bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Surface Sensor and Bone-Fixed Measurement of Humeral Motion
Authors: Ludewig Paula M. , Cook Thomas M. , Shields Richard K.
Published: August 2016

A common method of tracking humeral motion involves securing a thermoplastic cuff to the humerus with an electromagnetic sensor attached. The data on the accuracy of this technique are limited. This study addressed two questions: (a) How similar are surface and bone-fixed measurements of 3-D humeral rotations? (b) How similar are surface and bone-fixed measurements of 3-D humeral translations? Electromagnetic motion sensors were secured to a bone-fixed external humeral fixator, a surface humeral cuff, and the skin over the sternum and scapular acromion process. The 3-D data were collected during successive slow velocity (10–20°/second) repetitions of humeral active-assisted scapular plane abduction, sagittal plane flexion, and internal/external rotation with the arm adducted. Root mean square errors of surface measures compared to bone-fixed angular and translational values were calculated, and pairedt-tests were computed between the two methods. Root mean square errors for humeral rotations ranged from 1° (1%) for humeral elevation during scapular plane abduction to 7.5° (9%) for humeral internal/external rotation. Peak errors were under-representations of 5.7° for internal/external rotation during scapular plane abduction and 15.6° for internal rotation with the arm adducted at the side. Average translation errors ranged from 0.1 to 2.1 mm. Data from this study suggest that dynamic measurement of humeral motion with a surface humeral cuff sensor can be performed for certain slow velocity motions with root mean square errors less than 8°. Caution is called for when interpreting internal/external rotation values, which were underrepresented. Results may vary with one’s age, weight, or general physical condition, with different velocities of movement, or with different movements.
Dynamic Error Analysis of Ascension’s Flock of Birds™ Electromagnetic Tracking Device Using a Pendulum Model
Authors: McQuade Kevin J. , Finley Margaret A. , Harris-Love Michelle , McCombe-Waller Sandra
Published: August 2016

The use of magnetic tracking technology has become increasingly popular in recent years for human motion studies. However, there have been few independent evaluations of how these systems perform. The purpose of this study was to develop a dynamic pendulum calibration method to test the performance of magnetic tracking sensors. A nonmetallic pendulum was constructed and instrumented with a rotary potentiometer. A cube was attached to the distal end of the pendulum so that sensors could be mounted orthogonally. In this manner, it was possible to obtain simultaneous recordings of azimuth, elevation, and roll depending on the sensor mounting orientation relative to the axis of rotation of the pendulum. Sensor data, using Flock of Birds™ sensors, and potentiometer data were collected simultaneously during dynamic pendulum motion at two transmitter distances and then were compared. The results showed excellent trial-to-trial repeatability of 2% or better for the sensors, and high correlations between the sensor and potentiometer data. RMS errors range from about 3 to 10 mm depending on the angular velocity of the pendulum. Angular errors were less than 1 degree RMS for all speeds.
How Klapskate Hinge Position Affects Push-Off Mechanics in Speed Skating
Authors: Houdijk Han , de Koning Jos J. , Bobbert Maarten F. , de Groot Gert
Published: August 2016

In speed skating, the conventional skate has been replaced by the klapskate, in which the shoe can rotate around a hinge between shoe and blade. It has been hypothesized that the improved performance with klapskates vs. conventional skates can be attributed to the difference in the anterior/posterior position of the foot’s center of rotation relative to the ice. This study investigated the effect of the position of the foot’s center of rotation on push-off mechanics in speed skating. Eight elite speed skaters skated four 2000-m trials on instrumented klapskates at a fixed velocity. In each trial the hinge was placed at a different position between the 5th metatarso-phalangeal joint and the tip of the toes. 3-D kinematics and pushoff forces were measured to analyze push-off kinematics and kinetics. Shifting the hinge from the most posterior to the more anterior positions resulted in a delayed onset of foot rotation and longer duration of push-off. This delay coincided with an increase in angular displacement and peak angular velocity of the knee and hip joint, an increase in the flexing knee joint moment at the end of the push-off, and a reduction in work generated at the knee joint. Total work per stroke was similar for the various hinge positions. Besides the similar work per stroke, the observed effects are in accordance with the differences between klapskating and conventional skating. It was concluded that the position of the foot’s center of rotation affects the timing of foot rotation, and therefore the balanced pattern of segmental rotations. Although it could not be proven in this study, it was shown that this constraint could affect work per stroke and might explain the difference between klapskates and conventional skates.
Trunk Motion of Male Professional Golfers Using Two Different Golf Clubs
Authors: Lindsay David M. , Horton John F. , Paley Robert D.
Published: August 2016

