bluuebunny/crossref_metadata_2025 huggingface dataset:
Gender Comparisons between Unilateral and Bilateral Landings
Authors: Weinhandl Joshua T. , Joshi Mukta , O’Connor Kristian M.
Published: August 2016

The increased number of women participating in sports has led to a higher knee injury rate in women compared with men. Among these injuries, those occurring to the ACL are commonly observed during landing maneuvers. The purpose of this study was to determine gender differences in landing strategies during unilateral and bilateral landings. Sixteen male and 17 female recreational athletes were recruited to perform unilateral and bilateral landings from a raised platform, scaled to match their individual jumping abilities. Three-dimensional kinematics and kinetics of the dominant leg were calculated during the landing phase and reported as initial ground contact angle, ranges of motion (ROM) and peak moments. Lower extremity energy absorption was also calculated for the duration of the landing phase. Results showed that gender differences were only observed in sagittal plane hip and knee ROM, potentially due to the use of a relative drop height versus the commonly used absolute drop height. Unilateral landings were characterized by significant differences in hip and knee kinematics that have been linked to increased injury risk and would best be classified as “stiff” landings. The ankle musculature was used more for impact absorption during unilateral landing, which required increased joint extension at touchdown and may increase injury risk during an unbalanced landing. In addition, there was only an 11% increase in total energy absorption during unilateral landings, suggesting that there was a substantial amount of passive energy transfer during unilateral landings.
Dynamics and Energetics of Impacts in Crutch Walking
Authors: Carpentier Clément , Font-Llagunes Josep M. , Kövecses József
Published: August 2016

The impulsive dynamics associated with the impact of the crutch with the ground is an important topic of research, since this is known to be the main cause of energy loss during crutch gait. In this article, a four-segmental 2D model based on anthropometric body segment parameters is used to analyze various dynamics aspects of such impact. For this purpose, a novel formulation based on the decomposition of the tangent space of the biomechanical system to two subspaces associated with the constrained and admissible motions is developed. Detailed numerical analysis is presented to discuss the effects of body configuration and crutch length on the kinetic energy redistribution, velocity change and impulsive contact forces generated. The conclusions reached via this analysis give guidelines for optimal crutch selection or crutch-use teaching that can be applied to injured subjects. For instance, to reduce energy consumption which leads to a reduction of muscular fatigue.
One-Legged Stance as a Representative Static Body Position for Calculation of Hip Contact Stress Distribution in Clinical Studies
Authors: Debevec Hana , Pedersen Douglas R. , Iglic̆ Aleš , Daniel Matej
Published: August 2016

It was shown in several clinical studies that static one-legged stance may be a relevant body position to describe the loads acting at the hip. However, the stress distribution averaged during movement may better describe hip load than hip contact stress distribution in the static body position. Using data on the resultant hip force during walking taken from the measurements of Bergmann (2001), spatial distribution of contact stress over the articular surface was calculated by the HIPSTRESS method and compared with the stress distribution in one-legged stance. It is shown, that the shape of the contact stress distribution during one-legged stance closely resembled the averaged contact stress distribution during the walking cycle (Pearson’s correlation coefficient R2 = .986; p < .001). This finding presents a link between the hypothesis that the averaged contact stress distribution during a walking cycle is crucial for cartilage development and the results of clinical studies in which the calculated distribution of contact stress in one-legged stance was successfully used to predict the clinical status of the hip.
Trunk and Upper Limb Muscle Activation During Flat and Topspin Forehand Drives in Young Tennis Players
Authors: Rogowski Isabelle , Rouffet David , Lambalot Frédéric , Brosseau Olivier , Hautier Christophe
Published: August 2016

This study compared EMG activity of young tennis players’ muscles during forehand drives in two groups, GD—those able to raise by more than 150% the vertical velocity of racket-face at impact from flat to topspin forehand drives, and GND, those not able to increase their vertical velocity to the same extent. Upper limb joint angles, racket-face velocities, and average EMGrms values, were studied. At similar joint angles, a fall in horizontal velocity and a rise in racket-face vertical velocity from flat to topspin forehand drives were observed. Shoulder muscle activity rose from flat to topspin forehand drives in GND, but not for drives in GD. Forearm muscle activity reduced from flat to topspin forehand drives in GD, but muscle activation was similar in GND. The results show that radial deviation increased racket-face vertical velocity more at impact from the flat to topspin forehand drives than shoulder abduction.
Lower and Upper Extremity Loading in Nordic Walking in Comparison with Walking and Running
Authors: Hagen Marco , Hennig Ewald M. , Stieldorf Peter
Published: August 2016

