Dynamic stability evaluation of trunk accelerations during walking in blind and sighted individuals.

BACKGROUND: Dynamic stability is a fundamental goal in standing activities. In this regard, monitoring, analysis, and interventions made to improve stability is a research topic investigated in the biomechanics of human movements. Vision has a major role to play in controlling human movement. Nonetheless, little is known about the effects of visual deprivation, especially from birth on dynamic gait stability. METHODS: The current study was conducted on 20 congenital blind and 10 sighted people (15-38 years). To evaluate the dynamic stability, descriptive data, harmonic ratio (HR), improved harmonic ratio (iHR), and root mean square (RMS), based on trunk acceleration data were measured in three axes: anteroposterior (AP), vertical (V), and mediolateral (ML) while participants walked an eight-meter straight path. RESULTS: In the comparison of blind and sighted people (eyes open), standard deviation, HR, iHR, and RMS indices were found to be significantly different in both AP and V directions. All the mentioned parameters were significantly lower in blind than in sighted participants. In the comparison of blind people and sighted ones with closed eyes, changes were observed in the maximum, range, standard deviation, and RMS only in the AP axis. In the comparison between eyes open and closed in sighted people, a significant difference was found only in the harmonic ratio of the vertical axis. CONCLUSION: Visual deprivation led to a decrease in dynamic stability parameters in the AP and V axes. Even the movement of sighted people in unchallenged conditions is dependent on visual information.

Stability and Strength of Monolayer Polymeric C60.

Two-dimensional fullerene networks have been synthesized in several forms, and it is unknown which monolayer form is stable under ambient conditions. Using first-principles calculations, I show that the believed stability of the quasi-tetragonal phases is challenged by mechanical, dynamic, or thermodynamic stability. For all temperatures, the quasi-hexagonal phase is thermodynamically the least stable. However, the relatively high dynamic and mechanical stabilities suggest that the quasi-hexagonal phase is intrinsically stronger than the other phases under various strains. The origin of the high stability and strength of the quasi-hexagonal phase can be attributed to the strong covalent C-C bonds that strongly hold the linked C60 clusters together, enabling the closely packed hexagonal network. These results rationalize the experimental observations that so far only the quasi-hexagonal phase has been exfoliated experimentally as monolayers.

The application of the Lyapunov Exponent to analyse human performance: A systematic review.

Variability is a normal component of human movement, allowing one to adapt to environmental perturbations. It can be analysed from linear or non-linear perspectives. The Lyapunov Exponent (LyE) is a commonly used non-linear technique, which quantifies local dynamic stability. It has been applied primarily to walking gait and appears to be limited application in other movements. Therefore, this systematic review aims to summarise research methodologies applying the LyE to movements, excluding walking gait. Four databases were searched using keywords related to movement variability, dynamic stability, LyE and divergence exponent. Articles written in English, using the LyE to analyse movements, excluding walking gait were included for analysis. 31 papers were included for data extraction. Quality appraisal was conducted and information related to the movement, data capture method, data type, apparatus, sampling rate, body segment/joint, number of strides/steps, state space reconstruction, algorithm, filtering, surrogation and time normalisation were extracted. LyE values were reported in supplementary materials (Appendix 2). Running was the most prevalent non-walking gait movement assessed. Methodologies to calculate the LyE differed in various aspects resulting in different LyE values being generated. Additionally, test-retest reliability, was only conducted in one study, which should be addressed in future.

Base of Support, Step Length and Stride Width Estimation during Walking Using an Inertial and Infrared Wearable System.

The analysis of the stability of human gait may be effectively performed when estimates of the base of support are available. The base of support area is defined by the relative position of the feet when they are in contact with the ground and it is closely related to additional parameters such as step length and stride width. These parameters may be determined in the laboratory using either a stereophotogrammetric system or an instrumented mat. Unfortunately, their estimation in the real world is still an unaccomplished goal. This study aims at proposing a novel, compact wearable system, including a magneto-inertial measurement unit and two time-of-flight proximity sensors, suitable for the estimation of the base of support parameters. The wearable system was tested and validated on thirteen healthy adults walking at three self-selected speeds (slow, comfortable, and fast). Results were compared with the concurrent stereophotogrammetric data, used as the gold standard. The root mean square errors for the step length, stride width and base of support area varied from slow to high speed between 10-46 mm, 14-18 mm, and 39-52 cm2, respectively. The mean overlap of the base of support area as obtained with the wearable system and with the stereophotogrammetric system ranged between 70% and 89%. Thus, this study suggested that the proposed wearable solution is a valid tool for the estimation of the base of support parameters out of the laboratory.

