bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of the Quadriceps Muscles in Patients with Anterior Knee Pain
Authors: Suter Esther , Herzog Walter , De Souza Kelly , Bray Robert
Published: August 2016

The present study was aimed at determining muscle inhibition (MI) and knee extensor moments in 42 subjects with unilateral anterior knee pain syndrome. The results were compared to a normal, healthy population with no history of knee injury. Also, the effects of 1 week of a nonsteroidal anti-inflammatory drug (NSAID) on MI and knee extensor moments were tested in a randomized controlled trial. At baseline, the involved leg showed significantly higher MI than the noninvolved leg. In both legs, MI was significantly higher and knee extensor moments lower than the corresponding values of the nonimpaired subjects. There was a direct relationship between knee pain during testing and the extent of MI. Higher MI, in turn, was associated with lower knee extensor moments. The study demonstrated significant MI in the quadriceps muscles of the involved and noninvolved legs of subjects with unilateral anterior knee pain syndrome. The results indicate that the noninvolved leg cannot be considered a normal control for a contralateral injury. NSAIDs did not affect MI or knee extensor moments, despite significantly reducing pain. This finding suggests that factors other than pain are responsible for the MI observed in this specific subject population, or that after removal of pain, more time is required to fully restore muscle function.
A Neuromuscular and Metabolic Comparison between Forward and Reverse Pedaling
Authors: Bressel Eadric , Heise Gary D. , Bachman Greg
Published: August 2016

The purpose of this study was to determine how muscle activity and oxygen consumption are influenced by reverse pedaling (RP) compared to forward pedaling (FP). Seventeen physically active males performed FP and RP at an external workrate of 157 W (80 rpm) while EMG data were collected from five muscles: rectus femoris (RF), biceps femoris (BF), gastrocnemius (GN), tibialis anterior (TA), and vastus medialis (VM). Oxygen consumption (V̇O2 L·min-1) data were collected. On-time durations and EMG amplitudes were quantified for each half-cycle (first 180° and second 180° of crank angle). V̇O2 was similar between pedaling conditions while muscles RF and BF exhibited phasic shifts in response to RP with no amplitude change. VM showed an increase and GN displayed a decrease in EMG amplitude from FP to RP. The phasic shifts in muscle activation seen in RP, particularly in RF and BF, may alter the sequence of the knee extensor–hip extensor joint moments during the first half-cycle of pedaling.
Effort Distribution and Performance of Olympic Triple Jumpers
Authors: Hay James G.
Published: August 2016

The purposes of this study were to determine the frequency with which triple jumpers used hop-dominated, balanced, and jump-dominated techniques to achieve their best distances in Olympic competition; whether the use of one of these techniques generally yielded greater actual distances than did the use of the others; and how the actual distances achieved by specific athletes were related to the way in which they distributed their efforts through the three phases. Data were collected at the 1996 Olympic Games in Atlanta. About half the competitors used a hop-dominated technique. Balanced and jump-dominated techniques were just as effective as hop-dominated techniques. Four of the top eight finishers tended to use hop percentages that were longer than the optimum for them.
Contributions of Twisting Techniques Used in Backward Somersaults with One Twist
Authors: Yeadon Maurice R. , Kerwin David G.
Published: August 2016

At the 1996 Atlanta Olympic Games, 18 single somersaults with one twist in the women’s compulsory floor exercises were recorded using two video cameras. An 11 segment computer simulation model was used to analyze the twisting techniques used. It was found mat counter-rotation techniques accounted for less than one third of the twist for all gymnasts, indicating that the production of twist was mainly a consequence of the angular momentum and a non-zero tilt angle. Contributions to the tilt angle reached at the mid-twist position were used as measures of the twisting potential of various techniques. Contact techniques accounted for 30% of the tilt produced, the remainder being produced using aerial techniques, which primarily comprised a symmetrical lowering of the arms together with minor contributions from asymmetrical arm and hip movements. There was no evidence of a difference in technique between the highest and lowest scoring competitors.
Lower Extremity Joint Moments during Uphill Cycling
Authors: Caldwell Graham E. , Hagberg James M. , McCole Steve D. , Li Li
Published: August 2016

Lower extremity joint moments were investigated in three cycling conditions: level seated, uphill seated and uphill standing. Based on a previous study (Caldwell, Li, McCole, & Hagberg, 1998), it was hypothesized that joint moments in the uphill standing condition would be altered in both magnitude and pattern. Eight national caliber cyclists were filmed while riding their own bicycles mounted to a computerized ergometer. Applied forces were measured with an instrumented pedal, and inverse dynamics were used to calculate joint moments. In the uphill seated condition the joint moments were similar in profile to the level seated but with a modest increase in magnitude. In the uphill standing condition the peak ankle plantarflexor moment was much larger and occurred later in the downstroke than in the seated conditions. The extensor knee moment that marked the first portion of the down-stroke for the seated trials was extended much further into the downstroke while standing, and the subsequent knee flexor moment period was of lower magnitude and shorter duration. These moment changes in the standing condition can be explained by a combination of more forward hip and knee positions, increased magnitude of pedal force, and an altered pedal force vector direction. The data support the notion of an altered contribution of both muscular and non-muscular sources to the applied pedal force. Muscle length estimates and muscle activity data from an earlier study (Li & Caldwell, 1996) support the unique roles of mono-articular muscles for energy generation and bi-articular muscles for balancing of adjacent joint moments in the control of pedal force vector direction.
Quantification of Achilles Tendon Force Enhancement by Passively Induced Dorsiflexion Stretches
Authors: Nicol Caroline , Komi Paavo V.
Published: August 2016

