Resultant Reaction Force Research Articles

Angular Impulse and Balance Regulation During the Golf Swing.

Our aim was to determine how skilled players regulate linear and angular impulse while maintaining balance during the golf swing. Eleven highly-skilled golf players performed swings with a 6-iron and driver. Components contributing to linear and angular impulse generated by the rear and target legs (resultant horizontal reaction force [RFh], RFh-angle, and moment arm) were quantified and compared across the group and within a player (α = .05). Net angular impulse generated by both the rear and target legs was greater for the driver than the 6-iron. Mechanisms used to regulate angular impulse generation between clubs varied across players and required coordination between the legs. Increases in net angular impulse with a driver involved increases in target leg RFh. Rear leg RFh-angle was maintained between clubs whereas target leg RFh became more aligned with the target line. Net linear impulse perpendicular to the target line remained near zero, preserving balance, while net linear impulse along the target line decreased in magnitude. These results indicate that the net angular impulse was regulated between clubs by coordinating force generation of the rear and target legs while sustaining balance throughout the task.

A non-invasive electric current sensor employing a modified shear-mode cymbal transducer

This paper presents a non-invasive sensor for electric current monitoring in electric power grid. The sensor consists of a modified shear-mode cymbal transducer and a Halbach array attached on the transducer. The Halbach array generates concentrated magnetic flux density on the side where the electric wire is placed and lowers the magnetic field on the other side. The wire experiences an enhanced Ampere force when energized, and the resulting reaction force of the Ampere force is further amplified by the cymbal transducer. The transducer works in shear mode and produces a voltage proportional to the applied electric current. At low frequencies, the sensor exhibits a flat voltage response. The non-resonant sensitivity of the sensor reaches ∼6.98mV/A over the frequency range of 10–80Hz with a separating distance of d=3.0mm. The average sensitivity is 6.97mV/A with high linearity at the power-frequency of 50Hz, and a small current step change of 0.05A can be clearly distinguished.

The effect of glenosphere diameter and eccentricity on deltoid power in reverse shoulder arthroplasty.

The eccentric glenosphere was principally introduced into reverse shoulder arthroplasty to reduce the incidence of scapular notching. There is only limited information about the influence of its design on deltoid power and joint reaction forces. The aim of our study was to investigate how the diameter and eccentricity of the glenosphere affect the biomechanics of the deltoid and the resultant joint reaction forces. Different sizes of glenosphere and eccentricity were serially tested in ten cadaveric shoulders using a custom shoulder movement simulator. Increasing the diameter of the glenosphere alone did not alter the deltoid moment arm. However, using an eccentric glenosphere increased the moment arm of the deltoid, lowered the joint reaction force and required less deltoid force to generate movement. Eccentricity is an independent variable which increases deltoid efficiency and lowers joint reaction forces in a reverse shoulder arthroplasty. Cite this article: Bone Joint J 2016;98-B:218-23.

Determination of joint reactions in a rigid multibody system, two different approaches

In this paper two different methods for determination of frictionless joint reaction forces and moments are presented. The considered multibody system has an open kinematic chain structure. The first method refers to the determination of resultant joint reaction forces and moments based on the Rodrigues approach suitable for computation in a symbolic form. The second method presented is the method based on the so-called vectors of the body mass moments and vector rotators coupled for a pole and oriented axes. Both approaches are presented and discussed on the three- like rigid multibody system.

Combined Explicit Finite and Discrete Element Methods for Rotor Bearing Dynamic Modeling

This article presents a new approach in which the explicit finite element method (EFEM) and the discrete element method (DEM) are coupled to investigate dynamics of flexible rotor systems supported by deep-groove ball bearings. In this investigation, DEM is used to develop the bearing (dynamic motion) model in which all of the components of the bearing (i.e., inner and outer race, balls, and cage) have 6 degrees of freedom. The flexible shaft is modeled with a full 3D elastic formulation using the EFEM rather than the reduced form, which implements component mode synthesis. The EFEM and DEM were combined to investigate the dynamics of flexible shaft rotor systems supported by ball bearings. Rotor and inner races of the bearings are fully coupled such that both translation and rotation of the flexible rotor are transmitted to the bearings. At each time step, the translational motion and rotation/tilt angle of the rotor cross section at the location of an inner race are applied to the inner race of the bearing. The resulting reaction forces and moments calculated in the dynamic bearing model are in turn applied to the nodes of the shaft. The combined model is used to investigate the motions of the inner races and the resulting reaction forces and moments from the supporting bearings due to an applied load on the shaft. In the current coupled modeling approach, the deformation of the shaft affects the internal components of the bearing by altering the orientation of the inner race, which results in ball spin and slip.

