bluuebunny/crossref_metadata_2025 huggingface dataset:
In Situ Calibration and Motion Capture Transformation Optimization Improve Instrumented Treadmill Measurements
Authors: Goldberg Saryn R. , Kepple Thomas M. , Stanhope Steven J.
Published: August 2016

We increased the accuracy of an instrumented treadmill’s measurement of center of pressure and force data by calibrating in situ and optimizing the transformation between the motion capture and treadmill force plate coordinate systems. We calibrated the device in situ by applying known vertical and shear loads at known locations across the tread surface and calculating a 6 × 6 calibration matrix for the 6 output forces and moments. To optimize the transformation, we first estimated the transformation based on a locating jig and then measured center-of-pressure error across the treadmill force plate using the CalTester tool. We input these data into an optimization scheme to find the transformation between the motion capture and treadmill force plate coordinate systems that minimized the error in the center-of-pressure measurements derived from force plate and motion capture sources. When the calibration and transformation optimizations were made, the average measured error in the center of pressure was reduced to approximately 1 mm when the treadmill was stationary and to less than 3 mm when moving. Using bilateral gait data, we show the importance of calibrating these devices in situ and performing transformation optimizations.
The Influences of Impact Interface, Muscle Activity, and Knee Angle on Impact Forces and Tibial and Femoral Accelerations Occurring after External Impacts
Authors: Potthast Wolfgang , Brüggemann Gert-Peter , Lundberg Arne , Arndt Anton
Published: August 2016

The purpose of this study was to quantify relative contributions of impact interface, muscle activity, and knee angle to the magnitudes of tibial and femoral accelerations occurring after external impacts. Impacts were initiated with a pneumatically driven impacter under the heels of four volunteers. Impact forces were quantified with a force sensor. Segmental accelerations were measured with bone mounted accelerometers. Experimental interventions were hard and soft shock interfaces, different knee angles (0°, 20°, 40° knee flexion), and muscular preactivation (0%, 30%, 60% of maximal voluntary contraction) of gastrocnemii, hamstrings, and quadriceps. Greater knee flexion led to lower impact forces and higher tibial accelerations. Increased muscular activation led to higher forces and lower tibial accelerations. The softer of the two shock interfaces under study reduced both parameters. The effects on accelerations and forces through the activation and knee angle changes were greater than the effect of interface variations. The hardness of the two shock interfaces explained less than 10% of the variance of accelerations and impact forces, whereas knee angle changes explained 25–29%, and preactivation changes explained 35–48% of the variances. It can be concluded that muscle force and knee joint angle have greater effects in comparison with interface hardness on the severity of shocks on the lower leg.
Biomechanics of Off-Center Monoarticular Exercises with Lever Selectorized Equipment
Authors: Biscarini Andrea
Published: August 2016

We have developed a 2-D analytical biomechanical model for monoarticular open kinetic-chain exercises with lever selectorized equipment, and different relative placement between the joint center of rotation (J) and the center of rotation (C) of the resistance input lever (“off-center” exercises). All the relevant geometrical aspects of such exercises have been characterized: the change with the joint angle of the distance between the resistance pad (P) and J, and of the angle between CP and JP (i.e., the angle between the resistance input lever and the exercising limb). These changes may strongly affect the joint load and the muscle torque in inverse dynamic problems, given the joint kinematics and the mass of the selected weight stack. Therefore, the muscle torque, the shear and axial components of the joint load have been calculated analytically as a function of the relative positioning of C and J, and the length CP, in addition to the parameters that define the joint kinematics, the equipment mechanics, and the external load. From these results we have derived the optimal cam profiles for “off-center” exercises, as well as the geometrical “off-center” setting that minimizes the shear component of the tibiofemoral joint load in leg extension equipment.
Comparing Methods of Quantifying Tibial Acceleration Slope
Authors: Duquette Adriana M. , Andrews David M.
Published: August 2016

Considerable variability in tibial acceleration slope (AS) values, and different interpretations of injury risk based on these values, have been reported. Acceleration slope variability may be due in part to variations in the quantification methods used. Therefore, the purpose of this study was to quantify differences in tibial AS values determined using end points at various percentage ranges between impact and peak tibial acceleration, as a function of either amplitude or time. Tibial accelerations were recorded from 20 participants (21.8 ± 2.9 years, 1.7 m ± 0.1 m, 75.1 kg ± 17.0 kg) during 24 unshod heel impacts using a human pendulum apparatus. Nine ranges were tested from 5–95% (widest range) to 45–55% (narrowest range) at 5% increments. ASAmplitude values increased consistently from the widest to narrowest ranges, whereas the ASTime values remained essentially the same. The magnitudes of ASAmplitude values were significantly higher and more sensitive to changes in percentage range than ASTime values derived from the same impact data. This study shows that tibial AS magnitudes are highly dependent on the method used to calculate them. Researchers are encouraged to carefully consider the method they use to calculate AS so that equivalent comparisons and assessments of injury risk across studies can be made.
Pelvifemoral Kinematics while Ascending Single Steps of Different Heights
Authors: Bohannon Richard W. , Smutnick Jason
Published: August 2016

