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.     

Speed influences on the scaling behavior of gait cycle fluctuations during treadmill running

The current study examined the temporal structure of gait cycle fluctuations in running. Participants ran at 80%, 90%, 100%, 110% and 120% of preferred running speed for 8min trials. Kinematic and kinetic gait cycle variables were generated from ground reaction force data. Mean, SD and CV of the kinematic and kinetic variables changed linearly with speed, whereas U-shaped functions were found for the scaling exponent alpha in 5 of the 8 variables investigated. Our findings reveal that long range correlations are present in both kinetic and kinematic variables of the gait cycle. The dependent structure of the stride interval is reduced at preferred running speed and this is hypothesized to be related to the enhanced stability and flexibility of this gait speed.     

Bilateral asymmetry of running gait in competitive,recreational and novice runners at different speeds

The mechanisms and underlying causes of bilateral asymmetry among healthy runners of different levels remain unclear. This cross-sectional laboratory study aimed to investigate the effects of running speed and running experience or competitive level on bilateral symmetry during running. Eleven competitive runners, 9 recreational runners and 11 novice runners were recruited in this study. They ran on an instrumented treadmill for 3 min at each of 5 fixed speeds (8, 9, 10, 11 and 12 km/h) in a randomized order. Bilateral asymmetry was evaluated and quantified using symmetry index (SI) of temporal and kinetic parameters. Overall, SI ranged between 0.8% for stride time and 21.4% for vertical average loading rate. Significant speed effects were observed on SI of flight time (p = .012), which was significantly higher at 8 km/h than that of the other 4 speeds (p = .023, 0.005, 0.023 and 0.028, respectively). Group-by-speed interactions were detected on SI in time to peak vertical ground reaction force (p = .032) and vertical average loading rate (p = .002). The competitive runners presented linear reduction in the SI with increasing speed from 8 to 12 km/h (R² > 0.94); for the recreational runners, SI changed nonlinearly and presented a roughly U-shaped trend across speeds (R² > 0.88); and for the novice runners, changes of SI across speed were inconsistent and dependent on parameters of interest (R² > 0.64). Bilateral asymmetry was affected by both running speed and runners' running experience or competitive level. The competitive runners were found to run with a more symmetrical manner with a greater running speed, the recreational runners demonstrated the most symmetrical pattern at the critical speed, whereas the novice runners showed inconsistent trends.     

Successful adaptation of gait in healthy older adults during dual-task treadmill walking

Dual-task methods have been used to demonstrate increased prioritization of walking performance over cognition in healthy aging. This is expressed as greater dual-task costs in cognitive performance than in walking. However, other research shows that older adults can prioritize cognitive performance over walking when instructed to do so. We asked whether age-related cognitive prioritization would emerge by experimentally manipulating cognitive difficulty. Young and older adults performed mental arithmetic at two levels of difficulty, alone or while walking. Electromyography and footswitches were used to measure muscle activity and stride parameters. Under high cognitive load, older adults increased their stride time, stride length, and hamstring activity, while maintaining their cognitive performance. Young adults showed negligible dual-task costs in each domain. The older adults appeared to successfully adapt their stride in response to high cognitive demands. The results have implications for neural models of gait regulation, and age differences in task emphasis.     

Familiarisation of novice and experienced treadmill users during a running session: Group specific evidence,time and individual patterns

The elimination of familiarisation effects is a recurring topic in biomechanical testing during treadmill running among different experience levels. The two aims of this study were (i) to calculate familiarisation times of novice and experienced treadmill runners on a group level and (ii) to examine individual familiarisation patterns in order to classify those with similar characteristics. Twenty runners participated in this study by performing a treadmill running session with 3D motion capture. Familiarisation times for 9 kinematic variables among both groups (novices and experienced treadmill runners) were statistically analysed. Additionally a qualitative clustering process (supported by quantitative criteria) provided individual familiarisation patterns for all participants and variables. Group mean familiarisation times were inconsistent across variables (ranging from 3 to 14 min), with no general tendency for decreased familiarisation time in experienced compared to novice treadmill runners. The analysis of individual familiarisation patterns revealed that 30.5% were not stable after 15 min. Substantial changes compared to the initial state were observed in data sets with detected familiarisation pattern. Treadmill running experience does not affect familiarisation patterns since this process is highly individual and variable-specific. Consequently, no generalised familiarisation time can be provided and the elimination of familiarisation in biomechanical testing a priori does not seem to be possible in the first 15 min for approximately one third of the individual patterns studied. In conclusion, the common practice of collecting data subsequent to a pre-defined generalised familiarisation time ought to be replaced by measurements at several points in time during trials. This required procedure would allow for checking familiarisation patterns and fluctuations in order to exclude inappropriate data sets in future treadmill studies.     

