Kinematic Factors Research Articles

Movement direction impacts knee joint kinematics during elliptical exercise at varying incline angles

BackgroundElliptical trainers are a popular cardiovascular exercise for individuals with injuries or those post-operation. There is currently limited data on the impacts of direction while on elliptical trainers for knee joint kinematic risk factors. This study compared lower extremity kinematics between the forward and reverse direction at varying inclines on an elliptical trainer modified with converging footpath and reduced inter-pedal distance. MethodsTwenty-four college age participants exercised on the modified elliptical in both directions at four ramp inclines: 6°, 12°, 25°, and 35°. Three-dimensional kinematics were collected for each direction and ramp incline. A 2 × 4 (direction × incline) repeated measures analysis of variance was run with an alpha of 0.05. Simple effects analysis was run with Bonferroni correction for significant interaction or main effect of ramp incline. ResultsThe reverse direction had significantly greater peak knee valgus at 6° incline (mean difference [MD] = 1.35°, p < 0.014, d = 0.31) and 12° (MD = 2.41°, p < 0.001, d = 0.55), peak hip abduction at 6° (MD = 2.86°, p = 0.002, d = 0.49) and 12° (MD = 2.91°, p < 0.001, d = 0.51), but decreased peak knee flexion angles (p = 0.032) at all inclines. ConclusionsIndividuals with knee pathologies such as knee osteoarthritis or anterior knee pain should exercise in the reverse direction at lower inclines. However, switching to the forward direction and/or increasing incline may increase quadriceps strength during a safe activity such as elliptical trainers.

The effect of changing foot progression angle using real-time visual feedback on rearfoot eversion during running.

Atypical rearfoot in/eversion may be an important risk factor for running-related injuries. Prominent interventions for atypical rearfoot eversion include foot orthoses, footwear, and taping but a modification derived from gait retraining to correct atypical rearfoot in/eversion is lacking. We aimed to investigate changes in rearfoot in/eversion, subtalar pronation, medial longitudinal arch angle, and selected lower limb joint biomechanics while performing toe-in/toe-out running using real-time visual feedback. Fifteen female runners participated in this study. Subjects performed toe-in/toe-out running using real-time visual feedback on foot progression angle, which was set ±5° from habitual foot progression angle. 3D kinematics of rearfoot in/eversion, subtalar supination/pronation, medial longitudinal arch angle, foot progression angle, hip flexion, ab/adduction and internal/external rotation, knee flexion, ankle dorsiflexion, and ankle power were analyzed. A repeated-measures ANOVA followed by pairwise comparisons was used to analyze changes between three conditions. Toe-in running compared to normal and toe-out running reduced peak rearfoot eversion (mean difference (MD) with normal = 2.1°; p<0.001, MD with toe-out = 3.5°; p<0.001), peak pronation (MD with normal = -2.0°; p<0.001, MD with toe-out = -3.4; p = <0.001), and peak medial longitudinal arch angle (MD with normal = -0.7°; p = 0.022, MD with toe-out = -0.9; p = 0.005). Toe-out running significantly increased these kinematic factors compared to normal and toe-in running. Toe-in running compared to normal running increased peak hip internal rotation (MD = 2.3; p<0.001), and reduced peak knee flexion (MD = 1.3; p = 0.014). Toe-out running compared to normal running reduced peak hip internal rotation (MD = 2.5; p<0.001), peak hip ab/adduction (MD = 2.5; p<0.001), peak knee flexion (MD = 1.5; p = 0.003), peak ankle dorsiflexion (MD = 1.6; p<0.001), and peak ankle power (MD = 1.3; p = 0.001). Runners were able to change their foot progression angle when receiving real-time visual feedback for foot progression angle. Toe-in/toe-out running altered rearfoot kinematics and medial longitudinal arch angle, therefore supporting the potential value of gait retraining focused on foot progression angle using real-time visual feedback when atypical rearfoot in/eversion needs to be modified. It should be considered that changes in foot progression angle when running is accompanied by changes in lower limb joint biomechanics.