Human Occupants in Low-Speed Frontal Sled Tests: Effects of Pre-Impact Bracing on Chest Compression, Reaction Forces, and Subject Acceleration

Objectives: The purpose of this study was to investigate the effects of pre-impact bracing on the chest compression, reaction forces, and accelerations experienced by human occupants during low-speed frontal sled tests.Methods: A total of twenty low-speed frontal sled tests, ten low severity (∼2.5g, Δv = 5kph) and ten medium severity (∼5g, Δv = 10kph), were performed on five 50th-percentile male human volunteers. Each volunteer was exposed to two impulses at each severity, one relaxed and the other braced prior to the impulse. A 59-channel chestband, aligned at the nipple line, was used to quantify the chest contour and anterior-posterior sternum deflection. Three-axis accelerometer cubes were attached to the sternum, 7th cervical vertebra, and sacrum of each subject. In addition, three linear accelerometers and a three-axis angular rate sensor were mounted to a metal mouthpiece worn by each subject. Seatbelt tension load cells were attached to the retractor, shoulder, and lap portions of the standard three-point driver-side seatbelt. In addition, multi-axis load cells were mounted to each interface between the subject and the test buck to quantify reaction forces.Results: For relaxed tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, all belt forces, and three resultant reaction forces (right foot, seatpan, and seatback). For braced tests, the higher test severity resulted in significantly larger peak values for all resultant accelerations, and two resultant reaction forces (right foot and seatpan). Bracing did not have a significant effect on the occupant accelerations during the low severity tests, but did result in a significant decrease in peak resultant sacrum linear acceleration during the medium severity tests. Bracing was also found to significantly reduce peak shoulder and retractor belt forces for both test severities, and peak lap belt force for the medium test severity. In contrast, bracing resulted in a significant increase in the peak resultant reaction force for the right foot and steering column at both test severities. Chest compression due to belt loading was observed for all relaxed subjects at both test severities, and was found to increase significantly with increasing severity. Conversely, chest compression due to belt loading was essentially eliminated during the braced tests for all but one subject, who sustained minor chest compression due to belt loading during the medium severity braced test.Conclusions: Overall, the data from this study illustrate that muscle activation has a significant effect on the biomechanical response of human occupants in low-speed frontal impacts.

항공연료 질량을 고려한 대형항공기 충돌하중모델의 개발

In this paper, the aircraft impact force models of large commercial B747 aircraft were developed by using so called Missile-Target Interaction Method. The Lagrangian meshfree SPH concept was adopted to the fuel mass for impact force calculation. 240ton, 320ton, 420ton of aircraft mass were considered to meet with the previously proposed aircraft impact force model by OECE/NEA(2002) and Arros & Doumbalski(2007). The model of present studies are based on the model of OECE/NEA originally, and extended to the model of Arros & Doumbalski. To calculate and evaluate the aircraft impact force, the impact analyses were simulated by using commercial Hydrocde AUTODYN considering the fuel mass effect. The resultant reaction force of symmetric rigid wall is considered as the impact force of aircraft. The preparation of refined FE mesh and impact simulation were done by using AUTODYN. The aircraft and fuel debris and secondary trajectory effects were considered by the eroding effect on the FE shell element and the explicitly modeled fuel mass. To evaluate and verify the impact force of aircraft, the Riera approach were used for the reference impact time history graph. The rigid wall impact test shows that the finite element model of a B747 which considering the explicit fuel mass effect is good agreement with reference values and the applicability of fuel modelling approaches of this study.