Low back problems account for the largest proportion of injuries among amateur and professional golfers. However, there is little data on how the trunk or spine moves during a golf swing. Also, it may be that different golf clubs produce different trunk motion characteristics. The purpose of this study was to compare trunk range of motion (ROM) and velocity in three movement planes during the execution of a full golf swing using a driver and a 7-iron. Forty-four members of the Alberta Professional Golf Association volunteered to participate in this study. Trunk ROM and velocities in the sagittal, frontal, and transverse planes were measured using a triaxial electrogoniometer. Results showed that significantly more trunk flexion was required when setting up to hit the ball with the 7-iron compared to the driver,p< 0.05. During the swing, significantly greater maximum flexion and left-side-bend ROM occurred when using the 7-iron,p< 0.05. Maximum right-side-bending velocity during the golf swing was also significantly greater with a 7-iron. These findings suggest that differences in shaft length and ball positioning associated with the different clubs affects swing mechanics and trunk/spinal motion. In particular, the shorter club (7-iron) tended to place more emphasis on lateral trunk motion than did the driver. The results from this study may help clinicians better understand how the golf swing creates stress on the back as well as how club fitting may affect trunk motion characteristics.
Validation of the Volume Function within Jensen’s (1978) Elliptical Cylinder Model
Authors: Wicke Jason , Lopers Becky
Published: August 2016

An elliptical cylinder model developed by Jensen (1978) has been a widely accepted method for determining human segment inertial parameters. The goal of the present study was to evaluate the accuracy of the segment volume calculation step of this model. Three possible sources of error were examined: between-sex differences in body shape, image ratio, and human inconsistencies in digitizing. Volume estimates for the right lower arm + right hand, right lower leg + right foot, and whole body on 20 young men and women were calculated from digitized images at a ratio of 1:10 and 1:5 of the actual size (measured) and compared to values measured using an underwater displacement technique (criterion). Results showed no differences between the sexes on the accuracy of estimating the three volumes at either image ratio. Combining both sexes, the error in calculating segment volumes with an image-to-actual-size ratio of 1:10 were significantly larger, p < 0.05, than at a ratio of 1:5 for both the lower arm + hand (4.28 ± 2.92% vs. –0.43 ± 2.49%) and the whole body (4.80 ± 2.49% vs. 2.01 ± 2.17%). There was no significant change in mean for the lower leg + foot when the image was increased from 1:10 to 1:5 (–0.12 ± 3.92% vs. –0.81 ± 3.01%, respectively). Although not statistically significant, p > 0.05, a greater magnification seemed to have also reduced the influence of human inconsistencies, which was found to be a primary source of error. When the image-to-actual-size ratio is high (i.e., 1:5) and precaution is taken during digitization, the elliptical cylinder model provides accurate estimates of segment volumes of the whole body and extremities.
Lower Extremity Biomechanics Differ in Prepubescent and Postpubescent Female Athletes during Stride Jump Landings
Authors: Hass Chris J. , Schick Elizabeth A. , Chow John W. , Tillman Mark D. , Brunt Denis , Cauraugh James H.
Published: August 2016

Epidemiological evidence suggests the incidence of injury in female athletes is greater after the onset of puberty and that landing from a jump is a common mechanism of knee injury. This investigation compared lower extremity joint kinematics and joint resultant forces and moments during three types of stride jump (stride jump followed by a static landing; a ballistic vertical jump; and a ballistic lateral jump) between pre- and postpubescent recreational athletes to provide some insight into the increased incidence of injury. Sixteen recreationally active postpubescent women (ages 18–25 years) and 16 recreationally active prepubescent girls (ages 8–11 years) participated in this study. High speed 3D videography and force plate data were used to record each jumper’s performance of the stride jumps, and an inverse dynamic procedure was used to estimate lower extremity joint resultant forces and moments and power. These dependent variables were submitted to a 2 × 3 (Maturation Level × Landing Sequence) MANOVA with repeated measures on the last factor. The findings indicated that postpubescents landed with the knee more extended (4.4°) and had greater extension moments (approximately 30% greater hip and knee extension moments) and powers (40% greater knee power). Further, the post-pubescent athletes had greater knee anterior/posterior forces as well as medio-lateral resultant forces. The differences found between the two groups suggest there may be anatomical and physiological changes with puberty that lead to differences in strength or neuromuscular control which influence the dynamic restraint system in these recreational athletes. A combination of these factors likely plays a role in the increased risk of injury in postpubescent females.
Development and Reliability of a Measurement Device for Flexion Force of the First Metatarsophalangeal Joint
Authors: Swanenburg Jaap , Stappaerts Karel H. , Tirez Bart , Uebelhart Daniel , Aufdemkampe Geert
Published: August 2016

The purpose of this study was to present a method for repeated measurement of flexion force of the hallux in the metatarsophalangeal joint. The reliability of this measurement device was also examined. This device is suitable for situations where weight-bearing is contraindicated or when it is not possible for patients to bear load on their toes, such as hallux valgus patients. Since most such patients are female, the participants in this study were 24 healthy female volunteers. Age, weight, height, and leg dominance were determined for each. Muscle strength was measured using a device with a built-in MicroFET dynamometer. The result for the left hallux was ICC(3,1) .89 (95% CI .77–.95). The result for the right hallux was ICC(3,1) .94 (95% CI .87–.97). In the Bland and Altman plots, the reliability again appeared to be sufficient. The Pearson product-moment correlations gave poor results for the association between body weight, height, age, and mean force of the four trails. The test results indicate good reliability of the measurement device as used in this study. The advantage of this testing device is that it makes it easier to standardize measurements as opposed to the MicroFET used as a hand-held dynamometer. Also, patients can be tested in a nonload situation, which makes it possible to test hallux valgus at any time, and therefore it is possible to monitor variations in progression (or regression).
Quantifying Active Ankle Range of Motion in Cerebral Palsy Following Selective Dorsal Rhizotomy
Authors: Engsberg Jack R. , Ross Sandy A. , Park Tae S.
Published: August 2016