Pitching Mechanics: Do Certain Mechanics Predispose Pitchers to Shoulder Injuries?

Pitching mechanics require a complex biomechanical combination of energy production and transfer up the kinetic chain. The throwing motion can be broken down into six different phases: 1) wind-up, 2) stride/early cocking, 3) late cocking, 4) acceleration, 5) deceleration, and 6) follow-through. While variations in the throwing motion amongst pitchers are common, there are specific kinematic factors that may increase their risk of a significant shoulder injury. The objective of this chapter is to present the pitching mechanics which have been reported in the peer-reviewed literature to have a significant effect on upper extremity rotational kinetics and increase a pitcher's risk of shoulder injury. These include lead leg landing spot and knee flexion angle, trunk rotational timing and positioning, and shoulder range of motion and positioning.

Learning a reach trajectory based on binary reward feedback

Binary reward feedback on movement success is sufficient for learning some simple sensorimotor mappings in a reaching task, but not for some other tasks in which multiple kinematic factors contribute to performance. The critical condition for learning in more complex tasks remains unclear. Here, we investigate whether reward-based motor learning is possible in a multi-dimensional trajectory matching task and whether simplifying the task by providing feedback on one factor at a time (‘factorized feedback’) can improve learning. In two experiments, participants performed a trajectory matching task in which learning was measured as a reduction in the error. In Experiment 1, participants matched a straight trajectory slanted in depth. We factorized the task by providing feedback on the slant error, the length error, or on their composite. In Experiment 2, participants matched a curved trajectory, also slanted in depth. In this experiment, we factorized the feedback by providing feedback on the slant error, the curvature error, or on the integral difference between the matched and target trajectory. In Experiment 1, there was anecdotal evidence that participants learnt the multidimensional task. Factorization did not improve learning. In Experiment 2, there was anecdotal evidence the multidimensional task could not be learnt. We conclude that, within a complexity range, multiple kinematic factors can be learnt in parallel.

Lateral free-field responses and kinematic interaction of monopiles to obliquely incident seismic waves in offshore engineering

This paper studies the lateral free-field response and dynamic interaction of monopiles with a partially/fully saturated porous seabed under a seawater layer, subjected to vertically and obliquely incident P and SV wave excitations. The solution of the coupled three-dimensional water-pile-soil vibration problem is developed using a rigorous semi-analytical method. Results for the free-field soil displacement and kinematic interaction factors of the pile head are obtained: the presence of water layer will increase or decrease the lateral free-field displacement for the P wave case, depending on whether the soil is fully saturated or partially saturated; the presence of water layer will have little influence, increase or decrease the lateral free-field displacement for the SV wave case, depending on the incident angle. Besides, the non-dimensional lateral kinematic interaction factors for both P wave and SV wave cases, with different water depths, are illustrated over a broad non-dimensional frequency range. Similar to the free-field responses, monopile responses can generally be amplified or reduced with the presence of a water layer, depending on the saturation degrees of soil and incident angles in P wave case and SV wave case, respectively.

Method for calculating technical characteristics and parameters of movement of scale models of wheeled vehicles, ensuring the similarity of the processes during testing

Nowadays, when designing new vehicle models, there is a need to test certain solutions for the formation of a technical appearance both by simulation methods and on production samples. Full-scale road tests of vehicles make it possible to maintain full dynamic similarity during the experiment, but they can be carried out only after manufacturing of a vehicle prototype, which requires a lot of material costs. One of the ways to solve this problem is to create models that are a reduced copy of the designed vehicle. The main difficulty that appears when testing a scale model of vehicle is the need to accurately reproduce the conditions that occur when driving in real road conditions. The purpose of this paper is to find a relationship between the parameters of a production vehicle and a scale model for experimental development of algorithms for the dynamic stabilization of a wheeled vehicle. A method for calculating the technical characteristics and motion parameters of scale models for real full-scale wheeled vehicles while ensuring the similarity of the ongoing processes for scale models and for production vehicles is proposed on the basis of the theory of similarity. The main dependences for scale factors for force, kinematic and dimensional factors are obtained. The similarity of the occurring processes was confirmed by the methods of simulation modeling of the movement of a scale model and a full-scale wheeled vehicle.