Particular adaptations to potentially slippery surfaces: The effects of friction on consecutive postural adjustments (CPA)

This research deals with the postural adjustments that occur after the end of voluntary movement (“consecutive postural adjustments”: CPAs). The influence of a potentially slippery surface on CPA characteristics was considered, with the aim of exploring more deeply the postural component of the task-movement. Seven male adults were asked to perform a single step, as quickly as possible, to their own footprint marked on the ground. A force plate measured the resultant reaction forces along the antero-posterior axis (Rx) and the centre of pressure (COP) displacements along the antero-posterior and lateral axes (Xp and Yp). The velocity of the centre of gravity (COG) along the antero-posterior axis and the corresponding impulse (∫Rxdt) were calculated; the peak velocity (termed “progression velocity”: VxG) was measured. The required coefficient of friction (RCOF) along the progression axis (pμx) was determined. Two materials, differing by their COF, were laid at foot contact (FC), providing a rough foot contact (RoFC), and a smooth foot contact (SmFC) considered to be potentially slippery. Two step lengths were also performed: a short step (SS) and a long step (LS). Finally, the subjects completed four series of ten steps each. These were preceded by preliminary trials, to allow them to acquire the necessary adaptation to experimental conditions. The antero-posterior force time course presented a positive phase, that included APAs (“anticipatory postural adjustments”) and step execution (STEP), followed by a negative one, corresponding to CPAs. The backward impulse (CPI) was equal to the forward one (BPI), independently of friction and progression velocity. Moreover, VxG did not differ according to friction, but was faster when the step length was greater. Last CPA peak amplitudes (pCPA) were significantly greater and CPA durations (dCPA) shorter for RoFC and conversely for SmFC, contrary to APA. Finally, the results show a particular adaptation to the potentially slippery surface (SmFC). They suggest that adherence modulation at foot contact could be one of the rules for controlling COG displacement in single stepping. Consequently, the actual coefficient of friction value might be implemented in the motor programme at a higher level than the voluntary movement specific parameters.

Regulation of reaction forces during the golf swing

During the golf swing, the reaction forces applied at the feet control translation and rotation of the body–club system. In this study, we hypothesized that skilled players using a 6-iron would regulate shot distance by scaling the magnitude of the resultant horizontal reaction force applied to the each foot with minimal modifications in force direction. Skilled players (n = 12) hit golf balls using a 6-iron. Shot distance was varied by hitting the ball as they would normally and when reducing shot distance using the same club. During each swing, reaction forces were measured using dual force plates (1200 Hz) and three-dimensional kinematics were simultaneously captured (110 Hz). The results indicate that, on average, the peak resultant horizontal reaction forces of the target leg were significantly less than normal (5%, p < 0.05) when reducing shot distance. No significant differences in the orientation of the peak resultant horizontal reaction forces were observed. Resultant horizontal reaction force–angle relationships within leg and temporal relationships between target and rear legs during the swing were consistent within player across shot conditions. Regulation of force magnitude with minimal modification in force direction is expected to provide advantages from muscle activation, coordination, and performance points of view.

The Consecutive Postural Adjustments (CPAs) that follow foot placement in single stepping

This research deals with the postural adjustments that occur after the end of a voluntary movement (“Consecutive Postural Adjustments”: CPAs). With the aim of more fully characterizing the postural component of motor tasks, they are compared with those occurring before movement onset (“anticipatory postural adjustments”: APAs). Ten male adults were asked to perform a single step as quickly as possible to a target marked on the ground (STEP). A force plate measured the resultant reaction forces along the antero-posterior axis (Rx) and the Centre of Pressure (CoP) displacements along the antero-posterior and lateral axes (Xp and Yp). The velocity of the Centre of Gravity (COG) along the antero-posterior axis was calculated and the peak velocity (termed “progression velocity”: VxG) was measured. Antero-posterior linear impulses (∫Rxdt) were also calculated. Two step lengths were considered: a short and a long one (SS and LS conditions). Each session consisted of ten steps. The antero-posterior force time course presented two phases: a positive one that included the APA and the STEP periods, then a negative one corresponding to CPA. The corresponding backward impulse (CPIx) was equal to the forward one (BPIx), which identifies CPA as a counter-perturbation, that is, a process by which the central nervous system controls and stops a forward impulse. CPA durations and peak amplitudes (dCPA and pCPA) were significantly greater than the corresponding APA values (dAPA and pAPA). Moreover, when the step length was greater, that is, when the progression velocity was faster, pCPAs, like pAPAs, increased, suggesting that CPAs and APAs are parts of the same motor program. In addition, CPA duration and time to peak amplitude do not vary with progression velocity, which could be explained by the movement braking constraints. Finally, CPA can be viewed as a means of achieving a new “static” postural equilibrium as soon as possible after foot contact, and to prevent the risk of falling. The outcome provides additional knowledge on how a stable posture is achieved at the end of a task movement, and is discussed from a postural control perspective.