Magnitude of the reflex contribution to force enhancement was investigated in vivo during passive stretches of the Achilles tendon (AT) of one female subject. Thirty passive (5 × 6) dorsiflexions were induced by a motorized ankle ergometer. Achilles tendon force (ATF) was sensed by a buckle transducer applied surgically around the right AT. Single passive stretches resulted in a low but rather linear ATF increase in the absence of EMG (surface electrodes) activity. In the presence of reflexes, a clear ATF enhancement occurred 13–15 ms after the beginning of the EMG reflex responses. In double dorsiflexions at either 1.2 or 1.9 rad · s-1, which were separated by a maintained stretched position of either 40 or 90 ms, the first stretch resulted in initial linear ATF increase, followed by an additional force enhancement during the plateau phase. This reflexly induced increase represented 94 ± 4 N and 184 ± 1 N, respectively, for the 40 and the 90 ms plateaus, corresponding to 210 ± 85% and 486 ± 177% enhancements as compared to the first passive stretch effect. The results suggest further that timing of the stretch during the twitch response influences the magnitude and rate of force potentiation.
Bicycle Pedal Kinetics Following Force Symmetry Feedback Training in Subjects with Unilateral Cerebrovascular Accident
Authors: Perell Karen L. , Gregor Robert J. , Scremin A.M. Erika
Published: August 2016

The purpose of this sludy was to compare individual pedal reaclion force components following bicycle training with and without effective force feedback in subjects with unilateral cerebrovascular accident (CVA). Eight ambulatory subjects with CVA were studied on a recumbent bicycle equipped with custom-built pedals, which measure normal and tangential components of the load applied to the pedal surface. Comparisons of normal and tangential pedal reaction forces were made following 1 month of bicycle training (3 times/week for 4 weeks) during retention tests performed without feedback. The ratios of involved to contralateral (I/C ratios) force parameters were used to assess symmetry. Subjects were randomly assigned to 2 groups: (a) a feedback group that received visual/verbal feedback regarding effective force patterns, bilaterally, after each trial; and (b) a no-feedback group dial received no feedback. Two critical results were found: (a) tangential pedal forces were significantly more posteriorly directed bilaterally following training across all subjects, but the change was greater for the no-feedback group relative to the feedback group, and (b) effective force feedback training did not demonstrate improvements in the I/C ratios above that of the control group. A more posteriorly applied tangential pedal force may represent increased dorsiflexion and may suggest that bicycle training facilitated ankle control. The cyclical nature of cycling, however, may allow for natural patterns to develop without feedback or may require less frequent use of feedback based on retention test performance.
Mechanical Modeling of Tibial Axial Accelerations Following Impulsive Heel Impact
Authors: Andrews David M. , Dowling James J.
Published: August 2016

A fourth order mass/spring/damper (MSD) mechanical model with linear coefficients was used to estimate axial tibial accelerations following impulsive heel impacts. A generic heel pad with constant stiffness was modeled to improve the temporal characteristics of the model. Subjects (n= 14) dropped (~5 cm) onto a force platform (3 trials), landing on the right heel pad with leg fully extended at the knee. A uni-axial accelerometer was mounted over the skin on the anterior aspect of the medial tibial condyle inferior to the tibial plateau using a Velcro™ strap (normal preload ~45 N). Model coefficients for stiffness (k1, k2) and damping (c1, c2) were varied systematically until the minimum difference in peak tibial acceleration (%PTAmin) plus maximum rate of tibial acceleration (%RTAmax) between the estimated and measured curves was achieved for each trial. Model responses to mean subject and mean group model coefficients were also determined. Subject PTA and RTA magnitudes were reproduced well by the model (%PTAmin= 1.4 ± 1.0 %, %RTAmin= 2.2 ± 2.7%). Model estimates of PTA were fairly repeatable for a given subject despite generally high variability in the model coefficients, for subjects and for the group (coefficients of variation: CVk1= 57; CVk2= 59; CVc1= 48; CVc2= 85). Differences in estimated parameters increased progressively when subject and group mean coefficients (%PTAsub= 8.4 ± 6.3%, %RTAsub= 18.9 ± 18.6%, and %PTAgrp= 19.9 ± 15.2 %, %RTAgrp= 30.2 ± 30.2%, respectively) were utilized, suggesting that trial specific calibration of coefficients for each subject is required. Additional model refinement seems warranted in order to account for the large intra-subject variability in coefficients.
Issues in Quantifying Variability from a Dynamical Systems Perspective
Authors: Hamill Joseph , Haddad Jeffrey M. , McDermott William J.
Published: August 2016