Free Vibration of Axially Moving Functionally Graded Nanoplates Based on the Nonlocal Strain Gradient Theory

Using the nonlocal strain gradient theory, we explore vibration behaviours of initially bidirectional tensioned functionally graded nanoplates with axial speed. The governing equation of motion can be obtained based on the differential type of nonlocal strain gradient constitutive relation, which characters the dynamics of nanostructures containing kinematic relation. The simply supported boundary constraints on four sides are considered and subsequently the numerical results are determined. It shows that natural frequencies of axially moving nanoplates decrease when increasing the axial speed and the nonlocal parameter. Hence the nonlocal and kinematic factors cause the natural frequencies to decrease or, weaken the equivalent bending rigidity. On the other hand, natural frequencies increase with an increase in the axial tension and material characteristic scale. Hence the strain gradient and tensile stress factors cause the natural frequencies to increase or, strengthen the equivalent bending rigidity. In addition, the natural frequencies get higher with a larger aspect ratio of the functionally graded nanoplate. The larger one between the nonlocal parameter and the material characteristic scale plays a dominant role in the softening and stiffening mechanisms of the nonlocal strain gradient effect. In case of the same magnitude of the nonlocal parameter and the material characteristic scale, the softening and hardening phenomena disappear. The equivalent bending rigidity neither increases nor decreases in such a situation, and its value degenerates to the classical one.

Massive gravity from double copy

We consider the double copy of massive Yang-Mills theory in four dimensions, whose decoupling limit is a nonlinear sigma model. The latter may be regarded as the leading terms in the low energy effective theory of a heavy Higgs model, in which the Higgs has been integrated out. The obtained double copy effective field theory contains a massive spin-2, massive spin-1 and a massive spin-0 field, and we construct explicitly its interacting Lagrangian up to fourth order in fields. We find that up to this order, the spin-2 self interactions match those of the dRGT massive gravity theory, and that all the interactions are consistent with a Λ3 = (m2MPl)1/3 cutoff. We construct explicitly the Λ3 decoupling limit of this theory and show that it is equivalent to a bi-Galileon extension of the standard Λ3 massive gravity decoupling limit theory. Although it is known that the double copy of a nonlinear sigma model is a special Galileon, the decoupling limit of massive Yang-Mills theory is a more general Galileon theory. This demonstrates that the decoupling limit and double copy procedures do not commute and we clarify why this is the case in terms of the scaling of their kinematic factors.

Action observation improves sit-to-walk in patients with Parkinson's disease and freezing of gait. Biomechanical analysis of performance

IntroductionFreezing of gait (FoG) is one of the most disabling gait disorders in Parkinson's disease (PD), reflecting motor and cognitive impairments, mainly related to dopamine deficiency. Recent studies investigating kinematic and kinetic factors affecting gait in these patients showed a postural instability characterized by disturbed weight-shifting, inappropriate anticipatory postural adjustment, worse reactive postural control, and a difficulty executing complex motor tasks (i.e. sit-to-walk). These symptoms are difficult to alleviate and not very responsive to Levodopa. For this reason, additional therapeutic actions based on specific therapeutic protocols may help patients with their daily lives. We conducted a randomized control trial aimed to test if two clinical protocols for PD patients with FoG were effective to improve postural control. MethodsRehabilitation protocols, conceived to improve gait, were based on learning motor exercises with the Action Observation plus Sonification (AOS) technique, or by the use of external sensory cues. We collected biomechanical data (Center of Mass COM, Center of Pressure COP, and moving timings), using the sit-to-walk task as a measure of motor and gait performance. ResultsKinetic and kinematic data showed that when treatment effects consolidate, patients treated with AOS protocol are more efficient in merging subsequent motor tasks (sit-to-stand and gait initiation), and diminished the total moving time and the area of the COP positions. ConclusionWe demonstrated for the first time that PD patients with FoG treated with an AOS protocol aimed at relearning appropriate gait patterns increased balance control and re-acquired more efficient postural control.

