External Joint Research Articles

Joint forces in dynamics of the 3-RRR planar parallel robot

Recursive matrix relations for the complete dynamics of a 3-RRR planar parallel robot are established in this paper. Three identical planar legs connecting to the moving platform are located in the same vertical plane. Knowing the motion of the platform, we develop first the inverse kinematics problem and determine the positions, velocities and accelerations of the robot. Further, the inverse dynamic problem is solved using an approach based on the principle of virtual work. Finally, compact matrix equations and graphs of simulation for the input torques of three actuators, the external and internal joint forces are obtained.

Are external knee load and EMG measures accurate indicators of internal knee contact forces during gait?

Mechanical loading is believed to be a critical factor in the development and treatment of knee osteoarthritis. However, the contact forces to which the knee articular surfaces are subjected during daily activities cannot be measured clinically. Thus, the ability to predict internal knee contact forces accurately using external measures (i.e., external knee loads and muscle electromyographic [EMG] signals) would be clinically valuable. We quantified how well external knee load and EMG measures predict internal knee contact forces during gait. A single subject with a force-measuring tibial prosthesis and post-operative valgus alignment performed four gait patterns (normal, medial thrust, walking pole, and trunk sway) to induce a wide range of external and internal knee joint loads. Linear regression analyses were performed to assess how much of the variability in internal contact forces was accounted for by variability in the external measures. Though the different gait patterns successfully induced significant changes in the external and internal quantities, changes in external measures were generally weak indicators of changes in total, medial, and lateral contact force. Our results suggest that when total contact force may be changing, caution should be exercised when inferring changes in knee contact forces based on observed changes in external knee load and EMG measures. Advances in musculoskeletal modeling methods may be needed for accurate estimation of in vivo knee contact forces.

Acute effects of static and dynamic stretching on hamstring eccentric isokinetic strength and unilateral hamstring to quadriceps strength ratios

The main purposes of this study were to investigate the acute effects of static and dynamic lower limb stretching routines: (a) on peak torque, total external work and joint angle at peak torque of the hamstrings during maximal eccentric isokinetic leg flexion; (b) on unilateral hamstring to quadriceps (H/Q) strength ratios; as well as (c) to determine whether static and dynamic routines elicit similar responses. A total of 49 active adults completed the following intervention protocols in a randomised order on separate days: (a) non-stretching (control condition), (b) static stretching, and (c) dynamic stretching. After the stretching or control intervention, eccentric isokinetic peak torque, the angle of peak torque and total external work were assessed with participants prone at 1.04 and 3.14 rad · s−1. Unilateral strength ratios of the knee were also recorded. Measures were compared via a fully-within-groups factorial analysis of variance (ANOVA). There were no main effects for eccentric isokinetic peak torque, angle of peak torque, total external work and unilateral H/Q strength ratios. The results suggest that dynamic and static stretching has no influence on eccentric strength profile and unilateral H/Q strength ratios and hence both forms of stretching do not reduce these two primary risk factors for muscle injury.

Axial displacements in external and internal implant‐abutment connection

The purpose of this study was to evaluate the axial displacement of the abutments during clinical procedures by the tightening torque and cyclic loading. Two different implant-abutment connection systems were used (external butt joint connection [EXT]; internal tapered conical connection [INT]). The master casts with two implant replicas, angulated 10° from each other, were fabricated for each implant connection system. Four types of impression copings were assembled and tightened with the corresponding implants (hex transfer impression coping, non-hex transfer impression coping, hex pick-up impression coping, non-hex pick-up impression coping). Resin splinted abutments and final prosthesis were assembled. The axial displacement was measured from the length of each assembly, which was evaluated repeatedly, after 30 Ncm torque tightening. After 250 N cyclic loading of final prosthesis for 1,000,000 cycles, additional axial displacement was recorded. The mean axial displacement was statistically analyzed (repeated measured ANOVA). There was more axial displacement in the INT group than that of the EXT group in impression copings, resin splinted abutments, and final prosthesis. Less axial displacement was found at 1-piece non-hex transfer type impression coping than other type of impression copings in the INT group. There was more axial displacement at the final prosthesis than resin splinted abutments in the INT and the EXT groups. After 250 N cyclic loading of final prosthesis, the INT group showed more axial displacement than that of the EXT group. Internal tapered conical connection demonstrated a varying amount of axial displacement with tightening torque and cyclic loading.

