bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Simulation of an Airborne Movement: Applicability of the Body Segment Parameter Estimation Methods
Authors: Kwon Young-Hoo
Published: August 2016

The purpose of this study was twofold: (a) to investigate the effect of the method of body segment parameter (BSP) estimation on the accuracy of the experimental simulation of a complex airborne movement; and (b) to assess the applicability of selected BSP estimation methods in the experimental simulation. It was hypothesized that different BSP estimation methods would provide different simulation results. A sensitivity analysis was performed to identify the BSP items and segments responsible for the inter-method differences in the simulation accuracy. The applicability of the estimation methods was assessed based on the simulation results and the number of anthropometric parameters required. Ten BSP estimation methods classified into 3 groups (4 cadaver-based, 4 gamma mass scanning-based, and 2 geometric) were employed in a series of experimental simulations based on 9 double-somersault-with-full-twist H-bar dismounts performed by 3 male college gymnasts. The simulated body orientation angles were compared with the corresponding observed orientation angles in computing the simulation errors. The inclination and twist simulation errors revealed significant (p < .05) differences among the BSP estimation groups and methods. It was concluded that: (a) the method of BSP estimation significantly affected the simulation accuracy, and more individualized BSP estimation methods generally provided more accurate simulation results; (b) the mass items, and the lower leg and thorax/ abdomen were more responsible for the intermethod differences in the simulation accuracy than other BSP items and segments, respectively; (c) the ratio methods and the simple regression methods were preferable in simulation of the somersaulting motion due to the fewer anthropometric parameters required; (d) the geometric models and the cadaver-based stepwise regression method were superior to the other methods in the simulation of the complex airborne motion with twist.
Hindlimb Kinetics and Neural Control during Slope Walking in the Cat: Unexpected Findings
Authors: Gregor Robert J. , Smith Judith L. , Smith Dagan W. , Oliver Alanna , Prilutsky Boris I.
Published: August 2016

Different forms of locomotion have been studied in the cat in an effort to understand the neural mechanisms involved in movement control. Recent studies have focused on the roles of one- and two-joint muscles, the integration of central commands with sensory input, and the notion that the control system may be organized around the mechanical actions of muscles and the number of joints they span. To investigate the load-sharing between the two-joint medial gastrocnemius and one-joint soleus muscles, a single cat was trained to walk in an instrumented Plexiglas enclosed walkway at slopes ranging ±75%. Surgically implanted tendon force transducers monitored force output from each muscle. Equations in Newtonian mechanics were used to calculate joint kinetics. Results suggest that as slope angle decreased, the one-joint soleus became the primary contributor to the plantar-flexor moment calculated during stance. Unexpectedly, as slope angle increased, force in the one-joint soleus decreased while force in the two-joint medial gastrocnemius increased in the presence of the increased plantar-flexor moment calculated during stance. One explanation is that activation and force in the two-joint medial gastrocnemius should increase in the presence of a knee flexor and plantar-flexor moment. This was the case during upslope walking, as two-joint muscles increase their activation when they act as an agonist at both joints they cross. Additionally, a force-dependent inhibition of the soleus by the medial gastrocnemius has been described as part of a neural control system organized around the mechanical actions of muscles and the number of joints they span. Hence, a decrease in one-joint soleus force might be expected under certain conditions in upslope walking.
An Electromyographical Analysis of the Role of Dorsiflexors on the Gait Transition during Human Locomotion
Authors: Hreljac Alan , Arata Alan , Ferber Reed , Mercer John A. , Row Brandi S.
Published: August 2016

Previous research has demonstrated that the preferred transition speed during human locomotion is the speed at which critical levels of ankle angular velocity and acceleration (in the dorsiflexor direction) are reached, leading to the hypothesis that gait transition occurs to alleviate muscular stress on the dorsiflexors. Furthermore, it has been shown that the metabolic cost of running at the preferred transition speed is greater than that of walking at that speed. This increase in energetic cost at gait transition has been hypothesized to occur due to a greater demand being placed on the larger muscles of the lower extremity when gait changes from a walk to a run. This hypothesis was tested by monitoring electromyographic (EMG) activity of the tibialis anterior, medial gastrocnemius, vastus lateralis, biceps femoris, and gluteus maximus while participants (6 M, 3 F) walked at speeds of 70, 80, 90, and 100% of their preferred transition speed, and ran at their preferred transition speed. The EMG activity of the tibialis anterior increased as walking speed increased, then decreased when gait changed to a run at the preferred transition speed. Concurrently, the EMG activity of all other muscles that were monitored increased with increasing walking speed, and at a greater rate when gait changed to a run at the preferred transition speed. The results of this study supported the hypothesis presented.
Simulation of the Vertical Ground Reaction Force on Sport Surfaces during Landing
Authors: Peikenkamp Klaus , Fritz Martin , Nicol Klaus
Published: August 2016

