4 trials per subject using a within-subject design. We then compared plausibility of such power predictions to the empirically observed power from a study that required subjects to synchronize with a persistent fractal metronome. The results showed that the model adequately predicted the empirical pattern of results. Our power simulations could be used in conjunction with previous design guidelines in the literature when planning new gait variability experiments.

Nonlinear dynamics quantifies gait variability patterns, which can be useful in evaluating functional ability. A commonly used nonlinear technique is detrended fluctuation analysis (DFA). Safety support structures have previously been shown to alter DFA during gait. However, the effect of a nonweight-supporting treadmill harness on DFA during gait has yet to be determined. The purpose of this study was to determine whether a nonweight-supporting harness influenced the DFA alpha metric (DFA α) of variables typically used to examine gait function. Twenty participants (10 young adults and 10 older adults) were recruited for this study. Each participant completed one testing session on a treadmill consisting of three conditions: (1) no harness, (2) harnessed, but not attached to the support frame, and (3) harnessed and attached to the support frame. Participants walked for 15 min at the same self-selected speed for each condition. The gait variables of stride time, stride length, and step width for each condition were analyzed using DFA α to examine gait function. There were no significant interactions between age group and condition for DFA α of each variable. Additionally, there were no main effects for DFA α for age group or condition. These data indicate that a nonweight-supporting harness can be used for safety without impeding the emergence of natural gait dynamics when stride time, stride length, and step width are the primary variables of interest., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Previous work has shown that fractal patterns in gait can be altered by entraining to a fractal stimulus. However, little is understood about how long those patterns are retained or which factors may influence stronger entrainment or retention. In experiment one, participants walked on a treadmill for 45 continuous minutes, which was separated into three phases. The first 15 minutes (pre-synchronization phase) consisted of walking without a fractal stimulus, the second 15 minutes consisted of walking while entraining to a fractal visual stimulus (synchronization phase), and the last 15 minutes (post-synchronization phase) consisted of walking without the stimulus to determine if the patterns adopted from the stimulus were retained. Fractal gait patterns were strengthened during the synchronization phase and were retained in the post-synchronization phase. In experiment two, similar methods were used to compare a continuous fractal stimulus to a discrete fractal stimulus to determine which stimulus type led to more persistent fractal gait patterns in the synchronization and post-synchronization (i.e., retention) phases. Both stimulus types led to equally persistent patterns in the synchronization phase, but only the discrete fractal stimulus led to retention of the patterns. The results add to the growing body of literature showing that fractal gait patterns can be manipulated in a predictable manner. Further, our results add to the literature by showing that the newly adopted gait patterns are retained for up to 15 minutes after entrainment and showed that a discrete visual stimulus is a better method to influence retention.

Much has been learned about the characteristics of gait in overground and treadmill walking. However, there are many contexts in which overground or treadmill walking might not be possible, such as in home-based physical therapy. In those cases, a surrogate task to index gait behavior would be a valuable tool. Thus, the purpose of this study was to evaluate the stride behavior characteristics of stationary stepping compared with treadmill walking. Healthy young adults (N = 10) preformed two 15-minute tasks: (1) treadmill walking and (2) stationary stepping. Several stride behavior characteristics were recorded, including the number of strides taken, minimum and maximum knee angle, stride interval mean, stride interval standard deviation, and detrended fluctuation analysis (DFA) alpha of the stride interval time series. The results showed that stride behavior was similar between tasks when examined at the group level. However, when individual level analyses were used to examine the reliability of each metric between tasks, poor reliability was observed in most metrics, indicating that stationary stepping may not be an appropriate surrogate task for overground or treadmill walking. These results are discussed in the context of a gait dynamics framework, with attention to task constraints that may have influenced the findings.