Motion of the femur and pelvis during hip flexion has been examined previously, but principally in the sagittal plane and during nonfunctional activities. In this study we examined femoral elevation in the sagittal plane and pelvic rotation in the sagittal and frontal planes while subjects flexed their hips to ascend single steps. Fourteen subjects ascended single steps of 4 different heights leading with each lower limb. Motion of the lead femur and pelvis during the flexion phase of step ascent was tracked using an infrared motion capture system. Depending on step height and lead limb, step ascent involved elevation of the femur (mean 47.2° to 89.6°) and rotation of the pelvis in both the sagittal plane (tilting: mean 2.6° to 9.7°) and frontal plane (listing: mean 4.2° to 11.9°). Along with maximum femoral elevation, maximum pelvic rotation increased significantly (p < .001) with step height. Femoral elevation and pelvic rotation during the flexion phase of step ascent were synergistic (r = .852–.999). Practitioners should consider pelvic rotation in addition to femoral motion when observing individuals’ ascent of steps.
Detecting Postoperative Change in Children with Cerebral Palsy: Net Nondimensional versus Body Mass Oxygen Normalization
Authors: Švehlík Martin , Slabý Kryštof , Trc̆ Tomáš , Radvanský Jir̆í
Published: August 2016

The aim of the study is to investigate whether the net nondimensional oxygen utilization scheme is able to detect postoperative improvement in the energy cost of walking in children with cerebral palsy and to compare it with a body mass normalization scheme. We evaluated 10 children with spastic cerebral palsy before and 9 months after equinus deformity surgery. Participants walked at a given speed of 2 km/hr and 3 km/hr on a treadmill. Oxygen utilization was measured, and mass relative VO2 and net nondimensional VO2 were calculated. Coefficient of variation was used for the description of variability among subjects. Postoperatively, gait kinematics normalized and the mass relative VO2 and net nondimensional VO2 showed significant improvement. Net nondimensional VO2 is able to detect postoperative improvement with smaller variability among subjects than body mass related normalization in children with cerebral palsy.
The Loss of Dexterity in the Bilateral Lower Extremities in Patients With Stroke
Authors: Kiyama Ryoji , Fukudome Kiyohiro , Hiyoshi Toshiki , Umemoto Akihide , Yoshimoto Yoichi , Maeda Tetsuo
Published: August 2016

The aim of this study was to examine the dexterity of both lower extremities in patients with stroke. Twenty patients with stroke and 20 age-matched control subjects participated in this study. To determine the dexterity of the lower extremities, we examined the ability to control muscle force during submaximal contractions in the knee extensor muscles using a force tracking task. The root mean square errors were calculated from the difference between the target and response force. The root mean square error was significantly greater in the affected limb of patients with stroke compared with those of the unaffected limb and the control subjects, and in the unaffected limb compared with that of the control subjects. Furthermore, the root mean square error of the affected limb was related significantly to motor function as determined by Fugl-Myer assessment. These results demonstrate impairment of the dexterity of both the affected and the unaffected lower extremities in patients with stroke.
Differences on Spinal Curvature in Standing Position by Gender, Age and Weight Status Using a Noninvasive Method
Authors: Lang-Tapia Morin , España-Romero Vanesa , Anelo Juan , Castillo Manuel J.
Published: August 2016

This aim was to examine differences on lumbar lordosis and thoracic kyphosis in standing position by gender, age and weight status in healthy subjects using a noninvasive method. A total of 297 women (36.6 ± 7.3 years) and 362 men (39.8 ± 7.5 years) participated in this study. Participants were categorized according to the international BMI (kg/m2) cut-off points. Age was stratified by ten years increments starting from 20 y. Men showed smaller lumbar lordosis (17.3 ± 9.3) and larger thoracic kyphosis (42.8 ± 8.8°) than women (29.6 ± 11.3 and 40.4 ± 9.5° respectively; bothp< .001). Older groups presented smaller lumbar lordosis and larger thoracic kyphosis values compared with the 20–29 y group (20.9 ± 10.4, 20.8 ± 11.2 and 23.6 ± 12.6° for ≥50, 40–49 and 30–39 y, respectively vs. 26.7 ± 12.2° for 20–29 y in lumbar lordosis and 42.6 ± 9.8, 42.61 ± 8.7 and 41.8 ± 8.9° for ≥50, 40–49 and 30–39 y, respectively vs. 37.5 ± 10.9° for 20–29 y in thoracic kyphosis; bothp< .05). Finally, overweight and obese groups showed smaller lumbar lordosis (19.4 ± 11.1 and 20.9 ± 11.8° respectively) and larger thoracic kyphosis values (42.7 ± 8.9 and 42.8 ± 9.4° respectively) compared with nonoverweight participants (25.1 ± 12.4 and 40.6 ± 9.2° for lumbar lordosis and thoracic kyphosis respectively; allp< .05). However, when gender, age and weight status were take into account all together only gender seems to influence the lumbar lordosis curvature. The results of this study suggest that gender could be the only determinant factor of lumbar lordosis in healthy people.
Forces and Moments on the Knee During Kneeling and Squatting
Authors: Pollard Jonisha P. , Porter William L. , Redfern Mark S.
Published: August 2016