Variability is a critical aspect of a dynamical systems analysis. Because there are a number of numerical techniques that can be used in such an analysis, the calculation of variability has several issues that must be addressed. The purpose of this paper is to present a variety of quantitative methods for investigating variability from a dynamical systems perspective. The paper is divided into two major sections covering discrete and continuous methods. Each of these sections is subdivided into two sections. Within discrete methods, we discuss, first, the calculation of the discrete relative phase from a time-series history of two parameters and, second, the use of return maps. Using continuous methods, we present procedures for using angle-angle plots in the evaluation of relative phase. We then discuss the use of phase plots in the calculation of the continuous relative phase. Each of these methods presents unique problems for the researcher and the method to be used is determined by the nature of the question asked.
Movement Variability as a Clinical Measure for Locomotion
Authors: Heiderscheit Bryan C.
Published: August 2016

The purpose of this paper is to discuss the role of variability in human movement, with emphasis on locomotion variability. Based on the assessment of stride characteristics, movement variability has been associated with reduced gait stability and unsteadiness. However, based on the measure of joint coordination during locomotion, variability has been suggested to provide a source of adaptation. Therefore, it would appear that the assessment of movement coordination from either the task outcome (i.e., stride characteristics) or the joint coordination patterns provide distinctly opposing views of variability. This paper will discuss the use of the variability measures, specifically joint coordination variability, from a clinical perspective. Investigations will be presented in which a reduction in joint coordination variability has been associated with pathology. Finally, the clinical implications of these measures as well as treatment suggestions are discussed.
What Causes the Body to Roll in Front-Crawl Swimming?
Authors: Yanai Toshimasa
Published: August 2016

This study was conducted to describe the kinematics of bodyroll and investigate whether bodyroll was propelled primarily by the turning effect of the fluid forces (external torque) or by the reaction effect due to the acceleration of the limbs. The performances of 11 competitive swimmers were recorded using two panning periscopes, and the three-dimensional movement of the subjects was reconstructed from digitized video recordings. The external torque acting on the whole body was determined as the first time-derivative of the angular momentum of the whole body. The reaction effect of limb acceleration was determined as the first time-derivative of the angular momenta of the limbs. Shoulder roll and hip roll angles changed synchronously with the stroke frequency but their amplitudes were substantially different, indicating that the bodyroll consisted of a roll of the entire torso and a twist of the torso. The overall contribution of the external torque was to propel bodyroll, while that of the reaction effects of limb accelerations was to resist bodyroll. These results clearly indicate that the primary source for propelling bodyroll was the external torque. Implications towards the mechanical interactions among bodyroll, stroke frequency, and forward propulsion in front crawl swimming were discussed.
Relationship of Pelvis and Upper Torso Kinematics to Pitched Baseball Velocity
Authors: Stodden David F. , Fleisig Glenn S. , McLean Scott P. , Lyman Stephen L. , Andrews James R.
Published: August 2016

Generating consistent maximum ball velocity is an important factor for a baseball pitcher’s success. While previous investigations have focused on the role of the upper and lower extremities, little attention has been given to the trunk. In this study it was hypothesized that variations in pelvis and upper torso kinematics within individual pitchers would be significantly associated with variations in pitched ball velocity. Nineteen elite baseball pitchers were analyzed using 3-D high-speed motion analysis. For inclusion in this study, each pitcher demonstrated a variation in ball velocity of at least 1.8 m/s (range: 1.8–3.5 m/s) during his 10 fastball pitch trials. A mixed-model analysis was used to determine the relationship between 12 pelvis and upper torso kinematic variables and pitched ball velocity. Results indicated that five variables were associated with variations in ball velocity within individual pitchers: pelvis orientation at maximum external rotation of the throwing shoulder (p = .026), pelvis orientation at ball release (p = .044), upper torso orientation at maximum external rotation of the throwing shoulder (p = .007), average pelvis velocity during arm cocking (p = .024), and average upper torso velocity during arm acceleration (p = .035). As ball velocity increased, pitchers showed an increase in pelvis orientation and upper torso orientation at the instant of maximal external rotation of the throwing shoulder. In addition, average pelvis velocity during arm cocking and average upper torso velocity during arm acceleration increased as ball velocity increased. From a practical perspective, the athlete should be coached to strive for proper trunk rotation during arm cocking as well as strength and flexibility in order to generate angular velocity within the trunk for maximum ball velocity.
Interpretation of Ankle Joint Moments during the Stance Phase of Walking: A Comparison of Two Orthogonal Axes Systems
Authors: Hunt Adrienne E. , Smith Richard M.
Published: August 2016