Effects of restriction of forefoot rocker functions by immobilisation of metatarsophalangeal joints on kinematics and kinetics during walking

ObjectiveThis study was conducted to investigate the effects of restriction of forefoot rocker (FFR) functions by immobilisation of unilateral metatarsophalangeal joints (MPJs) on kinematic and kinetic factors during walking. MethodsEighteen healthy young adults participated in this study. To immobilise the MPJs of the right leg, an aluminium sole plate (AS) was fixed on the sole of the foot. Kinematic and kinetic data were collected while each subject walked at a comfortable speed with the AS and without. ResultsIn the AS condition, the walking speed and contralateral step length were significantly decreased, and an asymmetrical centre of mass (COM) movement was observed. The range of plantarflexion motion and positive work by the ankle joint were decreased markedly during the late stance of the AS limb. In contrast, maximum hip and knee flexion angles in the swing phase of the AS limb and positive work by the bilateral hip joints over the gait cycle were increased. ConclusionsThe results suggested that MPJ immobilisation may result in marked motion limitation of ankle plantarflexion and inhibition of push-off by the ankle joint despite no restrictions on the ankle joint. These changes may interfere with gait speed and a smooth and symmetrical COM shift during walking.

국궁 활쏘기 동작에서의 체중이동과 수행속도, 관절 근력의 관련성

The changes of kinematic factors during archery shooting motion are still unknown in Korean traditional archery. This study investigated to evaluate of kinematic factors and each joint muscle strength during archery shooting motion in Korean traditional archers. Ten men Korean traditional archers were divided into two groups according to the shooting stance; parallel stance group (PSG, n=5) and oblique stance group (OSG, n=5). The 3-phase time of PSG was significantly longer than that of OSG during shooting motion (p.01). On the other hand, there was no difference between the two groups in body weight movement measured by ground reaction force (NS). In the comparison of joint muscle strengths, dominant arm (draw arm) had significantly higher means in total upper limb muscle (TULS) with shoulder flexion+extension (SFES), shoulder external+internal rotation (SERIRS), total shoulder (TSS), wrist flexion+extension strength (WFES) than non-dominant arm(bow arm), respectively (p.05, p.001). As for the correlation between each variable, significant negative correlation was found between highest score and dominant body weight movement in the 3-phase time (p.01). However, significant correlation was found among bowstring tension and average hand grip strength, non-dominant hand grip (NDhand grip), wrist extension (NWES), and shoulder external rotation strength (NSERS), respectively (p.01). These results suggest that the muscular strength of joints in the dominant arms is an important factor for Korean traditional archery, and the parallel stance is might more advantageous to shoot than oblique stance.

Scaling of ctenes and consequences for swimming performance in the ctenophore Pleurobrachia bachei

AbstractCtenophores coordinate large macrociliary structures called ctenes to propel themselves through the water. The morphology and kinematics of the ctenes mediate swimming performance. We investigated morphological and kinematic factors affecting swimming performance in free‐swimming ctenophores (Pleurobrachia bachei) using high speed videography. Our morphological results showed that the relationship between body size and ctene morphology and arrangement in P. bachei were well described using linear (i.e., isometric) relationships, which suggests functional limitations of ctenes that vary among individuals of different sizes. Our kinematic results showed that isometric constraints on swimming performance can potentially be overcome by alterations in kinematics: (a) swimming speed in P. bachei increased with ctene beat frequency over a range of body lengths, and (b) the separation of ctenes into clumps of cilia allowed the ctene to increase in width during the effective stroke and decrease in width during recovery. Separation increases the surface area of the ctene during the effective stroke, likely increasing the thrust produced. The finding that ctenes are not monoliths and instead are separated into clumps of cilia has not been previously described, and we subsequently observed this trait in three other ctenophore species: Euplokamis dunlapae, Bolinopsis infundibulum, and Beroe mitrata. Flexibility in function may be a necessary corollary to isometric development of the ctenes as propulsive structures.