Euler angle decomposition and inverse dynamics were used to determine the knee angles and net forces and moments applied to the tibia during kneeling and squatting with and without kneepads for 10 subjects in four postures: squatting (Squat), kneeling on the right knee (One Knee), bilateral kneeling near full flexion (Near Full) and bilateral kneeling near 90° flexion (Near 90). Kneepads affected the knee flexion (p = .002), medial forces (p = .035), and internal rotation moments (p = .006). Squat created loading conditions that had higher varus (p < .001) and resultant moments (p = .027) than kneeling. One Knee resulted in the highest force magnitudes and net moments (p < .001) of the kneeling postures. Thigh-calf and heel-gluteus contact forces decreased the flexion moment on average by 48% during Squat and Near Full.
Commercial Video Frame Rates Can Produce Reliable Results for Both Normal and CP Spastic Gait’s Spatiotemporal, Angular, and Linear Displacement Variables
Authors: Nikodelis Thomas , Moscha Dimitra , Metaxiotis Dimitris , Kollias Iraklis
Published: August 2016

To investigate what sampling frequency is adequate for gait, the correlation of spatiotemporal parameters and the kinematic differences, between normal and CP spastic gait, for three sampling frequencies (100 Hz, 50 Hz, 25 Hz) were assessed. Spatiotemporal, angular, and linear displacement variables in the sagittal plane along with their 1st and 2nd derivatives were analyzed. Spatiotemporal stride parameters were highly correlated among the three sampling frequencies. The statistical model (2 × 3 ANOVA) gave no interactions between the factors group and frequency, indicating that group differences were invariant of sampling frequency. Lower frequencies led to smoother curves for all the variables, with a loss of information though, especially for the 2nd derivatives, having a homologous effect as the one of oversmoothing. It is proposed that in the circumstance that only spatiotemporal stride parameters, as well as angular and linear displacements are to be used, in gait reports, then commercial video camera speeds (25/30 Hz, 50/60 Hz when deinterlaced) can be considered as a low-cost solution to produce acceptable results.
Morphological and Mechanical Properties of Muscle and Tendon in Highly Trained Sprinters
Authors: Kubo Keitaro , Ikebukuro Toshihiro , Yata Hideaki , Tomita Minoru , Okada Masaji
Published: August 2016

The purpose of this study was to investigate muscle and tendon properties in highly trained sprinters and their relations to running performance. Fifteen sprinters and 15 untrained subjects participated in this study. Muscle thickness and tendon stiffness of knee extensors and plantar flexors were measured. Sprinter muscle thickness was significantly greater than that of the untrained subjects for plantar flexors, but not for knee extensors (except for the medial side). Sprinter tendon stiffness was significantly lower than that of the untrained subjects for knee extensors, but not for plantar flexors. The best official record of a 100-m race was significantly correlated to the muscle thickness of the medial side for knee extensors. In conclusion, the tendon structures of highly trained sprinters are more compliant than those of untrained subjects for knee extensors, but not for plantar flexors. Furthermore, a thicker medial side of knee extensors was associated with greater sprinting performance.
A Mechanics Comparison Between Landing From a Countermovement Jump and Landing From Stepping Off a Box
Authors: Afifi Mostafa , Hinrichs Richard N.
Published: August 2016

It is common practice to study jump landing mechanics by having subjects step off a box set at a certain height instead of landing from a jump. This practice assumes that the landing mechanics are similar between stepping off a box and a countermovement jump as long as the heights can be matched. The mechanics of the two methods had never been compared when landing from identical heights. Thus, the purpose of this study was to compare the mechanics of landing from a countermovement jump to landing from a step-off. Participants performed three maximal countermovement jumps. The mechanics of one countermovement jump was compared with a center of mass fall height matched step-off landing. The step-off landing showed a more rapid time to peak ground reaction force (GRF) in both genders and greater GRF peak and loading rate in males only. No difference was observed between joint angles at initial contact; however, the countermovement jump showed significantly greater joint flexion angles at peak GRF for both genders. EMG showed greater muscle activity during the countermovement jump condition in all subjects. It was concluded that countermovement jump landings are different from step-off landings; thus, results from analyses involving step-off landings should be taken with caution if the aim is to relate them to landing from a jump.
Kinetic Analysis of Ski Turns Based on Measured Ground Reaction Forces
Authors: Vaverka Frantisek , Vodickova Sona , Elfmark Milan
Published: August 2016

The objective of this study was to devise a method of kinetic analysis of the ground reaction force that enables the durations and magnitudes of forces acting during the individual phases of ski turns to be described exactly. The method is based on a theoretical analysis of physical forces acting during the ski turn. Two elementary phases were defined: (1) preparing to turn (initiation) and (2) actual turning, during which the center of gravity of the skier–ski system moves along a curvilinear trajectory (steering). The starting point of the turn analysis is a dynamometric record of the resultant acting ground reaction force applied perpendicularly on the ski surface. The method was applied to six expert skiers. They completed a slalom course comprising five gates arranged on the fall line of a 26° slope at a competition speed using symmetrical carving turns (30 evaluated turns). A dynamometric measurement system was placed on the carving skis (168 cm long, radius 16 m, data were recorded at 100 Hz). MATLAB procedures were used to evaluate eight variables during each turn: five time variables and three force variables. Comparison of the turn analysis results between individuals showed that the method is useful for answering various research questions associated with ski turns.
Tangential Finger Forces Use Mechanical Advantage During Static Grasping
Authors: Slota Gregory P. , Latash Mark L. , Zatsiorsky Vladimir M.
Published: August 2016