Influences of implant neck design and implant–abutment joint type on peri-implant bone stress and abutment micromovement: Three-dimensional finite element analysis

ObjectivesOcclusal overloading is one of the causes of peri-implant bone resorption, and many studies on stress distribution in the peri-implant bone by three-dimensional finite element analysis (3D FEA) have been performed. However, the FEA models previously reported were simplified and far from representing what occurs in clinical situations. In this study, 3D FEA was conducted with simulation of the complex structure of dental implants, and the influences of neck design and connections with an abutment on peri-implant bone stress and abutment micromovement were investigated. MethodsThree types of two-piece implant CAD models were designed: external joint with a conical tapered neck (EJ), internal joint with a straight neck (IJ), and conical joint with a reverse conical neck (CJ). 3D FEA was performed with the setting of a “contact” condition at the component interface, and stress distribution in the peri-implant bone and abutment micromovement were analyzed. ResultsThe shear stress was concentrated on the mesiodistal side of the cortical bone for EJ. EJ had the largest amount of abutment micromovement. While the von Mises and shear stresses around the implant neck were concentrated on the labial bone for IJ, they were distributed on the mesiodistal side of the cortical bone for CJ. CJ had the least amount of abutment micromovement. SignificanceImplants with a conical joint with an abutment and reverse conical neck design may effectively control occlusal overloading on the labial bone and abutment micromovement.

Body mass index affects knee joint mechanics during gait differently with and without moderate knee osteoarthritis

Obesity is a highly cited risk factor for knee osteoarthritis (OA), but its role in knee OA pathogenesis and progression is not as clear. Excess weight may contribute to an increased mechanical burden and altered dynamic movement and loading patterns at the knee. The objective of this study was to examine the interacting role of moderate knee OA disease presence and obesity on knee joint mechanics during gait. Gait analysis was performed on 104 asymptomatic and 140 individuals with moderate knee OA. Each subject group was divided into three body mass categories based on body mass index (BMI): healthy weight (BMI<25), overweight (25≤BMI≤30), and obese (BMI>30). Three-dimensional knee joint angles and net external knee joint moments were calculated and waveform principal component analysis (PCA) was applied to extract major patterns of variability from each. PC scores for major patterns were compared between groups using a two-factor ANOVA. Significant BMI main effects were found in the pattern of the knee adduction moment, the knee flexion moment, and the knee rotation moment during gait. Two interaction effects between moderate OA disease presence and BMI were also found that described different changes in the knee flexion moment and the knee flexion angle with increased BMI with and without knee OA. Our results suggest that increased BMI is associated with different changes in biomechanical patterns of the knee joint during gait depending on the presence of moderate knee OA.

Functional electrical stimulation elliptical stepping versus cycling in spinal cord-injured individuals

BackgroundThe cardiorespiratory responses and mechanical efficiencies of two modalities of functional electrical stimulation augmented leg exercises – isokinetic cycling and isokinetic elliptical stepping – were compared amongst individuals with spinal cord injury. MethodsFive subjects performed seated isokinetic evoked cycling and elliptical stepping leg exercise at 10, 20 and 30rev·min−1 pedal cadences. 3-D motion analysis and force transducers attached onto the foot pedals quantified the external forces and power outputs developed by each lower extremity. Hip, knee and ankle joints power were derived via inverse dynamics analysis. The subjects' cardiorespiratory responses during exercise were measured by respiratory gas analysis. FindingsEnsemble-averaged oxygen uptakes across pedal cadences were higher during stepping (448 (75) ml·min−1) compared to cycling (422 (54) ml·min−1). External power outputs and metabolic efficiencies during stepping (9.9 (8.3) W, 2.9 (3.2) %) were double those observed during cycling (5.3 (6.3) W, 1.6 (1.9) %). Cumulative internal and external leg joint powers during stepping were twice higher than cycling, but the stepping mechanical efficiencies derived from inverse dynamics analysis were comparable to cycling (76.3 (21.2) % and 63.6 (12.3) % respectively). Heart rate responses were similar between cycling and stepping, while carbon dioxide production and expired ventilation were slightly higher during elliptical stepping. InterpretationBoth exercise modalities could deliver appropriate training stimuli for improving the aerobic fitness and leg pedalling strength of spinal cord-injured individuals. However electrical stimulation-enhanced elliptical stepping might provide greater exercise dose-potency for leg muscle strengthening than electrically-enhanced cycling due to the higher power outputs observed.