Three-dimensional ankle joint moments were calculated in two separate coordinate systems, from 18 healthy men during the stance phase of walking, and were then compared. The objective was to determine the extent of differences in the calculated moments between these two commonly used systems and their impact on interpretation. Video motion data were obtained using skin surface markers, and ground reaction force data were recorded from a force platform. Moments acting on the foot were calculated about three orthogonal axes, in a global coordinate system (GCS) and also in a segmental coordinate system (SCS). No differences were found for the sagittal moments. However, compared to the SCS, the GCS significantly (p < .001) overestimated the predominant invertor moment at midstance and until after heel rise. It also significantly (p < .05) underestimated the late stance evertor moment. This frontal plane discrepancy was attributed to sensitivity of the GCS to the degree of abduction of the foot. For the transverse plane, the abductor moment peaked earlier (p < .01) and was relatively smaller (p < .01) in the GCS. Variability in the transverse plane was greater for the SCS, and attributed to its sensitivity to the degree of rearfoot inversion. We conclude that the two coordinate systems result in different calculations of nonsagittal moments at the ankle joint during walking. We propose that the body-based SCS provides a more meaningful interpretation of function than the GCS and would be the preferred method in clinical research, for example where there is marked abduction of the foot.
Anaerobic Cycling Power Output with Variations in Recumbent Body Configuration
Authors: Reiser Raoul F. , Peterson Michael L. , Broker Jeffrey P.
Published: August 2016

While the recumbent cycling position has become common for high-performance human-powered vehicles, questions still remain as to the influence of familiarity on recumbent cycling, the optimal riding position, and how recumbent cycling positions compare to the standard cycling position (SCP). Eight recumbent-familiar cyclists and 10 recreational control cyclists were compared using the 30-s Wingate test in 5 recumbent positions as well as the SCP. For the recumbent positions, hip position was maintained 15° below the bottom bracket while the backrest was altered to investigate body configuration angle (BCA: the angle between the bottom bracket, hip, and a marker at mid-torso) changes from 100° to 140° in 10° increments. Between-groups analysis found that only 4 of the 126 analyzed parameters differed significantly, with all trends in the same direction. Therefore both groups were combined for further analysis. Whole-group peak power (14.6 W/kg body mass) and average power (9.9 and 9.8 W/kg body mass, respectively) were greatest in the 130° and 140° BCA positions, with power dropping off as BCA decreased through 100° (peak = 12.4 W/kg body mass; avg. = 9.0 W/kg body mass). Power output in the SCP (peak = 14.6 W/kg body mass; avg. = 9.7 W/kg body mass) was similar to that produced in the 130° and 140° recumbent BCA. Average hip and ankle angles increased (became more extended/ plantar-flexed), 36° and 10°, respectively, with recumbent BCA, while knee angles remained constant. The lower extremity kinematics of the 130° and 140° BCA were most similar to those of the SCP. However, SCP hip and knee joints were slightly extended and the ankle joint was slightly plantar-flexed compared to these two recumbent positions, even though the BCA of the SCP was not significantly different. These findings suggest: (a) the amount of recumbent familiarity in this study did not produce changes in power output or kinematics; (b) BCA is a major determinant of power output; and (c) recumbent-position anaerobic power output matches that of the SCP when BCA is maintained, even though lower extremity kinematics may be altered.
Vector Coding: A Technique for Quantification of Intersegmental Coupling in Multicyclic Behaviors
Authors: Tepavac Dejan , Field-Fote Edelle Carmen
Published: August 2016

The evaluation of a vector coding technique to quantify intersegmental coupling within a limb over multiple cycles of walking is described. The angular position of the knee with respect to the hip during walking was examined based on relative motion plots generated from videographic data. Participants included one able-bodied individual and one with spinal cord injury; the latter was assessed before and after participating in an assisted walking program. Vector coding of the frame-to-frame changes in hip/knee relationship was used to quantify the relative motion plots. Vector analysis techniques were then used to produce a single value that represents the overall variability of the hip/knee coupling relationship over multiple cycles. Hypothetical and random data were also used to evaluate the coding algorithm. In addition, the technique was compared to an earlier method in the analysis of this same data. Vector coding provided an easily interpretable method of quantifying the intersegmental coupling relationships and assessing the degree of consistency in the intralimb coordination over multiple cycles. The measure is sensitive to change in the kinematic variables and appears to have good validity. In addition, this technique has advantages over prior techniques as it allows simultaneous comparison of multiple cycles, calculations are performed quickly, and the algorithm is easy to program.
A Measure of Motor Control at the Knee in Cerebral Palsy
Authors: Engsberg Jack R. , Wagner Joanne M. , Reitenbach Angela K. , Hollander Kevin W. , Standeven John W.
Published: August 2016

This investigation developed a measure of motor control for the knee extensors in adults with cerebral palsy (CP). Four adults with CP and 4 able-bodied (AB) adults participated. A KinCom dynamometer rotated the knee from approximately 90º of knee flexion to 10º/s less than the participant’s maximum knee extension at a speed of 10º/s, while the participant attempted to match a 44.5-N “target” force. The average, standard deviation, and median frequency of the force-time data were used to describe the test results. The individual force values for the AB group were near the target force and clustered together. The values for the CP group were also near the target force, but displayed greater variation. The average standard deviation for the CP group was more than three times larger than that of the AB group. The average median frequency for the CP group was less than that of the AB group. Results pointed to differing strategies for each group as they attempted to match the target force. The AB group attempted to match the target force with frequent small-magnitude force changes, while the CP group attempted to match the target force with fewer oscillations of greater magnitude. The methods employed in the present investigation are initial attempts to quantify one aspect of motor control, a visually guided tracking task.
Variations in Achilles Tendon Loading with Heel Lift Intervention in Heel-Toe Runners
Authors: Dixon Sharon J. , Kerwin David G.
Published: August 2016

