Measures Of Dynamic Stability Research Articles

Running barefoot leads to lower running stability compared to shod running - results from a randomized controlled study

Local dynamic running stability is the ability of a dynamic system to compensate for small perturbations during running. While the immediate effects of footwear on running biomechanics are frequently investigated, no research has studied the long-term effects of barefoot vs. shod running on local dynamic running stability. In this randomized single-blinded controlled trial, young adults novice to barefoot running were randomly allocated to a barefoot or a cushioned footwear running group. Over an 8-week-period, both groups performed a weekly 15-min treadmill running intervention in the allocated condition at 70% of their VO2 max velocity. During each session, an inertial measurement unit on the tibia recorded kinematic data (angular velocity) which was used to determine the short-time largest Lyapunov exponents as a measure of local dynamic running stability. One hundred running gait cycles at the beginning, middle, and end of each running session were analysed using one mixed linear multilevel random intercept model. Of the 41 included participants (48.8% females), 37 completed the study (drop-out = 9.7%). Participants in the barefoot running group exhibited lower running stability than in the shod running group (p = 0.037) with no changes during the intervention period (p = 0.997). Within a single session, running stability decreased over the course of the 15-min run (p = 0.012) without differences between both groups (p = 0.060). Changing from shod to barefoot running reduces running stability not only in the acute phase but also in the longer term. While running stability is a relatively new concept, it enables further insight into the biomechanical influence of footwear.

Altered Dynamic Postural Stability and Joint Position Sense Following British Army Foot-Drill.

Impaired proprioceptive acuity negatively affects both joint position sense and postural control and is a risk factor for lower-extremity musculoskeletal injury in athletes and military personnel. British Army foot-drill is an occupational military activity involving cyclical high impact loading forces greater than those observed in athletes during high level plyometrics. Foot-drill may contribute to the high rates of lower-extremity overuse injuries observed in recruits during basic training. There is limited research investigating foot-drill specific injury risk factors in women, despite greater incidences of musculoskeletal injury reported in women (522 vs. 417 per 1,000 personnel, OR: 1.53) when compared to men during basic training. This study aimed to quantify changes in ankle joint proprioception and dynamic postural stability following a period of British Army foot-drill. Fourteen women of similar age to British Army female recruits underwent pre-post foot-drill measures of frontal plane ankle joint position sense (JPS) and dynamic postural stability using the dynamic postural stability index (DPSI). Passive ankle JPS was assessed from relative test angles of inversion 30% (IN30%) and eversion 30% (EV30%) and IN60% of participants range of motion using an isokinetic dynamometer. The DPSI and the individual stability indices (medio-lateral [MLSI], anterior-posterior [APSI], and vertical [VSI]) were calculated from lateral and forward jump-landing conditions using force plates. Foot-drill was conducted by a serving British Army drill instructor. Significantly greater absolute mean JPS error for IN30% and EV30% was observed post foot-drill (p ≤ 0.016, d ≥ 0.70). For both the lateral and forward jump-landing conditions, significantly greater stability index scores were observed for MLSI, APSI, and DPSI (p ≤ 0.017, d ≥ 0.52). Significantly greater JPS error and stability index scores are associated with the demands of British Army foot-drill. These results provide evidence that foot-drill negatively affects lower-extremity proprioceptive acuity in recruit age-matched women, which has implications for increased injury risk during subsequent military physical activity, occurring in a normal training cycle.

Recovery From a Forward Falling Slip: Measurement of Dynamic Stability and Strength Requirements Using a Split-Belt Instrumented Treadmill

