DFA as a window into postural dynamics supporting task performance: does choice of step size matter?

Introduction: Detrended Fluctuation Analysis (DFA) has been used to investigate self-similarity in center of pressure (CoP) time series. For fractional gaussian noise (fGn) signals, the analysis returns a scaling exponent, DFA-α, whose value characterizes the temporal correlations as persistent, random, or anti-persistent. In the study of postural control, DFA has revealed two time scaling regions, one at the short-term and one at the long-term scaling regions in the diffusion plots, suggesting different types of postural dynamics. Much attention has been given to the selection of minimum and maximum scales, but the choice of spacing (step size) between the window sizes at which the fluctuation function is evaluated may also affect the estimates of scaling exponents. The aim of this study is twofold. First, to determine whether DFA can reveal postural adjustments supporting performance of an upper limb task under variable demands. Second, to compare evenly-spaced DFA with two different step sizes, 0.5 and 1.0 in log2 units, applied to CoP time series. Methods: We analyzed time series of anterior-posterior (AP) and medial-lateral (ML) CoP displacement from healthy participants performing a sequential upper limb task under variable demand. Results: DFA diffusion plots revealed two scaling regions in the AP and ML CoP time series. The short-term scaling region generally showed hyper-diffusive dynamics and long-term scaling revealed mildly persistent dynamics in the ML direction and random-like dynamics in the AP direction. There was a systematic tendency for higher estimates of DFA-α and lower estimates for crossover points for the 0.5-unit step size vs. 1.0-unit size. Discussion: Results provide evidence that DFA-α captures task-related differences between postural adjustments in the AP and ML directions. Results also showed that DFA-α estimates and crossover points are sensitive to step size. A step size of 0.5 led to less variable DFA-α for the long-term scaling region, higher estimation for the short-term scaling region, lower estimate for crossover points, and revealed anomalous estimates at the very short range that had implications for choice of minimum window size. We, therefore, recommend the use of 0.5 step size in evenly spaced DFAs for CoP time series similar to ours.

Intellectual Humility: How Recognizing the Fallibility of Our Beliefs and Owning Our Limits May Create a Better Relationship Between the Physical Therapy Profession and Disability

Despite the many advancements over the history of the profession, physical therapy remains in a somewhat paradoxical relationship with disability. The physical therapist profession values disability as diversity but continues to focus on the normalization of body functions as the primary means to promote functionality in people with disability. This focus, consistent with a medicalized view of disability, may prevent physical therapists from empowering individuals with disability to explore alternative, yet effective, perceptual-motor strategies to achieve their functional goals. Additionally, recent research documents implicit, negative biases of physical therapists and physical therapist assistants toward people with disability, again consistent with the medicalized view that disability is the product of an imperfectly functioning body. Dominant underlying beliefs in any profession are often difficult to counter because they are so pervasive, and those beliefs can be reinforced and made stronger when challenged. The purpose of this Perspective article is to introduce physical therapists to a rising construct in psychology-intellectual humility-that may help to facilitate the profession's relationship with disability. Intellectual humility is predicated on recognizing the fallibility of one's beliefs and related practices. Intellectual humility is a promising construct for physical therapy to address the disability paradox and confront implicit attitudes that have served as the basis for many dominant ideas about disability. This Perspective synthesizes views and evidence from the behavioral and social sciences, philosophy, and critical disability studies to contribute to the ongoing evolution of the profession with respect to disability.

IMPACT

The development of enhanced intellectual humility in physical therapy may help to challenge long-held beliefs among physical therapists about disability-many of which are unnoticed, unquestioned, and difficult to counter.

Precision aiming performance with the paretic upper limb is associated with center of pressure patterns in individuals with chronic stroke

BACKGROUND

Individuals with stroke commonly demonstrate upper-limb sensorimotor impairments. Upper-limb tasks occur against a background level of postural control and thus require a flexible postural control system to facilitate performance. Anterior precision aiming tasks, for example, benefit from lower medial-lateral (ML) center of pressure (COP) fluctuations (where increased fluctuations erode performance) relative to anterior-posterior (AP) fluctuations (where increased fluctuations do not strongly influence performance). After stroke, individuals may compensate for upper-limb impairments by increasing trunk movement which increases overall COP fluctuations and thus may make it more difficult to modulate COP in a task-sensitive manner.

RESEARCH QUESTION

Do upper-limb task demands modulate COP movement patterns after stroke?

METHODS

In this cross-sectional study, adults with chronic stroke (n = 23) and unilateral upper-limb impairments were immersed in a virtual environment displaying an anterior target. Participants aimed to maintain the position of a virtual laser pointer (via handheld controller) in the target with each hand. COP was concurrently recorded. Mixed effects models and correlations were used to detect differences in COP patterns between limbs and movement planes and evaluate associations between task performance and COP patterns, respectively.