This study was conducted to determine whether an objective and quantitative measure for active ankle range of motion would be sensitive to differences between persons of able body and those with cerebral palsy (CP), and between pre- and postselective dorsal rhizotomy (SDR). Twelve children with spastic diplegia CP were tested before undergoing an SDR, and again after 8 months of intensive physical therapy (SDR group). Fourteen other children with spastic diplegia were tested initially and again 8 months following no intervention but maintaining their existing level of physical therapy (CP group). Twenty age-matched children of able body were tested once (AB group). A video system recorded active sagittal plane ankle movements as the seated child independently performed maximum dorsiflexion and plantarflexion. The data were tracked and analyzed to determine end-range dorsiflexion and plantarflexion, and total active ankle range of motion. Repeated-measures ANOVA and Tukey post hoc tests were used to test for significant differences among and between groups,p< 0. 05. Results for the SDR group indicated a significant increase in end-range dorsiflexion and total range of motion following the surgery, with no changes in any measures for the CP group. Results for both groups with CP indicated differences vs. the AB group. The measure provided additional information from what has previously been reported for active ankle range of motion. The integration of this measure with other objective measures for quantifying impairments and presurgical function may be useful in predicting post-SDR gait status and other functional activities.
Trunk Flexion and Musculoskeletal Stress during Light Assembly Work
Authors: Paquet Victor , Nirmale Ranjit
Published: August 2016

Mild trunk flexion held during working tasks throughout the day is considered a risk factor for low back pain. Exactly how the duration of these postures impacts the low back musculature during work tasks is not well understood. The objective of this study was to evaluate the effects of the temporal variation of mild trunk flexion and erect standing postures on low back discomfort and muscular fatigue, defined as a decrease in torso extension strength, during a realistic light assembly task. Study participants performed light assembly tasks for 20 minutes while in mild trunk flexion for periods of either 30 or 60 seconds, followed by recovery periods in which they stood erect, for periods of either 15, 30, 60, or 120 sec. Localized muscle discomfort, decreases in torso extension strength, and muscle activity of erector spinae were recorded. Duration of recovery period had a statistically significant effect on localized muscle discomfort of the lower back, upper back, and shoulders. Duration of trunk flexion and recovery time had an interactive effect on decreases in torso extension strength, for which strength decreased with decreasing recovery time and was more pronounced for trunk flexion periods of 60 sec rather than 30 sec. The mean RMS erector spinae muscle activity during mild trunk flexion was approximately 25% of the measured maximum voluntary RMS muscle activity across all conditions. The results suggest that it is the temporal pattern of muscular trunk flexion, and not the total time spent in trunk flexion, that affects localized discomfort and muscular fatigue of the low back.
Musculoskeletal Loads in Ergometer Rowing
Authors: Hase Kazunori , Kaya Motoshi , Zavatsky Amy B. , Halliday Suzanne E.
Published: August 2016

Rowing ergometers can be found in most gyms and fitness centers, but many people who use them regularly have little or no instruction in rowing technique. It is not known whether nonrowers who regularly practice ergometer rowing are at risk of musculoskeletal problems. This study was done to quantify the differences in kinematics, kinetics, and musculoskeletal loading of competitive rowers and nonrowers during ergometer rowing. An experiment was performed to collect kinematic, external force, and EMG data during er-gometer rowing by 5 university-level competitive rowers and 5 nonrowers. Kinematic and external force data were input to a 3-D whole-body musculo-skeletal model which was used to calculate net joint forces and moments, muscle forces, and joint contact forces. The results showed that competitive rowers and nonrowers are capable of rowing an ergometer with generally similar patterns of kinematics and kinetics; however, there are some potentially important differences in how they use their legs and trunk. The competitive rowers generated higher model quadriceps (vastus) muscle forces and pushed harder against the foot cradle, extending their knees more and their trunks less than the nonrowers during the drive phase. They also had higher contact forces at the knee and higher peak lumbar and knee flexion moments. The ratio of average peak vastus force to average peak erector spinae force in the experienced rowers was 1.52, whereas it was only 1.18 in the nonexperienced rowers.
Use of Lumbar Point for the Estimation of Potential and Kinetic Mechanical Power in Running
Authors: Slawinski Jean , Billat Véronique , Koralsztein Jean-Pierre , Tavernier Michel
Published: August 2016