Constructing a resilient ecological network by considering source stability in the largest Chinese urban agglomeration.

The dynamics of ecological sources and their impact on the resilience of ecological networks (ENs) have attracted increasing attention from both researchers and managers. Although a couple of studies have recognized the source-loss effects on network resilience, there is a knowledge gap in integrating spatiotemporal changes of the sources while constructing resilient ENs. Here, we propose the concept of dynamic stability (DS) to explore the sources' changes over a certain period and improve source identification by grading the DS in the largest urban agglomeration located in the middle reaches of the Yangtze River in China. An investigation of the five selected ecosystem service (ES) indicators in 2000, 2010, and 2018 identified 49, 54, and 68 preliminary sources, respectively, from which 11, 14, and three sources were extracted, respectively, with high, moderate, and low levels of DS, respectively. A three-tier EN was constructed by considering both the ESs and DSs of the extracted sources. The constructed network was scale-free and featured in small world in topology analysis. Moreover, a carefully designed attack test found that this EN was of good resilience as the three critical nodes that might cause a marked decay of resilience were in high or moderate DSs and were preferentially protected by the Ecological Conservation Red Line policy in China. In conclusion, the improved approach of considering the DSs of sources may help to precisely identify and protect the critical nodes threatening network resilience, which is highly desired in constructing ENs facing various rapid changes, especially in large-scale urbanized areas.

Improved Core Viscosity Achieved by PDLLA10kCo-Incorporation Promoted Drug Loading and Stability of mPEG2k-b-PDLLA2.4k Micelles.

PURPOSE: This study aims to investigate the effect of poly(D, L-lactic acid)10K (PDLLA10K) incorporation on the drug loading and stability of poly(ethylene glycol)2K-block-poly(D, L-lactide)2.4K (mPEG2k-b-PDLLA2.4k) micelles. In addition, a suitable lyophilization protector was screened for this micelle to obtain favorable lyophilized products. METHODS: The incorporation ratios of PDLLA10k were screened based on the particle size and drug loading. The dynamic stability, core viscosity, drug release, stability in albumin, and in vivo pharmacokinetic characteristics of PDLLA10k incorporated micelles were compared with the original micelles. In addition, the particle size variation was used as an indicator to screen the most suitable lyophilization protectant for the micelles. DSC, FTIR, XRD were used to illustrate the mechanism of the lyophilized protectants. RESULTS: After the incorporation of 5 wt% PDLLA10K, the maximum loading of mPEG2k-b-PDLLA2.4k micelles for TM-2 was increased from 26 wt% to 32 wt%, and the in vivo half-life was increased by 2.25-fold. Various stability of micelles was improved. Also, the micelles with hydroxypropyl-ß-cyclodextrin (HP-ß-CD) as lyophilization protectants had minimal variation in particle size. CONCLUSIONS: PDLLA10k incorporation can be employed as a strategy to increase the stability of mPEG2k-b-PDLLA2.4k micelles, which can be attributed to the viscosity building effect. HP-ß-CD can be used as an effective lyophilization protectant since mPEG and HP-ß-CD form the pseudopolyrotaxanesque inclusion complexes.

Increased Attentional Focus on Walking by Older Adults Limits Maximum Speed and Is Related to Dynamic Stability.