When grasping and manipulating objects, the central controller utilizes the mechanical advantage of the normal forces of the fingers for torque production. Whether the same is valid for tangential forces is unknown. The main purpose of this study was to determine the patterns of finger tangential forces and the use of mechanical advantage as a control mechanism when dealing with objects of nonuniform finger positioning. A complementary goal was to explore the interaction of mechanical advantage (moment arm) and the role a finger has as a torque agonist/antagonist with respect to external torques (±0.4 N m). Five 6-dfforce/torque transducers measured finger forces while subjects held a prism handle (6 cm width × 9 cm height) with and without a single finger displaced 2 cm (handle width). The effect of increasing the tangential moment arm was significant (p< .01) for increasing tangential forces (in >70% of trials) and hence creating greater moments. Thus, the data provides evidence that the grasping system as a rule utilizes mechanical advantage for generating tangential forces. The increase in tangential force was independent of whether the finger was acting as a torque agonist or antagonist, revealing their effects to be additive.
Comparison of Endpoint Data Treatment Methods for the Estimation of Kinematics and Kinetics Near Impact During the Tennis Serve
Authors: Reid M. M. , Campbell Amity C. , Elliott B. C.
Published: August 2016

Tennis stroke mechanics have attracted considerable biomechanical analysis, yet current filtering practice may lead to erroneous reporting of data near the impact of racket and ball. This research had three aims: (1) to identify the best method of estimating the displacement and velocity of the racket at impact during the tennis serve, (2) to demonstrate the effect of different methods on upper limb kinematics and kinetics and (3) to report the effect of increased noise on the most appropriate treatment method. The tennis serves of one tennis player, fit with upper limb and racket retro-reflective markers, were captured with a Vicon motion analysis system recording at 500 Hz. The raw racket tip marker displacement and velocity were used as criterion data to compare three different endpoint treatments and two different filters. The 2nd-order polynomial proved to be the least erroneous extrapolation technique and the quintic spline filter was the most appropriate filter. The previously performed “smoothing through impact” method, using a quintic spline filter, underestimated the racket velocity (9.1%) at the time of impact. The polynomial extrapolation method remained effective when noise was added to the marker trajectories.
Magnitude of Head Impact Exposures in Individual Collegiate Football Players
Authors: Crisco Joseph J. , Wilcox Bethany J. , Machan Jason T. , McAllister Thomas W. , Duhaime Ann-Christine , Duma Stefan M. , Rowson Steven , Beckwith Jonathan G. , Chu Jeffrey J. , Greenwald Richard M.
Published: August 2016

The purpose of this study was to quantify the severity of head impacts sustained by individual collegiate football players and to investigate differences between impacts sustained during practice and game sessions, as well as by player position and impact location. Head impacts (N = 184,358) were analyzed for 254 collegiate players at three collegiate institutions. In practice, the 50th and 95th percentile values for individual players were 20.0 g and 49.5 g for peak linear acceleration, 1187 rad/s2 and 3147 rad/s2 for peak rotational acceleration, and 13.4 and 29.9 for HITsp, respectively. Only the 95th percentile HITsp increased significantly in games compared with practices (8.4%, p = .0002). Player position and impact location were the largest factors associated with differences in head impacts. Running backs consistently sustained the greatest impact magnitudes. Peak linear accelerations were greatest for impacts to the top of the helmet, whereas rotational accelerations were greatest for impacts to the front and back. The findings of this study provide essential data for future investigations that aim to establish the correlations between head impact exposure, acute brain injury, and long-term cognitive deficits.
Improving Regions of Deviation Gait Symmetry Analysis With Pointwise t Tests
Authors: DiBerardino Louis A. , Ragetly Chantal A. , Hong Sungjin , Griffon Dominique J. , Hsiao-Wecksler Elizabeth T.
Published: August 2016

The regions of deviation method has been proposed as a technique for identifying regions of the gait cycle where joint motion deviates from normal (Shorter et al., 2008). The original statistical analysis distinguished only peak values during stance and swing. In the current article, we extend the approach by examining deviations from normal throughout the entire gait cycle using pointwise t tests. These methods were demonstrated on hind-limb joint angles of 21 Labrador Retrievers without and with cranial cruciate ligament disease. Results were compared with peak difference analysis previously performed on these subjects. All points in the gait cycle where symmetry deviations were significantly affected by cranial cruciate ligament disease (via pointwise t tests) were defined as regions of deviation from symmetry. Discriminant function analysis was used to consider single subjects and validate that these regions were truly areas of difference between groups. Regions of deviation encompassed previously determined significant peak differences, while extending analysis to additional areas of asymmetry. Discriminant function analysis suggested that the region of deviation method is a viable approach for distinguishing motion pattern differences. This enhanced method may help researchers better understand the mechanisms behind lameness and compensation.
Modeling the Stance Leg in Two-Dimensional Analyses of Sprinting: Inclusion of the MTP Joint Affects Joint Kinetics
Authors: Bezodis Neil E. , Salo Aki I.T. , Trewartha Grant
Published: August 2016