Multifaceted Stereoselectivity in Polyatomic Reactions.

Stereoselectivity or stereorequirement refers to the enhancement of chemical reactivity resulting from the preferential alignment/orientation of the colliding reactants. This concept is deeply embodied in the pre-exponential A-factor of the Arrhenius rate expression or the entropy effect of thermal kinetics in physical chemistry textbooks. To understand its dynamical consequence and seek for its mechanistic origin, two different approaches of either selecting the rotational states of the reactant or aligning/orienting the reactant in the laboratory have traditionally been taken. Due to the experimental challenges, theory is far more advanced than experiment. However, even for the simple atom + diatom reaction, the physical interpretations of the calculated results can sometimes be ambiguous or controversial because of the entangled potential and kinematic factors. In this Feature Article, we try to experimentally tackle the problem for reactions with polyatomic reactants by adopting both approaches in parallel for the same reaction. By comparing the results from the two approaches as well as contrasting them with the analogous reactants-here, a symmetric-top CHD3 versus a spherical-top CH4, deeper physical insights are gained, which paves the road for future studies of complex systems and for establishing a more complete conceptual framework.

Recognition of Foot-Ankle Movement Patterns in Long-Distance Runners With Different Experience Levels Using Support Vector Machines.

Running practice could generate musculoskeletal adaptations that modify the body mechanics and generate different biomechanical patterns for individuals with distinct levels of experience. Therefore, the aim of this study was to investigate whether foot-ankle kinetic and kinematic patterns can be used to discriminate different levels of experience in running practice of recreational runners using a machine learning approach. Seventy-eight long-distance runners (40.7 ± 7.0 years) were classified into less experienced (n = 24), moderately experienced (n = 23), or experienced (n = 31) runners using a fuzzy classification system, based on training frequency, volume, competitions and practice time. Three-dimensional kinematics of the foot-ankle and ground reaction forces (GRF) were acquired while the subjects ran on an instrumented treadmill at a self-selected speed (9.5–10.5 km/h). The foot-ankle kinematic and kinetic time series underwent a principal component analysis for data reduction, and combined with the discrete GRF variables to serve as inputs in a support vector machine (SVM), to determine if the groups could be distinguished between them in a one-vs.-all approach. The SVM models successfully classified all experience groups with significant crossvalidated accuracy rates and strong to very strong Matthew’s correlation coefficients, based on features from the input data. Overall, foot mechanics was different according to running experience level. The main distinguishing kinematic factors for the less experienced group were a greater dorsiflexion of the first metatarsophalangeal joint and a larger plantarflexion angles between the calcaneus and metatarsals, whereas the experienced runners displayed the opposite pattern for the same joints. As for the moderately experienced runners, although they were successfully classified, they did not present a visually identifiable running pattern, and seem to be an intermediate group between the less and more experienced runners. The results of this study have the potential to assist the development of training programs targeting improvement in performance and rehabilitation protocols for preventing injuries.

Kinematic and kinetic factors associated with leg reach asymmetry during the Star Excursion Balance Test in division I athletes

ObjectivesTo explore which balance and movement factors contribute most to reach distance asymmetry during the Star Excursion Balance Test (SEBT) in Division I athletes. DesignCross-Sectional Study. SettingRehabilitation Biomechanics Laboratory, NCAA Division I Athletics Program. Participants36 Division I athletes (20 Male; 16 Female). Main outcome measuresCenter of Pressure, Kinematic and Kinetic variables were measured during performance of anterior, Posterior-Medial (PM), and Posterior-Lateral (PL) directions of the SEBT in order to determine which factors predict reach distance asymmetry. ResultsCOP variables approached significance in predicting asymmetry for the anterior direction (p <0.08), kinematic variables approached significance in predicting asymmetry in the PL direction (p < 0.06), and kinetic variables were significant in predicting asymmetry in the PM direction (p < 0.03). ConclusionsFindings suggest that different strategies could be used to improve leg reach asymmetry based on specific direction of the asymmetry. Improving ability to control COP area seems to be important for the anterior direction, while control of limb movement seems to be most important for leg reach asymmetry in the PM and PL directions.