RESULTS

Participants showed greater COP standard deviation and regularity in the AP compared to the ML direction. The magnitude of difference between AP and ML COP metrics was greater using the nonparetic limb. Task performance was moderately and positively associated with task-sensitive COP patterns (i.e., higher AP:ML ratios of COP metrics) using the paretic upper limb. Participants consistently demonstrated high levels of task performance and task-sensitive COP movement patterns using the nonparetic limb.

SIGNIFICANCE

Impairments in postural control after stroke may be related to the upper limb used. It is important to recognize the role of directional COP variability and regularity in the context of a task goal after stroke.

Narrowing the physiotherapy knowledge-practice gap: faculty training beyond the health sciences

Physiotherapists seek to improve client movement and promote function within an individual's unique environmental and social realities. Despite this intention, there is a well-noted knowledge-practice gap, that is, therapists generally lack sufficient foundational preparation to effectively navigate societal challenges impacting contemporary healthcare. As one step toward addressing the issue, we propose an educational solution targeting current and future physiotherapy faculty, whose responsibilities for entry-level course development and curriculum design substantially impact student readiness for clinical practice. We propose that physiotherapy faculty trained via postprofessional education in a non-biomedical field (e.g. psychology, education, and philosophy) will be uniquely prepared to provide students with tools for dealing with complex social issues facing their clients; critical analysis skills; statistical and technological training; and a deeper theoretical and philosophical understanding of practice. Taken together, such interdisciplinary tools could help address the knowledge-practice gap for physiotherapists and promote the ongoing evolution of the profession in concert with contemporary healthcare. Physiotherapists who pursue interdisciplinary studies may more deeply understand the challenges faced by clinicians and may be well-positioned to leverage knowledge and methods in another scientific discipline to expand and transform the scope of solutions to these challenges.

Personal factors understood through the Ecological-Enactive Model of Disability and implications for rehabilitation research

The International Classification of Functioning, Disability and Health (ICF) recognizes that disability arises from the interaction between an individual with a medical condition and the context in which they are embedded. Context in the ICF is comprised of environmental and personal factors. Personal factors, the background life and lifestyle of an individual, are poorly understood in rehabilitation. There is limited knowledge about how personal and environmental factors interact to shape the contextual conditions critical for explaining functioning and disability. In this paper, we explore how a newly proposed model of disability, the Ecological-Enactive Model of Disability, can enhance understanding of personal factors across multiple rehabilitation disciplines. We draw from a review of evidence and phenomenological interviews of individuals with Friedreich's Ataxia. We consider the practical impact of this understanding on disability and rehabilitation research and pathways for the future focusing on representative design.

The Intelligent Phenotypic Plasticity Platform (IP3) for Precision Medicine-Based Injury Prevention in Sport

The best predictor of future injury is previous injury and this has not changed in a quarter century despite the introduction of evidence-based medicine and associated revisions to post-injury treatment and care. Nearly nine million sports-related injuries occur annually, and the majority of these require medical intervention prior to clearance for the athlete to return to play (RTP). Regardless of formal care, these athletes remain two to four times more likely to suffer a second injury for several years after RTP. In the case of children and young adults, this sets them up for a lifetime of negative health outcomes. Thus, the initial injury is the tipping point for a post-injury cascade of negative sequelae exposing athletes to more physical and psychological pain, higher medical costs, and greater risk of severe long-term negative health throughout their life. This chapter details the technologies and method that make up the automated Intelligent Phenotypic Plasticity Platform (IP3)-a revolutionary new approach to the current standard of post-injury care that identifies and targets deficits that underly second injury risk in sport. IP3 capitalizes on the biological concept of phenotypic plasticity (PP) to quantify an athlete's functional adaptability across different performance environments, and it is implemented in two distinct steps: (1) phenomic profiling and (2) precision treatment. Phenomic profiling indexes the fitness and subsequent phenotypic plasticity of an individual athlete, which drives the personalization of the precision treatment step. IP3 leverages mixed-reality technologies to present true-to-life environments that test the athlete's ability to adapt to dynamic stressors. The athlete's phenotypic plasticity profile is then used to drive a precision treatment that systematically stresses the athlete, via a combination of behavioral-based and genetic fuzzy system models, to optimally enhance the athlete's functional adaptability. IP3 is computationally light-weight and, through the integration with mixed-reality technologies, promotes real-time prediction, responsiveness, and adaptation. It is also the first ever phenotypic plasticity-based precision medicine platform, and the first precision sports medicine platform of any kind.