The purpose of this study was to estimate the difference between potential and kinetic mechanical powers in running (Pke, Ppe) calculated from the center of mass and one anatomic point of the body located on the lower part of the runner's back, the “lumbar point.” Six runners undertook a treadmill run at constant velocity and were filmed individually with a video camera (25 Hz). The 3-D motion analysis system, ANIMAN3D, uses a numerical manikin (MAN3D) which compares a voluminal subject (the athlete) directly to the manikin which possesses the same voluminal properties. This analysis system allows the trajectories of the center of mass and the lumbar point to be calculated. Then, from these trajectories, potential and kinetic mechanical powers in running are calculated. The results show that the utilization of the lumbar point rather than the runner's center of mass leads to a significant overestimation of Pkeand a significant underestimation of Ppe(bothp< 0.05). In spite of these differences, however, both methods of calculating Pkeand Ppeare well correlated: respectively,r= 0.92;p≤ 0.01, andr= 0.68;p≤ 0.05. Taking into account that the trajectory of an anatomic point is experimentally easier to access than that of the center of mass, such a point could be used to estimate the evolution of kinetic or potential energy variation in different cases. However, when the lumbar point rather than the center of mass is used to estimate the mechanical energy produced in running, Pkecould appear to be a discriminating parameter, which it is not.
Forward Dynamics of Two-Dimensional Skeletal Models. A Newton-Euler Approach
Authors: Casius L.J. Richard , Bobbert Maarten F. , van Soest Arthur J.
Published: August 2016

Mathematical modeling and computer simulation play an increasingly important role in the search for answers to questions that cannot be addressed experimentally. One of the biggest challenges in forward simulation of the movements of the musculoskeletal system is finding an optimal control strategy. It is not uncommon for this type of optimization problem that the segment dynamics need to be calculated millions of times. In addition, these calculations typically consume a large part of the CPU time during forward movement simulations. As numerous human movements are two-dimensional (2-D) to a reasonable approximation, it is extremely convenient to have a dedicated, computational efficient method for 2-D movements. In this paper we shall present such a method. The main goal is to show that a systematic approach can be adopted which allows for both automatic formulation and solution of the equations of kinematics and dynamics, and to provide some fundamental insight in the mechanical theory behind forward dynamics problems in general. To illustrate matters, we provide for download an example implementation of the main segment dynamics algorithm, as well as a complete implementation of a model of human sprint cycling.
Effects of Various Midsole Densities of Basketball Shoes on Impact Attenuation during Landing Activities
Authors: Zhang Songning , Clowers Kurt , Kohstall Charles , Yu Yeon-Joo
Published: August 2016

The purpose of this study was to examine effects of shoe midsole densities and mechanical demands (landing heights) on impact shock attenuation and lower extremity biomechanics during a landing activity. Nine healthy male college athletes performed 5 trials of step-off landing in each of 9 test conditions, i.e., a combination of landings in shoes of 3 midsole densities (soft, normal, hard) from each of 3 landing potential energy (PE) levels (low, median, high). Ground reaction forces (GRF), accelerations (ACC) of the tibia and forehead, and sagittal kinematic data were sampled simultaneously. A 3 × 3 two-way (surface × height) repeated-measures analysis of variance (ANOVA) was performed on selected kinematic, ACC, and GRF variables; a 3 × 3 × 3 three-way (surface × height × joint) ANOVA was performed on variables related to eccentric muscular work. The GRF results showed that the forefoot peak GRF in the normal and hard midsoles was significantly greater than the soft midsole at the low and median PEs. Rearfoot peak GRF was significantly greater for the hard midsole than for the soft and normal midsoles at the median and high PEs, respectively. The peak head and tibia peak ACC were also attenuated in similar fashion. Kinematic variables did not vary significantly across different midsoles, nor did energy absorbed through lower extremity extensors in response to the increased shoe stiffness. Knee joint extensors were shown to be dominant in attenuating the forefoot impact force across the landing heights. The results showed limited evidence of impact-attenuating benefits of the soft midsole in the basketball shoes.
Estimation of Passive Ankle Joint Moment during Standing and Walking
Authors: Muraoka Tetsuro , Muramatsu Tadashi , Takeshita Daisuke , Kanehisa Hiroaki , Fukunaga Tetsuo
Published: August 2016

This study estimated the passive ankle joint moment during standing and walking initiation and its contribution to total ankle joint moment during that time. The decrement of passive joint moment due to muscle fascicle shortening upon contraction was taken into account. Muscle fascicle length in the medial gastrocnemius, which was assumed to represent muscle fascicle length in plantarflexors, was measured using ultrasonography during standing, walking initiation, and cyclical slow passive ankle joint motion. Total ankle joint moment during standing and walking initiation was calculated from ground reaction forces and joint kinematics. Passive ankle joint moment during the cyclical ankle joint motion was measured via a dynamometer. Passive ankle joint moment during standing and at the time (Tp) when the MG muscle-tendon complex length was longest in the stance phase during walking initiation were 2.3 and 5.4 Nm, respectively. The muscle fascicle shortened by 2.9 mm during standing compared with the length at rest, which decreased the contribution of passive joint moment from 19.9% to 17.4%. The muscle fascicle shortened by 4.3 mm at Tp compared with the length at rest, which decreased the contribution of passive joint moment from 8.0% to 5.8%. These findings suggest that (a) passive ankle joint moment plays an important role during standing and walking initiation even in view of the decrement of passive joint moment due to muscle fascicle shortening upon muscle contraction, and (b) muscle fascicle shortening upon muscle contraction must be taken into account when estimating passive joint moment during movements.
Gender Differences in Lower Extremity Coupling Variability during an Unanticipated Cutting Maneuver
Authors: Pollard Christine D. , Heiderscheit Bryan C. , van Emmerik Richard E.A. , Hamill Joseph
Published: August 2016