Aim: Falls commonly occur from trips and slips while walking. Recovery strategies from trips and backward falling slips have been extensively studied. However, until recently, forward falling slips (FFSs) have been considered less dangerous and have been understudied. This study aimed first to create an application to realistically simulate FFSs using a split-belt instrumented treadmill and then to understand the biomechanical requirements for young adults to recover from an FFS.Methods: We developed a semi-automatic custom-made application on D-Flow that triggered FFSs by briefly and unexpectedly increasing the speed (a = 5 m·s−2) of the right belt during stance. To validate the protocol, we tested against criteria defined for an ecologically and experimentally valid FFS: unexpected occurrence of the slip, increased foot velocity, forward loss of balance during the slip and consistent perturbation timing. We evaluated the recovery strategies of 17 young adults by measuring dynamic stability, joint moments and ground reaction force (GRF) vector angles before, during and on 15 steps following the FFS.Results: The application successfully triggered FFSs, according to the criteria we defined. Participants' balance returned to normal for a minimum of three consecutive steps in 10.9 (7.0) steps. Recovery from the FFSs was characterised by larger hip flexor and knee extensor moments to support the centre of mass during the slip, and a longer first recovery step with large hip extensor moments to arrest the fall followed by large knee extensor moments to raise and advance the centre of mass into the next step (p < 0.001 compared with normal gait). Subsequent steps progressively returned to normal.Conclusion: This is the first study to experimentally simulate FFSs meeting the aforementioned criteria, and to measure their effects on the dynamic balance and kinetic parameters. The split-belt instrumented treadmill proved a promising tool to better study the mechanisms of falls and recovery. The required large hip and knee joint moments generally agree with findings on trips and backward falling slips and provide an indication of the functional capacities that should be targeted in fall-prevention interventions. These findings should be used to better understand and target the mechanisms of balance loss and falls in older adults following FFSs.

The relationship between eccentric hamstring strength and dynamic stability in elite academy footballers

ABSTRACT Objectives Previous research describes dynamic stability and functional strength as key aetiological risk factors associated with lower limb non-contact musculoskeletal injury. Due to the multifactorial nature of injury risk, relationships between the two factors will inform injury management and training design. Methods A total of 59 elite academy footballers from two English premier league category 1-status academies completed the study. All players completed measures of eccentric hamstring strength and dynamic stability. Relationships between directional stability (Anteroposterior (Ant), Posteromedial (PM) and Posterolateral (PL)) and eccentric strength metrics (PkT, AvT, PkF, AvF and Ɵ) bilaterally were identified for analysis. Results Significant correlations were identified bilaterally for functional hamstring strength metrics and PM and PL stability (P ≤. 0.05). No significant relationships were identified between anterior stability and eccentric hamstring strength parameters (P > 0.05). Conclusions Eccentric hamstring strength has a positive influence on directional stability through two planes, PM and PL. The lack of influence of eccentric hamstring strength on Ant directional stability could be attributed to increased ACL risk. Careful consideration of the significance of the relationships between eccentric hamstring strength and directional stability must be given when quantifying injury risk in elite academy footballers.

Local Dynamic Stability of Gait in People With Early Multiple Sclerosis and No-to-Mild Neurological Impairment.

Poor dynamic balance, such as poor walking stability, is a hallmark of multiple sclerosis. Instrumental measures of local dynamic stability (LDS, e.g. short-term Lyapunov's exponents, sLyEs) are genuine measures of walking stability and increasingly used as dynamic balance indicators. The current work aims to investigate if people with multiple sclerosis (PWMS) with no clinical evidence of gait impairment suffer poor LDS of gait. Eighty PWMS with minimal impairment (EDSS ≤2.5) and twenty controls completed the Six-Minute Walk Test (6MWT) at their maximum speed, wearing inertial sensors. sLyEs were calculated from trunk vertical, mediolateral and anteroposterior (sLyEAP) acceleration. PWMS also completed a full clinical assessment including gait, balance and fatigue. Gait speed was lower in PWMS than controls (-15%), while sLyEs were larger in PWMS (+12%), even when adjusting for the different gait speed. High sLyEAP was associated with low gait speed, high impact of disease (including high fatigue) and poor balance, the three variables returned by a principal component analysis of the dataset of clinical measures. PWMS suffer poor LDS of gait, as indicated by large sLyEs. The association between high sLyEAP and poor balance supports the validity of sLyEAP as a dynamic balance measure. The inverse relationship between sLyEAP and gait speed is in line with the view that good balance is decisive for high gait speed. Finally, these findings are in line with the vicious circle linking poor balance and fatigue in PWMS, with fatigue worsening balance and poor balance leading to fatigue.