Two-dimensional analyses of sprint kinetics are commonly undertaken but often ignore the metatarsal-phalangeal (MTP) joint and model the foot as a single segment. The aim of this study was to quantify the role of the MTP joint in the early acceleration phase of a sprint and to investigate the effect of ignoring the MTP joint on the calculated joint kinetics at the other stance leg joints. High-speed video and force platform data were collected from four to five trials for each of three international athletes. Resultant joint moments, powers, and net work at the stance leg joints during the first stance phase after block clearance were calculated using three different foot models. Considerable MTP joint range of motion (>30°) and a peak net MTP plantar flexor moment of magnitude similar to the knee joint were observed, thus highlighting the need to include this joint for a more complete picture of the lower limb energetics during early acceleration. Inclusion of the MTP joint had minimal effect on the calculated joint moments, but some of the calculated joint power and work values were significantly (P < .05) and meaningfully affected, particularly at the ankle. The choice of foot model is therefore an important consideration when investigating specific aspects of sprinting technique.
Measurement of Power in Selectorized Strength-Training Equipment
Authors: Biscarini Andrea
Published: August 2016

The author derived the exact analytical expression of the instantaneous joint power in exercises with single-joint, variable-resistance, selectorized strength-training equipment, taking into account all the relevant geometric, kinematic, and dynamic variables of both the movable equipment elements (resistance input lever, cam–pulley system, weight stack) and of the user’s exercising limb. A numerical algorithm was also designed to express, in the presence of a cam, the rectilinear kinematic variables of the weight stack as a function of the rotational kinematic variables of the resistance input lever, and vice versa. Given that information, one can measure the value of the instantaneous and mean joint power exclusively by means of a linear encoder placed on the weight stack or, alternatively, only by the use of an angular encoder placed on the rotational axis of the resistance lever. The results highlight that, for knee extension exercises with leg extension equipment, the real values of both instantaneous and mean joint power may differ by more than 50% in comparison with the values obtained by taking into account only the mass and velocity of the weight stack. These differences are notable not only in explosive exercises, but also whenever considerable joint velocities/accelerations occur within the range of motion.
Persons With Multiple Sclerosis Show Altered Joint Kinetics During Walking After Participating in Elliptical Exercise
Authors: Huisinga Jessie M. , Schmid Kendra K. , Filipi Mary L. , Stergiou Nicholas
Published: August 2016

Patients with multiple sclerosis (MS) experience abnormal gait patterns and reduced physical activity. The purpose of this study was to determine if an elliptical exercise intervention for patients with MS would change joint kinetics during gait toward healthy control values. Gait analysis was performed on patients with MS (n = 24) before and after completion of 15 sessions of supervised exercise. Joint torques and powers were calculated, while also using walking velocity as a covariate, to determine the effects of elliptical exercise on lower extremity joint kinetics during gait. Results show that elliptical exercise significantly altered joint torques at the ankle and hip and joint powers at the ankle during stance. The change in joint power at the ankle indicates that, after training, patients with MS employed a walking strategy that is more similar to that of healthy young adults. These results support the use of elliptical exercise as a gait training tool for patients with MS.
Person-Specific Changes in Motor Performance Accompany Upper Extremity Functional Gains After Stroke
Authors: DeJong Stacey L. , Birkenmeier Rebecca L. , Lang Catherine E.
Published: August 2016

In animal models, hundreds of repetitions of upper extremity (UE) task practice promote neural adaptation and functional gain. Recently, we demonstrated improved UE function following a similar intervention for people after stroke. In this secondary analysis, computerized measures of UE task performance were used to identify movement parameters that changed as function improved. Ten people with chronic poststroke hemiparesis participated in high-repetition UE task-specific training 3 times per week for 6 weeks. Before and after training, we assessed UE function with the Action Research Arm Test (ARAT), and evaluated motor performance using computerized motion capture during a reach-grasp-transport-release task. Movement parameters included the duration of each movement phase, trunk excursion, peak aperture, aperture path ratio, and peak grip force. Group results showed an improvement in ARAT scores (p = .003). Although each individual changed significantly on at least one movement parameter, across the group there were no changes in any movement parameter that reached or approached significance. Changes on the ARAT were not closely related to changes in movement parameters. Since aspects of motor performance that contribute to functional change vary across individuals, an individualized approach to upper extremity motion analysis appears warranted.
Impact Response and Simulation of Damaged Ulna With Internal Fixation
Authors: Coates Cameron , Goeser Priya , Coates-Clark Camille , Jenkins Mark
Published: August 2016

The objectives of this work were to explore a methodology that combines static and dynamic finite element (FE) analysis, linear elastic fracture mechanics (LEFM) and experimental methods to investigate a worst-case scenario in which a previously damaged bone plate system is subjected to an impact load. Cadaver ulnas with and without midshaft dynamic compression plates are subjected to a static three-point bend test and loaded such that subcritical crack growth occurs as predicted by a hybrid method that couples LEFM and static FE. The plated and unplated bones are then unloaded and subsequently subjected to a midshaft transverse impact test. A dynamic strain-based FE model is also developed to model the midshaft transverse impact test. The average value of the impact energy required for failure was observed to be 10.53% greater for the plated set. There appears to be a trade-off between impact damage and impact resistance when ulnas are supported by fixation devices. Predictions from the dynamic FE model are shown to corroborate inferences from the experimental approach.
Preoperative Predictors for Noncopers to Pass Return to Sports Criteria After ACL Reconstruction
Authors: Hartigan Erin H. , Zeni Joseph , Di Stasi Stephanie , Axe Michael J. , Snyder-Mackler Lynn
Published: August 2016