Nordic walking (NW) was compared with walking (W) and running (R) with respect to upper and lower limb injury risks. 24 NW-instructors performed W, NW, and R trials on a runway covered with artificial turf at controlled speeds. Foot pronation and ground reaction forces were measured as well as shock wave transmission to the right wrist. Comparison of NW and W shows similar results for all of the four chosen velocities (5 km/h, 7 km/h, 8 km/h, 8.5 km/h). Except for the 2nd peak of the vertical ground reaction force, NW results in higher loading rates and horizontal forces as well as higher pronation and pronation velocity values as compared with W. Wrist acceleration values up to 7.6 times gravitational acceleration were recorded in NW. Compared with R at the same speeds (8 km/h and 8.5 km/h), NW can be recommended as low impact sport with 36% lower loading rates and 59% lower pronation velocities. However, the high wrist accelerations in NW reveal that the upper extremities are exposed to considerable repetitive shocks, which may cause overuse injuries of the upper extremities. Thus, additional preventive exercises for the upper limb muscles are recommended as well as using shock absorbing walking poles.
Shoulder Muscular Activity During Isometric Three-Point Kneeling Exercise on Stable and Unstable Surfaces
Authors: de Araújo Rodrigo Cappato , de Andrade Rodrigo , Tucci Helga Tatiana , Martins Jaqueline , de Oliveira Anamaria Siriani
Published: August 2016

The purpose of this study was to determine if performing isometric 3-point kneeling exercises on a Swiss ball influenced the isometric force output and EMG activities of the shoulder muscles when compared with performing the same exercises on a stable base of support. Twenty healthy adults performed the isometric 3-point kneeling exercises with the hand placed either on a stable surface or on a Swiss ball. Surface EMG was recorded from the posterior deltoid, pectoralis major, biceps brachii, triceps brachii, upper trapezius, and serratus anterior muscles using surface differential electrodes. All EMG data were reported as percentages of the average root mean square (RMS) values obtained in maximum voluntary contractions for each muscle studied. The highest load value was obtained during exercise on a stable surface. A significant increase was observed in the activation of glenohumeral muscles during exercises on a Swiss ball. However, there were no differences in EMG activities of the scapulothoracic muscles. These results suggest that exercises performed on unstable surfaces may provide muscular activity levels similar to those performed on stable surfaces, without the need to apply greater external loads to the musculoskeletal system. Therefore, exercises on unstable surfaces may be useful during the process of tissue regeneration.
Relative Net Vertical Impulse Determines Jumping Performance
Authors: Kirby Tyler J. , McBride Jeffrey M. , Haines Tracie L. , Dayne Andrea M.
Published: August 2016

The purpose of this investigation was to determine the relationship between relative net vertical impulse and jump height in a countermovement jump and static jump performed to varying squat depths. Ten college-aged males with 2 years of jumping experience participated in this investigation (age: 23.3 ± 1.5 years; height: 176.7 ± 4.5 cm; body mass: 84.4 ± 10.1 kg). Subjects performed a series of static jumps and countermovement jumps in a randomized fashion to a depth of 0.15, 0.30, 0.45, 0.60, and 0.75 m and a self-selected depth (static jump depth = 0.38 ± 0.08 m, countermovement jump depth = 0.49 ± 0.06 m). During the concentric phase of each jump, peak force, peak velocity, peak power, jump height, and net vertical impulse were recorded and analyzed. Net vertical impulse was divided by body mass to produce relative net vertical impulse. Increasing squat depth corresponded to a decrease in peak force and an increase in jump height and relative net vertical impulse for both static jump and countermovement jump. Across all depths, relative net vertical impulse was statistically significantly correlated to jump height in the static jump (r = .9337, p < .0001, power = 1.000) and countermovement jump (r = .925, p < .0001, power = 1.000). Across all depths, peak force was negatively correlated to jump height in the static jump (r = –0.3947, p = .0018, power = 0.8831) and countermovement jump (r = –0.4080, p = .0012, power = 0.9050). These results indicate that relative net vertical impulse can be used to assess vertical jump performance, regardless of initial squat depth, and that peak force may not be the best measure to assess vertical jump performance.
Dynamic Optimization of the Sit-to-Stand Movement
Authors: Yamasaki Hiroshi R. , Kambara Hiroyuki , Koike Yasuharu
Published: August 2016