Salp Swarm Optimization Algorithm-Based Fractional Order PID Controller for Dynamic Response and Stability Enhancement of an Automatic Voltage Regulator System

Owing to the superior transient and steady-state performance of the fractional-order proportional-integral-derivative (FOPID) controller over its conventional counterpart, this paper exploited its application in an automatic voltage regulator (AVR) system. Since the FOPID controller contains two more control parameters (µ and λ ) as compared to the conventional PID controller, its tuning process was comparatively more complex. Thus, the intelligence of one of the most recently developed metaheuristic algorithms, called the salp swarm optimization algorithm (SSA), was utilized to select the optimized parameters of the FOPID controller in order to achieve the optimal dynamic response and enhanced stability of the studied AVR system. To validate the effectiveness of the proposed method, its performance was compared with that of the recently used tuning methods for the same system configuration and operating conditions. Furthermore, a stability analysis was carried out using pole-zero and bode stability criteria. Finally, in order to check the robustness of the developed system against the system parameter variations, a robustness analysis of the developed system was undertaken. The results show that the proposed SSA-based FOPID tuning method for the AVR system outperformed its conventional counterparts in terms of dynamic response and stability measures.

Comparative Response on Flotation of Coal by Using Process and De-Ionized Water

ABSTRACT Recycling of the process water is an essential aspect for the mineral and coal processing industries to address the challenges on the sustainability of the environment. In this study, the influence of dissolved ions presents in the process water of an Indian coal preparation plant is investigated on flotation behavior of coal by a combination of release analysis, batch flotation tests, dynamic froth stability measurements, surface tension measurements, contact angle measurements, zeta potential measurements, and Fourier-transform infrared spectroscopy measurements. Also, comparison studies are conducted with de-ionized water to float the same coal for the evaluation.

Dynamic stability during walking in children with and without cerebral palsy

BackgroundCerebral palsy (CP) is associated with a high risk of falling during walking. Many gait abnormalities associated with CP likely alter foot placement and center of mass (CoM) movement in a way that affects anterior or lateral dynamic stability, in turn influencing fall risk. Research questionDo children with CP demonstrate altered anterior or lateral dynamic stability compared to typically-developing (TD) children? MethodsIn this case-control, observational study, we measured gait kinematics of two groups of children (15 CP, 11 GMFCS level I, 4 GMFCS level II; 14 TD; age 5–12) in walking conditions of a preferred speed, a fast speed, and a preferred speed while completing a cognitive task. For dominant and non-dominant limbs, the margin of stability (MoS), a spatial measure of dynamic stability, was calculated as the distance between the edge of the base of support and the CoM position after accounting for scaled velocity. Statistical comparisons of were made using mixed factorial ANOVAs. Post hoc comparisons were Sidak adjusted. ResultsThe anterior MoS before foot strike and at mid-swing differed between each condition but not between groups. Based on the minimum lateral MoS, children with CP had more stability when bearing weight on their non-dominant limb compared to TD children. These differences were not apparent when on the dominant limb. SignificanceThis high-functioning group of children with CP exhibited a more conservative lateral stability strategy during walking when bearing weight with the non-dominant limb. This strategy may be protective against lateral falls. We observed no between-group differences in anterior stability. Because CP has been previously associated with impaired anterior balance reactions, and there was no observed compensation in anterior gait stability, this lack of group differences could contribute to a higher risk of falling in that direction.

Reliability of measures of dynamic stability for the assessment of balance recovery after a forward loss of balance