The surface-athlete interaction is discussed as one possible factor in overuse injuries, as the ground reaction force does not depend only on the athlete’s movement during surface contact but also on the mechanical properties of the playing surface. Since it is extremely difficult to measure the ground reaction force on an area-elastic surface, two damped linear-spring models were combined to calculate both the vertical ground reaction force on area-elastic surfaces and their deformations during the athlete’s landing from a jump height of 0.45 m. The athlete model consists of 4 segments (feet, shanks, thighs, and rest of the body) and the surface model consists of 5 segments each connected (a) to the concrete and (b) to each other via an additional imaginary segment. While the connections to the concrete were kept constant, the surface mass and the connections between the segments were varied in order to consider different degrees of area-elasticity of the simulated surfaces. With this approach it was shown that both the passive and active maximum of the vertical ground reaction force depend only on the maximum deformation of the surface, whereas the force rates vary greatly for identical maximum deformations. It appears that these differences increase with increasing maximum deformation. Therefore, in constructing area-elastic sport surfaces, the maximum deformation allowed should be as large as would coincide with other functions the surface must fulfill. Subsequently, the surface mass interacting with the athlete during landing should be large and the damping properties between these mass-segments should be very small.
Cycle Rate, Length, and Speed of Progression in Human Locomotion
Authors: Hay James G.
Published: August 2016

There have been few attempts to synthesize the knowledge gleaned from the study of cyclic human locomotion and, specifically, to determine whether there are general laws that describe or govern all such forms of locomotion. The purpose of this paper was to test the hypothesis that, when a human participant performs multiple trials of a given form of cyclic locomotion at a wide range of speeds (S) and without constraint on cycle rate (CR) or cycle length (CL), the relationships of CR vs. S and CL vs. S have the same basic characteristics as do those for any other form of cyclic locomotion. Data were gathered from published and unpublished sources. For each participant and form of locomotion, CR-vs.-S and CL-vs.-S relationships were plotted on a common scattergram with S on the abscissa and both CR and CL on the ordinate. Analysis of data collected on 49 participants and 12 forms of locomotion showed that, for every combination of participant and form of locomotion considered (excluding combinations involving simulated locomotion), the relationships of CR vs. S and CL vs. S had the same basic characteristics. These relationships were quadratic in form with CR-vs.-S concave upward and CL-vs.-S concave downward. The factor that made the greater contribution to increases in S was a function of S, with CL the primary factor at low S and CR the primary factor at high S. In short, the results obtained provided unequivocal support for the hypothesis of the study. The basic CR-vs.-S and CL-vs.-S relationships observed for forms of actual locomotion were also observed for some, but not all, of the forms of simulated locomotion examined.
Optimal System Values for Producing a Large Velocity of the Distal Endpoint during Flail-Like Motion
Authors: LeBlanc Michele , Dapena Jesús
Published: August 2016

Equations that clarify the mechanical relationships between various parameter values and the velocity of the distal endpoint of a two-segment kinetic chain modeling the human arm were developed and analyzed. In particular, a single equation was presented that relates the distal endpoint velocity to the system’s angular momentum (as an indicator of muscular torque input), the ratio of the distal segment’s angular velocity to that of the proximal segment (the flail ratio), and the angle between the two segments (the configuration angle). These three system variables were analyzed to examine which values are best for creating a large value for the velocity of the distal endpoint. In addition, a sensitivity analysis was conducted to determine whether the relationships between the system values and the distal endpoint velocity were consistent for varying segment parameters. The relationships found were consistent for the various segment parameters. For any given values of the flail ratio and the configuration angle, the larger the value of the system angular momentum, the larger the value of the distal endpoint velocity. For any given values of the system angular momentum and the configuration angle, the larger the flail ratio, the larger the value of the distal endpoint velocity. For given values of the system angular momentum and the flail ratio, the optimal configuration angle that maximizes the distal endpoint velocity depends on the flail ratio value. While it may be impossible to generate simultaneously the combination of optimal parameter values determined, the knowledge of the relationships of these parameters with each other and with the distal endpoint velocity will aid in the search for an attainable optimal compromise.
Optimal Shoulder Abduction Angles during Baseball Pitching from Maximal Wrist Velocity and Minimal Kinetics Viewpoints
Authors: Matsuo Tomoyuki , Matsumoto Tsuyoshi , Mochizuki Yoshiyuki , Takada Yoshihiro , Saito Kenji
Published: August 2016

Baseball coaches train pitchers to keep their shoulder abduction at 90º during delivery, because this angle is believed to maximize ball speed and reduce the stress on the throwing arm. In fact, however, the shoulder abduction angle for some pitchers, including professional pitchers, deviates from 90º. There likely are reasons for such deviation. The purposes of this study, therefore, were to investigate the effects of shoulder abduction angle on ball velocity and on the injury-related joint kinetic variable, and to determine why the shoulder abduction angle varies among pitchers. Eleven professional pitchers were videotaped with two high-speed cameras. The resulting kinematic data were used to simulate several pitching motions by varying the shoulder abduction angle from the actual angle. Maximum wrist velocity was used as a reasonable approximation of ball velocity. Elbow varus torque was used as a kinetic variable. The square torque for the throwing arm and torque change for the throwing arm were used to investigate the cause of the variation. It was found that the shoulder abduction angle of 90º did not always maximize wrist velocity nor minimize elbow varus torque. The actual shoulder abduction angle for each pitcher was highly consistent with the angle that minimized both square torque and torque change. The results suggested that the proficient throwers in this study moved their pitching arm so as to minimize mechanical cost while at the same time optimizing performance.
A Modified Cryo-Jaw for in Vitro Biomechanical Testing of Tendons
Authors: Morelli Federico , Ferretti Andrea , Conteduca Fabio , Nanni Francesca , Monteleone Lucilla , Valente Marco
Published: August 2016