The purpose of this study was to determine if gender differences exist in the variability of various lower extremity (LE) segment and joint couplings during an unanticipated cutting maneuver. 3-D kinematics were collected on 24 college soccer players (12 M, 12 F) while each performed the cutting maneuver. The following intralimb couplings were studied: thigh rotation (rot)/leg rot; thigh abduction-adduction/leg abd-add; hip abd-add/knee rot; hip rot/knee abd-add; knee flexion-extension/knee rot; knee flx-ext/hip rot. A vector-coding technique applied to angle-angle plots was used to quantify the coordination of each coupling. The average between-trial standard deviation of the coordination pattern during the initial 40% of stance was used to indicate the coordination variability. One-tailed t-tests were used to determine differences between genders in coordination variability for each coupling. Women had decreased variability in four couplings: 32% less thigh rot/leg rot variability; 40% less thigh abd-add/leg abd-add variability; 46% less knee flx-ext/knee rot variability; and 44% less knee flx-ext/hip rot variability. These gender differences in LE coordination variability may be associated with the increased incidence of ACL injury in women. If women exhibit less flexible coordination patterns during competition, they may be less able to adapt to the environmental perturbations experienced during sports. These perturbations applied to a less flexible system may result in ligament injury.
An Ankle-Foot Orthosis Powered by Artificial Pneumatic Muscles
Authors: Ferris Daniel P. , Czerniecki Joseph M. , Hannaford Blake
Published: August 2016

We developed a pneumatically powered orthosis for the human ankle joint. The orthosis consisted of a carbon fiber shell, hinge joint, and two artificial pneumatic muscles. One artificial pneumatic muscle provided plantar flexion torque and the second one provided dorsiflexion torque. Computer software adjusted air pressure in each artificial muscle independently so that artificial muscle force was proportional to rectified low-pass-filtered electromyography (EMG) amplitude (i.e., proportional myoelectric control). Tibialis anterior EMG activated the artificial dorsiflexor and soleus EMG activated the artificial plantar flexor. We collected joint kinematic and artificial muscle force data as one healthy participant walked on a treadmill with the orthosis. Peak plantar flexor torque provided by the orthosis was 70 Nm, and peak dorsiflexor torque provided by the orthosis was 38 Nm. The orthosis could be useful for basic science studies on human locomotion or possibly for gait rehabilitation after neurological injury.
Kinematics and Kinetics of the Racket-Arm during the Soft-Tennis Smash under Match Conditions
Authors: Ida Hirofumi , Kusubori Seiji , Ishii Motonobu
Published: August 2016

The purposes of this study were to (a) describe the racket-arm kinematics and kinetics of the soft-tennis smash during match rallies, and (b) assess the characteristics of this smash vs. the laboratory-simulated smash of our previous study. In the current study we recorded soft-tennis smash motions during match play of the 3rd East Asian Games. Racket-arm anatomical joint angular velocity and anatomical joint torque were calculated from 3-D coordinate data of 13 collected motions obtained using the direct linear transformation procedure. The results showed that most of the maximum values of the anatomical joint torques were qualitatively smaller than those of the tennis serve. Peak elbow extension, shoulder internal rotation, and elbow varus torques in match play were significantly greater than values reported for laboratory-simulated conditions. The greater forward swing torques did not result in significantly different racket head velocity, possibly because there was a significantly shorter forward swing phase in match conditions. In particular, a clear peak of the elbow extension torque during the forward swing phase was the most characteristic pattern in the smashes under match conditions, for it was 160% greater than laboratory-simulated conditions. These results supported our hypothesis that racket-arm kinematic and kinetic characteristics of the smash under match conditions differ from those under laboratory-simulated conditions. Possible explanations include the time-pressure conditions of the competitive situation in a match, and the Hawthorne effect (Hudson et al., 1986), both of which alter performance between match conditions and laboratory-simulated conditions.
Measurement of in Vivo Lumbar Intervertebral Disc Pressure during Spinal Manipulation: A Feasibility Study
Authors: Lisi Anthony J. , O’Neill Conor W. , Lindsey Derek P. , Cooperstein Robert , Cooperstein Elaine , Zucherman James F.
Published: August 2016