Task dynamics define the contextual emergence of human corralling behaviors

Social animals have the remarkable ability to organize into collectives to achieve goals unobtainable to individual members. Equally striking is the observation that despite differences in perceptual-motor capabilities, different animals often exhibit qualitatively similar collective states of organization and coordination. Such qualitative similarities can be seen in corralling behaviors involving the encirclement of prey that are observed, for example, during collaborative hunting amongst several apex predator species living in disparate environments. Similar encirclement behaviors are also displayed by human participants in a collaborative problem-solving task involving the herding and containment of evasive artificial agents. Inspired by the functional similarities in this behavior across humans and non-human systems, this paper investigated whether the containment strategies displayed by humans emerge as a function of the task's underlying dynamics, which shape patterns of goal-directed corralling more generally. This hypothesis was tested by comparing the strategies naïve human dyads adopt during the containment of a set of evasive artificial agents across two disparate task contexts. Despite the different movement types (manual manipulation or locomotion) required in the different task contexts, the behaviors that humans display can be predicted as emergent properties of the same underlying task-dynamic model.

The Effect of Navigation Demand on Decision Making in a Dynamic, Sport-Inspired Virtual Environment

Athletes commonly make decisions about the passability of closing gaps when navigating sport environments. This study examined whether increased temporal pressure to arrive at a desired location modifies these decisions. Thirty participants navigated toward a waypoint in a virtual, sport-inspired environment. To do so, they had to decide whether they could pass through closing gaps of virtual humans (and take the shortest route) or steer around them (and take a longer route). The decision boundary of participants who were time pressured to arrive at a waypoint was biased toward end gaps of smaller sizes and was less reliably defined, resulting in a higher number of collisions. Effects of temporal pressure were minimized with experience in the experimental task. Results indicate that temporal pressure affects perceptual-motor processes supporting information pickup and shapes the information-action coupling that drives compliance with navigation demands. Theoretical and practical implications are discussed.

Grasping Embodiment: Haptic Feedback for Artificial Limbs

Upper-limb prostheses are subject to high rates of abandonment. Prosthesis abandonment is related to a reduced sense of embodiment, the sense of self-location, agency, and ownership that humans feel in relation to their bodies and body parts. If a prosthesis does not evoke a sense of embodiment, users are less likely to view them as useful and integrated with their bodies. Currently, visual feedback is the only option for most prosthesis users to account for their augmented activities. However, for activities of daily living, such as grasping actions, haptic feedback is critically important and may improve sense of embodiment. Therefore, we are investigating how converting natural haptic feedback from the prosthetic fingertips into vibrotactile feedback administered to another location on the body may allow participants to experience haptic feedback and if and how this experience affects embodiment. While we found no differences between our experimental manipulations of feedback type, we found evidence that embodiment was not negatively impacted when switching from natural feedback to proximal vibrotactile feedback. Proximal vibrotactile feedback should be further studied and considered when designing prostheses.

Author Correction: The dynamics of plant nutation

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Concurrent Validation and Reference Values of Gluteus Medius Clinical Test

CONTEXT

The hip abductor muscles, mainly the gluteus medius, are responsible for controlling hip adduction in a closed kinetic chain. Frontal plane knee alignment, assessed during functional activities such squatting, jumping and running, may overload joint structures, like the anterior cruciate ligament and patellofemoral joint. The hand-held dynamometer is reliable and effective for testing the muscular strength of the hip abductors.

OBJECTIVES

1. To assess the concurrent validity between the gluteus medius clinical test and a maximum isometric force test of the hip abductors using the hand-held dynamometer; (2) to determine the intra and inter-examiner reliability for the application of the gluteus medius clinical test; and (3) to describe reference values of gluteus medius clinical test on a population of youth athletes.

DESIGN

Cross-sectional.

METHODS

Thirty healthy individuals were recruited for validity and reliability testing. On the first day, participants performed the maximal isometric test of the hip abductors, measured via hand-held dynamometry. On the following week, the gluteus medius clinical test was performed. Intraclass correlation coefficients (ICC2,2) were computed for the reliability analysis, with a 95% confidence interval. To generate reference values, the gluteus medius clinical test was performed on 273 athletes.

RESULTS

The results of this study indicated a weak positive correlation (r = 0.436, p = 0.001) between tests, which indicates that they examine different domains of gluteus medius muscle function, likely endurance and muscle strength. The magnitude of computed ICCs (>0.95) indicates excellent intra- and inter-examiner reliability.

CONCLUSION

The findings of the current study indicate that the gluteus medius clinical test is reliable and examines a domain of muscular function not fully captured by HHD. The clinical test developed in this study is low-cost and can be included for gluteus medius assessment.

LEVEL OF EVIDENCE

Level 3.