The purpose of this study was to develop a new device, which represents a modification of the Cryo-Jaw described by Riemersa and Schamhardt and modified by Hamner et al., for in vitro biomechanical testing of tendons which allows the lower clamp to move in every direction and thus simulate a pathological dislocation of the knee. Tendons are fixed to the device by freezing the clamped part with dry ice. After fixation of their free ends, the lower clamp was rotated 45°, translated 1 cm, and angled 40° to simulate a knee sprain. Various configurations of bundles were tested: parallel, twisted, and braided. Tests were performed on 10 paired bovine bifurcated digital extensor tendons and 6 paired human hamstring tendons. Grafts were then tested to failure subjected to impulsive load, using a servohydraulic machine. The highest ultimate load recorded for parallel bundles was 4662 ± 565.71 N for bovine bifurcated digital extensor tendons, and 3057 ± 475.44 N for human hamstring tendons. In any case, the tendons ruptured midway, well clear of the frozen part; in no case was slippage of the tendons observed. Thus the device proposed allows one to test what happens to the graft of an ACL reconstructed knee during physiological and pathological movements because it can be easily displaced in every direction.
Rearfoot Kinematics during Initial Takeoff of Elite High Jumpers: Estimation of Spatial Position and Orientation of Subtalar Axis
Authors: Van Gheluwe Bart , Roosen Philip , Desloovere Kaat
Published: August 2016

As the spatial position and orientation of the subtalar ankle axis documented in biomechanical literature has mainly been estimated in unloaded conditions, it was hypothesized that high loads on the subtalar joint during very dynamic movements may force the respective axis away from its normal anatomical location. Therefore, high jump takeoffs of two elite athletes were selected to estimate and analyze the kinematic behavior of the subtalar axis during initial takeoff. The subtalar motion of the calcaneus was reconstructed using 3-D high-speed cinematography and a three-segment ankle model expressing subtalar pronation as the movement of the calcaneus around the talus. Results revealed that the subtalar axis moved away from its initial orientation and position at first heel impact, respectively more horizontally and laterally. The pronational angular displacement and velocity were calculated for all jumps and reached maximal values close to 30°, respectively 2000°/s. They compared surprisingly well with values obtained from frontal plane projections as used in a conventional cinematographical approach. But values corresponding to a subtalar axis fitting conventional anatomical descriptions showed consistently larger discrepancies, up to 10° for pronational displacement and close to 600°/s for pronational velocity. Finally, a comparison with results obtained from helical or screw axes produced nearly identical findings, suggesting good validity of the analytical techniques applied in this study for the 3-D reconstruction of the subtalar axis.
Frequency-Domain Analysis Detects Previously Unidentified Changes in Ground Reaction Force with Visually Guided Foot Placement
Authors: Wearing Scott C. , Smeathers James E. , Urry Stephen R.
Published: August 2016

Studies investigating the effect of targeting on gait have focused on the analysis of ground reaction force (GRF) within the time domain. Analysis within the frequency domain may be a more sensitive method for evaluating variations in GRF. The aim of the present study was to investigate the effect of visual targeting on GRF analyzed within the frequency domain. A within-subject repeated-measures design was used to measure the mediolateral, vertical, and antero-posterior components of the GRF of 11 healthy volunteers while walking at their own pace over a paper-covered walkway. A 30 × 24-cm target area was superimposed over a hidden Kistler force plate mounted at the midpoint of the walkway. GRF were recorded with and without the target and were analyzed within the frequency domain. Although visually guided foot placement has previously been undetected by traditional time-domain measures, targeting was found to significantly increase the frequency content of both the mediolateral (t10 = -4.07, p < 0.05) and antero-posterior (t10 = -2.52, p < 0.05) components of GRF. Consequently, it appears that frequency analysis is a more sensitive analytic technique for evaluating GRF. These findings have methodological implications for research in which GRF is used to characterize and assess anomalies in gait patterns.
A Predicted Optimal Performance of the Yurchenko Layout Vault in Women’s Artistic Gymnastics
Authors: Koh Michael , Jennings Leslie , Elliott Bruce , Lloyd David
Published: August 2016