The purpose of this study was to clarify criteria that can predict trajectories during the sit-to-stand movement. In particular, the minimum jerk and minimum torque-change models were examined. Three patterns of sit-to-stand movement from a chair, i.e., upright, natural, and leaning forward, were measured in five young participants using a 3-D motion analysis device (200 Hz). The trajectory of the center of mass and its smoothness were examined, and the optimal trajectories predicted by both models were evaluated. Trajectories of the center of mass predicted by the minimum torque-change model, rather than the minimum jerk model, resembled the measured movements in all rising movement patterns. The upright pattern required greater extension torque of the knee and ankle joints at the instant of seat-off. The leaning-forward pattern required greater extension hip torque and higher movement cost than the natural and upright patterns. These results indicate that the natural sit-to-stand movement might be a result of dynamic optimization.
Varying Treadmill Speed and Inclination Affects Spontaneous Synchronization When Two Individuals Walk Side by Side
Authors: Nessler Jeff A. , Kephart Gerald , Cowell Jason , De Leone Charles J.
Published: August 2016

Studying spontaneous synchronization of stepping as two individuals walk on side-by-side treadmills may be useful for understanding the control of bipedal locomotion and may have implications for gait rehabilitation. Existing data suggest that this behavior is related to differences in leg length, walkway slope, and overground speed between partners, and might be promoted by altering these variables. This idea was evaluated here as 24 pairs of subjects stepped on side-by-side treadmills under several conditions of relative speed and slope. Overall, pairings that demonstrated very little spontaneous synchronization with the same treadmill speed and slope exhibited significant increases in this behavior when one treadmill was manipulated. Conversely, pairings that demonstrated a tendency to synchronize under normal conditions exhibited significant decreases in this behavior when either treadmill was altered.
Three-Dimensional Model to Predict Muscle Forces and Their Relation to Motor Variances in Reaching Arm Movements
Authors: Tibold Robert , Fazekas Gabor , Laczko Jozsef
Published: August 2016

A three-dimensional (3-D) arm movement model is presented to simulate kinematic properties and muscle forces in reaching arm movements. Healthy subjects performed reaching movements repetitively either with or without a load in the hand. Joint coordinates were measured. Muscle moment arms, 3-D angular acceleration, and moment of inertias of arm segments were calculated to determine 3-D joint torques. Variances of hand position, arm configuration, and muscle activities were calculated. Ratios of movement variances observed in the two conditions (load versus without load) showed no differences for hand position and arm configuration variances. Virtual muscle force variances for all muscles except deltoid posterior and EMG variances for four muscles increased significantly by moving with the load. The greatly increased variances in muscle activity did not imply equally high increments in kinematic variances. We conclude that enhanced muscle cooperation through synergies helps to stabilize movement at the kinematic level when a load is added.
In Vivo Measurements of Moment Arm Lengths of Three Elbow Flexors at Rest and During Isometric Contractions
Authors: Akagi Ryota , Iwanuma Soichiro , Hashizume Satoru , Kanehisa Hiroaki , Yanai Toshimasa , Kawakami Yasuo
Published: August 2016

The purpose of this study was to determine in vivo moment arm lengths (MAs) of three elbow flexors at rest and during low- and relatively high-intensity contractions, and to examine the contraction intensity dependence of MAs at different joint positions. At 50°, 80° and 110° of elbow flexion, MAs of the biceps brachii, brachialis and brachioradialis were measured in 10 young men using sagittal images of the right arm obtained by magnetic resonance imaging, at rest and during 20% and 60% of isometric maximal voluntary elbow flexion. In most conditions, MAs increased with isometric contractions, which is presumably due to the contraction-induced thickening of the muscles. This phenomenon was especially evident in the flexed elbow positions. The influence of the contraction intensities on the increases in MAs varied across the muscles. These results suggest that in vivo measurements of each elbow flexor MA during contractions are essential to properly examine the effects on the interrelationships between elbow flexion torque and individual muscle forces.
On the Estimate of the Two Dominant Axes of the Knee Using an Instrumented Spatial Linkage
Authors: Gatti Gianluca
Published: August 2016