Failure characteristics of the isolated distal radius in response to dynamic impact loading

We examined the mechanical response of the distal radius pre-fracture and at fracture under dynamic impact loads. The distal third of eight human cadaveric radii were potted and placed in a custom designed pneumatic impact system. The distal intra-articular surface of the radius rested against a model scaphoid and lunate, simulating 45° of wrist extension. The scaphoid and lunate were attached to a load cell that in turn was attached to an impact plate. Impulsive impacts were applied at increasing energy levels, in 10 J increments, until fracture occurred. Three 45° stacked strain gauge rosettes were affixed along the length of the radius quantifying the bone strains. The mean (SD) fracture energy was 45.5 (16) J. The mean (SD) resultant impact reaction force (IRFr) at failure was 2,142 (1,229) N, resulting in high compressive strains at the distal (2,718 (1,698) µε) and proximal radius (3,664 (1,890) µε). We successfully reproduced consistent fracture patterns in response to dynamic loads. The fracture energy and forces reported here are lower and the strains are higher than those previously reported and can likely be attributed to the controlled, incremental, dynamic nature of the applied loads.

Review: Laser-Ablation Propulsion

LASER ablation propulsion (LAP) is a major new electric propulsion concept with a 35-year history. In LAP, an intense laser beam [pulsed or continuous wave (CW)] strikes a condensedmatter surface (solid or liquid) and produces a jet of vapor or plasma. Just as in a chemical rocket, thrust is produced by the resulting reaction force on the surface. Spacecraft and other objects can be propelled in this way. In some circumstances, there are advantages for this technique compared with other chemical and electric propulsion schemes. It is difficult to make a performance metric for LAP, because only a few of its applications are beyond the research phase and because it can be applied in widely different circumstances that would require entirely different metrics. These applications range from milliwatt-average-power satellite attitude-correction thrusters through kilowatt-average-power systems for reentering near-Earth space debris and megawatt-to-gigawatt systems for direct launch to lowEarth orbit (LEO). We assume an electric laser rather than a gas-dynamic or chemical laser driving the ablation, to emphasize the performance as an electric thruster. How is it possible for moderate laser electrical efficiency to givevery high electrical efficiency? Because laser energy can be used to drive an exothermic reaction in the target material controlled by the laser input, and electrical efficiency only measures the ratio of exhaust power to electrical power. This distinction may seem artificial, but electrical efficiency is a key parameter for space applications, in which electrical power is at a premium. The laser system involved in LAP may be remote from the propelled object (on another spacecraft or planet-based), for example, in laser-induced space-debris reentry or payload launch to low planetary orbit. In other applications (e.g., the laser–plasma microthruster that we will describe), a lightweight laser is part of the propulsion engine onboard the spacecraft.

Postural control in isometric ramp pushes: the role of Consecutive Postural Adjustments (CPAs)

Postural adjustments, which occur after the end of a voluntary movement (termed Consecutive Postural Adjustments: CPAs), were studied and compared to the corresponding Anticipatory Postural Adjustments (APAs). Seven right-handed male adults were asked to perform horizontal two-handed maximal ramp pushes as quickly as possible, while sitting. A dynamometric bar measured the reaction to push force ( F x ) and a custom-designed device measured the resultant reaction forces along the antero-posterior axis ( R x ). Two ischio-femoral contacts (100 BP: full ischio-femoral contact of the ischio-femoral length; and 30 BP: one-third contact) were considered. Each session consisted of ten pushes. The reaction forces, as well as push force, increased continuously, displaying similar time course profiles. However, R x continued to increase after the end of push rise, which ascertained CPAs. CPAs were showed to be consistent kinetic phenomena, using a biomechanical analysis, based on time courses of reaction forces and CoG kinematics. Their coherence was checked precisely, by comparing theoretical and experimental occurrences of remarkable points (extrema and zero crossings). CPA durations and peak amplitudes (dCPA and pCPA) were significantly greater than the corresponding APA values (dAPA and pAPA). Moreover, dAPAs and dCPAs increased ( p < 0.001), as did pCPAs ( p < 0.001) and pAPAs ( p < 0.05) when the peak push force was greater (30 BP), showing that the probability of finding a statistically significant difference is greater for APA duration than amplitude, unlike CPAs. Finally, the present results were discussed in relation to the hypothesis according to which the focal and the postural components are parts of the same motor program.