The Yurchenko layout vault is the base vault from which more advanced forms of the Yurchenko family of vaults have evolved. The purpose of the study was to predict an individual’s optimal Yurchenko layout vault by modifying selected critical mechanical variables. The gymnast’s current performance characteristics were determined using the Peak-Motus video analysis system. Body segment parameters were determined using the elliptical zone mathematical modeling technique of Jensen (1978). A 5-segment computer simulation model was personalized for the gymnast comprising the hands, upper limbs, upper trunk, lower trunk, and lower limbs. Symmetry was assumed, as the motion was planar in nature. An objective function was identified which translated the subjective points-evaluation scheme of the Federation of International Gymnastics (FIG) Code of Points to an analytic expression that was mathematically tractable. The objective function was composed of performance variables that, if maximized, would result in minimal points being deducted and bonus points being allocated. A combined optimal control and optimal parameter selection approach was applied to the model to determine an optimum technique. The predicted optimal vault displayed greater postflight amplitude and angular momentum when compared with the gymnast’s best trial performance. Increased angular velocity, and consequently greater angular momentum at impact and greater shoulder flexion angle at impact with the horse, were related with this optimum technique. The impact phase therefore serves to increase the angular momentum during horse contact. Since the optimized parameters at impact with the horse were within the accepted physical capacity limits observed for the individual, the predicted vault is viable.
Similarities and Differences in Finger Interaction across Typical and Atypical Subpopulations
Authors: Latash Mark L. , Gao Fan , Zatsiorsky Vladimir M.
Published: August 2016

The method of multidimensional scaling was applied to matrices of finger interaction (IFM) computed for individual participants for finger force production tasks. When IFMs for young controls, elderly, and persons with Down syndrome were pooled, only two dimensions described interpersonal differences; these were related to total force and to the total amount of enslaving. When IFMs for each group were analyzed separately, subpopulation-specific dimensions were found. Potentially, this analysis can be applied to discover meaningful dimensions that reflect differences in indices of finger interaction across and within subpopulations which differ in their apparent ability to use the hand. It may also be useful for tracking changes in finger interaction that occur in the process of specialized training or motor rehabilitation.
Contribution of Inertia on Venous Flow in the Lower Limb during Stationary Gait
Authors: Aubert Jean-Thomas , Ribreau Christian
Published: August 2016

Blood flows toward the heart through collapsible vessels, the veins. The equations of flow in collapsible tubes in motion show a strong dependence on body forces resulting from gravity and acceleration. This paper analyzes the contribution of body forces to venous blood flow during walking on level ground. It combines the biomechanics of gait and theory of collapsible tubes to point out that body forces due to gravity and limb acceleration cannot be overlooked when considering the determinants of venous blood flow during locomotion. The study involved the development of a kinematic model of the limb as a multi-pendulum arrangement in which the limb segments undergo angular displacements. Angular velocities and accelerations were determined and the body forces were calculated during various phases of the gait cycle. A vascular model of the leg's major venous system was also constructed, and the accelerations due to body and gravity forces were calculated in specific venous segments, using the data from the kinematic model. The results showed there were large, fast variations in the axial component (Gx–Mx) of the body forces in veins between the hip and the ankle. Acceleration peaks down to –2G were obtained at normal locomotion. At fast locomotion, a distal vein in the shank displayed values of (Gx–Mx)/G equal to –3.2. Given the down-to-up orientation of the x-axis, the axial component Mx was usually positive in the axial veins, and Mx could shift from positive to negative during the gait cycle in the popliteal vein and the dorsal venous arch.
Effect of Arm Cranking Direction on EMG, Kinematic, and Oxygen Consumption Responses
Authors: Bressel Eadric , Heise Gary D.
Published: August 2016

The purpose of this study was to compare muscle activity, kinematic, and oxygen consumption characteristics between forward and reverse arm cranking. Twenty able-bodied men performed 5-min exercise bouts of forward and reverse arm cranking while electromyographic (EMG), kinematic, and oxygen consumption data were collected. EMG activity of biceps brachii, triceps brachii, deltoid, and infraspinatus muscles were recorded and analyzed to reflect on-time durations and amplitudes for each half-cycle (first 180° and second 180° of crank cycle). Kinematic data were quantified from digitization of video images, and oxygen consumption was calculated from expired gases. Dependent measures were analyzed with a MANOVA and follow-up univariate procedures; alpha was set at .01. The biceps brachii, deltoid, and infraspinatus muscles displayed greater on-time durations and amplitudes for select half-cycles of reverse arm cranking compared to forward arm cranking (p< 0.01). Peak wrist flexion was 9% less in reverse arm cranking (p< 0.01), and oxygen consumption values did not differ between conditions (p= 0.25). Although there were no differences in oxygen consumption and only minor differences kinematically, reverse arm cranking requires greater muscle activity from the biceps brachii, deltoid, and infraspinatus muscles. These results may allow clinicians to more effectively choose an arm cranking direction that either minimizes or maximizes upper extremity muscle activity depending on the treatment objectives.
Experimental and Computational Modeling of Joint and Ligament Mechanics
Authors: Debski Richard E. , Darcy Shon P. , Woo Savio L-Y.
Published: August 2016