Grip force anticipation of nonlinear, underactuated load force

Feedforward internal model-based control enabled by efference copies of motor commands is the prevailing theoretical account of motor anticipation. Grip force control during object manipulation-a paradigmatic example of motor anticipation-is a key line of evidence for that account. However, the internal model approach has not addressed the computational challenges faced by the act of manipulating mechanically complex objects with nonlinear, underactuated degrees of freedom. These objects exhibit complex and unpredictable load force dynamics which cannot be encoded by efference copies of underlying motor commands, leading to the prediction from the perspective of an efference copy-enabled feedforward control scheme that grip force should either lag or fail to coordinate with changes in load force. In contrast to that prediction, we found evidence for strong, precise, anticipatory grip force control during manipulations of a complex object. The results are therefore inconsistent with the internal forward model approach and suggest that efference copies of motor commands are not necessary to enable anticipatory control during active object manipulation.NEW & NOTEWORTHY From the perspective of feedforward internal model-based control, precise, anticipatory grip force (GF) control when manipulating a complex object should not be possible as the object's changing load forces (LFs) cannot be encoded by efference copies of the underlying movements. However, we observed that GF exhibited strong, precise, anticipatory coupling with LF during extended manipulations of a complex object. These findings suggest that an alternative theoretical framework is needed to account for anticipatory GF control.

Children and adolescents with cerebral palsy flexibly adapt grip control in response to variable task demands

BACKGROUND

Children and adolescents with cerebral palsy demonstrate impairments in grip control with associated limitations in functional grasp. Previous work in cerebral palsy has focused on grip control using relatively predictable task demands, a feature which may limit generalizability of those study results in light of recent evidence in typically developing adults suggesting that grip control strategies are task-dependent. The purpose of this study was to determine whether and how varying upper extremity task demands affect grip control in children and adolescents with cerebral palsy.

METHODS

Children and adolescents with mild spastic cerebral palsy (n = 10) and age- and gender-matched typically developing controls (n = 10) participated. Participants grasped an object while immersed in a virtual environment displaying a moving target and a virtual representation of the held object. Participants aimed to track the target by maintaining the position of the virtual object within the target as it moved in predictable and unpredictable trajectories.

FINDINGS

Grip control in children with cerebral palsy was less efficient and less responsive to object load force than in typically developing children, but only in the predictable trajectory condition. Both groups of participants demonstrated more responsive grip control in the unpredictable compared to the predictable trajectory condition.

INTERPRETATION

Grip control impairments in children with cerebral palsy are task-dependent. Children and adolescents with cerebral palsy demonstrated commonly observed grip impairments in the predictable trajectory condition. Unpredictable task demands, however, appeared to attenuate impairments and, thus, could be exploited in the design of therapeutic interventions.

The dynamics of plant nutation

In this article we advance a cutting-edge methodology for the study of the dynamics of plant movements of nutation. Our approach, unlike customary kinematic analyses of shape, period, or amplitude, is based on three typical signatures of adaptively controlled processes and motions, as reported in the biological and behavioral dynamics literature: harmonicity, predictability, and complexity. We illustrate the application of a dynamical methodology to the bending movements of shoots of common beans (Phaseolus vulgaris L.) in two conditions: with and without a support to climb onto. The results herewith reported support the hypothesis that patterns of nutation are influenced by the presence of a support to climb in their vicinity. The methodology is in principle applicable to a whole range of plant movements.

Early learning differences between intra- and interpersonal interlimb coordination

Intrinsic coordination patterns exist between limbs such that 1) coordination at these states is inherently stable, 2) any other pattern requires learning to produce, and 3) this learning is subject to interference from a systemic bias towards intrinsic patterns. The dynamics that govern intrapersonal interlimb coordination also govern interpersonal coordination. However, intrapersonal coordination exhibits greater coupling strength and thus more stable intrinsic dynamics than interpersonal coordination. Because the strength of intrinsic coordination tendencies has consequences for learning coordination patterns, the differences in coupling strength between intra- and interpersonal coordination should impact the ability to perform new coordination patterns via greater or less interference from intrinsic dynamics. This was investigated by measuring participants' performance as they learned a new coordination pattern alone (intrapersonal) or in pairs (interpersonal). Participants were implicitly tasked with learning the pattern as they separately controlled the vertical and horizontal position of an on-screen cursor to trace a circling target. We observed better performance of dyads on first trial and steeper learning trajectories for individuals. Overall, these results indicate that individuals experienced greater interference from stronger intrinsic coordination dynamics during early learning but could overcome this interference and achieve similar performance to that of dyads with very little practice.