Fractal patterns characterize healthy biological systems and are considered to reflect the ability of the system to adapt to varying environmental conditions. Previous research has shown that fractal patterns in gait are altered following natural aging or disease, and this has potential negative consequences for gait adaptability that can lead to increased risk of injury. However, the flexibility of a healthy neurological system to exhibit different fractal patterns in gait has yet to be explored, and this is a necessary step toward understanding human locomotor control. Fifteen participants walked for 15min on a treadmill, either in the absence of a visual stimulus or while they attempted to couple the timing of their gait with a visual metronome that exhibited a persistent fractal pattern (contained long-range correlations) or a random pattern (contained no long-range correlations). The stride-to-stride intervals of the participants were recorded via analog foot pressure switches and submitted to detrended fluctuation analysis (DFA) to determine if the fractal patterns during the visual metronome conditions differed from the baseline (no metronome) condition. DFA α in the baseline condition was 0.77±0.09. The fractal patterns in the stride-to-stride intervals were significantly altered when walking to the fractal metronome (DFA α=0.87±0.06) and to the random metronome (DFA α=0.61±0.10) (both p<.05 when compared to the baseline condition), indicating that a global change in gait dynamics was observed. A variety of strategies were identified at the local level with a cross-correlation analysis, indicating that local behavior did not account for the consistent global changes. Collectively, the results show that a gait dynamics can be shifted in a prescribed manner using a visual stimulus and the shift appears to be a global phenomenon., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Gait performance exhibits patterns within the stride-to-stride variability that can be indexed using detrended fluctuation analysis (DFA). Previous work employing DFA has shown that gait patterns can be influenced by constraints, such as natural aging or disease, and they are informative regarding a person's functional ability. Many activities of daily living require concurrent performance in the cognitive and gait domains; specifically working memory is commonly engaged while walking, which is considered dual-tasking. It is unknown if taxing working memory while walking influences gait performance as assessed by DFA. This study used a dual-tasking paradigm to determine if performance decrements are observed in gait or working memory when performed concurrently. Healthy young participants (N = 16) performed a working memory task (automated operation span task) and a gait task (walking at a self-selected speed on a treadmill) in single- and dual-task conditions. A second dual-task condition (reading while walking) was included to control for visual attention, but also introduced a task that taxed working memory over the long term. All trials involving gait lasted at least 10 min. Performance in the working memory task was indexed using five dependent variables (absolute score, partial score, speed error, accuracy error, and math error), while gait performance was indexed by quantifying the mean, standard deviation, and DFA α of the stride interval time series. Two multivariate analyses of variance (one for gait and one for working memory) were used to examine performance in the single- and dual-task conditions. No differences were observed in any of the gait or working memory dependent variables as a function of task condition. The results suggest the locomotor system is adaptive enough to complete a working memory task without compromising gait performance when walking at a self-selected pace.

Variable practice may be beneficial for learning novel motor patterns. The purpose of this study was to determine the effect of a variable practice intervention during treadmill walking on the dynamic properties of gait. Using a counterbalanced design, 16 subjects with hemiparesis following chronic stroke performed 20 min of treadmill walking in constant speed training (CST) and variable speed training (VST) conditions. The dynamic properties of the hip and knee sagittal plane angles for two minutes before (pre-data) and two minutes after (post-data) CST and VST were examined using detrended fluctuation analysis and sample entropy. A main effect for time was observed for sample entropy of the knee angle; no other differences were observed between the pre/post data for the CST or VST conditions. While variable practice conditions are intended to promote movement errors for improved learning, we were unable to detect immediate changes in movement variability as a function of practice condition following a single session of gait training for individuals post-stroke., (Copyright © 2012 Elsevier B.V. All rights reserved.)

During locomotion over uneven terrain, gait must be adapted to avoid a trip. In the event of a foot-obstacle contact, the body reactively responds to the perturbation. However, it is unknown if any proactive adjustments are made in subsequent strides to reduce the likelihood of another contact, and how long any proactive adaptations persist. This study examined gait behavior while stepping over a 10cm obstacle placed in the middle of an 8m walkway. The four obstacle crossings that preceded a spontaneous obstacle contact were compared to the eight obstacle crossings subsequent to the contact. Foot position before the obstacle was not modified following the obstacle contact. However, toe clearance and peak toe elevation increased in the limb that was tripped; the unperturbed limb showed no differences. These findings demonstrate that the sensory information of the perturbed limb proactively influenced the ipsilateral but not the contralateral limb, supporting the idea that the lead and trail limb are controlled independently during obstacle crossing. The proactive adaptation lasted for at least eight trials, suggesting that an unexpected perturbation influences the control of adafptive gait well after obstacle contact., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Purpose: Injuries from falls are a serious health issue. Approaches to preventing falls should consider increasing relevant visual information of an obstacle. Obstacle parameters, such as position and height, may be specified by the visible structure of an obstacle. The present study examined the relationship between visible structure of an obstacle and locomotor behaviour. This relationship may be modified as a function of experience with navigating obstacles. Since workers at construction sites must navigate through cluttered environments with varied obstacles, these workers may have superior skills at avoiding obstacles. Therefore, the effect of work experience was also examined., Methods: Nine construction workers and 10 age- and gender-matched control subjects participated. Subjects stepped over obstacles in an 8 m walkway. Three different obstacles were examined, arranged according to a hierarchy ranging from most to least visible structure: a solid obstacle, a three-edge outline obstacle and a top-edge obstacle. The obstacles were 10, 20 or 30 cm high. In addition, visual information was decreased with goggles which obstructed the lower visual field, removing information of the obstacle and foot-relative-to-obstacle in the two steps before the obstacle. All conditions were presented randomly., Results: Higher risk of contact and higher lead and trail toe clearance variability were observed for the top-edge obstacle. Higher risk of contact was observed when the lower visual field was obstructed and for the 30 cm obstacle. Work experience did not influence risk of contact. Construction workers had lower trail toe clearances and lower trail toe clearance variability for the 10 cm obstacle, but were not different from controls for the 30 cm obstacle., Conclusions: Decreased visible structure of an obstacle resulted in increased gait variability and increased risk of contact. The changes are consistent with decreased accuracy of the sensory-to-motor transformation used to control the lead and trail limb during obstacle crossing when only the top-edge was visible. There is some evidence that construction workers were better able to transform the visual information to motor actions, as reflected by decreased gait variability, but these findings were not supported by decreased risk of obstacle contact., (© 2011 The College of Optometrists.)