Less than 50% of athletes pass criteria to return to sports (RTS) 6 months after ACL reconstruction (ACLR). Using data on 38 noncopers, we hypothesized that preoperative age, quadriceps strength index (QI), and knee flexion moments (KFM) during gait would predict the ability to pass/fail RTS criteria and that preoperative quadriceps strength gains would be predictive of passing RTS criteria. Gait analysis and strength data were collected before and after a preoperative intervention and 6 months after ACLR. Age, QI, and KFM each contributed to the predictability to pass or fail RTS criteria 6 months after ACLR. Collectively, the variables predict 69% who would pass and 82% who would fail RTS criteria 6 months after ACLR. Younger athletes who have symmetrical quadriceps strength and greater KFM were more likely to pass RTS criteria. Further, 63% of those who increased preoperative quadriceps strength passed RTS criteria, whereas 73% who did not failed. Increasing quadriceps strength in noncopers before ACLR seems warranted.
Influence of Shear Stress on Behaviors of Piezoelectric Voltages in Bone
Authors: Fu Donghui , Hou Zhende , Qin Qing-Hua , Xu Lianyun , Zeng Yanjun
Published: August 2016

The piezoelectric properties of bone play an important role in the bone remodeling process and can be employed in clinical bone repair. In this study, the piezo-voltage of bone between two surfaces of a bone beam under bending deformation was measured using an ultra-high-input impedance bioamplifier. The influence of shear stress on the signs of piezo-voltages in bone was determined by comparing and contrasting the results from three-point and four-point bending experiments. From the three-point bending experiment, the study found that the signs of piezo-voltages depend only on shear stress and are not sensitive to the normal stress.
Adolescent Baseball Pitching Technique: Lower Extremity Biomechanical Analysis
Authors: Milewski Matthew D. , Õunpuu Sylvia , Solomito Matthew , Westwell Melany , Nissen Carl W.
Published: August 2016

Documentation of the lower extremity motion patterns of adolescent pitchers is an important part of understanding the pitching motion and the implication of lower extremity technique on upper extremity loads, injury and performance. The purpose of this study was to take the initial step in this process by documenting the biomechanics of the lower extremities during the pitching cycle in adolescent pitchers and to compare these findings with the published data for older pitchers. Three-dimensional motion analysis using a comprehensive lower extremity model was used to evaluate the fast ball pitch technique in adolescent pitchers. Thirty-two pitchers with a mean age of 12.4 years (range 10.5–14.7 years) and at least 2 years of experience were included in this study. The pitchers showed a mean of 49 ± 12° of knee flexion of the lead leg at foot contact. They tended to maintain this position through ball release, and then extended their knee during the follow through phase (ball release to maximal internal glenohumeral rotation). The lead leg hip rapidly progressed into adduction and flexion during the arm cocking phase with a range of motion of 40 ± 10° adduction and 30 ± 13° flexion. The lead hip mean peak adduction velocity was 434 ± 83°/s and flexion velocity was 456 ± 156°/s. Simultaneously, the trailing leg hip rapidly extended approaching to a mean peak extension of –8 ± 5° at 39% of the pitch cycle, which is close to passive range of motion constraints. Peak hip abduction of the trailing leg at foot contact was –31 ± 12°, which also approached passive range of motion constraints. Differences and similarities were also noted between the adolescent lower extremity kinematics and adult pitchers; however, a more comprehensive analysis using similar methods is needed for a complete comparison.
Biomechanical Evaluation of Fractured Tibia Externally Fixed With an LCP
Authors: Kanchanomai Chaosuan , Phiphobmongkol Vajara
Published: August 2016

A locking compression plate (LCP) can serve as an external fixation for fractured tibia. However, there is concern about the stability and endurance during partial weight bearing. This study was experimentally evaluated the effects of fracture gap sizes (1, 5, and 10 mm) on the stability and endurance of fractured tibia externally fixed with a 316L-stainless LCP. For stable fractured tibia (1-mm fracture gap), the large contact area of fracture surfaces resulted in nearly similar stiffness to that of intact tibia. The partial weight bearing is therefore possible. Whereas smaller contact area and no contact of fracture surfaces were observed for tibias with 5-mm and 10-mm fracture gaps, respectively. Their stiffnesses were significantly lower than those of intact tibia and tibia with 1-mm fracture gap. Thus, the partial weight bearing should be considered carefully in early phase of treatment. All LCP-tibial models were cyclically loaded beyond 500,000 cycles, that is, approximately 6 months of healing, without any failure of LCP. Thus, the failure of LCP is unlikely a critical issue for the present cases.
Impact Characteristics of Female Children Running in Adult Versus Youth Shoes of the Same Size
Authors: Forrest Dana , Dufek Janet S. , Mercer John A.
Published: August 2016