Contrôle de l’équilibre et port unilatéral d’une orthèse rigide de cheville. Partie I : effets sur des sujets sains évalués debout en unipédie

In order to assess the effects induced by wearing a rigid ankle orthosis, 14 healthy adults, without traumatic previous injuries at this level, were tested in a one-legged postural task. The subjects stood upright on a force platform and were required to remain still, eyes open. Ten trials lasting 32 s were recorded in a random order in two conditions: with a rigid orthosis model worn at the ankle level of the supporting leg (Thuasne, Ligastrap Immo ®) and with an elastic stocking. Balance strategies have been quantified by studying the centre of pressure (CP) trajectories, that is, the successive positions of the resultant reaction forces, and processed through a frequency analysis. The results indicate that slight decreases occur for the CP displacements intervening along the medio-lateral axis whereas statistically significant trends were found for those intervening along the anteroposterior one. This finding a priori suggests that wearing a rigid orthosis affects one-legged standing in healthy individuals but mainly along an axis not usually weakened by sprained ankles.

Are sound dogs mechanically symmetric at trot?

A two-year-old, sound Labrador Retriever was determined to be 'right hind limb dominant' by comparison of total hind limb moments of support using inverse dynamics. Net joint moments at the hip, tarsal and meta-tarsophalangeal joints were larger on the right side. Vertical joint reaction forces at the stifle were larger on the right, and horizontal stifle joint reaction forces were smaller on the right. The crus segment was more cranially inclined on the right side through most of stance, but the angle of the resultant stifle joint reaction force vector against the long axis of the crus segment was identical between the right and left sides. The cranially inclined crus segment orientation on one side, coupled with the larger vertical joint reaction force, may result in an internal asymmetry in stifle joint mechanics, although the effects of this on cruciate ligament stresses remain to be determined.

Test‐retest reliability of an instrumented speculum for measuring vaginal closure force

The study aimed to: a) determine reliability of an instrumented speculum designed for measuring intravaginal closure pressure, and b) compare findings with a comparable device reported in the literature. The goal of these new devices is to reduce subjectivity, improve precision, and acknowledge reliability issues in quantifying levator ani closure force acting on the vagina. The instrumented speculum consisted of two parallel aluminum bills, similar in size to a Peterson speculum. Strain gages located near the root of each bill measure the magnitude of force exerted in the distal vagina. A contraction of the "U-shaped" levator ani muscle closes the levator hiatus with resultant reaction force measured by the speculum in the mid-sagittal plane. We tested the device in twelve nulliparous women making repeated measures within and across 3 different visit days. All measures were made by the same investigator. Same day measures were repeatable within +/-3.8 N by the third visit, with lesser repeatability on the 1st and 2nd visit days. Across days, repeatability was improved by Visits 2 and 3 with a coefficient of repeatability between those days of +/-5.5 N. Better repeatability was obtained using averaged scores rather than 'best effort' ; but average scores can underestimate best effort. Reasonable within-visit repeatability was found. Across-visit repeatability is consistent with the known difficulty that women have in maximally isolating and activating their levator ani muscles. The results corroborate the repeatability results of Dumoulin et al. [2004] using a similar type of dynamometer.