Background: During locomotion, vision is used to perceive environmental obstacles that could potentially threaten stability; locomotor action is then modified to avoid these obstacles. Various factors such as lighting and texture can make these environmental obstacles appear larger or smaller than their actual size. It is unclear if gait is adapted based on the actual or perceived height of these environmental obstacles. The purposes of this study were to determine if visually guided action is scaled to visual perception, and to determine if task experience influenced how action is scaled to perception., Methodology/principal Findings: Participants judged the height of two obstacles before and after stepping over each of them 50 times. An illusion made obstacle one appear larger than obstacle two, even though they were identical in size. The influence of task experience was examined by comparing the perception-action relationship during the first five obstacle crossings (1-5) with the last five obstacle crossings (46-50). In the first set of trials, obstacle one was perceived to be 2.0 cm larger than obstacle two and subjects stepped 2.7 cm higher over obstacle one. After walking over the obstacle 50 times, the toe elevation was not different between obstacles, but obstacle one was still perceived as 2.4 cm larger., Conclusions/significance: There was evidence of locomotor adaptation, but no evidence of perceptual adaptation with experience. These findings add to research that demonstrates that while the motor system can be influenced by perception, it can also operate independent of perception.

Gait asymmetries are a common problem in clinical populations, such as those with a history of stroke or Parkinson's disease. The use of a split-belt treadmill is one way to enhance gait symmetry but relies on specialty (and typically expensive) equipment. Alternatively, visual cues have been shown as a method to alter gait mechanics, but their utility in altering gait symmetry has been relatively understudied. Before deploying this method to clinical populations, a proof-of-concept study is needed to explore using visual cues to alter gait symmetry in healthy adults. Therefore, the purpose of this study was to examine the extent to which healthy adults could synchronize to an asymmetric visual cue with a small or large gait asymmetry using wearable sensors to measure gait asymmetries. Seventy-two healthy adults (ages: 23.89 ± 6.08 years) walked on the treadmill for two conditions: with and without the visual cue. Each walking condition lasted 10 min at the participant's preferred walking speed. Inertial sensors were used to measure gait asymmetries. Some participants did not respond to the visual cue, and groups were separated into responders and non-responders. Participants in the small and large asymmetry-responder groups exhibited statistically significant increased asymmetries in single limb support % (p < 0.01) and step duration (s) (p < 0.05, p < 0.01, respectively). Only the large asymmetry-responder group showed statistically significant (p < 0.01) increased asymmetries in stride length. Overall, asymmetrical walking visual cues can alter gait asymmetries, and inertial sensors were sensitive enough to detect small changes in gait asymmetries. [ABSTRACT FROM AUTHOR]

Background: Neurologic rehabilitation aims to restore function, address barriers to activity, and improve quality of life in those with injury to the nervous system. Virtual reality (VR) has emerged as a useful tool to enhance neurorehabilitation interventions and outcomes. However, the manner in which VR-based neurorehabilitation has been manipulated to optimize outcomes using theory-based frameworks has not been documented. Behavior Change Techniques (BCTs) are described as the smallest active ingredient in an intervention aimed to change behavior via theoretically-proposed pathways. The purpose of this review was to investigate the ways VR is being used in neurorehabilitation to improve upright mobility, and systematically code those VR interventions for active BCTs. Methods: Keyword searches were performed using database searches of PubMed, SPORTDiscus, and psycINFO. The search yielded 32 studies for inclusion. Coding for BCTs was conducted using the Behavior Change Techniques Taxonomy v1 (BCTTv1). Results: Behavioral Practice, Graded Tasks, Biofeedback, and Explicit Feedback were the most commonly used BCTs. All studies reported improvements in motor performance outcomes. However, none of the studies investigated the efficacy of each component of their VR intervention making it difficult to point to the most effective components of VR interventions overall. Conclusions: This review suggests that investigation into the specific components of VR interventions, along with purposeful implementation and reporting of BCTs will help improve understanding of the efficacy of VR as a neurorehabilitation tool. Future research could benefit from incorporating BCTs into the design process of VR interventions to produce optimal rehabilitation potential. [ABSTRACT FROM AUTHOR]