The purpose of this study was to determine if ground reaction forces were influenced by shoe design (adult vs. youth) for female children when running. Subjects (n = 10, 12.0 ± 1.1 years old; 154 ± 4.9 cm; 46.2 ± 14.3 kg; shoe size 3.5–7 youth) were fit with a shoe model available in youth and adult sizes. Subjects ran 10 trials per shoe condition across a force platform placed in the middle of a 9-m runway. Impact force, second maximum force, loading rate, stance time and average vertical ground reaction forces were recorded for each trial. Shoes underwent a mechanical impact test with peak force, peak acceleration, and percent energy returned recorded. Each variable was compared between shoe conditions. From the impact testing, it was determined that peak force, peak acceleration and percent energy return were 7.1%, 7.1%, and 18.9% greater, respectively, for the youth vs. adult shoe (p < .001). From the running tests, it was determined that loading rate was different (p = .009) between shoe conditions whereas impact force, second maximum force, average force and stance time were not different between shoes (p > .01). Young girls had a greater loading rate when running in youth vs. adult shoes even though the shoe size was the same.
Estimated Force and Moment of Shoulder External Rotation Muscles: Differences Between Transverse and Sagittal Planes
Authors: de Castro Marcelo Peduzzi , Ribeiro Daniel Cury , Forte Felipe de Camargo , de Toledo Joelly Mahnic , Krug Roberto Costa , Loss Jefferson Fagundes
Published: August 2016

The aim of this study was to compare shoulder muscle force and moment production during external rotation performed in the transverse and sagittal planes. An optimization model was used for estimating shoulder muscle force production of infraspinatus, teres minor, supraspinatus, anterior deltoid, middle deltoid and posterior deltoid muscles. The model uses as input data the external rotation moment, muscle moment arm magnitude, muscle physiologic cross-sectional area and muscle specific tension. The external rotation moment data were gathered from eight subjects in transverse and six subjects in sagittal plane using an isokinetic dynamometer. In the sagittal plane, all studied muscles presented larger estimated force in comparison with the transverse plane. The infraspinatus, teres minor, supraspinatus and posterior deltoid muscles presented larger moment in sagittal when compared with transverse plane. When prescribing shoulder rehabilitation exercises, therapists should bear in mind the described changes in muscle force production.
Relationships Between Fast Bowling Technique and Ball Release Speed in Cricket
Authors: Worthington Peter J. , King Mark A. , Ranson Craig A.
Published: August 2016

The aim of this study was to identify the key aspects of technique that characterize the fastest bowlers. Kinematic data were collected for 20 elite male fast bowlers with 11 kinematic parameters calculated, describing elements of fast bowling technique that have previously been linked to ball release speed. Four technique variables were identified as being the best predictors of ball release speed, explaining 74% of the observed variation in ball release speed. The results indicate that the fastest bowlers have a quicker run-up and maintain a straighter knee throughout the front foot contact phase. The fastest bowlers were also observed to exhibit larger amounts of upper trunk flexion up to ball release and to delay the onset of arm circumduction. This study identifies those technique variables that best explain the differences in release speeds among fast bowlers. These results are likely to be useful in both the coaching and talent identification of fast bowlers.
Does Wearing a Prophylactic Ankle Brace During Drop Landings Affect Lower Extremity Kinematics and Ground Reaction Forces?
Authors: Simpson Kathy J. , Yom Jae P. , Fu Yang-Chieh , Arnett Scott W. , O’Rourke Sean , Brown Cathleen N.
Published: August 2016

The objective of the study was to determine if prophylactic ankle bracing worn by females during landings produces abnormal lower extremity mechanics. Angular kinematic and ground reaction force (GRF) data were obtained for 16 athletically experienced females who performed brace and no-brace drop landings. The brace condition displayed reduced in/external rotation and flexion displacements about the ankle and knee joints and increased vertical and mediolateral GRF peak magnitudes and rate of vertical GRF application (paired t test, P < .05). The ankle and knee joints landed in a less plantar flexed and more flexed position, respectively. No significant ab/adduction outcomes may have occurred due to interparticipant variability and/or a lack of brace restriction. Conclusion: During typical landings, this lace-up brace increases vertical GRF, decreases ankle and knee joint displacements of flexion and int/external rotation, but minimally affects ab/adduction displacements.
Numerical Simulation of Two-Phase Flow Around Flatwater Competition Kayak Design-Evolution Models
Authors: Mantha Vishveshwar R. , Silva António J. , Marinho Daniel A. , Rouboa Abel I.
Published: August 2016