Antifragility in Climbing: Determining Optimal Stress Loads for Athletic Performance Training

In the past decades, much research has examined the negative effects of stressors on the performance of athletes. However, according to evolutionary biology, organisms may exhibit growth under stress, a phenomenon called antifragility. For both coaches and their athletes, a key question is how to design training conditions to help athletes develop the kinds of physical, physiological, and behavioral adaptations underlying antifragility. An answer to this important question requires a better understanding of how individual athletes respond to stress or loads in the context of relevant sports tasks. In order to contribute to such understanding, the present study leverages a theoretical and methodological approach to generate individualized load-response profiles in the context of a climbing task. Climbers (n = 37) were asked to complete different bouldering (climbing) routes with increasing loading (i.e. difficulty). We quantified the behavioral responses of each individual athlete by mathematically combining two measures obtained for each route: (a) maximal performance (i.e. the percentage of the route that was completed) and (b) number of attempts required to achieve maximal performance. We mapped this composite response variable as a function of route difficulty. This procedure resulted in load-response curves that captured each athlete's adaptability to stress, termed phenotypic plasticity (PP), specifically operationalized as the area under the generated curves. The results indicate individual load-response profiles (and by extension PP) for athletes who perform at similar maximum levels. We discuss how these profiles might be used by coaches to systematically select stress loads that may be ideally featured in performance training.

Effects of baby walker use on the development of gait by typically developing toddlers

BACKGROUND

Decisions about the use of baby walker are in part predicated on caregivers´ beliefs about its effect on gait development. The actual effects of baby walkers, however, have not been established.

RESEARCH QUESTION

What are the effects of the use of baby walker prior to gait onset on age of acquisition of this milestone and on early walking kinematics?

METHODS

Thirty-two toddlers, 16 in the baby walker group (BWG) and 16 in the non-users group (BWNG), were evaluated in the week of gait acquisition and monthly up to six months after this event. Spatial and temporal gait parameters and lower limb kinematics during walking were assessed using a tridimensional motion analysis system. An independent t-test compared age of gait acquisition between groups. A mixed ANOVA examined the effects of group, moment of assessment and the group x moment of assessment interaction effect on the amplitude of joint motions during walking and on spatial and temporal gait parameters.

RESULTS

The age of gait acquisition was not different between groups. BWG had lower gait speed (specifically in the first, third, fourth, and fifth months after gait acquisition) and longer duration of stance and swing phases than BWNG. Additionally, BWG had smaller knee amplitude and greater hip amplitude in sagittal plane than BWNG in the week of gait acquisition.

SIGNIFICANCE

The results demonstrated that there is no delay in the age of gait acquisition, but there are differences in kinematics. These results can contribute to evidence-based recommendations by health care professionals about the use of baby walker by toddlers during emergence and early development of gait.

Flexible organization of grip force control during movement frequency scaling

The grip force applied to maintain grasp of a handheld object has been typically reported as tightly coupled to the load force exerted by the object as it is actively manipulated, occurring proportionally and consistently in phase with changes in load force. However, continuous grip force-load force coupling breaks down when overall load force levels and oscillation amplitudes are lower (Grover F, Lamb M, Bonnette S, Silva PL, Lorenz T, Riley MA. Exp Brain Res 236: 2531–2544, 2018) or more predictable (Grover FM, Nalepka P, Silva PL, Lorenz T, Riley MA. Exp Brain Res 237: 687–703, 2019). Under these circumstances, grip force is instead only intermittently coupled to load force; continuous coupling is prompted only when load force levels or variations become sufficiently high or unpredictable. The current study investigated the nature of the transition between continuous and intermittent modes of grip force control by scaling the load force level and the oscillation amplitude continuously in time by means of scaling the required frequency of movement oscillations. Participants grasped a cylindrical object between the thumb and forefinger and oscillated their arm about the shoulder in the sagittal plane. Oscillation frequencies were paced with a metronome that scaled through an ascending or descending frequency progression. Due to greater accelerations, faster frequencies produced greater overall load force levels and more pronounced load oscillations. We observed smooth but nonlinear transitions between clear regimes of intermittent and continuous grip force-load force coordination, for both scaling directions, indicating that grip force control can flexibly reorganize as parameters affecting grasp (e.g., variations in load force) change over time.

NEW & NOTEWORTHY Grip force (GF) is synchronously coupled to changing load forces (LF) during object manipulation when LF levels are high or unpredictable, but only intermittently coupled to LF during less challenging grasp conditions. This study characterized the nature of transitions between synchronous and intermittent GF-LF coupling, revealing a smooth but nonlinear change in intermittent GF modulation in response to continuous scaling of LF amplitude. Intermittent, “drift-and-act” control may provide an alternative framework for understanding GF-LF coupling.