We examined sagittal-plane thigh angular kinematics in individuals with and without recurrent ankle sprains using a clinical smartphone app called AccWalker. Sagittal-plane ankle kinematics were also compared to ascertain that altered ankle dorsiflexion, which is typically displayed with chronic ankle instability, is also present in individuals with recurrent ankle sprains. Participants with (n = 22) and without (n = 22) recurrent ankle sprains were evaluated on average sagittal-plane ankle kinematics during walking and average sagittal-plane thigh angular kinematics during stepping-in-place with AccWalker. Significant group-by-limb interactions were found for sagittal-plane ankle kinematics (F (1,42) = 63.786, P <.010) during walking and sagittal-plane average thigh angular range-of-motion (F (1,42) = 6.166, P =.017) with AccWalker. Individuals with recurrent ankle sprains displayed more ankle dorsiflexion in affected (P <.001) and unaffected (P =.001) limbs during walking than healthy controls and exhibited more ankle dorsiflexion in their affected-limb compared to their unaffected-limb (P <.001). The average sagittal-plane thigh angular range-of-motion was lower in the unaffected-limb for recurrent ankle sprains compared to their affected-limb (P =.038) and the assigned unaffected-limb of healthy controls (P =.035). Increased dorsiflexion was present in both limbs of the recurrent ankle sprain group with walking. AccWalker does not assess ankle movement, but uniquely identified thigh motion impairments associated with recurrent ankle sprains in their unaffected-limb, potentially identifying central deficits associated with recurrent ankle sprains. This app has clinical implications for assessing potential pathological movement that can be corrected through rehabilitation. • The Recurrent Ankle Sprains group walked with more dorsiflexion in the affected-limb. • Lower sagittal thigh motion in the limb with ankle sprains was found with stepping-in-place. • The current study has set the groundwork for AcWalker's potential clinical application. [ABSTRACT FROM AUTHOR]

Gait control challenges commonly coincide with vestibular dysfunction and there is a long history in using balance and gait activities to enhance functional mobility in this population. While much has been learned using traditional rehabilitation exercises, there is a new line of research emerging that is using visual stimuli in a very specific way to enhance gait control. For example, avatars can be created in an individualized manner to incorporate specific gait characteristics. The avatar could then be used as a visual stimulus to which the patient can synchronize their own gait cycle. This line of research builds upon the rich history of sensorimotor control research in which augmented sensory information (visual, haptic, or auditory) is used to probe, and even enhance, human motor control. This review paper focuses on gait control challenges in patients with vestibular dysfunction, provides a brief historical perspective on how various visual displays have been used to probe sensorimotor and gait control, and offers some recommendations for future research. [ABSTRACT FROM AUTHOR]

Gait asymmetries are commonly observed in neurological populations and linked to decreased gait velocity, balance decrements, increased fall risk, and heightened metabolic cost. Interventions designed to improve gait asymmetries have varying methods and results. The purpose of this systematic review was to investigate non-pharmacological interventions to improve gait asymmetries in neurological populations. Keyword searches were conducted using PubMed, CINAHL, and Academic Search Complete. The search yielded 14 studies for inclusion. Gait was assessed using 3D motion capture systems (n = 7), pressure-sensitive mats (e.g., GAITRite; n = 5), and positional sensors (n = 2). The gait variables most commonly analyzed for asymmetry were step length (n = 11), stance time (n = 9), and swing time (n = 5). Interventions to improve gait asymmetries predominantly used gait training techniques via a split-belt treadmill (n = 6), followed by insoles/orthoses (n = 3). The literature suggests that a wide range of methods can be used to improve spatiotemporal asymmetries. However, future research should further examine kinematic and kinetic gait asymmetries. Additionally, researchers should explore the necessary frequency and duration of various intervention strategies to achieve the greatest improvement in gait asymmetries, and to determine the best symmetry equation for quantifying gait asymmetries. [ABSTRACT FROM AUTHOR]