BackgroundFalls are common and serious events, which mostly occur during locomotion, that are associated with deficient dynamic balance. An experimental approach that simulates falling forward has become increasing popular to investigate dynamic balance. However, research has not been conducted to examine the test-retest reliability of this experimental approach. Research questionWhat is the reliability of dynamic stability measures that are used for the assessment of balance recovery after forward loss of balance? MethodsNineteen healthy young adults (24.3 ± 2.8 yrs; nine females) volunteered for this study. They reported twice to the laboratory to perform two tests: (i) a stepping task, in which they were instructed to recover balance by taking a step after being suddenly released from an inclined forward position; and (ii) a standing task, in which we aimed to identify the maximum forward leaning angle they were able to compensate for without taking a step. Intra-class correlation coefficients (ICC) were calculated for the margin of stability (MoS) and spatiotemporal parameters for both tests. ResultsThe reliability of the stepping task variables ranged from poor to excellent, with ICCs tending to increase with the number of trials included in the analysis. Intra-session analysis (one-way rm ANOVA) revealed a significant trial effect for the MoS, indicating that stepping responses changed across repeated trials. With respect to the standing task, test-retest reliability was only fair for the maximal initial leaning angle. SignificanceIn essence, these results indicate that the inter-session reliability of the stepping task is acceptable, depending on the measures used and the number of trials conducted. However, one must be aware that behavioral adaptations arise with repeated exposure to simulated forward falls. Finally, this study’s results suggest that the reproducibility of the standing task is limited.

Статодинамическая устойчивость тела спортсменок, занимающихся художественной гимнастикой, на этапе специализированной базовой подготовки

Objective. To assess biomechanical measures of static dynamic stability of the body of rhythmic gymnastics female athletes in the basic balances at the stage of specialized basic training. Methods. Theoretical analysis and generalization of scientific literature, methodological and practical experience of the trainers; method of expert assessments using video analysis of the technique of performing basic balances; stabiloanalyzer "Stabilan 01-2" to record the movements of the common center of pressure (COP) of the feet on the support, i.e. the coordinates at different time points that reflect the features of static dynamic stability. Three basic balance tests were performed. The study involved young female gymnasts of the Republican Complex Children and Youth Sports School "Avangard" (Kуiv) aged 10-14 years (n = 30), of which 20 athletes have the rank of Candidate for Master of Sport and 10 gymnasts have the rank of First-Class Sportsman. Results. It has been found that, at the stage of specialized basic training, female athletes in rhythmic gymnastics, along with a stable demonstration of competitive compositions, have technical errors that are associated with an insufficient level of development of sensorimotor coordination, orientation in space and time, and static dynamic stability of the body. Indicators of biomechanical analysis of stabilograms, which were recorded during the performance of the basic balances by the subjects, show that stability control is achieved both through macro and micro-oscillations of the body, as well as the controlled ratio of the trajectory lengths of the common center of pressure on the support along the frontal and sagittal line. In some gymnasts, when performing basic tests, displacements along frontal and sagittal lines approached the ratio of 1:1 that indicates the effective formation of a system of symmetric motor actions for the control of static dynamic stability. Conclusion. On the basis of individual measures of static dynamical stability of the body of rhythmic gymnastics female athletes at the stage of specialized basic training, an instructional program of exercises should be developed that will be aimed at development and improvement of static dynamic stability of the body using the technology of biological feedback in the system gymnast–stabilograph. Key words: rhythmic gymnastic, basic training, balances, body stability, technique, stabilography, competitive compositions.

The effect of pulp bubble size on the dynamic froth stability measurement

The measurement of dynamic and static froth stability has found widespread application in the characterisation of froth performance. However, little attention has been given to scale parameters in the performance of these measurements. This study focussed on the effect of pulp bubble size on froth stability. Different pulp bubble sizes were generated in a non-overflowing column and time-dependent froth characteristics such as froth height, side-of-froth and top-of-froth bubble size were measured. An inverse relationship was found between apparent, measured froth stability and pulp bubble size. It was also shown that top-of-froth bubble size is independent of pulp bubble size. A normalised froth height parameter is used to generate a bubble growth curve which is independent of pulp bubble size. It is proposed that this type of analysis may present an avenue into a truly scale-independent analysis of froth stability.