Influence of soil non-homogeneity on the base shear force of piled structures subjected to harmonic seismic waves

This paper aims at analyzing the effects of soil non-homogeneity on the dynamic behavior of piled structures. In order to fulfil this objective a procedure based on a substructuring model, which includes soil-structure interaction effects, is used to compute the dynamic response of slender and non-slender structures supported on several pile group configurations embedded in four different linear-elastic Gibson soil profiles. A numerical model based on the integral formulation of the elastodynamic problem and Green’s functions for the layered half space is used for the purpose of determining the foundation dynamic response in terms of impedances and kinematic interaction factors. The results obtained in terms of structural base shear force for each one of the variable-with-depth soil profiles are compared to those computed for an equivalent homogeneous soil. A significant influence of the soil profile on the structural harmonic response to seismic waves is observed in terms of maximum shear force at the base of the structure. The homogeneous assumption when modelling depth-varying soil profiles yields, in many cases, non-conservative results when predicting the structural dynamic behavior.

Varus alignment after total knee arthroplasty results in greater axial rotation during deep knee bend activity

BackgroundsThe correlation between in vivo knee kinematics and alignment has not been fully elucidated. Recently, similar or better clinical outcomes have been reported by restoration of mild varus alignment after total knee arthroplasty for preoperative varus knees. The aim of this study was to evaluate the effect of postoperative alignment on knee kinematics during a deep knee bend activity. MethodsIn vivo knee kinematics of 36 knees (25 patients) implanted with tri-condylar total knee arthroplasty were analyzed with a three dimensional model fitting approach using fluoroscopy. Under fluoroscopic surveillance, individual video frames were digitized at 30° increments from full extension to maximum flexion. Postoperative coronal and sagittal alignments were assessed using radiographs, and rotational alignment was assessed with computed tomography. Pearson correlation coefficients were calculated to determine the correlations between the alignment data and kinematic factors. FindingsCorrelation analysis showed that coronal alignment was significantly correlated with knee kinematics. The varus alignment of the limb and tibial component led to a greater axial rotation from full extension to maximum flexion and more rotated position in the mid to deep flexion range. Neither the rotational alignment of the femoral nor tibial components showed significant correlation with axial rotation from full extension to maximum flexion. InterpretationVarus alignment resulted in greater axial rotation, which could represent near-normal knee kinematics. The current study can be a kinematic rationale reporting similar or better clinical and functional outcomes for the total knee arthroplasty with residual varus alignment.

Patellofemoral Mechanics: a Review of Pathomechanics and Research Approaches.

The patellofemoral joint is a complicated articulation of the patella and femur that is prone to pathologies. The purpose of this review is to report on the current methods of investigating patellofemoral mechanics, factors that affect joint function, and future directions in patellofemoral joint research with emerging technologies and techniques. While previous hypotheses have suggested that the patella is only a moment arm extender, recent literature has suggested that the patella influences the control of knee moments and forces acting on the tibia as well as contributes to various aspects of patellar function with minimal neural input. With advancements in simulating a six-degrees-of-freedom patellofemoral joint, we have gained a better understanding of patella motion and have shown that geometry and muscle activations impact patella mechanics. Research into influences on patella mechanics from other joints such as the hip and foot has become more prevalent. In this review, we report current in vivo, in vitro, and in silico approaches to studying the patellofemoral joint. Kinematic and anatomical factors that affect patellofemoral joint function such as patella alta and tilt or bone morphology and ligaments are discussed. Moving forward, we suggest that advanced in vivo dynamic imaging methods coupled to musculoskeletal simulation will provide further understanding of patellofemoral pathomechanics and allow engineers and clinicians to design interventions to mitigate or prevent patellofemoral pathologies.