This study investigated the influence of heel lift interventions on the loading of the Achilles tendon for heel-toe runners. It was hypothesized that the peak Achilles tendon force and peak rate of loading would be reduced by the increase in heel lift, and that the peak Achilles tendon force would occur significantly later in stance. Achilles tendon forces were determined by calculating sagittal-plane ankle joint moments using inverse-dynamics techniques and dividing these moments by Achilles tendon moment arm lengths. Methods for estimating Achilles tendon moment arm length using skin markers were justified via MRI data for one participant. Seven participants underwent running trials under three heel lift conditions: zero, 7.5-mm, and 15-mm heel lift. Average magnitude and occurrence time of peak Achilles tendon force and peak rate of loading were determined for each condition over the 7 participants. Despite group reductions in peak Achilles tendon force and peak rate of loading for the increased heel lift conditions, statistical analysis (ANOVA) revealed no significant differences for these variables, p > 0.05. Individual participant observations highlighted varied responses to heel lift; both increases and decreases in peak Achilles tendon force were observed. For the group data, the time of peak impact force occurred significantly later in the 15-mm heel lift condition than in the zero heel lift, p < 0.05. It is suggested that the success of increased heel lift in treating Achilles tendon injury may be due to a later occurrence of peak Achilles tendon force in response to this intervention, reducing Achilles tendon average rate of loading. In addition, the individuality of Achilles tendon peak force changes with heel lift intervention highlights the need for individual participant analysis.
A Software Tool for Faster Development of Complex Models of Musculoskeletal Systems and Sensorimotor Controllers in SimulinkTM
Authors: Davoodi Rahman , Loeb Gerald E.
Published: August 2016

Computer models of the neuromusculoskeletal systems can be used to study different aspects of movement and its control in humans and animals. SIMM with Dynamics Pipeline (Musculographics Inc., Chicago) and SD-Fast (Symbolic Dynamics Inc., Mountain View, CA) are software packages commonly used for graphic and dynamic simulation of movement in musculoskeletal systems. Building dynamic models with SIMM requires substantial C programming, however, which limits its use. We have developed Musculoskeletal Modeling in Simulink (MMS) software to convert the SIMM musculoskeletal and kinetics models to Simulink (Mathworks Inc., Natick, MA) blocks. In addition, MMS removes SIMM’s run-time constraints so that the resulting blocks can be used in simulations of closed-loop sensorimotor control systems.
Effect of Strike Pattern and Orthotic Intervention on Tibial Shock during Running
Authors: Laughton Carrie A. , Davis Irene McClay , Hamill Joseph
Published: August 2016

The main purpose of this study was to investigate the effects of both strike pattern (forefoot vs. rearfoot strike pattern) and orthotic intervention on shock to the lower extremity. Semi-rigid orthotic devices were manufactured for 15 injury-free recreational runners. Tibial accelerometry, ground reaction force, and 3D kinematic data were collected on their right leg in four conditions: forefoot strike (FFS) and rearfoot strike (RFS) with and without orthotics. Two-way repeated-measures analysis of variance tests were used to assess the effects of strike pattern and orthotic intervention on tibial acceleration; angular excursions of the ankle and knee; ground reaction force (GRF) vertical and anteroposterior peaks and load rates; and ankle, knee, and leg stiffness. There was a significant increase in tibial acceleration for the FFS pattern compared to the RFS pattern. This may be explained in part by the significantly greater peak vertical GRF, peak anteroposterior GRF, anteroposterior GRF load rates, knee stiffness, and leg stiffness found in the FFS pattern compared to the RFS pattern. Tibial acceleration and rearfoot eversion excursions were similar between the orthotic and no-orthotic conditions. Knee flexion excursion and average GRF vertical load rates were significantly decreased while dorsiflexion excursion and knee stiffness were significantly increased in the orthotic condition. No significant interactions were found between strike pattern and orthotic condition for any variables assessed.
Neuromusculoskeletal Modeling: Estimation of Muscle Forces and Joint Moments and Movements from Measurements of Neural Command
Authors: Buchanan Thomas S. , Lloyd David G. , Manal Kurt , Besier Thor F.
Published: August 2016

This paper provides an overview of forward dynamic neuromusculoskeletal modeling. The aim of such models is to estimate or predict muscle forces, joint moments, and/or joint kinematics from neural signals. This is a four-step process. In the first step,muscle activation dynamicsgovern the transformation from the neural signal to a measure of muscle activation—a time varying parameter between 0 and 1. In the second step,muscle contraction dynamicscharacterize how muscle activations are transformed into muscle forces. The third step requires a model of themusculoskeletal geometryto transform muscle forces to joint moments. Finally, theequations of motionallow joint moments to be transformed into joint movements. Each step involves complex nonlinear relationships. The focus of this paper is on the details involved in the first two steps, since these are the most challenging to the biomechanician. The global process is then explained through applications to the study of predicting isometric elbow moments and dynamic knee kinetics.
Differences between Grab Rail Position and Orientation during the Assisted Sit-to-Stand for Able-Bodied Older Adults
Authors: O’Meara Damien M. , Smith Richard M.
Published: August 2016