Fractal fluctuations in exploratory movements predict differences in dynamic touch capabilities between children with Attention-Deficit Hyperactivity Disorder and typical development

Children with Attention-Deficit Hyperactivity Disorder (ADHD) struggle to perform a host of daily activities. Many of these involve forceful interaction with objects and thus implicate dynamic touch. Therefore, deficits in dynamic touch could underlie functional difficulties presented by ADHD children. We investigated whether performance on a dynamic touch task (length perception by wielding) differ between children with ADHD and age-matched controls. We further examined whether this difference could be explained by fractal temporal correlations (wielding dynamics). Forty-two children (ADHD: 21; typically developing: 21) wielded unseen wooden rods and reported their perceived length in the form of magnitude productions. The rods varied in the magnitude of the first principal moment of inertia (I₁). Three-dimensional displacements of hand and rod positions were submitted to Detrended Fluctuation Analysis to estimate trial-by-trial temporal correlations. Children with ADHD reported shorter length for rods with higher I₁ than their typically developing peers, indicative of reduced sensitivity to mechanical information supporting dynamic touch. Importantly, temporal correlations in wielding dynamics moderated children’s usage of I_1. This finding points to a role of exploratory movements in perceptual deficits presented by children with ADHD and, thus, should be considered a new potential target for interventions.

The association between extended spectrum beta-lactamase (ESBL) and ampicillin C (AmpC) beta-lactamase genes with multidrug resistance in Escherichia coli isolates recovered from turkeys in Brazil

1. The aim of this study was to analyse the association between Escherichia coli isolates recovered from turkeys and the expression of beta-lactamase genes, such as extended spectrum beta-lactamase (ESBL) and ampicillin class C (AmpC). The phenotype of the resistance profile was examined using the association between amoxicillin and ceftiofur resistance. 2. Results showed that 84% from the turkey isolates harboured 4 or 5 genes associated with the CoIV plasmid. In an antibiogram test, 82% of the isolates were multidrug-resistant, the highest levels of resistance being against erythromycin (99%) and amoxicillin (76.1%). ESBL-positive groups were 31% positive for the ctx-m-2 gene, 6.8% were positive for ctx-m-8 and 70% harboured the tem wild gene. 3. All positive isolates from the AmpC beta-lactamase-positive group harboured the cmy-2 gene. The presence of the cmy-2 gene was associated with both the CTX-group genes and resistance to ceftiofur. 4. There was a high prevalence of avian pathogenic E. coli in suspected cases of colibacillosis in turkeys and a high antimicrobial resistance index. The results highlighted the risk of ceftiofur resistance and the presence of both ESBL and AmpC beta-lactamase E. coli in the turkey production chain.

Reliability of Foot Posture Index individual and total scores for adults and older adults

BACKGROUND

Previous studies have suggested that the Foot Posture Index (FPI-6) is valid and reliable to evaluate foot posture of adults and children. However, studies with adults had some important limitations. In addition, it is not clear if FPI-6 is reliable for older adults. Variations in foot structure, such as edema, bone callosity and bunions, are more frequent in older adults, which may compromise FPI-6 reliability for this population.

OBJECTIVES

To investigate test-retest and inter-rater reliability of FPI-6 total and individual scores for the assessment of foot posture of adults and older adults.

METHODS

Twenty-one adults and 19 older adults participated in this study. The examiners performed FPI-6 on two days of data collection. We used Cohen Weighted Kappa and Intraclass Correlation Coefficient for categorical and continuous variables, respectively.

RESULTS

For adults, FPI-6 scores demonstrated test-retest reliability varying from fair to substantial and inter-rater reliability varying from fair to almost perfect. For older adults, FPI-6 scores demonstrated test-retest reliability varying from not reliable to moderate and inter-rater reliability varying from fair to almost perfect. The examiners demonstrated more than 80% of agreement in all FPI-6 scores for adults and older adults.

CONCLUSIONS

The relatively low reliability in light of this high level of agreement suggest that the current version of FPI-6 can be a useful tool to assess foot posture for adults and should be further examined. On the other hand, FPI-6 should be cautiously used for older adults.

Comparison of different degrees of variability in tidal volume to prevent deterioration of respiratory system elastance in experimental acute lung inflammation

BACKGROUND

Variable ventilation improves respiratory function, but it is not known whether the amount of variability in tidal volume (VT) can be reduced in recruited lungs without a deterioration of respiratory system elastance.

METHODS

Acute lung inflammation was induced by intratracheal instillation of lipopolysaccharide in 35 Wistar rats. Twenty-eight animals were anaesthetized and ventilated in volume-controlled mode. Lungs were recruited by random variation of VT (mean 6 ml kg(-1), coefficient of variation 30%, normal distribution) for 30 min. Animals were randomly assigned to different amounts of VT variability (n=7 for 90 min per group): 30, 15, 7.5, or 0%. Lung function, diffuse alveolar damage, and gene expression of biological markers associated with cell mechanical stress, inflammation, and fibrogenesis were assessed. Seven animals were not ventilated and served as controls for post-mortem analyses.