BACKGROUND AND PURPOSE: Older adults with lower balance confidence demonstrate a reduced willingness to experience instability as the task of walking becomes more challenging (i.e., walking with a faster speed). However, the specific reason why is not known. The purpose of this study was to investigate the extent to which capacity of increasing walking speeds relates to the attentional requirements (i.e., automaticity) of walking. METHODS: Sixteen young (31 ± 5.85 years) and 15 older participants (69 ± 3.04 years) began walking on a treadmill at 0.4 m/s, and speed was increased by 0.2 m/s until the participant either chose to stop or reached a speed of 2.0 m/s. Sixty steps were collected at steady-state speed for each walking trial. Kinematic data were collected, and the margin of stability in the anterior direction (MOSAP) at heelstrike was quantified for each step. The timed up and go (TUG) and TUG dual (TUGdual) task were performed, from which an automaticity index (TUG/TUGdual × 100) was calculated. Older individuals were grouped based on whether they did or did not complete all walking speeds (i.e., completers [n = 9] or noncompleters [n = 6]). The fastest walking speed attempted (FSA), automaticity index, and MOSAP were compared, and correlations were assessed between the FSA/MOSAP and the automaticity index. RESULTS: A significant difference was identified in an average MOSAP at heelstrike between older completer and noncompleter groups (p < 0.001). Further, older adults with lower automaticity index choose to stop walking at lower speeds (p = 0.001). The FSA was positively correlated with the automaticity index (ρ = 0.81, p < 0.001). Finally, the average MOSAP at FSA and the automaticity index were also negatively correlated (r = -0.85, p < 0.001). CONCLUSION: Older adults with lower automaticity of walking choose to stop walking at speeds before they completed all walking speeds, which may relate with increased attentional demands required to maintain dynamic stability at higher walking speeds. Given that these were otherwise healthy adults, the combination of FSA and an automaticity of walking may help to identify individuals who should be considered for an assessment to identify walking problems.

Ankle strategy assistance to improve gait stability using controllers based on in-shoe center of pressure in 2 degree-of-freedom powered ankle-foot orthoses: a clinical study.

BACKGROUND: Although the ankle strategy is important for achieving frontal plane stability during one-leg stance, previously developed powered ankle-foot orthoses (PAFOs) did not involve ankle strategies because of hardware limitations. Weakness of movement in frontal plane is a factor that deteriorates gait stability and increases fall risk so it should not be overlooked in rehabilitation. Therefore, we used PAFO with subtalar joint for frontal plane movement and tried to confirm that the existence of it is important in balancing through clinical experiments. METHODS: We developed a proportional CoP controller to assist ankle strategy or stabilizing moment and enhance eversion to compensate for the tilting moment with 2 dof PAFO. It was true experimental study, and we recruited seven healthy subjects (30 ± 4 years) who did not experience any gait abnormality participated in walking experiments for evaluating the immediate effect of subtalar joint of PAFO on their gait stability. They walked on the treadmill with several cases of controllers for data acquisitions. Indices of gait stability and electromyography for muscle activity were measured and Wilcoxon signed-rank tests were used to identify meaningful changes. RESULTS: We found that subjects were most stable during walking (in terms of largest Lyapunov exponents, p < 0.008) with the assistance of the PAFO when their electromyographic activity was the most reduced (p < 0.008), although postural sway increased when a proportional CoP controller was used to assist the ankle strategy (p < 0.008). Other indices of gait stability, kinematic variability, showed no difference between the powered and unpowered conditions (p > 0.008). The results of the correlation analysis indicate that the actuator of the PAFO enhanced eversion and preserved the location of the CoP in the medial direction so that gait stability was not negatively affected or improved. CONCLUSIONS: We verified that the developed 2 dof PAFO assists the ankle strategy by compensating for the tilting moment with proportional CoP controller and that wearer can walk in a stable state when the orthosis provides power for reducing muscle activity. This result is meaningful because an ankle strategy should be considered in the development of PAFOs for enhancing or even rehabilitating proprioception. Trial registration 7001988-202003-HR-833-03.

Nonlinear Dynamic Measures of Walking in Healthy Older Adults: A Systematic Scoping Review.