The aim of this study was to compare the effects of grab rail position, orientation, and number of hands used on the kinetics of assisted sit-to-stand transfers. Participants were 12 able-bodied older adults between the ages of 69 and 88 years. While each one performed the sit-to-stand transfer, a motion analysis system with 9 cameras recording at 60 Hz tracked the 3-D trajectories of retroreflective markers. Bilateral 3-D platform, grab rail, and seat force data were collected at 200 Hz and normalized to participant body weight. Four lateral conditions were tested: vertical, 45° inclined, and horizontal with the hand placed at 150 mm and 400 mm forward of the seat front edge. Four anterior conditions were tested: vertical and horizontal orientations with the use of one hand and two hands. Posterior grab rail force increased with anterior assistance and with two-hand use compared to lateral assistance and single hand use, respectively. The selection of grab rail position and the number of hands incorporated during assistance also determined the symmetry of an-teroposterior net joint forces, net joint moments, and joint powers. Grab rail orientation determined the height of the gripping hand which influenced the assistance strategy. Grab rail position, orientation, and the amount of upper body contribution influenced the assisted sit-to-stand transfer. These kinetic responses to grab rail location require careful consideration in order to optimize grab rail assistance during the sit-to-stand transfer.
Effects of Turn Angle and Pivot Foot on Lower Extremity Kinetics during Walk and Turn Actions
Authors: Xu Dali , Chow John W. , Wang Y. Tai
Published: August 2016

This study examined lower extremity joint moments during walk and turn with different turn angles and pivot feet. Seven young adults (age 21 ± 1.3 yrs) were asked to walk at a self-selected speed (1.35 ± 0.15 m/s) and to turn to the right using right (spin turn) and left (step turn) pivot feet at turn angles of 0° (walking straight), 45°, and 90°. Video and forceplate systems were employed for kinematic and kinetic data collection. Inverse dynamics approach was used to compute joint moments using segmental kinematics, ground reaction forces, and moments. The participants decreased their forward speed by increasing the ankle plantar flexion moment as the turn angle increased. The peak ankle plantar flexion moment during the braking phase increased with increasing turn angle for both spin and step turns. Ankle invertor moments were observed only in spin turns, suggesting that more ankle muscles are involved in spin turns than in step turns. The turn angle had a significant effect on the transverse plane moment profiles at the different lower extremity joints. The results suggest that the loading patterns of different anatomical structures in the lower extremity are affected by both turn angle and pivot foot during walk and turn actions.
Influence of Shoulder Abduction and Lateral Trunk Tilt on Peak Elbow Varus Torque for College Baseball Pitchers during Simulated Pitching
Authors: Matsuo Tomoyuki , Fleisig Glenn S. , Zheng Naiquan , Andrews James R.
Published: August 2016

Elbow varus torque is a primary factor in the risk of elbow injury during pitching. To examine the effects of shoulder abduction and lateral trunk tilt angles on elbow varus torque, we conducted simulation and regression analyses on 33 college baseball pitchers. Motion data were used for computer simulations in which two angles— shoulder abduction and lateral trunk tilt—were systematically altered. Forty-two simulated motions were generated for each pitcher, and the peak elbow varus torque for each simulated motion was calculated. A two-way analysis of variance was performed to analyze the effects of shoulder abduction and trunk tilt on elbow varus torque. Regression analyses of a simple regression model, second-order regression model, and multiple regression model were also performed. Although regression analyses did not show any significant relationship, computer simulation indicated that the peak elbow varus torque was affected by both angles, and the interaction of those angles was also significant. As trunk tilt to the contralateral side increased, the shoulder abduction angle producing the minimum peak elbow varus torque decreased. It is suggested that shoulder abduction and lateral trunk tilt may be only two of several determinants of peak elbow varus torque.
Musculotendon Parameters and Musculoskeletal Pathways Within the Human Foot
Authors: Lachowitzer Melissa R. , Ranes Anne , Yamaguchi Gary T.
Published: August 2016

In order to create a flexible model of the foot for dynamic musculoskeletal models, anthropometric data combined with geometric information describing the intrinsic musculature are needed. In this study, the left feet of two male and two female cadavers were dissected to expose the intrinsic musculotendon pathways. Three-dimensional coordinates of bony landmarks, tendon origins, insertions, and via points were digitized to submillimeter accuracy. Muscle architectural parameters were also measured, including volume, weight, and pennation angle and sarcomere, fascicle, and free tendon lengths. Optimal muscle fascicle lengths, pennation angles at optimal length, physiological cross-sectional areas (PCSA), and tendon slack lengths were calculated from the directly measured values. Fascicle length and pennation angle varied greatly within each subject. Average fascicle lengths normalized by optimal fascicle length varied between 0.73 and 1.25, with 75% of the formalin-preserved muscles being found in a shortened state. The muscle volume and PCSA also had a large variability within subjects but less variation between subjects. The ratio of tendon slack length to optimal fascicle length was found to vary between 1.05 and 9.56. Using this data, a deformable model of the foot can now be created. It is envisioned that deformable feet will significantly improve
The Role of Effective Mass and Hand Speed in the Performance of Kung Fu Athletes Compared with Nonpractitioners
Authors: Neto Osmar Pinto , Magini Marcio , Saba Marcelo M. F.
Published: August 2016