Commentary on Child-Adult Differences in Muscle Activation–A Review

Comparing muscle strength and function between subjects differing in size, age, sex and possible motivation is a complex task. Many possible factors may contribute to the observed differences, including muscle size, histology, specific tension, agonist and antagonist muscle activation, internal and external joint leverage and tendon mechanical properties, some of which are difficult to measure directly or estimate from experimental measurements and require several simplifications and assumptions. Assessing these variables in children is even more complex as it is a time consuming process with ethical restrictions. Most previous studies on the differences in strength between adults and children have concentrated only on differences in muscle size (e.g., 6,8,14–16) or have considered only a small selection of the other contributing factors mentioned above (e.g., 3,4,13,17,19,24). These studies have typically come to the conclusion that specific tension, an index of muscle quality, must increase together with the obvious increases in muscle bulk, or quantity, with maturation. However, two studies that quantified specific tension in adults and children reported contrasting findings; O’Brien et al. (23) found no difference between adults and children of either sex, while Morse et al. (20) found specific tension to be greater in boys than men. To understand the cause(s) of the observed differences in muscular performance between children and adults we require detailed studies that measure all possible contributing factors precisely, not estimations of a few at a time, as was recently proposed (5). Robust hypotheses explaining some of the observed phenomena can be valuable in the absence of evidence, providing a basis for the design of rigorous experiments. Dotan et al. (7) have presented a hypothesis, that children recruit fast type II motor units to a lesser extent than adults. This hypothesis is founded on widely reported evidence that children recruit a lower proportion of their muscle during voluntary

THE MOORE'S CLOSURE FOR ANALYZING RELATIONSHIPS BETWEEN AGENTS IN INDUSTRIAL CLUSTERS

Industrial clusters try to exploit the effect of external economies and joint actions that come from the collaboration between their agents. But in order that these effects arise it is needed close cooperation partnerships between the agents in the industrial cluster, which could improve competitiveness. It's obvious, therefore, that analyzing which are the relationships between the agents in the industrial cluster is critical to make strategic decisions that promote and improve the competitiveness of the industrial cluster. This paper proposes a methodology based on obtaining a fuzzy relation from which, applying Moore's closure in an uncertain situation, we can identify subrelations that group industrial cluster agents depending on their degree of affinity based on the intensity of their relationships.Keywords: affinity, moore's closure, fuzzy relations, industrial clusterJEL Classification: C69, L14(ProQuest: ... denotes formulae omitted.)1. INTRODUCTION: INDUSTRIAL CLUSTER CONCEPTThe emergence of a flexible specialization production model has brought industrial dispersal or diffuse industrialization strategies, based on decentralized production models characterized by the concentration of companies in an industry in a environment geographically delimited, to acquire an increasing role, increasingly more intensely [3]. The different currents of thought that have analyzed this phenomenon have called it using different names (industrial districts, innovative environments, local production systems, etc.), but, nowadays, [20] proposal of industrial cluster has become the most used to refer to groups of companies in the same sector located in the same geographic area to share resources and capabilities and increase their competitiveness, both individually and globally.Industrial clusters allow companies to improve their competitiveness because they take advantage of agglomeration economies, obtaining benefit from their proximity, from the existence of certain infrastructure and equipment in the territory, from diversified customer markets and labour markets, from a better access to information and knowledge, and from a social, cultural and institutional environment focused on the development of the main industrial cluster activity. Within the industrial cluster appear productive relations of cooperation of a certain intensity and consistency, based on the complementarity of the different production processes carried out by various companies in the same sector. When we analyze industrial clusters in a dynamic perspective we can see how their performance is a result of the integration of multiple different actions where many actors are involved, both individually and collectively [1]. The fact that this integration requires physical proximity relations, involves the configuration of unique spatial units in production, social, cultural, technological, political and institutional terms [15]. In that sense, [20] introduces the concept of industrial cluster, as the natural union of the companies in a particular sector, and with other related industries in a given territory. These companies develop connections with a large number of support services to generate synergies, externalities, cooperation and dissemination of technology; characteristics that give the industry cluster competitive advantages.An industrial cluster is a group of companies and institutions geographically close, and related to a particular field, linked by common and complementary features. In other words, the specialization of human capital, the flow of information, the innovation processes and the diffusion of technology, and the relations between suppliers and customers, provide the ideal framework for the emergence of external economies to the firm but internal to the territories. Geographic proximity facilitates communication, technological externalities, leads to efficient delivery of intermediate inputs at lower costs, and allows a greater market share of inputs and outputs, as well as a reserve of qualified local labour. …

Effect of rollover footwear on metabolic cost of ambulation, lower limb kinematics, kinetics, and EMG related muscle activity during walking