BACKGROUND: Maintaining a healthy gait into old age is key to preserving the quality of life and reducing the risk of falling. Nonlinear dynamic analyses (NDAs) are a promising method of identifying characteristics of people who are at risk of falling based on their movement patterns. However, there is a range of NDA measures reported in the literature. The aim of this review was to summarise the variety, characteristics and range of the nonlinear dynamic measurements used to distinguish the gait kinematics of healthy older adults and older adults at risk of falling. METHODS: Medline Ovid and Web of Science databases were searched. Forty-six papers were included for full-text review. Data extracted included participant and study design characteristics, fall risk assessment tools, analytical protocols and key results. RESULTS: Among all nonlinear dynamic measures, Lyapunov Exponent (LyE) was most common, followed by entropy and then Fouquet Multipliers (FMs) measures. LyE and Multiscale Entropy (MSE) measures distinguished between older and younger adults and fall-prone versus non-fall-prone older adults. FMs were a less sensitive measure for studying changes in older adults' gait. Methodology and data analysis procedures for estimating nonlinear dynamic measures differed greatly between studies and are a potential source of variability in cross-study comparisons and in generating reference values. CONCLUSION: Future studies should develop a standard procedure to apply and estimate LyE and entropy to quantify gait characteristics. This will enable the development of reference values in estimating the risk of falling.

Trunk Dynamic Stability Assessment for Individuals With and Without Nonspecific Low Back Pain During Repetitive Movement.

OBJECTIVE: This study aimed to employ nonlinear dynamic approaches to assess trunk dynamic stability with speed, symmetry, and load during repetitive flexion-extension (FE) movements for individuals with and without nonspecific low back pain (NSLBP). BACKGROUND: Repetitive trunk FE movement is a typical work-related LBP risk factor contingent on speed, symmetry, and load. Improper settings/adjustments of these control parameters could undermine the dynamic stability of the trunk, hence leading to low back injuries. The underlying stability mechanisms and associated control impairments during such dynamic movements remain elusive. METHOD: Thirty-eight male volunteers (19 healthy, 19 NSLBP) enrolled in the current study. All participants performed repetitive trunk FE movements at high/low speeds, in symmetric/asymmetric directions, with/without a wearable loaded vest. Trunk instantaneous rotation angle was computed for each trial to be assessed in terms of local and orbital stability, using maximum finite-time Lyapunov exponents (LyEs) and Floquet multipliers (FMs), respectively. RESULTS: Both groups demonstrated equivalent competency in terms of trunk control and stability, suggesting functional adaptation strategies may be used by the NSLBP group. Wearing the loaded vest magnified the effects of trunk control impairment for the NSLBP group. The combined presence of high-speed and symmetrical FE movements was associated with least trunk local stability. CONCLUSION: Nonlinear dynamic techniques, particularly LyE, are potentially effective for assessing trunk dynamic stability dysfunction for individuals with NSLBP during various activities. APPLICATION: This work can be applied toward the development of quantitative personalized spinal evaluation tools with a wide range of potential occupational and clinical applications.

On the Low Degree of Entropy Implied by the Solutions of Modern Macroeconomic Models.

The non-causal ("forward-looking") solution used routinely in academic macroeconomics may represent a violation of a law of entropy, namely that the direction of time is one way (from the past and towards the present), and that the variance of economic processes increases with time. In order to re-establish a degree of compatibility with the law of entropy, so called hybrid forms are required add-ins to DSGE (Dynamic Stochastic General Equilibrium) models. However, the solution that uses hybrid forms is a particular special case of a causal solutions of autoregressive distributed lags, VARs and recursive and simultaneous equations models well known from empirical macro econometrics. Hence, hybrid forms of small scale DSGE models can be analysed and tested against competing model equations, using an econometric encompassing framework.

Use of the margin of stability to quantify stability in pathologic gait - a qualitative systematic review.

BACKGROUND: The Margin of Stability (MoS) is a widely used objective measure of dynamic stability during gait. Increasingly, researchers are using the MoS to assess the stability of pathological populations to gauge their stability capabilities and coping strategies, or as an objective marker of outcome, response to treatment or disease progression. The objectives are; to describe the types of pathological gait that are assessed using the MoS, to examine the methods used to assess MoS and to examine the way the MoS data is presented and interpreted. METHODS: A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Guidelines (PRISMA) in the following databases: Web of Science, PubMed, UCL Library Explore, Cochrane Library, Scopus. All articles measured the MoS of a pathologically affected adult human population whilst walking in a straight line. Extracted data were collected per a prospectively defined list, which included: population type, method of data analysis and model building, walking tasks undertaken, and interpretation of the MoS. RESULTS: Thirty-one studies were included in the final review. More than 15 different clinical populations were studied, most commonly post-stroke and unilateral transtibial amputee populations. Most participants were assessed in a gait laboratory using motion capture technology, whilst 2 studies used instrumented shoes. A variety of centre of mass, base of support and MoS definitions and calculations were described. CONCLUSIONS: This is the first systematic review to assess use of the MoS and the first to consider its clinical application. Findings suggest the MoS has potential to be a helpful, objective measurement in a variety of clinically affected populations. Unfortunately, the methodology and interpretation varies, which hinders subsequent study comparisons. A lack of baseline results from large studies mean direct comparison between studies is difficult and strong conclusions are hard to make. Further work from the biomechanics community to develop reporting guidelines for MoS calculation methodology and a commitment to larger baseline studies for each pathology is welcomed.