Quantitative data on the mechanics of diarthrodial joints and the function of ligaments are needed to better understand injury mechanisms, improve surgical procedures, and develop improved rehabilitation protocols. Therefore, experimental and computational approaches have been developed to determine joint kinematics and the in-situ forces in ligaments and their replacement grafts using human cadaveric knee and shoulder joints. A robotic/universal force-moment sensor testing system is used in our research center for the evaluation of a wide variety of external loading conditions to study the function of ligaments and their replacements; it has the potential to reproduce in-vivo joint motions in a cadaver knee. Two types of computational models have also been developed: a rigid body spring model and a displacement controlled spring model. These computational models are designed to complement and enhance experimental studies so that more complex loading conditions can be examined and the stresses and strains in the soft tissues can be calculated. In the future, this combined approach will improve our understanding of these joints and soft tissues during in-vivo activities and serve as a tool to aid surgical planning and development of rehabilitation protocols.
Gender Comparisons of Mechanomyographic Amplitude and Mean Power Frequency versus Isometric Torque Relationships
Authors: Beck Travis W. , Housh Terry J. , Johnson Glen O. , Weir Joseph P. , Cramer Joel T. , Coburn Jared W. , Malek Moh H.
Published: August 2016

This study compared the patterns of mechanomyographic (MMG) amplitude and mean power frequency vs. torque relationships in men and women during isometric muscle actions of the biceps brachii. Seven men (mean age 23.9 ± 3.5 yrs) and 8 women (mean 21.0 ± 1.3 yrs) performed submaximal to maximal isometric muscle actions of the dominant forearm flexors. Following determination of the isometric maximum voluntary contraction (MVC), they randomly performed submaximal step muscle actions in 10% increments from 10% to 90% MVC. Polynomial regression analyses indicated that the MMG amplitude vs. isometric torque relationship for the men was best fit with a cubic model (R2 = 0.983), where MMG amplitude increased slightly from 10% to 20% MVC, increased rapidly from 20% to 80% MVC, and plateaued from 80% to 100% MVC. For the women, MMG amplitude increased linearly (r2 = 0.949) from 10% to 100% MVC. Linear models also provided the best fit for the MMG mean power frequency vs. isometric torque relationship in both the men (r2 = 0.813) and women (r2 = 0.578). The results demonstrated gender differences in the MMG amplitude vs. isometric torque relationship, but similar torque-related patterns for MMG mean power frequency. These findings suggested that the plateau in MMG amplitude at high levels of isometric torque production for the biceps brachii in the men, but not the women, may have been due to greater isometric torque, muscle stiffness, and/or intramuscular fluid pressure in the men, rather than to differences in motor unit activation strategies for modulating isometric torque production.
Characterization of a System for Studying Human Gait during Slope Walking
Authors: Lay Andrea N. , Hass Chris J. , Smith D. Webb , Gregor Robert J.
Published: August 2016

Sloped walking surfaces provide a unique environment for examining the bio-mechanics and neural control of locomotion. While sloped surfaces have been used in a variety of studies in recent years, the current literature provides little if any discussion of the integrity, i.e., validity, of the systems used to collect data. The goal of this study was to develop and characterize a testing system capable of evaluating the kinetics of human locomotion on sloped surfaces. A ramped walkway system with an embedded force plate was constructed and stabilized. Center of pressure and reaction force data from the force plate were evaluated at 6 ramp grades (0, 5, 15, 25, 35, and 39%). Ground reaction force data at 0% grade were effectively the same as data from the same force plate when mounted in the ground and were well within the range of intrasubject variability. Collectively, data from all tests demonstrate the fidelity of this ramp system and suggest it can be used to evaluate human locomotion over a range of slope intensities.
Vertical Jumping Reorganization with Aging: A Kinematic Comparison between Young and Elderly Men
Authors: Haguenauer Marianne , Legreneur Pierre , Monteil Karine M.
Published: August 2016

To our knowledge jumping kinematics have never been studied in elderly persons. This study was aimed at examining the influence of aging on vertical jump performance and on interjoint coordination. Two groups of adults, 11 young men ages 18–25 years and 11 older men ages 79–100 years, were filmed while performing a maximal squat jump. Compared to young adults, jump height was significantly decreased by 28 cm in the elderly. Older adults spontaneously jumped from a more extended position of the hip. Results showed a decrease in hip, knee, and ankle linear velocity and angular amplitude with aging. The decrease in jump height was attributed to a decrease in explosive force and in the range of shortening of extensor muscles. In agreement with the literature, a proximo-distal coordination pattern was observed in young adults. Older adults used a simultaneous pattern. This may indicate that adults adjust their pattern of joint coordination as they age.
Biomechanical Behavior of Muscle-Tendon Complex during Dynamic Human Movements
Authors: Fukashiro Senshi , Hay Dean C. , Nagano Akinori
Published: August 2016