BackgroundFootwear with a curved sole profile shifts the point of contact between the shoe and floor anteriorly compared to a flat shoe. There have been various reports of changes in ground reaction forces, external joint moments, and (rather inconclusively) muscle activity and energy consumption during walking in this “rollover” footwear [1-6]. The aim of this study was to investigate the effect of two types of rollover footwear (one a new prototype) on walking speed, metabolic cost of gait, lower limb kinematics, kinetics and EMG muscle activity.MethodsTwenty subjects walked in four footwear conditions: (1) a flat control shoe; (2) a flat control shoe weighted to match the mass of the new rollover shoe prototype; (3) the new prototype rollover shoe; (4) a MBT shoe. Data relating to metabolic energy and temporal aspects of gait were collected during a 6 minute walk test. Data on the lower limb kinematics, joint moments, muscle activity and foot pressure were collected during walking on a straight 10 metre course.ResultsThe curved sole moved the contact point under the shoe anteriorly during early stance. This altered ankle moments and reduced ankle plantarflexion after initial contact. In mid stance the roll over footwear reduced ankle dorsiflexion and overall the ankle moved less in roll over footwear. Ground reaction force loading rates were increased by the rollover footwear. There were notable elevations in early stance calf EMG activity. Effects on energy cost of ambulation were negligible. Rollover footwear reduced plantar pressures under the heel and forefoot, and redistributed pressure towards the midfoot. Shoe weight had no effect on any parameters.ConclusionRollover footwear is able to modify ankle kinematics and moments and the activity of some ankle musculature. Effects proximal to the leg were small. There were no effects on the temporal or energy aspects of gait.

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

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

A Pilot Study to Assess Use of Passive Extension Bias to Facilitate Finger Movement for Repetitive Task Practice After Stroke

Background and Purpose: The purpose of this study was to investigate whether active range of finger motion could be increased through the introduction of passive, external extension joint torques in stroke survivors. Participants: Five chronic stroke survivors with severe hand impairment resulting from hemiparesis took part in the study. Method: Participants completed 2 experimental sessions in which hand movement and function were assessed. In one session, they wore a custom orthotic glove (X-Glove) that passively supplied extension torques to the joints of the fingers. In the second session, they performed the same tasks as in the other session, but without the glove. Outcome measures consisted of active range of motion, distance of the fingertip from the hand, selected tasks from the Graded Wolf Motor Function Test (GWMFT), and the Box and Blocks (BB) test. Primary results with and without the glove were compared using paired t tests with a Bonferroni correction. Results: Active range of motion improved significantly by over 50%, from 4.4 cm to 6.7 cm, when the X-Glove was worn (P = .011). The distance of the fingertip from the metacarpophalangeal joint increased by an average of 2.2 cm for 4 of the subjects, although this change was not significant across all 5 subjects (P = .123). No significant differences were observed in the BB or GWMFT whether the X-Glove was worn or not. Discussion and Conclusion: Introduction of passive extension torque can improve active range of motion for the fingers, even in chronic stroke survivors with substantial hand impairment. The increased range of motion would facilitate therapeutic training of the hand, potentially even in the home environment, although the bulk of the orthosis should be minimized to facilitate interactions with real objects.

The effect of first ballet classes in the community on various postural parameters in young girls

Objective To examine the effect of first season ballet classes in the community on the thoracic kyphosis (TK), lumbar lordosis (LL), hip external rotation (ER) and joint flexibility in young girls. Design Longitudinal single blinded cohort control study. Setting Institutional. Participants 30 girls aged 6–9, recruited from the same primary school were divided equally into 2 groups: a group bi-weekly community ballet class and a sedentary control group. Intervention All girls were assessed prior to ballet classes (t 0), at the conclusion (t 1) (6 months), and approximately one year later (t fu). Main outcome measures Beighton score for joint hyper-flexibility, peak of TK and LL, range of hip ER, ratio TK/LL, and individual’s height, weight and BMI. Results LL at t1 became greater in the ballet girls’ group (23.7°± 6) as opposed to the controls (19.5°±3.9) due to a decrease in LL in the controls from t0 to t1 (mean difference = −16.5°) (cut-off score = 3.45°) ( p < 0.05). TK decreased from t0 to t1 in the ballet girls’ group (mean difference = −26.1°) and controls (mean difference = −31.3°) (cut-off score = 4.85°) ( p < 0.05). Left hip ER decreased only in the controls from t0 to t1 (mean difference = −13.8°) (cut-off score = 5.43°) ( p < 0.05). Beighton score at tfu was greater in the ballet girls’ group (6.1 ± 2.3) as opposed to the controls (4.4 ± 1.5) ( p < 0.05). Conclusions First season ballet classes for young girls in the community can be associated with relatively greater LL, and left hip ER and joint hyper-flexibility.