Dynamic stability during running gait termination: Predictors for successful control of forward momentum in children and adults

Reported differences between children and adults with respect to COM horizontal and vertical position to maintain dynamic stability during running deceleration suggest that this relationship may not be as important in children. This study challenged the current dynamic stability paradigm by determining the features of whole body posture that predicted forward velocity and momentum of running gait termination in adults and children. Sixteen adults and 15 children ran as fast as possible and stopped at pre-determined location. Separate regression analyses determined whether COM posterior and vertical positions and functional limb length (distance between COM and stance foot) predicted velocity and momentum for adults and children. COM posterior position was the strongest predictor of forward velocity and momentum in both groups supporting the previously established relationship during slower tasks. COM vertical position also predicted momentum in children, not adults. Higher COM position in children was related to greater momentum; consistent with previously reported differences between children and adults in COM position across running deceleration. COM vertical position was related to momentum but not velocity in children suggesting that strategies used to terminate running may be driven by demands imposed not just by velocity, but also the mass being decelerated.     

A scoping review of non-linear analysis approaches measuring variability in gait due to lower body injury or dysfunction

ObjectivesThe aim of this review is to evaluate and summarize existing literature using non-linear analysis methodology to consider variability of human movement due to lower limb injury or dysfunction.DesignScoping review.MethodsAn electronic keyword search was performed on three databases to identify appropriate research. This research was then examined for details of measures and methodology, use of control groups and general study characteristics to identify related themes.ResultsFifteen papers were reviewed and synthesized. A range of conditions were studied, mainly affecting knee and ankle joints, and each using different non-linear methods and different equipment (motion capture, accelerometry, and muscle activation) to evaluate the mathematically chaotic nature of the movement and assess the variability in gait. Sample sizes and effect sizes are commonly small in these studies.ConclusionsNon-linear analysis is a potentially useful tool in both diagnosis and evaluation of injury, and this should inform future clinical processes when dealing with injury and movement variability. Despite numerous studies evaluating neurological conditions and ageing, focus on injury is limited, with notable gaps in terms of considering other joints and joint actions, so this should be a promising area of research to develop our understanding of injury and rehabilitation and how this affects gait variability.     

Development of postural adjustment during gait initiation: kinematic and EMG analysis

The authors studied the development of postural adjustments associated with the initiation of gait in children by using kinematic and electromyographic (EMG) analysis. Participants (N = 28) included infants with 1-4 and 9-17 months of walking experience, children 4-5 years of age, and adults. Anticipatory postural adjustments (APA) were present in the youngest age groups, including a clear anticipatory lateral tilt of the pelvis and the stance leg, which enabled the child to unload the opposite leg shortly before its swing phase. An anticipatory activation of the hip abductor of the leg in stance phase prior to heel-off was found, suggesting pelvis stabilization. APA did not appear consistently until 4-5 years of age. A decrease in segmental oscillations occurred across the ages, indicating better control of intersegmental coordination in the frontal and sagittal planes during the postural phase of gait initiation. Young walkers presented APA involving movements of both the upper and the lower parts of the body, whereas, like adults, 4- to 5-year-olds were able to laterally shift only the pelvis and the stance leg. The oldest children and the adults also showed lower activation levels of hip and knee muscles but higher activation at the ankle level. Those kinematic and EMG results taken together suggest a clear developmental sequence from an en bloc operation of the body through an articulated operation with maturation, walking experience, or both.     