This paper reviews the research findings regarding the force and length changes of the muscle-tendon complex during dynamic human movements, especially those using ultrasonography and computer simulation. The use of ultrasonography demonstrated that the tendinous structures of the muscle-tendon complex are compliant enough to influence the biomechanical behavior (length change, shortening velocity, and so on) of fascicles substantially. It was discussed that the fascicles are a force generator rather than a work generator; the tendinous structures function not only as an energy re-distributor but also as a power amplifier, and the interaction between fascicles and tendinous structures is essential for generating higher joint power outputs during the late pushoff phase in human vertical jumping. This phenomenon could be explained based on the force-length/velocity relationships of each element (contractile and series elastic elements) in the muscle-tendon complex during movements. Through computer simulation using a Hill-type muscle-tendon complex model, the benefit of making a countermovement was examined in relation to the compliance of the muscle-tendon complex and the length ratio between the contractile and series elastic elements. Also, the integral roles of the series elastic element were simulated in a cyclic human heel-raise exercise. It was suggested that the storage and reutilization of elastic energy by the tendinous structures play an important role in enhancing work output and movement efficiency in many sorts of human movements.
Tibiofemoral Joint Contact Force in Deep Knee Flexion and Its Consideration in Knee Osteoarthritis and Joint Replacement
Authors: Nagura Takeo , Matsumoto Hideo , Kiriyama Yoshimori , Chaudhari Ajit , Andriacchi Thomas P.
Published: August 2016

The aim of the study was to estimate the tibiofemoral joint force in deep flexion to consider how the mechanical load affects the knee. We hypothesize that the joint force should not become sufficiently large to damage the joint under normal contact area, but should become deleterious to the joint under the limited contact area. Sixteen healthy knees were analyzed using a motion capture system, a force plate, a surface electromyography, and a knee model, and then tibiofemoral joint contact forces were calculated. Also, a contact stress simulation using the contact areas from the literature was performed. The peak joint contact forces (M ± SD) were 4566 ± 1932 N at 140 degrees in rising from full squat and 4479 ± 1478 N at 90 degrees in rising from kneeling. Under normal contact area, the tibiofemoral contact stresses in deep flexion were less than 5 MPa and did not exceed the stress to damage the cartilage. The contact stress simulation suggests that knee prosthesis having the contact area smaller than 200 mm2 may be problematic since the contact stress in deep flexion would become larger than 21 MPa, and it would lead damage or wear of the polyethylene.
Validation of Power Measurement Techniques in Dynamic Lower Body Resistance Exercises
Authors: Cormie Prue , McBride Jeffrey M. , McCaulley Grant O.
Published: August 2016

The objective of this study was to investigate the validity of power measurement techniques utilizing various kinematic and kinetic devices during the jump squat (JS), squat (S) and power clean (PC). Ten Division I male athletes were assessed for power output across various intensities: 0, 12, 27, 42, 56, 71, and 85% of one repetition maximum strength (1RM) in the JS and S and 30, 40, 50, 60, 70, 80, and 90% of 1RM in the PC. During the execution of each lift, six different data collection systems were utilized; (1) one linear position transducer (1-LPT); (2) one linear position transducer with the system mass representing the force (1-LPT+MASS); (3) two linear position transducers (2-LPT); (4) the force plate (FP); (5) one linear position transducer and a force plate (1-LPT+FP); (6) two linear position transducers and a force place (2-LPT+FP). Kinetic and kinematic variables calculated using the six methodologies were compared. Vertical power, force, and velocity differed significantly between 2-LPT+FP and 1-LPT, 1-LPT+MASS, 2-LPT, and FP methodologies across various intensities throughout the JS, S, and PC. These differences affected the load–power relationship and resulted in the transfer of the optimal load to a number of different intensities. This examination clearly indicates that data collection and analysis procedures influence the power output calculated as well as the load–power relationship of dynamic lower body movements.
A Simple Method to Obtain Consistent and Clinically Meaningful Pelvic Angles from Euler Angles during Gait Analysis
Authors: Wren Tishya A.L. , Mitiguy Paul C.
Published: August 2016

Clinical gait analysis usually describes joint kinematics using Euler angles, which depend on the sequence of rotation. Studies have shown that pelvic obliquity angles from the traditional tilt-obliquity-rotation (TOR) Euler angle sequence can deviate considerably from clinical expectations and have suggested that a rotation-obliquity-tilt (ROT) Euler angle sequence be used instead. We propose a simple alternate approach in which clinical joint angles are defined and exactly calculated in terms of Euler angles from any rotation sequence. Equations were derived to calculate clinical pelvic elevation, progression, and lean angles from TOR and ROT Euler angles. For the ROT Euler angles, obliquity was exactly the same as the clinical elevation angle, rotation was similar to the clinical progression angle, and tilt was similar to the clinical lean angle. Greater differences were observed for TOR. These results support previous findings that ROT is preferable to TOR for calculating pelvic Euler angles for clinical interpretation. However, we suggest that exact clinical angles can and should be obtained through a few extra calculations as demonstrated in this technical note.
Computational Determination of the Critical Microcrack Size That Causes a Remodeling Response in a Trabecula: A Feasibility Study
Authors: Gefen Amit , Neulander Ron
Published: August 2016