RESULTS

A VT variability of 30%, but not 15, 7.5, or 0%, prevented deterioration of respiratory system elastance [Mean (SD) -7.5 (8.7%), P<0.05; 21.1 (9.6%), P<0.05; 43.3 (25.9), P<0.05; and 41.2 (16.4), P<0.05, respectively]. Diffuse alveolar damage was lower with a VT variability of 30% than with 0% and without ventilation, because of reduced oedema and haemorrhage. A VT variability of 30, 15, or 7.5% reduced the gene expression of amphiregulin, cytokine-induced neutrophil chemoattractant-1, and tumour necrosis factor α compared with a VT variability of 0%.

CONCLUSIONS

In this model of acute lung inflammation, a VT variability of 30%, compared with 15 and 7.5%, was necessary to avoid deterioration of respiratory system elastance and was not associated with lung histological damage.

'What's my risk of sustaining an ACL injury while playing football (soccer)?' A systematic review with meta-analysis

OBJECTIVE

To estimate the incidence proportion (IP) and incidence rate (IR) of ACL injury in football players.

DESIGN

Systematic review with meta-analysis.

DATA SOURCES

PubMed, CINAHL and SPORTDiscus electronic databases were searched from inception to 20 January 2017.

ELIGIBILITY CRITERIA FOR SELECTING STUDY

Studies that reported the total number of participants/population by sex, total number of ACL injuries by sex and total person-time by sex were included.

RESULTS

Twenty-eight studies were included. The IP and IR of ACL injury in female football players were 2.0% (95% CI 1.2% to 3.1%) and 2.0/10 000 athlete exposures (AEs) (95% CI 1.6 to 2.6; I²=91%) over a period of one season to 4 years. The IP and IR of ACL injury in male players were 3.5% (95% CI 0.7% to 8.2%) and 0.9/10 000 AEs (95% CI 0.7 to 1.1; I²=94%). Studies that evaluated matched cohorts of female and male players showed no difference in IP (relative risk=1.2; 95% CI 0.9 to 1.6; P=0.47) over a period of one season to 4 years. Women were at greater risk than men (incidence rate ratio (IRR)=2.2; 95% CI 1.6 to 3.1; I²=83%; P<0.001). When accounting for participation level, the difference in IR between women and men was greatest for intermediate players (IRR=2.9; 95% CI 2.4 to 3.6) compared with amateur (IRR=2.6; 95% CI 1.4 to 4.8) and elite (IRR=2.0; 95% CI 1.1 to 3.4) players.

SUMMARY/CONCLUSION

Overall, more men sustained ACL injury in football. There was no difference in the relative risk of ACL injury between female and male football players in a window that spanned one season to 4 years. The IR of ACL injury among women was 2.2 times higher than the IR of ACL injury among men. The reported sex disparity in ACL injury was independent of participation level.

External rotation elastic bands at the lower limb decrease rearfoot eversion during walking: a preliminary proof of concept

Background

Reducing rearfoot eversion is a commonly desired effect in clinical practice to prevent or treat musculoskeletal dysfunction. Interventions that pull the lower limb into external rotation may reduce rearfoot eversion.

Objective

This study investigated whether the use of external rotation elastic bands, of different levels of stiffness, will decrease rearfoot eversion during walking. We hypothesized that the use of elastic bands would decrease rearfoot eversion and that the greater the band stiffness, the greater the eversion reduction.

Method

Seventeen healthy participants underwent three-dimensional kinematic analysis of the rearfoot and shank. The participants walked on a treadmill with and without high- and low-stiffness bands. Frontal-plane kinematics of the rearfoot-shank joint complex was obtained during the stance phase of walking. Repeated-measures ANOVAs were used to compare discrete variables that described rearfoot eversion-inversion: mean eversion-inversion; eversion peak; and eversion-inversion range of motion.

Results

The low-stiffness and high-stiffness bands significantly decreased eversion and increased mean eversion-inversion (p≤0.037) and eversion peak (p≤0.006) compared with the control condition. Both bands also decreased eversion-inversion range of motion (p≤0.047) compared with control by reducing eversion. The high-stiffness band condition was not significantly different from the low-stiffness band condition for any variables (p≥0.479).

Conclusion

The results indicated that the external rotation bands decreased rearfoot eversion during walking. This constitutes preliminary experimental evidence suggesting that increasing external rotation moments at the lower limb may reduce rearfoot eversion, which needs further testing.

The Effect of Walking Speed on Foot Kinematics is Modified When Increased Pronation is Induced

BACKGROUND

The relation between walking speed and foot kinematics during gait is not well established, and neither is it clear whether this relation is modified in the presence of factors expected to increase pronation (eg, abnormal foot alignment). Understanding how foot kinematics is affected by walking speed under varying conditions could contribute to our understanding of stresses to the musculoskeletal system during walking. We evaluated the effect of walking speed on foot kinematics in the frontal plane during gait and determined whether this effect is modified by using medially inclined insoles that force the foot into increased pronation.