Measuring Gait Stability in People with Multiple Sclerosis Using Different Sensor Locations and Time Scales.

The evaluation of local divergence exponent (LDE) has been proposed as a common gait stability measure in people with multiple sclerosis (PwMS). However, differences in methods of determining LDE may lead to different results. Therefore, the purpose of the current study was to determine the effect of different sensor locations and LDE measures on the sensitivity to discriminate PwMS. To accomplish this, 86 PwMS and 30 healthy participants were instructed to complete a six-minute walk wearing inertial sensors attached to the foot, trunk and lumbar spine. Due to possible fatigue effects, the LDE short (~50% of stride) and very short (~5% of stride) were calculated for the remaining first, middle and last 30 strides. The effect of group (PwMS vs. healthy participants) and time (begin, mid, end) and the effect of Expanded Disability Status Scale (EDSS) and time were assessed with linear random intercepts models. We found that perturbations seem to be better compensated in healthy participants on a longer time scale based on trunk movements and on a shorter time scale (almost instantaneously) according to the foot kinematics. Therefore, we suggest to consider both sensor location and time scale of LDE when calculating local gait stability in PwMS.

Validity and Sensitivity of an Inertial Measurement Unit-Driven Biomechanical Model of Motor Variability for Gait.

Motor variability in gait is frequently linked to fall risk, yet field-based biomechanical joint evaluations are scarce. We evaluated the validity and sensitivity of an inertial measurement unit (IMU)-driven biomechanical model of joint angle variability for gait. Fourteen healthy young adults completed seven-minute trials of treadmill gait at several speeds and arm swing amplitudes. Trunk, pelvis, and lower-limb joint kinematics were estimated by IMU- and optoelectronic-based models using OpenSim. We calculated range of motion (ROM), magnitude of variability (meanSD), local dynamic stability (λmax), persistence of ROM fluctuations (DFAα), and regularity (SaEn) of each angle over 200 continuous strides, and evaluated model accuracy (RMSD: root mean square difference), consistency (ICC2,1: intraclass correlation), biases, limits of agreement, and sensitivity to within-participant gait responses (effects of speed and swing). RMSDs of joint angles were 1.7-9.2° (pooled mean of 4.8°), excluding ankle inversion. ICCs were mostly good to excellent in the primary plane of motion for ROM and in all planes for meanSD and λmax, but were poor to moderate for DFAα and SaEn. Modelled speed and swing responses for ROM, meanSD, and λmax were similar. Results suggest that the IMU-driven model is valid and sensitive for field-based assessments of joint angle time series, ROM in the primary plane of motion, magnitude of variability, and local dynamic stability.

Acceleration and Jerk After a Jump Stabilization Task in Individuals With and Without Chronic Ankle Instability.

Studies have demonstrated that individuals with chronic ankle instability (CAI) have diminished dynamic stability. Jerk-based measures have been utilized to examine dynamic balance because of their ability to quantify changes in acceleration and may provide an understanding of the postural corrections that occur during stabilizing following a jumping task. The purpose of this study was to compare acceleration and jerk following a jump stabilization task between individuals with CAI and the uninjured controls. Thirty-nine participants volunteered to participate in this case control study. Participants completed a jump stabilization task requiring them to jump off 2 feet, touch a marker set at 50% of their maximal vertical jump height, land on a single limb, and maintain balance for 3 seconds. Acceleration was calculated as the second derivative, and jerk was calculated as the third derivative of the displacement of the resultant vector position. Participants with CAI had greater acceleration (mean difference = 55.6 cm/s2; 95% confidence interval, 10.3 to 100.90; P = .017) and jerk compared with the uninjured controls (mean difference = 1804.5 cm/s3; 95% confidence interval, 98.7 to 3510.3; P = .039). These results suggest that individuals with CAI made faster and more frequent active postural control corrections to regain balance following a jump compared with the uninjured controls.