Bone is a living tissue, which undergoes continuous renewal to repair local defects. Two separate processes, adaptation and remodeling, are involved when a defect appears. The defect produces stress concentrations that provoke regional adaptation, and is gradually repaired, first by resorption and then by deposition of new bone. Using a mathematical formulation of the adaptation mechanism in trabeculae of cancellous bone, we hypothesize that in some cases, where a microcrack is small enough relative to the dimensions of the trabecula, the adaptation response of the whole trabecula may be sufficient to regain homeostatic mechanical conditions (with no need for a remodeling process). The simulation results showed that for trabeculae with nominal length of 900 µm and nominal thickness of 80–800 µm, a microcrack with minimal length of 48 µm and minimal depth of 13% of the trabecula’s thickness was required to initiate a remodeling process. A longer (100 µm) but shallower (depth of 7% of the trabecula’s thickness) crack also triggered remodeling. These computational results support our hypothesis that when a microcrack small enough relative to the dimensions of the trabecula occurs, adaptation of the whole trabecula may be sufficient to regain homeostatic mechanical conditions with no need for a local remodeling process.
Torque and Force Production during Shoulder External Rotation: Differences between Transverse and Sagittal Planes
Authors: de Toledo Joelly Mahnic , Krug Roberto Costa , Castro Marcelo Peduzzi , Ribeiro Daniel Cury , Loss Jefferson Fagundes
Published: August 2016

In joints with 3 degrees of freedom, such as the shoulder joint, the association of different movements results in changes in the behavior of the moment arm of the muscles. The capacity of torque production for the same movement can be changed when movements take place in a different plane. The objective of this study is to quantify differences between torque production and resultant force estimated during the shoulder external rotation in two movement planes: the transverse and sagittal planes (with 90° of shoulder abduction). Eight individuals were evaluated using an isokinetic dynamometer and an eletrogoniometer for movements in the transverse plane and six individuals for movements in the sagittal plane. The results showed that the execution of the external rotation in the sagittal plane allowed greater torque magnitudes and resultant force compared with those in the transverse plane, probably owing to a prestretching of infraspinatus and teres minor.
Relationships between Spinal Landmarks and Skin Surface Markers
Authors: Engsberg Jack R. , Lenke Lawrence G. , Bridwell Keith H. , Uhrich Mary L. , Trout Connie M.
Published: August 2016

This investigation determined relationships between coronal vertical alignment (CVA) and sagittal vertical alignment (SVA) variables calculated from radiographs and surface markers representing bony landmarks. Biplanar radiographs were taken on 28 subjects (standing) after 2 metallic surface markers were placed on the skin superficial to C7 and S2. The CVA-R and SVA-R were measured on the radiographs. Similar variables were calculated from the surface markers (CVA-P-R, SVA-P-R). Correlation between CVA-R and CVA-P-R was 0.894 (p < 0.000), and between SVA-R and SVA-P-R was 0.946 (p < 0.000). Results lead to three recommendations: (1) obtain surface marker data when radiographs are taken to establish relationships between the two sets of data, (2) take care in providing instructions to the subjects if measures are to be taken at different times, and (3) observe caution in interpreting results when simultaneous x-ray and surface marker data were not recorded.
Manual Materials Handling in Simulated Motion Environments
Authors: Holmes Michael W. , MacKinnon Scott N. , Matthews Julie , Albert Wayne J. , Mills Steven
Published: August 2016

Seafaring occupations have been shown to place operators at an increased risk for injury. The purpose of this study was to understand better the demands of a moving environment on the ability of a person to perform specific lifting tasks. Subjects lifted a 15-kg load under four different lifting conditions. A 6-degree-of-freedom ship motion simulator imposed repeatable deck motions under foot while subjects executed the lifting tasks. Subjects were oriented in three different positions on the simulator floor to inflict different motion profiles. Electromyographic records of four muscles were collected bilaterally, and thoracolumbar kinematics were measured. A repeated-measures ANOVA was employed to assess trunk motions and muscle activities across lifting and motion conditions. The erector spinae muscles showed a trend toward significant differences for motion effects. Maximal sagittal velocities were significantly smaller for all motion states in comparison with the stable condition (p ≤ .01), whereas maximum twisting and lateral bending velocities were higher (p ≤ .05). Results suggest working in a moving environment will likely increase the operator’s risk for overexertion injuries, particularly to the trunk region.
Lower Extremity Muscle Functions during Full Squats
Authors: Robertson D.G.E. , Wilson Jean-Marie J. , Pierre Taunya A. St.
Published: August 2016

The purpose of this research was to determine the functions of the gluteus maximus, biceps femoris, semitendinosus, rectus femoris, vastus lateralis, soleus, gastrocnemius, and tibialis anterior muscles about their associated joints during full (deep-knee) squats. Muscle function was determined from joint kinematics, inverse dynamics, electromyography, and muscle length changes. The subjects were six experienced, male weight lifters. Analyses revealed that the prime movers during ascent were the monoarticular gluteus maximus and vasti muscles (as exemplified by vastus lateralis) and to a lesser extent the soleus muscles. The biarticular muscles functioned mainly as stabilizers of the ankle, knee, and hip joints by working eccentrically to control descent or transferring energy among the segments during ascent. During the ascent phase, the hip extensor moments of force produced the largest powers followed by the ankle plantar flexors and then the knee extensors. The hip and knee extensors provided the initial bursts of power during ascent with the ankle extensors and especially a second burst from the hip extensors adding power during the latter half of the ascent.
Spanning Set May Not Be Appropriate for Measuring Knee Kinematic Variability for the Entire Gait Cycle during Over-Ground Barefoot Running
Authors: Kong Pui W. , Candelaria Norma G.
Published: August 2016