Biomechanical and metabolic performance of a new orthotic knee joint principle for stance phase safety

Fig. 2. Changes in inclination angle associated with peak joint reaction forces during stance with increasing NSA. UM is the reference undeformed model. ing a decrease in the peak mediolateral component with increasing NSA. A distinct trend to increased peak vertical joint reaction forces with increased NSA was found. As a result, the inclination angle of the resultant reaction force in the frontal plane decreased substantially with decreasing NSA, introducing a more vertical alignment of the reaction force at peak loading (Fig. 2). Although, the sagittal plane angle showed variations in the individual model, no clear relation with the changes in NSA could be established. When halving the abductor muscle force generating capacity, all components of the reaction forces decreased. However, the previously described relations of the joint reaction forces with NSA were unchanged. 6. Discussion The interaction between hip geometry, muscle moment generating capacity and hip loading can be analyzed using inverse dynamics based on personalized musculoskeletal modeling. Our results show an important interaction between NSA and mediolateral reaction forces, causing a more vertical inclination angle in the frontal plane during gait. This therefore will result in a more vertical loading of the implant when peak reaction forces are applied during gait. Although we did not analyze the interaction between NSA, NL and PW, our findings do suggest that a minimal NSA angle needs to be preserved in order to limit the mediolateral force component and limit the resulting bending stress in the femoral shaft. The calculation of individual hip loading by use of musculoskeletal modeling and inverse analysis may contribute to understanding the effect of hip joint loading on bone remodeling and implant load shearing.

Offset acetabular cups: A solution to wear?

Change of tribological properties has been the main goal in the effort to augment the longevity of total hip arthroplasty, while the reduction of forces acting across the artificial joint space has received little attention. Spurred by recent reports of wear behaviour and good clinical results of the offset low friction arthroplasty cups, the authors, using the simplified free body technique, estimated the resultant hip joint reaction force and the angle of its application on 100 individual anteroposterior pelvic radiographs, by templating on the same hip a conventional concentric cup and an offset eccentric one. The results showed a highly significant reduction (p<0.0001) of the resultant hip joint reaction force in the offset group by 28.8% or 1.02 body weight and of the angle of the hip joint reaction force by 2.8 degrees. The authors believe that the reduction of the resultant hip joint reaction force in the offset cup group is the result of lowering and medialising the centre of rotation of the hip, a previously reported fact on non-clinically applicable conditions. They are also tempted to propose the generalized use of the offset type acetabular cup, since adverse events are not anticipated. (Hip International 2005; 15: 149-54).

Offset acetabular cups: A solution to wear?

Change of tribological properties has been the main goal in the effort to augment the longevity of total hip arthroplasty, while the reduction of forces acting across the artificial joint space has received little attention. Spurred by recent reports of wear behaviour and good clinical results of the offset low friction arthroplasty cups, the authors, using the simplified free body technique, estimated the resultant hip joint reaction force and the angle of its application on 100 individual anteroposterior pelvic radiographs, by templating on the same hip a conventional concentric cup and an offset eccentric one. The results showed a highly significant reduction (p<0.0001) of the resultant hip joint reaction force in the offset group by 28.8% or 1.02 body weight and of the angle of the hip joint reaction force by 2.8 degrees. The authors believe that the reduction of the resultant hip joint reaction force in the offset cup group is the result of lowering and medialising the centre of rotation of the hip, a previously reported fact on non-clinically applicable conditions. They are also tempted to propose the generalized use of the offset type acetabular cup, since adverse events are not anticipated. (Hip International 2005; 15: 149-54).

Inverse and forward dynamics: models of multi-body systems.

Connected multi-body systems exhibit notoriously complex behaviour when driven by external and internal forces and torques. The problem of reconstructing the internal forces and/or torques from the movements and known external forces is called the 'inverse dynamics problem', whereas calculating motion from known internal forces and/or torques and resulting reaction forces is called the 'forward dynamics problem'. When stepping forward to cross the street, people use muscle forces that generate angular accelerations of their body segments and, by virtue of reaction forces from the street, a forward acceleration of the centre of mass of their body. Inverse dynamics calculations applied to a set of motion data from such an event can teach us how temporal patterns of joint torques were responsible for the observed motion. In forward dynamics calculations we may attempt to create motion from such temporal patterns, which is extremely difficult, because of the complex mechanical linkage along the chains forming the multi-body system. To understand, predict and sometimes control multi-body systems, we may want to have mathematical expressions for them. The Newton-Euler, Lagrangian and Featherstone approaches have their advantages and disadvantages. The simulation of collisions and the inclusion of muscle forces or other internal forces are discussed. Also, the possibility to perform a mixed inverse and forward dynamics calculation are dealt with. The use and limitations of these approaches form the conclusion.