This paper presents the first reported measurements of lumbar intervertebral disc pressure in vivo during spinal manipulation. A pressure transducer was inserted into the nucleus pulposus of one normal-appearing lumbar disc in an asymptomatic adult volunteer. Pressures were recorded during several body positions and maneuvers, then during spinal manipulation, and lastly during a repetition of the preintervention body positions. Baseline pressures in the prone and side-lying positions measured 110 kPa and 150 kPa, respectively. During the manipulation, pressure rose to a peak of 890 kPa over 250 ms. Immediately following, pressures in the prone and side-lying positions measured 150 kPa and 165 kPa, respectively. These data do not support the hypotheses that manipulation can reduce a herniation by decreasing intradiscal pressure, or cause a herniation by raising pressure to failure levels. Further work may lead to a better understanding of this treatment method.
The Roche Vault Performed by Elite Gymnasts: Somersaulting Technique, Deterministic Model, and Judges’ Scores
Authors: Takei Yoshiaki
Published: August 2016

The purpose of the study was to determine the mechanical variables that are related to successful post-flight somersaulting performance of the Roche vault. The 23 Roche vaults performed during the 2000 Olympic Games were filmed by a 16-mm camera operating at 100 Hz. The 2-D direct linear transformation technique was used for spatial calibration. Approximately 60 frames were digitized per vault. The method of Hay and Reid (1988) was used to develop a deterministic model to identify the mechanical variables that govern linear and angular motions of the vault. Correlational analysis was used to establish the strength of the relationship between the mechanical variables identified and the judges’ scores. Significant correlations indicated that the higher judges’ scores were negatively related to five mechanical variables and positively related to seventeen variables in the model. The normalized horizontal displacement of body center of mass (CM) from the knee grasp to the peak of post-flight was the best single predictor of the judges’ score and accounted for 50% of variation in the judges’ score. Finally, the landing point deductions and the official horizontal distance of post-flight collectively accounted for 86% of the variance in the judges’ scores.
The Ray Projection Method: A Numerical Approach for Determining Ideal Camera Placement
Authors: Manal Kurt , Gardinier Joseph
Published: August 2016

Data piloting is important to ensure accurate marker coordinate data and to minimize camera dropout. Camera dropout results when a camera fails to image a marker, which often occurs when markers merge or become occluded. In this article, we present the conceptual framework for a numerical method of determining where video cameras, if placed, would have an occluded or a merged view of the tracking markers. Experimental data are presented to demonstrate the efficacy of the method as a tool to complement existing data piloting procedures.
The Effect of a Knee Support on the Biomechanical Response of the Low Back
Authors: Shu Yu , Jiang Zongliang , Xu Xu , Mirka Gary A.
Published: August 2016

Stooping and squatting postures are seen in a number of industries (e.g., agriculture, construction) where workers must work near ground level for extended periods of time. The focus of the current research was to evaluate a knee support device designed to reduce the biomechanical loading of these postures. Ten participants performed a series of sudden loading tasks while in a semisquat posture under two conditions of knee support (no support and fully supported) and two conditions of torso flexion (45 and 60°). A weight was released into the hands of the participants who then came to steady state while maintaining the designated posture. As they performed this task, the EMG responses of the trunk extensors (multifidus and erector spinae) were collected, both during the “sudden loading” phase of the trial as well as the steady weight-holding phase of the trial. As expected, the effects of torso flexion angle showed significant decreases in the activation of the multifidus muscles with greater torso angle (indicating the initiation of the flexion–relaxation response). Interestingly, the results showed that the knee support device had no effect on the activation levels of the sampled muscles, indicating that the loss of the degree of freedom from the ankle joint during the knee support condition had no impact on trunk extensor muscle response. The a priori concern with regard to these supports was that they would tend to focus loading on the low back and therefore would not serve as a potential ergonomic solution for these stooping/semisquatting tasks. Because the results of this study did not support this concern, further development of such an intervention is underway.
Fusion Integration: COM Trajectory from a Force Platform
Authors: Brodie Matthew , Walmsley Alan , Page Wyatt
Published: August 2016

A fusion integration algorithm is used to estimate the one-dimensional center of mass (COM) trajectory from force platform data. The resulting COM trajectory combines the best attributes of several established algorithms used to estimate the COM trajectory, and it appears to have the advantage of being robust, accurate, continuous in its higher derivatives, and fast to obtain. In current research projects, variations of the fusion integration algorithm have been adapted by the authors for the analysis of postural balance and the sensing of limb orientations with inertial measurement units.
Differential Specific Mechanical Energy as a Quality Parameter in Racing Alpine Skiing
Authors: Supej Matej
Published: August 2016

An important question in alpine skiing is how to determine characteristics of well-performed ski turns, an issue that has become more crucial with the arrival of new carving skis. This article introduces a new method for estimating the quality of skiing at each point of observation based on mechanical energy behavior that can be measured using established motion analysis techniques. It can be used for single-or multiple-skier analyses for evaluation of skiing technique as well as racing tactics. An illustration of its use is shown by analyzing 16 top-level racers using a 3-D kinematical system and video recorded during an alpine ski world cup race. Based on energy behavior of several racers, it is demonstrated that the most direct line with shortest radius of turn is not necessarily the most effective strategy in contrast to what some coaches believe.
Discrepancies in Knee Joint Moments Using Common Anatomical Frames Defined by Different Palpable Landmarks
Authors: Thewlis Dominic , Richards Jim , Bower Judith
Published: August 2016