Judgments of happiness during trail running: Pleasure,engagement, and meaning

ObjectivesIt has been theorized that happiness is derived from three major, unique sets of life experience: pleasure, engagement, and meaning. The present study examined the mental processes by which individuals combined five information cues (relatedness, autonomy, competence, mental vitality and physical vitality) when judging the degree of happiness felt by a trail runner during a run.Design/methodThe participants (104 adult male athletes; M_age = 32.70; SD = 10.86) rated pleasure, engagement, and meaning in 32 scenarios built from combinations of these cues.ResultsThe results of multivariate and univariate analyses of variance indicated that all five cues had a positive effect on judgments of pleasure, engagement, and meaning. The participants used three different information integration rules, depending on the pathway to happiness being probed.ConclusionsThe information integration and the integration rules highlighted the different contributions of pleasure, engagement, and meaning in cognitive building of happiness.     

The influence of exercise duration and cognitions during running on feeling states in an indoor running track environment

Objectives. To examine the influence of different durations of aerobic exercise and cognitions during running on exercise-induced feeling state changes in an indoor running track environment once baseline differences in feeling states were controlled.Method. Physically active females (n=69) participated in one of three experimental conditions: a) a 25 min run at 70% heart rate reserve (HRR), b) a 40 min run at 70% HRR, or c) a 40 min no exercise control. Pre-post feeling states (EFI) were assessed and cognitions during running were recorded with 5 min left in the run.Results. Multilevel modeling analyses revealed that positive engagement and revitalization significantly increased from pre- to post-exercise in comparison to the control condition regardless of exercise duration whereas physical exhaustion was significantly reduced. However, tranquility significantly increased only in the 25 min run condition. Finally, cognitions during exercise moderated the changes in feeling states from pre- to post-exercise above and beyond exercise duration with participants reporting dissociative-external thoughts reporting greater increases in revitalization and decreases in physical exhaustion.Conclusions. Both objective demands of the exercise task (i.e., exercise duration) and subjective intrapsychic phenomena (i.e., cognitions during running) may aid in explaining exercise-induced feeling state changes.     

Feature analysis and the role of similarity in preattentive vision

Texture arrays of line elements at various orientations were used to study three phenomena of preattentive vision. Subjects were asked (1) to discriminate texture areas and to distinguish their form (experiments on texture segmentation); (2) to detect salient or vertical line elements (experiments on pop-out); and (3) to identify configurations of similar or dissimilar targets (experiments on grouping). Within the patterns, line orientation was systematically varied to distinguish the effect of differences between areas from the effect of similarity within areas. In all of the experiments, performance was found to depend on local orientation contrast at texture borders rather than on the analysis of line orientation itself. Texture areas were correctly identified only when the orientation contrast at the border well exceeded the overall variation of line orientation in the pattern. Similarly, only target elements with high local orientation contrast were detected fast and “in parallel.” Targets with an orientation contrast lower than background variation required serial search. Preattentive grouping was found to depend on saliency, as defined by local orientation contrast, but not on the similarity of line elements. In addition to local orientation contrast, which played an important role in all of the visual phenomena studied, influences from the alignment of line elements with the outline of a figure were also seen.     

Feature analysis and the role of similarity in preattentive vision.

Texture arrays of line elements at various orientations were used to study three phenomena of preattentive vision. Subjects were asked (1) to discriminate texture areas and to distinguish their form (experiments on texture segmentation); (2) to detect salient or vertical line elements (experiments on pop-out); and (3) to identify configurations of similar or or dissimilar targets (experiments on grouping). Within the patterns, line orientation was systematically varied to distinguish the effect of differences between areas from the effect of similarity within areas. In all of the experiments, performance was found to depend on local orientation contrast at texture borders rather than on the analysis of line orientation itself. Texture areas were correctly identified only when the orientation contrast at the border well exceeded the overall variation of line orientation in the pattern. Similarly, only target elements with high local orientation contrast were detected fast and "in parallel". Targets with an orientation contrast lower than background variation required serial search. Preattentive grouping was found to depend on saliency, as defined by local orientation contrast, but not on the similarity of line elements. In addition to local orientation contrast, which played an important role in all of the visual phenomena studied, influences from the alignment of line elements with the outline of a figure were also seen.     