Test-Retest Reliability of Single-Leg Time to Stabilization Following a Drop-Landing Task in Healthy Individuals.

CONTEXT: Single-leg stability has been associated with injury risk and is a key component of many injury prevention interventions. Methods of measuring single-leg stability are varied yet often unreliable. OBJECTIVE: To establish within- and between-day test-retest reliability for single-leg time to stabilization (SL-TTS) following a drop-landing maneuver of 20 cm in height among a healthy cohort. DESIGN: Test-retest reliability study. SETTING: Healthy cohort from a third-level educational institution. PARTICIPANTS: Nineteen (11 females and 8 males) healthy individuals. MAIN OUTCOME MEASURES: The SL-TTS in the vertical plane. RESULTS: The SL-TTS showed good within-day (intraclass correlation coefficient = .715) and excellent between-day (intraclass correlation coefficient = .83) test-retest reliability. The minimal detectable change was calculated as 171.6 ms for within-day contexts and 123.8 ms for between-day contexts. CONCLUSIONS: This method of measuring SL-TTS is reliable and could be used to detect changes over time in a healthy cohort. This could be of value to clinicians in injury risk factor identification or assessing the effectiveness of single-leg stability training. However, further research is needed to investigate its reliability in pathological populations.

Manipulating sensory information: obstacle crossing strategies between typically developing children and young adults.

Individuals constantly adapt their locomotion to navigate through complex environments. However, little known about anticipatory strategies used by children during adaptive locomotion. The purpose of this study was to compare the effects of manipulating visual and somatosensory information during a multiple obstacle crossing task between children and adults. It was hypothesized that compared to young adults, children would have difficulty with anticipatory motor planning and online control during a multiple obstacle crossing task when sensory information was manipulated. Children (N = 16, [Formula: see text] = 9 ± 1.07 years) and young adults (N = 16, [Formula: see text] = 22 ± 0.96 years) walked along a 7 m pathway towards a goal while avoiding stepping on one, or two virtual obstacles placed 5 m from the start. Visual information regarding the number of obstacles was either presented at the start of steady-state locomotion, or two steps prior to the first obstacle. Each participant completed 36 trials, 18 on flat ground and 18 on foam terrain. Results indicated that in comparison to young adults, children's foot positions were significantly closer to the first obstacle when visual information about the obstacle was delayed. On flat ground, children demonstrated similar Trail foot positions relative to the first and second obstacles, suggesting children planned for the avoidance of the obstacles separately. On foam terrain, children performed similar to young adults, such that their Trail foot position relative to the first obstacle was significantly closer to the obstacle compared to their Trial foot position relative to the second obstacle. The results suggest that children plan for the avoidance of multiple obstacles differently compared to young adults. When stability is challenged, maintaining forward progression of locomotion overrides the planning of obstacle crossing, such that children perform similar to young adults. Therefore, it appears that children have difficulties with online control and anticipatory motor strategies during a multiple obstacle crossing task.

Pulsed Nd:YAG laser: effects on pain, postural stability, and weight-bearing pattern in children with hemophilic ankle arthropathy.

Hemophilic ankle arthropathy features joint pain, impaired postural control, and abnormal weight-bearing pattern. This study was designed to investigate the effects of pulsed Nd:YAG laser on pain, postural stability, and weight-bearing pattern in children with hemophilic ankle arthropathy. Forty children diagnosed with hemophilia type A (age, 8-16 years) were randomly allocated to either the treatment group (n = 20) who received a three-phase active therapy with pulsed Nd:YAG laser thrice/week (total energy was 1500 J) plus a physical exercise program for four consecutive weeks, or the placebo group (n = 20) who received placebo laser plus the physical exercise program. Pain, postural control (i.e., directional control [DC], endpoint excursion [EE], center-of-gravity movement velocity [CoG-MV], and maximum excursion [MXE]), and weight-bearing pattern (i.e., pressure peaks of the hindfoot [PP-HF] and forefoot [PP-FF], and the foot contact area [FCA]) were assessed pre- and post-treatment. The treatment group showed greater improvement in pain (P = .004), DC (P = .02), EE (P = .003), and CoG-MV (P = .003) compared to the placebo group. However, there was no statistically significant difference between both groups regarding the MXE (P = .15). In addition, the treatment group achieved favorable improvements in PP-HF (P = .003), PP-FF (P = .027), and FCA (P = .002) relative to the placebo group. Pulsed Nd:YAG laser is a potentially effective therapy for pain relief, postural control enhancement, and weight-bearing pattern adjustment in children with hemophilic ankle arthropathy.