The aim was to investigate the effects of three anatomical frames using palpable anatomical landmarks of the knee on the net knee joint moments. The femoral epicondyles, femoral condyles, and tibial ridges were used to define the different anatomical frames and the segment end points of the distal femur and proximal tibia, which represent the origin of the tibial coordinate system. Gait data were then collected using the calibrated anatomical system technique (CAST), and the external net knee joint moments in the sagittal, coronal, and transverse planes were calculated based upon the three anatomical frames. Peak knee moments were found to be significantly different in the sagittal plane by approximately 25% (p ≤ 0.05), but no significant differences were seen in the coronal or transverse planes. Based on these findings it is important to consider the definition of anatomical frames and be aware that the use of numerous anatomical landmarks around the knee can have significant effects on knee joint moments.
Upper-Limb Kinematics and Coordination of Short Grip and Classic Drives in Field Hockey
Authors: Brétigny Perrine , Seifert Ludovic , Leroy David , Chollet Didier
Published: August 2016

The aim of this study was to compare the upper-limb kinematics and coordination of the short grip and classic drives in field hockey. Ten elite female players participated in the experiment. The VICON system was used to record the displacement of markers placed on the stick and the players’ joints during five short grip and five classic drives. Kinematic and coordination parameters were analyzed. The ball’s velocity was recorded by a radar device that also served as the drive target. Kinematic differences were noted between the two drive conditions, with shorter duration and smaller overall amplitude in the short grip drive, explained by the shorter lever arm and the specific context in which it is used. No differences were noted for upper-limb coordination. In both types of stick holding, an interlimb dissociation was noted on the left side, whereas the right interlimb coordination was in phase. Moreover, the time lag increased in the disto-proximal direction, suggesting wrist uncocking before impact and the initiation of descent motion by the left shoulder. Mediolateral analysis confirmed these results: coordination of left-right limbs converged at the wrist but dissociated with more proximal joints (elbows and shoulders).
Evaluation of a Cruciate Ligament Model: Sensitivity to the Parameters during Drawer Test Simulation
Authors: Bertozzi Luigi , Stagni Rita , Fantozzi Silvia , Cappello Angelo
Published: August 2016

The knowledge of how cruciate ligaments stabilize the knee joint could be very useful during the execution of daily living activities for the development of clinical procedures. The objective of this study was to evaluate a cruciate ligament model that could achieve this knowledge while avoiding any destructive measurements in living healthy subjects. Subject-specific geometries and kinematic data, acquired from a living subject, were the foundations of the devised model. Each cruciate ligament was modeled with 25 linear-elastic elements and their geometrical properties were subject specific. The anteroposterior drawer test was simulated, and the sensitivity to the reference length and the elastic modulus was performed. Laxity, anterior, and posterior stiffness were calculated and compared with the literature. The laxity was most sensitive to reference length but fitted the literature well considering the reference length estimated from the subject. Both stiffnesses were most sensitive to elastic modulus variations. At full extension, anterior stiffness overestimated the literature, but at 90° good comparisons with the literature were obtained. Posterior stiffness showed smaller overestimations. The devised model, when properly improved, could evaluate the role of the cruciate ligaments of a living subject during the execution of daily living activities.
Shorter Oars Are More Effective
Authors: Nolte Volker
Published: August 2016

The purpose of this investigation was to clarify the effects of blade design and oar length on performance in rowing. Biomechanical models and equations of motion were developed to identify the main forces that affect rowing performance. In addition, the mechanical connection between the propelling blade force and the force that the rower applies on the handle was established. On this basis it was found that the blade design and oar dimensions play a significant role on the rowing performance. While rowers have found empirically that larger and/or hydrodynamically more efficient blade shapes need to be rowed with shorter oars, this article explains this tendency from a biomechanical point of view. Based on the presented evidence, it can be concluded that shorter oars will allow rowers to improve the propelling forces without increasing the handle forces. These findings explain tendencies that started with the introduction of new blade shapes in 1991. A 2 × 2 factorial ANOVA was used to test the significance of the oar shortenings that occurred with the introduction of larger blade surfaces while international record times improved during all those years. Consequently, the findings of this investigation encourage coaches to further experiment with shorter oars and oar manufacturers to continue their blade development that would lead to even shorter oars, with the goal of continuous rowing performance improvements.
A Comparison between Two Models of Shoulder Muscle Force Estimation
Authors: Ribeiro Daniel Cury , de Toledo Joelly Mahnic , Krug Roberto Costa , Loss Jefferson Fagundes
Published: August 2016