This article presents the validation of a technique to assess the appropriateness of a 2 degree-of-freedom model for the human knee, and, in which case, the dominant axes of flexion/extension and internal/external longitudinal rotation are estimated. The technique relies on the use of an instrumented spatial linkage for the accurate detection of passive knee kinematics, and it is based on the assumption that points on the longitudinal rotation axis describe nearly circular and planar trajectories, whereas the flexion/extension axis is perpendicular to those trajectories through their centers of rotation. By manually enforcing a tibia rotation while bending the knee in flexion, a standard optimization algorithm is used to estimate the approximate axis of longitudinal rotation, and the axis of flexion is estimated consequently. The proposed technique is validated through simulated data and experimentally applied on a 2 degree-of-freedom mechanical joint. A procedure is proposed to verify the fixed axes assumption for the knee model. The suggested methodology could be possibly valuable in understanding knee kinematics, and in particular for the design and implant of customized hinged external fixators, which have shown to be effective in knee dislocation treatment and rehabilitation.
Unilateral Stance Strategies of Athletes With ACL Deficiency
Authors: Di Stasi Stephanie L. , Hartigan Erin H. , Snyder-Mackler Lynn
Published: August 2016

Aberrant movement strategies are characteristic of ACL-deficient athletes with recurrent knee instability (non-copers), and may instigate premature or accelerate joint degradation. Biomechanical evaluation of kinematic changes over time may elucidate noncopers’ responses to neuromuscular intervention and ACL reconstruction (ACLR). Forty noncopers were randomized into a perturbation group or a strength training only group. We evaluated the effects of perturbation training, and then gender on knee angle and tibial position during a unilateral standing task before and after ACLR. No statistically significant interactions were found. Before surgery, the strength training only group demonstrated knee angle asymmetry, but 6 months after ACLR, both groups presented with similar knee flexion between limbs. Aberrant and asymmetrical tibial position was found only in females following injury and ACLR. Neither treatment group showed distinct unilateral standing strategies following intervention; however, males and female noncopers appear to respond uniquely to physical therapy and surgery.
Comparison Between Overground and Dynamometer Manual Wheelchair Propulsion
Authors: Koontz Alicia M. , Worobey Lynn A. , Rice Ian M. , Collinger Jennifer L. , Boninger Michael L.
Published: August 2016

Laboratory-based simulators afford many advantages for studying physiology and biomechanics; however, they may not perfectly mimic wheelchair propulsion over natural surfaces. The goal of this study was to compare kinetic and temporal parameters between propulsion overground on a tile surface and on a dynamometer. Twenty-four experienced manual wheelchair users propelled at a self-selected speed on smooth, level tile and a dynamometer while kinetic data were collected using an instrumented wheel. A Pearson correlation test was used to examine the relationship between propulsion variables obtained on the dynamometer and the overground condition. Ensemble resultant force and moment curves were compared using cross-correlation and qualitative analysis of curve shape. User biomechanics were correlated (Rranging from 0.41 to 0.83) between surfaces. Overall, findings suggest that although the dynamometer does not perfectly emulate overground propulsion, wheelchair users were consistent with the direction and amount of force applied, the time peak force was reached, push angle, and their stroke frequency between conditions.
Influence of Lower Body Pressure Support on the Walking Patterns of Healthy Children and Adults
Authors: Kurz Max J. , Deffeyes Joan E. , Arpin David J. , Karst Gregory M. , Stuberg Wayne A.
Published: August 2016

The purpose of this investigation was to evaluate the effect of a lower body positive pressure support system on the joint kinematics and activity of the lower extremity antigravity musculature of adults and children during walking. Adults (age = 25 ± 4 years) and children (age = 13 ± 2 years) walked at a preferred speed and a speed that was based on the Froude number, while 0–80% of their body weight was supported. Electrogoniometers were used to monitor knee and ankle joint kinematics. Surface electromyography was used to quantify the magnitude of the vastus lateralis and gastrocnemius muscle activity. There were three key findings: (1) The lower extremity joint angles and activity of the lower extremity antigravity muscles of children did not differ from those of adults. (2) The magnitude of the changes in the lower extremity joint motion and antigravity muscle activity was dependent upon an interaction between body weight support and walking speed. (3) Lower body positive pressure support resulted in reduced activation of the antigravity musculature, and reduced range of motion of the knee and ankle joints.
Explanations Pertaining to the Hip Joint Flexor Moment During the Stance Phase of Human Walking
Authors: Simonsen Erik B. , Cappelen Katrine L. , Skorini Ragnhild í , Larsen Peter K. , Alkjær Tine , Dyhre-Poulsen Poul
Published: August 2016