Differential effects of muscle fatigue on dynamic spine stability: Implications for injury risk

This study was designed to assess the utility of using a measure of dynamic spine stability in an unfatigued, rested state as a predictor of dynamic spine stability in a challenged, fatigued state. Participants completed three trials (Day 1: Rested, Fatigued; Day 2: Recovery) during which the dynamic stability of the spine was assessed over 30 repeated flexion/extension motions using maximum finite-cycle Lyapunov exponents. Multiple sets of dynamic trunk extensions were performed to fatigue the trunk extensor muscles. Across the sample population, an increase in dynamic spine stability when fatigued was observed, as well as a moderate correlation between the level of dynamic stability when rested and a stabilizing response when fatigued. Further analysis of the data on a person-by-person basis revealed three distinct responses in which participants either stabilized, destabilized or had no change in dynamic spine stability when fatigued. Therefore, the mean response of the sample population did not adequately represent the true, meaningful response of individuals within the population. These results illustrate the importance of considering individualized responses when examining dynamic stability measures, and provide preliminary evidence that suggests that individual injury risk cannot be completely captured by measures taken in an unchallenged, rested state.

Study on feet forces' distributions, energy consumption and dynamic stability measure of hexapod robot during crab walking

• During crab walking of hexapod, impact forces are generated, whenever the swing leg touches the ground. • Both specific energy consumption and dynamic stability margin decrease with the increase in trunk body velocity. • Specific energy consumption increases but dynamic stability margin decreases with the increase in body height. • Both specific energy and dynamic stability margin increase with the body stroke, lateral offset, crab angle. • Both specific energy consumption and dynamic stability margin increase with the increase in duty factor. This paper deals with the development of a dynamical model related to crab walking of a hexapod robot to determine the feet forces' distributions, energy consumption and dynamic stability measure considering the inertial effects of the legs on the system, which has not been attempted before. Both forward and inverse kinematic analyses of the robot are carried out with an assigned fixed global frame and subsequent local frames in the trunk body and joints of each leg. Coupled multi-body dynamic model of the robot is developed based on free-body diagram approach. Optimal feet forces and corresponding joint torques on all the legs are determined based on the minimization of the sum of the squares of joint torques, using quadratic programming (QP) method. An energy consumption model is developed to determine the minimum energy required for optimal values of feet forces. To ensure dynamically stable gaits, dynamic gait stability margin (DGSM) is determined from the angular momentum of the system about the supporting edges. Computer simulations have been carried out to test the effectiveness of the developed dynamic model with crab wave gaits on a banking surface. It is observed that when the swing leg touches the ground, impact forces (sudden shoot outs) are generated and their effects are also observed on the joints of the legs. The effects of walking parameters, namely trunk body velocity, body stroke, leg offset, body height, crab angle etc. on power consumption and stability during crab motion for duty factors (DFs) like 1/2, 2/3, 3/4 have also been studied.

Effect of Ankle Taping on Dynamic Balance and Perception of Stability

Purpose: The purpose of this study was to examine the actual and perceived effect of taping on dynamic stability. Methods: 21 physically active subjects [12 females (age = 20.33 ± 1.44 years, height = 165 ± 0.05 cm, mass = 68.76 ± 12.69 kg), and 9 males (age = 21.33 ± 1.66 years, height = 180 ± 0.10 cm, mass = 86.54 ± 9.46 kg)] participated in this study. Dynamic stability and perception of stability were assessed barefoot and with the ankle taped. The taped ankle condition used a standard preventive tape application including two anchors, three stirrups, close downs, horseshoes, two heel locks per side and two figures of eight. The Biodex Balance System SD was used to measure medial-lateral and anterior-posterior stability. Dynamic balance was assessed in a single leg stance during three 20-second trials at stability level 4. A 30-second rest period was provided between trials. Perception of stability was assessed using a 4-point Likert scale (1 = very unstable, 2 = unstable, 3 = stable, 4 = very stable) after each test session. Independent variables were counter-balanced to minimize the effects of fatigue associated with the testing procedures. A Repeated measures ANOVA was used to analyze the difference between barefoot and ankle tape for medial-lateral and anterior-posterior dynamic stability indices and perception of stability. All tests of significance were carried out at an alpha level = 0.05. The Bonferroni post hoc test was used for all paired comparisons. Results: Significant differences were not found for medial-lateral stability (Barefoot = 1.24 ± 0.63, Taped = 1.21 ± 0.72) nor anterior-posterior stability (Barefoot = 1.70 ± 1.07, Taped = 1.50 ± 0.89). Significant differences were found for perception of stability (Barefoot = 2.57 ± 0.60, Taped = 3.32 ± 0.67, p = 0.000). Conclusions: The use of ankle taping had no influence on dynamic stability measures in this study. Ankle taping did cause an increased perception of stability suggesting that ankle taping may have more of a placebo effect in uninjured ankles.