Calibration and control of a redundant robotic workcell for milling tasks

This article deals with the tuning of a complex robotic workcell of eight joints devoted to milling tasks. It consists of a KUKA™ manipulator mounted on a linear track and synchronised with a rotary table. Prior to any machining, the additional joints require an in situ calibration in an industrial environment. For this purpose, a novel planar calibration method is developed to estimate the external joint configuration parameters by means of a laser displacement sensor and avoiding direct contact with the pattern. Moreover, a redundancy resolution scheme on the joint rate level is integrated within a computer aided manufacturing system for the complete control of the workcell during the path tracking of a milling task. Finally, the whole system is tested in the prototyping of an orographic model.

Flexural behaviour of external R/C steel fibre reinforced beam-column joints

ABSTRACT A softened strut-and-tie macro model able to reproduce the flexural behaviour of external beam-column joint is presented. The model is specific for concrete with hooked steel fibres (FRC) and it is designed to calculate the flexural response, as load-deflection curve, of a beam-column sub-assemblages. The model considers the presence of a constant vertical load acting on the column and of a monotonically increasing lateral force applied at the tip of the beam.

Variation in the total lengths of abutment/implant assemblies generated with a function of applied tightening torque in external and internal implant-abutment connection

Settling (embedment relaxation), which is the main cause for screw loosening, is developed by microroughness between implant and abutment metal surface. The objective of this study was to evaluate and compare the relationship between the level of applied torque and the settling of abutments into implants in external and internal implant-abutment connection. Five different implant-abutment connections were used (Ext, External butt joint + two-piece abutment; Int-H2, Internal hexagon + two-piece abutment; Int-H1, Internal hexagon + one-piece abutment; Int-O2, Internal octagon + two-piece abutment; Int-O1, Internal octagon + one-piece abutment). All abutments of each group were assembled and tightened with corresponding implants by a digital torque gauge. The total lengths of implant-abutment samples were measured at each torque (5, 10, 30 N cm and repeated 30 N cm with 10-min interval) by an electronic digital micrometer. The settling values were calculated by changes between the total lengths of implant-abutment samples. All groups developed settling with repeated tightening. The Int-H2 group showed markedly higher settling for all instances of tightening torque and the Ext group was the lowest. Statistically significant differences were found in settling values between the groups and statistically significant increases were observed within each group at different tightening torques (P<0.05). After the second tightening of 30 N cm, repeated tightening showed almost constant settling values. Results from the present study suggested that to minimize the settling effect, abutment screws should be retightened at least twice at 30 N cm torque at a 10-min interval in all laboratory and clinical procedures.

A novel tool for objective assessment of femorotibial rotation: a cadaver study

Traumatic rupture of the anterior cruciate ligament (ACL) of the knee is one of the most frequent orthopaedic sports' injuries. However, the best operative reconstruction technique is still the focus of current discussions among experts. While single-bundle reconstruction primarily addresses anterior-posterior instability, the anatomical double-bundle reconstruction aims to stabilise anterior-posterior as well as rotational instability. So far no definite evidence to favour the one or the other technique exists due to the lack of an objective method for quantifying rotational knee stability. In this context several authors have recently reported on devices for the analysis of femorotibial rotation. However, most of these tools are still in the developmental stage. Therefore, the aim of this study was (1) to develop a new instrument for assessing rotational knee stability independent from the surrounding soft tissue with an adequate method of analysis and (2) to establish the possible field of application of this device in a human cadaver study. The so-called torsiometer evaluated was designed to assess internal and external knee joint rotation objectively in different flexion angles. Measurements were performed implying internal and external rotation at 90°, 30° and 0° knee flexion with and without intact ACL, respectively. Each measurement revealed valid and reproducible values. The restraint in ACL-absent knees was clearly lower and the course of rotation explicitly higher than in knee joints with intact ACL.