The main goal of this article is to quantify the contribution of effective mass (me) and hand-speed (shi) on the palm strike performance of kung fu athletes (kung fu group) compared with nonpractitioners (control group). All subjects were asked to strike a basketball. Hand and ball speed (sbf) were determined by high-speed video analysis. The value for me was determined by an equation that does not depend upon post-impact measurement of the hand speed. The results show that kung fu athletes had greater shi (6.67 [SD 1.42] m/s), p = 0.042), higher me (2.62 [SD 0.33] kg, p = 0.004), and greater sbf (9.00 [SD 1.89] m/s), p = 0.004) than the nonpractitioners (5.04 [SD 0.57] m/s, 1.33 [SD 0.19] kg, and 5.72 [SD 0.44] m/s, respectively). Comparing the average values obtained for me and hand and forearm mass (m), it was found that for the control group me is statistically equal to m (p = 0.917), whereas for the kung fu group me is significant greater than m (p = 0.003). It is suggested that for impacts against heavier objects, the effective mass would be the main factor to distinguish a martial artstrained from an untrained subject.
Postural Preparation to Making a Step: Is There a “Motor Program” for Postural Preparation?
Authors: Degani Adriana M. , Danna-Dos-Santos Alessander , Latash Mark L.
Published: August 2016

We tested the hypothesis that a sequence of mechanical events occurs preceding a step that scales in time and magnitude as a whole in a task-specific manner, and is a reflection of a “motor program.” Young subjects made a step under three speed instructions and four tasks: stepping straight ahead, down a stair, up a stair, and over an obstacle. Larger center-of-pressure (COP) and force adjustments in the anteriorposterior direction and smaller COP and force adjustments in the mediolateral direction were seen during stepping forward and down a stair, as compared with the tasks of stepping up a stair and over an obstacle. These differences were accentuated during stepping under the simple reaction time instruction. These results speak against the hypothesis of a single motor program that would underlie postural preparation to stepping. They are more compatible with the reference configuration hypothesis of whole-body actions.
Estimating Segment Inertial Parameters Using Fan-Beam DXA
Authors: Wicke Jason , Dumas Genevieve A.
Published: August 2016

Body segment inertial parameters are required as input parameters when the kinetics of human motion is to be analyzed. However, owing to interindividual differences in body composition, noninvasive inertial estimates are problematic. Dual-energy x-ray absorptiometry (DXA) is a relatively new imaging approach that can provide cost- and time-effective means for estimating these parameters with minimal exposure to radiation. With the introduction of a new generation of DXA machines, utilizing a fan-beam configuration, this study examined their accuracy as well as a new interpolative data-reduction process for estimating inertial parameters. Specifically, the inertial estimates of two objects (an ultra-high molecular density plastic rod and an animal specimen) and 50 participants were obtained. Results showed that the fan-beam DXA, along with the new interpolative data-reduction process, provided highly accurate estimates (0.10–0.39%). A greater variance was observed in the center of mass location and moment of inertia estimates, likely as a result of the course end-point location (1.31 cm). However, using a midpoint interpolation of the end-point locations, errors in the estimates were greatly reduced for the center of mass location (0.64–0.92%) and moments of inertia (–0.23 to –0.48%).
The Relationship between Joint Strength and Standing Vertical Jump Performance
Authors: Cheng Kuangyou B.
Published: August 2016

The effect of joint strengthening on standing vertical jump height is investigated by computer simulation. The human model consists of five rigid segments representing the feet, shanks, thighs, HT (head and trunk), and arms. Segments are connected by frictionless revolute joints and model movement is driven by joint torque actuators. Each joint torque is the product of maximum isometric torque and three variable functions of instantaneous joint angle, angular velocity, and activation level, respectively. Jumping movements starting from a balanced initial posture and ending at takeoff are simulated. A matching simulation reproducing the actual jumping movement is generated by optimizing joint activation level. Simulations with the goal of maximizing jump height are repeated for varying maximum isometric torque of one joint by up to ±20% while keeping other joint strength values unchanged. Similar to previous studies, reoptimization of activation after joint strengthening is necessary for increasing jump height. The knee and ankle are the most effective joints in changing jump height (by as much as 2.4%, or 3 cm). For the same amount of percentage increase/decrease in strength, the shoulder is the least effective joint (which changes height by as much as 0.6%), but its influence should not be overlooked.
Effects of Velocity and Weight Support on Ground Reaction Forces and Metabolic Power during Running
Authors: Grabowski Alena M. , Kram Rodger
Published: August 2016