Effect of dissolved gases in natural water on the flotation behavior of coal

The effect of dissolved gases in natural water on the flotation behavior of coal was investigated by a combination of flotation tests, dynamic froth stability measurements, pulp rheology measurements, settling tests and induction time measurements. Better flotation performance with a lower dynamic froth stability (DFS) value was achieved in natural water compared to degassed water. Both pulp rheology and settling results showed that the gases dissolved in natural water enhance the formation of bubble-included aggregates. In addition, dissolved gases reduce the induction time between coal particles and bubbles, resulting in the easier capture of coal particles by the bubbles. All these variables are responsible for the improved flotation performance observed in natural water.

The effects of unexpected mechanical perturbations during treadmill walking on spatiotemporal gait parameters, and the dynamic stability measures by which to quantify postural response.

Most falls occur after a loss of balance following an unexpected perturbation such as a slip or a trip. Greater understanding of how humans control and maintain stability during perturbed walking may help to develop appropriate fall prevention programs. The aim of this study was to examine changes in spatiotemporal gait and stability parameters in response to sudden mechanical perturbations in medio-lateral (ML) and anterior-posterior (AP) direction during treadmill walking. Moreover, we aimed to evaluate which parameters are most representative to quantify postural recovery responses. Ten healthy adults (mean = 26.4, SD = 4.1 years) walked on a treadmill that provided unexpected discrete ML and AP surface horizontal perturbations. Participants walked under no perturbation (normal walking), and under left, right, forward, and backward sudden mechanical perturbation conditions. Gait parameters were computed including stride length (SL), step width (SW), and cadence, as well as dynamic stability in AP- (MoS-AP) and ML- (MoS-ML) directions. Gait and stability parameters were quantified by means, variability, and extreme values. Overall, participants walked with a shorter stride length, a wider step width, and a higher cadence during perturbed walking, but despite this, the effect of perturbations on means of SW and MoS-ML was not statistically significant. These effects were found to be significantly greater when the perturbations were applied toward the ML-direction. Variabilities, as well as extremes of gait-related parameters, showed strong responses to the perturbations. The higher variability as a response to perturbations might be an indicator of instability and fall risk, on the same note, an adaptation strategy and beneficial to recover balance. Parameters identified in this study may represent useful indicators of locomotor adaptation to successfully compensate sudden mechanical perturbation during walking. The potential association of the extracted parameters with fall risk needs to be determined in fall-prone populations.

Biomechanical assessment of dynamic balance: Specificity of different balance tests

Dynamic balance is vitally important for most sports and activities of daily living, so the assessment of dynamic stability has become an important issue. In consequence, a large number of balance tests have been developed. However, it is not yet known whether these tests (i) measure the same construct and (ii) can differentiate between athletes with different balance expertise. We therefore studied three common dynamic balance tests: one-leg jump landings, Posturomed perturbations and simulated forward falls. Participants were 24 healthy young females in regular training in either gymnastics (n = 12) or swimming (n = 12). In each of the tests, the participants were instructed to recover balance as quickly as possible. Dynamic stability was computed by time to stabilization and margin of stability, deduced from force plates and motion capture respectively. Pearson’s correlations between the dynamic balance tests found no significant associations between the respective dynamic stability measures. Furthermore, independent t-tests indicated that only jump landings could properly distinguish between both groups of athletes. In essence, the different dynamic balance tests applied did not measure the same construct but rather task-specific skills, each of which depends on multifactorial internal and external constraints. Our study therefore contradicts the traditional view of considering balance as a general ability, and reinforces that dynamic balance measures are not interchangeable. This highlights the importance of selecting appropriate balance tests.