The aim of the current study was to analyze the hydrodynamics of three kayaks: 97-kg-class, single-rower, flatwater sports competition, full-scale design evolution models (Nelo K1 Vanquish LI, LII, and LIII) of M.A.R. Kayaks Lda., Portugal, which are among the fastest frontline kayaks. The effect of kayak design transformation on kayak hydrodynamics performance was studied by the application of computational fluid dynamics (CFD). The steady-state CFD simulations where performed by application of the k-omega turbulent model and the volume-of-fluid method to obtain two-phase flow around the kayaks. The numerical result of viscous, pressure drag, and coefficients along with wave drag at individual average race velocities was obtained. At an average velocity of 4.5 m/s, the reduction in drag was 29.4% for the design change from LI to LII and 15.4% for the change from LII to LIII, thus demonstrating and reaffirming a progressive evolution in design. In addition, the knowledge of drag hydrodynamics presented in the current study facilitates the estimation of the paddling effort required from the athlete during progression at different race velocities. This study finds an application during selection and training, where a coach can select the kayak with better hydrodynamics.
Average Torsion Axis Location of Athletic Movements: Subject Specific or Movement Specific?
Authors: Graf Eveline S. , Stefanyshyn Darren J.
Published: August 2016

Foot torsion angles have previously been studied for different athletic movements. Sport shoes often contain a torsion element even though the location of the rotation axis of the foot is unknown. Therefore, the purpose of this study was to quantify the torsion axis location and determine if the location is influenced by the movement or the subject. The torsion axis location was calculated using a modified finite helical axis approach, which allowed the calculation of the rotation axis between the forefoot and the rearfoot without the influence of forefoot flexion. The torsion axis location during the lateral jab was 9.72 mm below and 26.96 mm lateral to a marker located at the posterior, central heel, whereas the shuffle cut resulted in an axis location of 9.59 mm below and 26.19 mm lateral to the reference marker. There was no significant difference for the average axis location between movements. There was, however, a significant difference for the location between subjects, indicating a subject specificity of the torsion axis. The results of the current study are the first to quantify the torsion axis location of the human foot during athletic movements.
Examination of Knee Joint Moments on the Function of Knee-Ankle-Foot Orthoses During Walking
Authors: Andrysek Jan , Klejman Susan , Kooy John
Published: August 2016

The goal of this study was to investigate clinically relevant biomechanical conditions relating to the setup and alignment of knee-ankle-foot orthoses and the influence of these conditions on knee extension moments and orthotic stance control during gait. Knee moments were collected using an instrumented gait laboratory and concurrently a load transducer embedded at the knee-ankle-foot orthosis knee joint of four individuals with poliomyelitis. We found that knee extension moments were not typically produced in late stance-phase of gait. Adding a dorsiflexion stop at the orthotic ankle significantly decreased the knee flexion moments in late stance-phase, while slightly flexing the knee in stance-phase had a variable effect. The findings suggest that where users of orthoses have problems initiating swing-phase flexion with stance control orthoses, an ankle dorsiflexion stop may be used to enhance function. Furthermore, the use of stance control knee joints that lock while under flexion may contribute to more inconsistent unlocking of the stance control orthosis during gait.
Sensors on the Humerus Are Not Necessary for an Accurate Assessment of Humeral Kinematics in Constrained Movements
Authors: Lin Yin-Liang , Karduna Andrew R.
Published: August 2016

The measurement of humeral kinematics with a sensor on the humerus is susceptible to large errors due to skin motion artifacts. An alternative approach is to use data from a forearm sensor, combined with data from either a scapular or thoracic sensor. We used three tasks to assess the errors of these approaches: humeral elevation, elbow flexion and humeral internal rotation. Compared with the humeral method, the forearm methods (using either a scapular or thoracic sensor) demonstrated significantly smaller root mean square errors in humeral elevation and humeral internal rotation tasks. Although the errors of the forearm methods were significantly larger than those of the humeral method during elbow flexion, the errors of the forearm methods still were below 3°. Therefore, these forearm methods may be able to accurately measure humeral motion. In addition, since no difference was found between the forearm methods using the scapular or thoracic sensor, it may be possible to accurately assess both shoulder and elbow kinematics with only two sensors: one on the forearm and one on the scapula.
Functional and Morphological Adaptations to Aging in Knee Extensor Muscles of Physically Active Men
Authors: Baroni Bruno Manfredini , Geremia Jeam Marcel , Rodrigues Rodrigo , Borges Marcelo Krás , Jinha Azim , Herzog Walter , Vaz Marco Aurélio
Published: August 2016

It is not known if a physically active lifestyle, without systematic training, is sufficient to combat age-related muscle and strength loss. Therefore, the purpose of this study was to evaluate if the maintenance of a physically active lifestyle prevents muscle impairments due to aging. To address this issue, we evaluated 33 healthy men with similar physical activity levels (IPAQ = 2) across a large range of ages. Functional (torque-angle and torque-velocity relations) and morphological (vastus lateralis muscle architecture) properties of the knee extensor muscles were assessed and compared between three age groups: young adults (30 ± 6 y), middle-aged subjects (50 ± 7 y) and elderly subjects (69 ± 5 y). Isometric peak torques were significantly lower (30% to 36%) in elderly group subjects compared with the young adults. Concentric peak torques were significantly lower in the middle aged (18% to 32%) and elderly group (40% to 53%) compared with the young adults. Vastus lateralis thickness and fascicles lengths were significantly smaller in the elderly group subjects (15.8 ± 3.9 mm; 99.1 ± 25.8 mm) compared with the young adults (19.8 ± 3.6 mm; 152.1 ± 42.0 mm). These findings suggest that a physically active lifestyle, without systematic training, is not sufficient to avoid loss of strength and muscle mass with aging.