This study aimed to 1) determine the suitability of using spanning set (SS) to measure knee angle variability in the entire gait cycle and 2) assess the sensitivity of SS magnitude to the order of polynomial fitted to the standard deviation (SD) curves of the mean ensemble curves. Eight runners performed 10 over-ground barefoot running trials, followed by 8 min of accommodation, and then another 10 trials. Knee angle variabilities before and after accommodation were assessed using the SS and two conventional methods: mean coefficient of variation and mean SD. The sensitivity of the SS magnitude was assessed by calculating SS using (n–2), (n–1), (n+1), and (n+2)th orders of polynomials, where nth is the best fit order. Variability decreased after accommodation using the conventional methods (p < .05) but not the SS. The SS magnitude was sensitive to the order of polynomial. It is concluded that the SS may not be appropriate for measuring knee kinematic variability in the entire gait cycle during over-ground barefoot running.
Influence of the Crosshead Rate on the Mechanical Properties of Fixation Systems of ACL Tendon Grafts
Authors: Martel Oscar , Cárdenes Juan F. , Garcés Gerardo , Carta José A.
Published: August 2016

Anterior cruciate ligament (ACL) reconstruction is one of the most important aspects of knee surgery. For this purpose, several fixation devices have been developed, although the interference screw is the most frequently used. The most typical biomechanical test of these devices consists of placing them in a testing machine and subjecting them to a pull-out test. However, insufficient attention has been paid to the influence of the displacement test rate on the mechanical properties of the fixation system. The aim of this study is to compare the influence of the crosshead rate in the biomechanical test of two different devices for the fixation of ACL tendon grafts. One hundred in vitro tests were performed using porcine tibiae and bovine tendons. The fixation devices used were (1) an interference screw and (2) a new expansion device. All ACL reconstructions were subjected to pull-out test to failure. Five crosshead rates were employed in a range from 30 mm/min to 4000 mm/min. Statistical analyses of the results show that, for the two devices, the rate has a significant effect on both maximum force and stiffness. Moreover, the new expansion device showed lesser dependency on the crosshead rate than the interference screw.
Differences in End-Point Force Trajectories Elicited by Electrical Stimulation of Individual Human Calf Muscles
Authors: Giordano Sara B. , Segal Richard L. , Abelew Thomas A.
Published: August 2016

The purpose of this study was to investigate the end-point force trajectories of the fibularis longus (FIB), lateral gastrocnemius (LG), and medial gastrocnemius (MG) muscles. Most information about individual muscle function has come from studies that use models based on electromyographic (EMG) recordings. In this study (N = 20 subjects) we used electrical stimulation (20 Hz) to elicit activity in individual muscles, recorded the end-point forces at the foot, and verified the selectivity of stimulation by using magnetic resonance imaging. Unexpectedly, no significant differences were found between LG and MG force directions. Stimulation of LG and MG resulted in downward and medial or lateral forces depending on the subject. We found FIB end-point forces to be significantly different from those of LG and MG. In all subjects, stimulation of FIB resulted in downward and lateral forces. Based on our results, we suggest that there are multiple factors determining when and whether LG or MG will produce a medial or lateral force and FIB consistently plays a significant role in eversion/abduction and plantar flexion. We suggest that the intersubject variability we found is not simply an artifact of experimental or technical error but is functionally relevant and should be addressed in future studies and models.
Modeling of Monofin Swimming Technique: Optimization of Feet Displacement and Fin Strain
Authors: Rejman Marek , Ochmann Bartosz
Published: August 2016

The aim of this study was to develop a functional model of monofin swimming by assigning numerical forms to certain technique parameters. The precise determination of optimal foot displacement and monofin strain points toward a model aspect for increasing swimming speed. Eleven professional swimmers were filmed underwater. The kinematic data were then used as entry variable for an artificial neural network, which itself created the foundation for a model of monofin swimming technique. The resulting network response graphs indicate a division set of standard deviation values in which the examined angular parameters of foot and monofin displacement achieve optimal values in terms of gaining maximal swimming speed. During the upward movement, it is essential to limit dorsal foot flexion (–20°) from the parallel position toward the shin (180°). During the downward movement, plantar flexion should not exceed 180°. The optimal scope of the proximal part of the fin strain is 35° in the downward movement and (–)27° in the upward; the angles of attack of the distal part of the fn and its entire surface are limited to 37° in the downward movement and (–)26° in the upward. Optimization criteria allowed for movement modification to gain and maintain maximal velocity during both cycle phases and to limit cycle velocity decrease.