INFLUENCE OF LOWER EXTREMITY STATIC ALIGNMENT ON DYNAMIC KNEE VALGUS IN ADOLESCENTS FOLLOWING ACL RECONSTRUCTION

Background:Dynamic limb valgus, particularly high knee abduction moments, are a known risk factor for anterior cruciate ligament (ACL) injury. High knee abduction moments may result from poor static anatomic limb alignment, faulty biomechanics, or a combination of both. The distinction is important because anatomic limb alignment is difficult to change, while dynamic factors can be addressed through neuromuscular or biomechanical training.Hypothesis/Purpose:This study assessed the influence of static (lower extremity anatomic alignment) and dynamic (kinematic and kinetic) factors on external knee abduction moments during side-step cutting in uninjured adolescent athletes.Methods:This retrospective study included 43 adolescents with recent unilateral ACL reconstruction (mean age 15.3 years, SD 2.0, range 10-21; 17/43 female; 3-12 months post-surgery, mean 6.5, SD 2.1). Frontal plane hip to ankle imaging (EOS) was used to measure mechanical axis deviation (perpendicular distance from the center of the femoral condyles to the mechanical axis line connecting the center of the femoral head to the center of the talar dome) and tibial-femoral angle. Femoral anteversion was measured during physical examination. 3D motion capture provided lower extremity kinematics and kinetics during quiet standing and during the loading phase (initial contact to peak knee flexion) of an anticipated 45° side-step cut, with 2-3 trials per limb averaged for analysis. Relationships among imaging, static motion capture, and dynamic motion capture measures were investigated using correlation, and backward stepwise linear regression was used to evaluate potential predictors of average dynamic knee abduction moment.Results:Dynamic knee abduction moment was best predicted by a combination of dynamic measures: knee and hip abduction, external knee rotation, lateral trunk lean towards the planting foot, and ankle inversion during cutting (Table 1.1). Although EOS frontal plane tibial-femoral angle was correlated with dynamic knee abduction moment (r=0.24, p=0.02), no static/anatomic variables entered the model once the dynamic measures were included.Conclusion:Knee abduction moments during side-step cutting were related to dynamic factors reflecting frontal plane trunk, hip, knee, and ankle motion, as well as external knee rotation. Static (anatomic) lower limb alignment did not influence knee abduction moments once these dynamic factors were considered. Knee abduction moments and ACL injury risk are therefore not dictated by anatomic alignment and can be altered through neuromuscular/biomechanical training.Table 1.1.Multivariable prediction of average knee abduction moment during cutting (R2=0.69) βPDynamic ankle eversion-0.35<0.001Dynamic knee external rotation0.69<0.001Dynamic hip abduction0.180.004Dynamic trunk contralateral lean0.170.007Dynamic knee abduction0.39<0.001

Orbital analysis of passive dynamic bipeds; the effect of model parameters and stabilizing arm

In this paper the effect of different parameters on the periodic orbits of an under-actuated passive biped is studied. The system is designed to follow a periodic orbit in the phase plane, starting from an initial condition and walking down a slope. The dynamic motion of the system is cast as an optimization problem under constraints that impose the periodicity with optimal behavior. The effect of dynamics and kinematics factors such as inertia and length characteristics of the biped and slope angle on the stability and bifurcation phenomena is extensively studied. In the following, it is shown how an under-actuated arm can perfectly synchronize its stabilizing motion with walking. The effect of dynamics parameters of the arm on the locomotion of the biped, stability criteria and the robustness of the whole system is extensively investigated. The results of the paper clearly illustrate the effects of dynamics parameters as well as the stabilizing arm on the stability, energy, and step characteristics of locomotion.