Feasibility of a gait retraining strategy for reducing knee joint loading: Increased trunk lean guided by real-time biofeedback

The purpose of this feasibility study was to examine changes in frontal plane knee and hip walking biomechanics following a gait retraining strategy focused on increasing lateral trunk lean and to quantify reports of difficulty and joint discomfort when performing such a gait modification. After undergoing a baseline analysis of normal walking, 9 young, healthy participants were trained to modify their gait to exhibit small (4°), medium (8°), and large (12°) amounts of lateral trunk lean. Training was guided by the use of real-time biofeedback of the actual trunk lean angle. Peak frontal plane external knee and hip joint moments were compared across conditions. Participants were asked to report the degree of difficulty and the presence of any joint discomfort for each amount of trunk lean modification. Small (4°), medium (8°), and large (12°) amounts of lateral trunk lean reduced the peak external knee adduction moment (KAM) by 7%, 21%, and 25%, respectively, though the peak KAM was only significantly less in the medium and large conditions (p<0.001). Increased trunk lean also significantly reduced the peak external hip adduction moments (p<0.001). All participants reported at least some difficulty performing the exaggerated trunk lean pattern and three participants reported ipsilateral knee, hip, and/or lower spine discomfort. Results from this study indicate that a gait pattern with increased lateral trunk lean can effectively reduce frontal plane joint moments. Though these findings have implications for pathological populations, learning this gait pattern was associated with some difficulty and joint discomfort.

Robust features of knee osteoarthritis in joint moments are independent of reference frame selection

Background Changes in lower-limb joint moments are important outcome measures for treatment and prevention of knee osteoarthritis. However, it is known that both the magnitude and amplitude of joint moments are affected by the choice of anatomical reference frame. The purpose of this study was to identify features of joint moment waveforms that, regardless of the choice of reference frame, are different for subjects with knee osteoarthritis as compared to asymptomatic control subjects. Methods External joint moments during the stance phase of gait were calculated for 44 subjects with moderate knee osteoarthritis and 44 asymptomatic subjects. Moments were then expressed using four anatomical reference frames: Joint Coordinate System, Plane of Progression, Proximal, and Distal. Principal component analysis was used to extract features of the moment waveforms that differed between control and osteoarthritis groups across all reference frames. Findings Principal component analysis revealed that, regardless of the choice of reference frame, subjects with knee osteoarthritis exhibited significantly decreased overall hip adduction moment magnitudes, increased overall knee adduction moment magnitudes, decreased knee internal rotation moment amplitudes, and increased early-stance ankle adduction magnitudes. Interpretation The four robust features identified in this study are sensitive to the effect of knee osteoarthritis, but independent of changes in the anatomical reference frame. These features can be solely attributed to the pathogenesis of the disease, and not to the artifact of reference frame selection.

The Effects of Resistance Training with and without Trunk Stabilization Exercises on Cutting Mechanics

While trunk stabilization exercises or "core" training are often prescribed to improve performance and prevent injury, no conclusive evidence exists to quantitatively show that these types of training improve lower extremity biomechanics in ways that might reduce risk of ACL rupture. PURPOSE: To investigate the effects of trunk stabilization training on dynamic loading of the lower extremity during unanticipated cutting maneuvers in athletes. METHODS: Fifteen healthy male college students (age = 20.9 ± 1.0 yrs, height = 1818 ± 55 mm, mass = 84.6 ± 6.3 kg) who played football in high school with no previous history of ACL tear were recruited for the study. Subjects were randomly assigned to a 6-week resistance training (RT) program or a 6-week trunk stabilization (TS) program. RT participants performed 4 sets of bilateral resistance training with free weights for the upper and lower extremities during 3 1-hr sessions per week. TS participants performed the same resistance exercises but replaced the first set with trunk stabilization exercises. A pre-test/post-test design was used. All subjects performed a 45° unanticipated cutting maneuver task at pre- and post-testing. An opto-electronic motion capture system and 2 force plates were utilized for data collection. The Point Cluster Technique was used for measuring femur and tibia kinematics and inverse dynamics were used to estimate net external joint moments, which were normalized to weight and height [%BW*ht]. Three dominant leg trials were analyzed for external knee abduction and tibial internal rotation moments. The models were adjusted for speed and cut angle. RESULTS: No significant interactions in knee abduction moment (p=0.49) or tibial internal rotation moment (p=0.23) were observed from pre- to post-test for the intervention group (TS). CONCLUSION: This study found that trunk stabilization training had no effect on knee abduction or tibial internal rotation moments. Due to the small sample size, further research may be warranted to confirm these findings. Future studies investigating other training approaches to improve dynamic trunk control during functional activity may also provide additional insight into the relationships between trunk control and lower extremity cutting mechanics. Funded by NFL Charities Foundation