Shoulder injuries are often related to rotator cuff muscles. Although there are various models for muscle force estimation, it is difficult to ensure that the results obtained with such models are reliable. The aim of the current study was to compare two models of muscle force estimation. Eight subjects, seven male and one female (mean age of 24 yr; mean height of 1.83 m), performed five isokinetic maximum concentric contractions of internal and external shoulder rotation. Two models with different algorithms were used. In both, the input data consisted of the measured internal rotation moment. Comparisons were made between the difference and the average results obtained with each model of muscle force estimation. There was reasonable agreement among the results for force between the two models for subscapularis, pectoralis major, and anterior deltoideus muscles results. Conversely, poor correlation was found for the latissimus dorsi, teres major, and middle deltoid. These results suggest that the algorithm structure might have a strong effect on muscle force estimation results.
Material Property Sensitivity Analysis on Resonant Frequency Characteristics of the Human Spine
Authors: Guo Li-Xin , Wang Zhao-Wen , Zhang Yi-Min , Lee Kim-Kheng , Teo Ee-Chon , Li He , Wen Bang-Chun
Published: August 2016

The aim of this study is to investigate the effect of material property changes in the spinal components on the resonant frequency characteristics of the human spine. Several investigations have reported the material property sensitivity of human spine under static loading conditions, but less research has been devoted to the material property sensitivity of spinal biomechanical characteristics under a vibration environment. A detailed three-dimensional finite element model of the human spine, T12– pelvis, was built and used to predict the influence of material property variation on the resonant frequencies of the human spine. The simulation results reveal that material properties of spinal components have obvious influences on the dynamic characteristics of the spine. The annulus ground substance is the dominant component affecting the vertical resonant frequencies of the spine. The percentage change of the resonant frequency relative to the basic condition was more than 20% if Young’s modulus of disc annulus is less than 1.5 MPa. The vertical resonant frequency may also decrease if Poisson’s ratio of nucleus pulposus of intervertebral disc decreases.
Torso and Hip Muscle Activity and Resulting Spine Load and Stability while Using the ProFitter 3-D Cross Trainer
Authors: Banerjee Priyanka , Brown Stephen H.M , Howarth Samuel J. , McGill Stuart M.
Published: August 2016

The ProFitter 3-D Cross Trainer is a labile surface device used in the clinic and claimed to train spine stability. The purpose of this study was to quantify the spine mechanics (compression and shear forces and stability), together with muscle activation mechanics (surface electromyography) of the torso and hip, during three ProFitter exercises. Trunk muscle activity was relatively low while exercising on the device (<25%MVC). Gluteus medius activity was phasic with the horizontal sliding position, especially for an experienced participant. Sufficient spinal stability was achieved in all three exercise conditions. Peak spinal compression values were below 3400 N (maximum 3188 N) and peak shear values were correspondingly low (under 500 N). The exercises challenge whole-body dynamic balance while producing very conservative spine loads. The motion simultaneously integrates hip and torso muscles in a way that appears to ensure stabilizing motor patterns in the spine. This information will assist with clinical decision making about the utility of the device and exercise technique in rehabilitation and training programs.
The Effects of Walking Speed on Multisegment Foot Kinematics in Adults
Authors: Tulchin Kirsten , Orendurff Michael , Adolfsen Stephen , Karol Lori
Published: August 2016

Multisegment foot models provide researchers more-detailed information regarding foot mechanics compared with single rigid body foot models. Previous work has shown that walking speed significantly affects sagittal plane ankle motion. It is important to distinguish changes in intersegment foot mechanics following treatment that are due to clinical intervention versus those due to walking speed alone. Foot and ankle kinematics were collected on 24 adults walking at 5 speeds. Significant differences were seen at the ankle using a single rigid body foot model, as well as at the hindfoot and forefoot using a multisegment foot model, with all motions exhibiting a shift toward plantar flexion and decreased stance time with increasing speed. When evaluating foot mechanics using a multisegment foot model across groups or conducting intrasubject comparison over time/treatments, it is imperative that walking speed be accounted for or controlled.
Foot Orthotic Devices Decrease Transverse Plane Motion during Landing from a Forward Vertical Jump in Healthy Females
Authors: Jenkins Walter L. , Williams Dorsey Shelton , Durland Alex , Adams Brandon , O’Brien Kevin
Published: August 2016

The use of foot orthoses has been evaluated during a variety of functional activities. Twelve college-aged active females wore two types of foot orthoses and performed a vertical jump to determine the biomechanical effect of the orthoses on lower extremity transverse plane movement during landing. Data collection included three-dimensional analysis of the tibia, knee, and hip. A repeated-measures ANOVA was performed to determine the differences between no orthoses, over-the-counter, and custom-made orthoses with transverse plane motion. At the hip joint, there was significantly less internal rotation (p < .05) in the over-the-counter condition as compared with the no orthoses condition. There was significantly less tibial internal rotation (p < .05) in the custom-made condition as compared with no orthoses. Over-the-counter devices decreased transverse plane motion at the hip, whereas custom-made devices decreased transverse plane motion of the tibia.