The biomechanical and metabolic demands of human running are distinctly affected by velocity and body weight. As runners increase velocity, ground reaction forces (GRF) increase, which may increase the risk of an overuse injury, and more metabolic power is required to produce greater rates of muscular force generation. Running with weight support attenuates GRFs, but demands less metabolic power than normal weight running. We used a recently developed device (G-trainer) that uses positive air pressure around the lower body to support body weight during treadmill running. Our scientific goal was to quantify the separate and combined effects of running velocity and weight support on GRFs and metabolic power. After obtaining this basic data set, we identified velocity and weight support combinations that resulted in different peak GRFs, yet demanded the same metabolic power. Ideal combinations of velocity and weight could potentially reduce biomechanical risks by attenuating peak GRFs while maintaining aerobic and neuromuscular benefits. Indeed, we found many combinations that decreased peak vertical GRFs yet demanded the same metabolic power as running slower at normal weight. This approach of manipulating velocity and weight during running may prove effective as a training and/or rehabilitation strategy.
The Effect of Fatigue on the Underwater Arm Stroke Motion in the 100-m Front Crawl
Authors: Suito Hiroshi , Ikegami Yasuo , Nunome Hiroyuki , Sano Shinya , Shinkai Hironari , Tsujimoto Norio
Published: August 2016

The purpose of this study was to indicate the effect of fatigue on the underwater right arm stroke motion during the 100-m front crawl. The arm stroke motions of eight male competitive swimmers were captured three-dimensionally at 60 Hz in the positions of 15 m and 65 m from the start. The hand velocity, the arm angular velocities and the relative contribution of the arm angular velocities to the hand velocity were computed at each instant during the arm stroke motion. A significant decrease of the hand velocity and the peak angular velocity of shoulder adduction were observed in the second half than in the first half. The contribution of shoulder adduction was especially large in the pull phase and subsequently that of shoulder horizontal abduction became dominant in the push phase. However, in the second half, the contribution of shoulder adduction tended to decrease while that of shoulder internal rotation tended to increase. Thus, it is quite likely that the arm stroke motion of swimmers were driven to be influenced by induced fatigue and resulted in an increase in the contribution of shoulder internal rotation to compensate the decreased contribution of shoulder adduction angular velocity.
In Vivo Three-Dimensional Mechanical Actions of Individual Flexor-Pronator Muscles: Role in Elbow Valgus Stability
Authors: Hsu Jason E. , Peng Qiyu , Schafer David A. , Koh Jason L. , Nuber Gordon W. , Zhang Li-Qun
Published: August 2016

The flexor-pronator mass is thought to be the primary dynamic valgus stabilizer of the elbow and protects the ulnar collateral ligament. However, in vivo multiaxis actions of individual muscles of the flexor-pronator group and their roles in valgus stability have not been investigated quantitatively. This study tested the hypothesis that individual muscles of the flexor-pronator muscle group produce a significant varus moment that provides elbow valgus stability. The flexor carpi ulnaris, flexor carpi radialis, and pronator teres were selectively activated, and the resulting multiaxis moments at the elbow measured at 0°, 30°, 60°, and 90° of elbow flexion using a six-axis force sensor were analyzed for their role in generating varus moment and protecting the ulnar collateral ligament. Considerable off-axis moments were generated by each muscle tested. Through the range of elbow flexion, the varus moment was the major component of the multiaxis action of the flexor carpi ulnaris (p< .001). The flexor carpi radialis and pronator teres had significant actions as elbow flexors and pronators (p≤ .032); these muscles also had a significant varus contribution at 90° elbow flexion (p≤.019). The results suggest that the flexor-pronator muscle group plays an important role in valgus stability of the elbow. In particular, the flexor carpi ulnaris creates a significant varus moment, which is important in unloading and protecting the ulnar collateral ligament. Rehabilitation and strengthening of the flexor-pronator muscle group may help prevent failure of the ulnar collateral ligament and may also help compensate for a medially insufficient elbow.
Comparison of Selected Lateral Cutting Activities Used to Assess ACL Injury Risk
Authors: O’Connor Kristian M. , Monteiro Sarika K. , Hoelker Ian A.
Published: August 2016

The purpose of this study was to compare the knee joint dynamics for males and females performing constrained cutting tasks to an unanticipated running and cutting maneuver. Sixteen male and 17 female recreational athletes were recruited to perform four cutting tasks; unanticipated run and cut (CUT), stride land and cut (SLC), far box-land and cut (FLC), and close box-land and cut (CLC). Three-dimensional knee joint kinematics and kinetics were recorded. Data were compared across gender and task with a 2 × 4 ANOVA (p < .05), and a factor analysis was performed to examine task relationships. There were significant group mean differences between the tasks and across genders. The factor analysis revealed high correlations between the three constrained tasks, but for variables typically associated with ACL injury risk there was a poor relationship to the CUT task. This was particularly true for the frontal plane variables. The constrained tasks were only moderately useful in predicting cutting mechanics.