METHODS

Twenty-six healthy young adults were assessed while walking on a treadmill wearing flat insoles and wearing medially inclined insoles. Foot kinematics in the frontal plane was measured with a three-dimensional motion analysis system. Data were analyzed during the stance phase of gait.

RESULTS

There was no main effect of speed on average calcaneal position. However, there was a significant insole type × walking speed interaction effect. In the flat insole condition, increased walking speed was associated with a less inverted average calcaneal position (or greater magnitudes of eversion), whereas in the inclined insole condition, higher speeds were associated with a less everted average calcaneal position (or increased magnitudes of inversion).

CONCLUSIONS

The magnitude of foot eversion increases at faster gait speeds under typical conditions. In the presence of factors that induce excessive pronation, however, this effect is reversed. Results suggest that individuals use greater active control of foot motion at faster speeds in the presence of excessive pronation to improve push-off efficiency. Potential clinical consequences of this functional strategy are discussed.

Task difficulty and inertial properties of hand-held tools: An assessment of their concurrent effects on precision aiming

Aiming hand-held tools at targets in space entails adjustments in the dynamical organization of aiming patterns according to the required precision. We asked whether and how these adjustments are modified by the tool's mass distribution. Twelve participants performed reciprocal aiming movements with a 50-cm long wooden probe. Kinematic patterns of probe movements were used as a window into the behavioral dynamic underlying performance of a reciprocal aiming task. We crossed three levels of task difficulty (IDs 2.8, 4.5 and 6.1) with two types of probe varying in their mass distribution (proximal vs distal loading). Movement duration was affected by task difficulty and probe loading (shorter for larger targets and proximal probe loading). Progressive deviations from a sinusoidal movement pattern were observed as task difficulty increased. Such deviations were more pronounced with proximal probe loading. Results point to a higher degree of non-linearity in aiming dynamics when the probe was loaded proximally, which might reflect employment of additional perceptual-motor processes to control the position of its less stable tip at the vicinity of the targets. More generally, the effects of probe loading on aiming pattern and dynamics suggest that perceptual-motor processes responding to task level constraints are sensitive to, and not independent from, biomechanical, end-effector constraints.

Forefoot midsole stiffness affects forefoot and rearfoot kinematics during the stance phase of gait

BACKGROUND

The forefoot midsole stiffness of the shoe may affect the kinematics of the foot segments. We evaluated the effects of two different levels of forefoot midsole stiffness on the angular displacement of the forefoot and rearfoot in the three planes of motion during the stance phase of gait.

METHODS

Thirty-six participants walked on a 10-m walkway at their self-selected speed wearing shoes having either low or high forefoot midsole stiffness. Three-dimensional kinematic data of the foot segments were obtained during the stance phase of gait using an eight-camera motion analysis system synchronized with a force platform. The dependent variables were forefoot and rearfoot total range of motion and maximum and minimum angle values in the sagittal, frontal, and transverse planes of motion.

RESULTS

Reduced forefoot midsole stiffness produced significantly greater forefoot total range of motion in the sagittal plane (1.59°). The low-stiffness condition also increased the magnitude of the forefoot dorsiflexion angles (4.14°). Furthermore, the low-stiffness condition increased the magnitude of the rearfoot inversion (1.21°) and adduction (11.38°) angles and reduced the rearfoot abduction angle (12.1°).

CONCLUSIONS

It is likely that reduced stiffness of the forefoot midsole stretched the plantar fascia, increasing rearfoot stability during the stance phase of gait. Increased muscular contraction may also explain increases in rearfoot stability. Therefore, the integrity of the plantar fascia and ankle muscles' force and resistance should be considered when choosing a shoe with reduced or increased forefoot midsole stiffness for walking.

The role of haptic information in shaping coordination dynamics: inertial frame of reference hypothesis

Current research suggests that non-visual perception of the spatial orientation of body segments is tied to vectors representative of their mass moment distribution (v(mm)). Our question was whether the relative orientation of v(mm) of right and left hands (Δv(mm)=v(mm) left-v(mm) right) constitutes haptic information supporting bimanual coordination and, if so, how it contributes to coordination dynamics. Blindfolded participants coordinated the motions of a pair of cross-shaped, hand-held pendulums that were either symmetrically loaded (Δv(mm)=0) or asymmetrically loaded (Δv(mm)≠0). The sign and magnitude of Δv(mm), in particular of the first moment vector, systematically affected the pattern of coordination (indexed by mean relative phase ϕ), but not its stability. These results suggest that (1) Δv(mm) specifies a frame of reference about which coordination is organized; and (2) that the changes in pattern were a function of the experimentally induced biases in this perceptual frame of reference and not a function of a functional asymmetry akin to detuning. The implications of the findings to the understanding of perceptual regulation of interlimb coordination were discussed.