创造性思维中语义搜索过程：基于答案累积时间函数和语义相似性的量化分析

通过描绘发散性思维测验(物品多用途, AUT)中答案生成在累积函数和语义相似性等一系列参数上的量化特征, 揭示创造性思维的语义搜索过程。结果发现：(1)新颖AUT条件中, 语义搜索呈现与自由联想类似的负加速特点, 但搜索速度较寻常AUT条件更慢。(2)新颖AUT条件中所生成的答案与题目(即物品)均具有较低的语义相似性, 且显著小于寻常AUT条件。(3)新颖AUT条件中生成的答案比寻常AUT条件表现出显著更低的聚类程度, 其中可聚类答案和未聚类答案与题目的语义相似度均较低, 且不存在显著差异, 二者在新颖性上也不存在显著差异。以上结果说明了创造性思维的语义信息搜索过程具有与自由联想类似的激活扩散特征, 但总体搜索速度较慢。新颖性要求使得个体在最初搜索时便开始摆脱题目的语义限制而进行远距离搜索(避免就近搜索), 并倾向于在每个语义场中只生成一个答案(避免局部搜索), 但也可能会在远离题目的语义场中生成多个同类别答案。     

Energy redistribution analysis of dynamic mechanisms of multi-body, multi-joint kinetic chain movement during soccer instep kicks

The purpose of this study is to develop a model to analyze energy redistribution mechanisms of a multi-joint limb system and to examine the mechanisms underlying the production of the mechanical energy of the system during instep kicking. Kicking movements of 11 collegiate soccer players were recorded using a motion capture system, and ground reaction force during kicks was measured. Using the experimental data and the state-space power analysis developed in the current study, the kinetic energy change of the modeled segments was decomposed into causal components due to various dynamic factors (muscular and non-muscular interactive moments). The results showed that the increase of the kinetic energy of the kicking limb resulted from the energy transfer mechanisms between the decelerated segment (a proximal segment) and accelerated segment (a distal segment), induced by a non-muscular interactive moment due to the external joint force or the centrifugal force. The proximal (thigh) to distal (shank) sequential motion pattern observed was due to the energy transfer mechanism induced by the centrifugal effect acting to accelerate the shank and decelerate the thigh. The fact suggests that effective use of that mechanism may be advantageous to enhance the kinetic energy of the kicking shank. In conclusion, energy transfer mechanisms likely play a greater role in dynamic kicking than muscle power output, and better coordination to exchange kinetic energy among segments makes kicking more efficient.     

Measures of invariance and comparability in factor analysis for fixed variables

New procedures are presented for measuring invariance and matching factors for fixed variables and for fixed or different subjects. Two of these, the coefficient of invariance for factor loadings and the coefficient of factor similarity, utilize factor scores computed from the different sets of factor loadings and one of the original standard score matrices. Another, the coefficient of subject invariance, is obtained by using one of the sets of factor loadings in conjunction with the different standard score matrices. These coefficients are correlations between factor scores of the appropriate matrices. When the best match of factors is desired, rather than degree of resemblance, the method of assignment is proposed.     

Trunk and center of mass movements during gait in children with juvenile idiopathic arthritis

Motion of the body center of mass (CoM) can often indicate the overall effect of the strategy of forward progression used. In the present study, focus is placed on trunk movements in the sagittal, coronal, and transverse/rotation plane, as well as placement of the CoM, during gait in children with juvenile idiopathic arthritis (JIA). Seventeen children with JIA, all with polyarticular lower extremity involvement were examined before and approximately two weeks after treatment with intra-articular cortico-steroid injections. Movement was recorded with a 6-camera 3D motion analysis system in both the children with JIA and in 21 healthy controls. Trunk and center of mass movements were compared between JIA and controls, and effects of intra-articular cortico-steroid treatment were evaluated. Children with JIA were more posteriorly tilted in the trunk, contrary to the common clinical impression, and had their CoM placed more posterior and off-centred, which may have been a result of pain. With such knowledge, it might be possible to better understand the effects of their pain and involvement, and ultimately to plan a treatment strategy for improving their gait patterns.     