Fluctuating interaction network and time-varying stability of a natural fish community.

Ecological theory suggests that large-scale patterns such as community stability can be influenced by changes in interspecific interactions that arise from the behavioural and/or physiological responses of individual species varying over time. Although this theory has experimental support, evidence from natural ecosystems is lacking owing to the challenges of tracking rapid changes in interspecific interactions (known to occur on timescales much shorter than a generation time) and then identifying the effect of such changes on large-scale community dynamics. Here, using tools for analysing nonlinear time series and a 12-year-long dataset of fortnightly collected observations on a natural marine fish community in Maizuru Bay, Japan, we show that short-term changes in interaction networks influence overall community dynamics. Among the 15 dominant species, we identify 14 interspecific interactions to construct a dynamic interaction network. We show that the strengths, and even types, of interactions change with time; we also develop a time-varying stability measure based on local Lyapunov stability for attractor dynamics in non-equilibrium nonlinear systems. We use this dynamic stability measure to examine the link between the time-varying interaction network and community stability. We find seasonal patterns in dynamic stability for this fish community that broadly support expectations of current ecological theory. Specifically, the dominance of weak interactions and higher species diversity during summer months are associated with higher dynamic stability and smaller population fluctuations. We suggest that interspecific interactions, community network structure and community stability are dynamic properties, and that linking fluctuating interaction networks to community-level dynamic properties is key to understanding the maintenance of ecological communities in nature.

Dynamic Varus and the Development of Iliotibial Band Syndrome.

Although the risk of osteoarthritis development after acute knee injury has been widely studied, the long-term consequences of knee overuse injury are not well understood. To identify the relationship between gait-related risk factors associated with osteoarthritis and the development of iliotibial band syndrome (ITBS) in members of a single University Army Reserve Officers' Training Corps unit. Prospective cohort study. Biomechanics laboratory. Sixty-eight cadets undergoing standardized physical fitness training. Three-dimensional lower extremity kinematics (240 Hz) and kinetics (960 Hz) were collected for 3 bilateral trials during shod running at 4.0 m/s ± 10%. Injury tracking was conducted for 7 months of training. Biomechanical variables, including varus thrust and knee-adduction moment, were compared between the injured and control groups. Twenty-six cadets with no history of overuse injury served as the control group, whereas 6 cadets (7 limbs) who developed ITBS that required them to modify their training program or seek medical care (or both) served as the injured group. Maximum varus velocity was higher ( P = .006) and occurred sooner during stance ( P = .04) in the injured group than in the control group, indicating greater varus thrust. Maximum knee-varus angle and maximum knee-adduction moment were higher ( P = .02 and P = .002, respectively) and vertical stiffness was lower ( P = .03) in the injured group. Measures of dynamic varus stability appeared to be altered in individuals who developed ITBS. Biomechanical knee variables previously identified as increasing the risk for knee osteoarthritis were also associated with the development of ITBS in healthy adults.

Comparison of jump-landing protocols with Biodex Balance System as measures of dynamic postural stability in athletes

The objective of the study was to determine whether a relationship exists between the two common methods for assessing postural stability in athletes: the time-to-stabilisation (TTS) via force-plate and the Biodex Balance System (BBS). The conditions under which these measurements assess dynamic postural control may not provide sufficient feedback to practitioners. Fourty-four amateur soccer players with no history of musculoskeletal disorders volunteered for the study. Pearson correlation was used to compare the anterior–posterior (AP), medio-lateral (ML), and the overall stability indexes measured by BBS, with the corresponding parameters of TTS assessed via force plate. There was no significant correlation between any parameters of dynamic stability measured by force-plate and the stability indexes. However, there was a significant correlation between the resulting vectors and the AP component of TTS for each jump protocol. Furthermore, forward drop landing exhibited shortest TTS in AP direction, while lateral drop landing resulted in longer ML TTS relative to both forward jumps (p < 0.001). These results demonstrate that the TTS and BBS stability indexes should be used as distinct measures of dynamic postural stability. TTS protocols may be modified to target a specific training conditions or athletic population.