The Effect of Proprioceptive Training on Directional Dynamic Stabilization.

OBJECTIVES: Significant loss of playing time and the impact of treatment costs due to lower limb injury in football demonstrates a need for improved protocols for injury risk reduction. The aim of the present study is to assess the effect of a proprioceptive training program on the lower limb dynamic stability of elite footballers. METHODS: A total of 16 elite premier league footballers were randomly allocated by matched pair design to a 8-week proprioception training group (group A, n = 8) or nontraining group (group B, n = 8), to determine the effect of this training over a 16-week period. Group A completed 8 weeks of bilateral proprioceptive training, 5 times per week for 10 minutes. The Biodex Stability System measures of overall stability index, anterior-posterior (A-P), and medial-lateral stability (M-L) at levels 8-6-4-1 were taken for both groups at baseline, 4, 8, and 16 weeks. Main effects of time, level of stability, and direction of stability were determined, with comparisons of effect made between the 2 groups. RESULTS: The training group displayed significant differences for multidirectional stability at week 8 (P ≤ .05). The A-P stability within the training group displayed significant differences between baseline measures and 16 weeks (P > .05), with significant increases in scores displayed for M-L and A-P stability between weeks 8 and 16 (P ≤ .05), representing a detraining effect. No significant differences were detected at any time point for the nontraining group (P > .05). CONCLUSIONS: Proprioceptive training over 8 weeks has a positive effect on all directions of stability. Greater declines in A-P stability were evident at 16 weeks when compared with M-L and overall stability index. Consideration must be given to the increased stability scores presented pretesting for A-P when compared with M-L. Findings of this work present implications for training design.

Retention and generalizability of balance recovery response adaptations from trip perturbations across the adult life span.

For human locomotion, varying environments require adjustments of the motor system. We asked whether age affects gait balance recovery adaptation, its retention over months, and the transfer of adaptation to an untrained reactive balance task. Healthy adults (26 young, 27 middle-aged, and 25 older; average ages 24, 52, and 72 yr, respectively) completed two tasks. The primary task involved treadmill walking: either unperturbed (control; n = 39) or subject to unexpected trip perturbations (training; n = 39). A single trip perturbation was repeated after a 14-wk retention period. The secondary transfer task, before and after treadmill walking, involved sudden loss of balance in a lean-and-release protocol. For both tasks, the anteroposterior margin of stability (MoS) was calculated at foot touchdown. For the first (i.e., novel) trip, older adults required one more recovery step (P = 0.03) to regain positive MoS compared with younger, but not middle-aged, adults. However, over several trip perturbations, all age groups increased their MoS for the first recovery step to a similar extent (up to 70%) and retained improvements over 14 wk, although a decay over time was found for older adults (P = 0.002; middle-aged showing a tendency for decay: P = 0.076). Thus, although adaptability in reactive gait stability control remains effective across the adult life span, retention of adaptations over time appears diminished with aging. Despite these robust adaptations, the perturbation training group did not show superior improvements in the transfer task compared with age-matched controls (no differences in MoS changes), suggesting that generalizability of acquired fall-resisting skills from gait-perturbation training may be limited.NEW & NOTEWORTHY The human neuromotor system preserves its adaptability across the adult life span. However, although adaptability in reactive gait stability control remains effective as age increases, retention of recovery response adaptations over time appears to be reduced with aging. Furthermore, acquired fall-resisting skills from single-session perturbation training seem task specific, which may limit the generalizability of such training to the variety of real-life falls.