Response inhibition and avoidance of virtual obstacles during gait in healthy young and older adults

Adjustments of preplanned steps are essential for fall avoidance and require response inhibition. Still, inhibition is rarely tested under conditions resembling daily living. We evaluated the ability of young and older adults to modify ongoing walking movements using a novel precision step inhibition (PSI) task combined with an auditory Stroop task.Healthy young (YA, n = 12) and older (OA, n = 12) adults performed the PSI task at 4 individualized difficulty levels, as a single and dual task (DT). Subjects walked on a treadmill by stepping on virtual stepping stones, unless these changed color during approach, forcing the subjects to avoid them. OA made more failures (40%) on the PSI task than YA (16%), but DT did not affect their performance. In combination with increased rates of omitted Stroop task responses, this indicates a “posture first” strategy. Yet, adding obstacles to the PSI task significantly deteriorated Stroop performance in both groups (the average Stroop composite score decreased by 13% in YA and 27% in OA). Largest deficit of OA was observed in rates of incorrect responses to incongruent Stroop stimuli (OA 35% and YA 12%), which require response inhibition. We concluded that the performance of OA suffered specifically when response inhibition was required.     

Changes in coordination and variability during running as a function of head stability demands

The purpose of this study was to identify changes in segment/joint coordination and coordination variability in running with increasing head stability requirements. Fifteen strides from twelve recreational runners while running on a treadmill at their preferred speed were collected. Head stability demands were manipulated through real-time visual feedback that required head-gaze orientation to be contained within boxes of different sizes, ranging from 21 to 3 degrees of visual angle in 3-degree decrements. Coordination patterns and coordination variability were assessed between head and trunk segments, hip and knee joints, and knee and ankle joints in the three cardinal planes, respectively. Mean coupling angles and the standard deviation of the coupling angles at each individual point of the stance phase were calculated using a modified vector coding technique and circular statistics. As head stability demands increased, transverse plane head-trunk coordination was more anti-phase and showed increased head‑leading and decreased trunk‑leading patterns; for the lower extremity, there was increased in-phase and decreased anti-phase sagittal plane coordination. Increased head stability demands also resulted in an increase in coordination variability for both upper body and lower extremity couplings during the second half of the stance phase. Overall, the results provide evidence that coordinative adaptations to increasing head stability demands occur throughout the entire body: 1) through more independent control of the head relative to the trunk; 2) by increasing in-phase coordination between lower extremity joints, and 3) through increased coordination variability in the second half of stance in both upper body segmental and lower extremity joint couplings. These adaptations likely contribute to the reduction of the range of motion of the trunk in vertical direction.     

Reexamining the phonological similarity effect in immediate serial recall: The roles of type of similarity,category cuing,and item recall

Study of the phonological similarity effect (PSE) in immediate serial recall (ISR) has produced a conflicting body of results. Five experiments tested various theoretical ideas that together may help integrate these results. Experiments 1 and 2 tested alternative accounts that explain the effect of phonological similarity on item recall in terms of feature overlap, linguistic structure, or serial order. In each experiment, the participants' ISR was assessed for rhyming, alliterative, and similar nonrhyming/nonalliterative lists. The results were consistent with the predictions of the serial order account, with item recall being higher for rhyming than for alliterative lists and higher for alliterative than for similar nonrhyming/nonalliterative lists. Experiments 3 and 4 showed that these item recall differences are reduced when list items repeat across lists. Experiment 5 employed rhyming and dissimilar one-syllable and two-syllable lists to demonstrate that recall for similar (rhyming) lists can be better than that for dissimilar lists even in a typical ISR task in which words are used, providing a direct reversal of the classic PSE. These and other previously published results are interpreted and integrated within a proposed theoretical framework that offers an account of the PSE.