A hip joint flexor moment in the last half of the stance phase during walking has repeatedly been reported. However, the purpose of this moment remains uncertain and it is unknown how it is generated. Nine male subjects were instructed to walk at 4.5 km/h with their upper body in three different positions: normal, inclined and reclined. Net joint moments were calculated about the hip, knee and ankle joint. The peak hip joint flexor moment during late stance was significantly lower during inclined walking than in the two other conditions. During normal walking the iliacus muscle showed no or very weak activity and first at the transition from stance to swing. When walking reclined, a clear but rather low activity level of the iliacus muscle was seen in the first half of the stance phase, which could contribute to the hip moment. In the inclined condition the iliacus showed much increased activity but only in the swing phase. It is concluded that the hip flexor moment in question is largely generated by passive structures in the form of ligaments resisting hip joint extension.
Potentiation of Vertical Jump Performance During a Snatch Pull Exercise Session
Authors: Chiu Loren Z.F. , Salem George J.
Published: August 2016

Potentiation has been reported in power tasks immediately following a strength stimulus; however, only whole-body performance has been assessed. To determine the acute effects of weightlifting on vertical jump joint kinetics, performance was assessed before, during, and after snatch pull exercise in male athletes. Jumping was assessed using 3D motion analysis and inverse dynamics. Jump height was enhanced at the midpoint (5.77%; p = .001) and end (5.90%; p < .001) of the exercise session, indicating a greater powergenerating ability. At the midpoint, knee extensor net joint work was increased (p = .05) and associated with increased jump height (r = .57; p = .02). Following exercise, ankle plantar flexor net joint work was increased (p = .02) and associated with increased jump height (r = .67; p = .006). Snatch pull exercise elicited acute enhancements in vertical jump performance. At the midpoint of the exercise session, greater work at the knee joint contributed to enhanced performance. At the end of the exercise session, greater work at the ankle contributed to enhanced performance. Consequently, potentiation is not elicited uniformly across joints during multijoint exercise.
An Isovelocity Dynamometer Method to Determine Monoarticular and Biarticular Muscle Parameters
Authors: Conceição Filipe , King Mark A. , Yeadon Maurice R. , Lewis Martin G.C. , Forrester Stephanie E.
Published: August 2016

This study aimed to determine whether subject-specific individual muscle models for the ankle plantar flexors could be obtained from single joint isometric and isovelocity maximum torque measurements in combination with a model of plantar flexion. Maximum plantar flexion torque measurements were taken on one subject at six knee angles spanning full flexion to full extension. A planar three-segment (foot, shank and thigh), two-muscle (soleus and gastrocnemius) model of plantar flexion was developed. Seven parameters per muscle were determined by minimizing a weighted root mean square difference (wRMSD) between the model output and the experimental torque data. Valid individual muscle models were obtained using experimental data from only two knee angles giving a wRMSD score of 16 N m, with values ranging from 11 to 17 N m for each of the six knee angles. The robustness of the methodology was confirmed through repeating the optimization with perturbed experimental torques (±20%) and segment lengths (±10%) resulting in wRMSD scores of between 13 and 20 N m. Hence, good representations of maximum torque can be achieved from subject-specific individual muscle models determined from single joint maximum torque measurements. The proposed methodology could be applied to muscle-driven models of human movement with the potential to improve their validity.
The Roles of Whole Body Balance, Shoe-Floor Friction, and Joint Strength During Maximum Exertions: Searching for the “Weakest Link”
Authors: Fischer Steven L. , Picco Bryan R. , Wells Richard P. , Dickerson Clark R.
Published: August 2016

Exerting manual forces is critical during occupational performance. Therefore, being able to estimate maximum force capacity is particularly useful for determining how these manual exertion demands relate to available capacity. To facilitate this type of prediction requires a complete understanding of how maximum force capacity is governed biomechanically. This research focused on identifying how factors including joint moment strength, balance and shoe-floor friction affected hand force capacity during pulling, pressing downward and pushing medially. To elucidate potential limiting factors, joint moments were calculated and contrasted with reporte joint strength capacities, the balancing point within the shoe-floor interface was calculated and expresess relative to the area defined by the shoe-floor interface, and the net applied horizontal forces were compare with the available friction. Each of these variables were calculated as participants exerted forces in a series o conditions designed to systematically control or restrict certain factors from limiting hand force capacity. The results demonstrated that hand force capacity, in all tested directions, was affected by the experimental conditions (up to 300%). Concurrently, biomechanical measures reached or surpassed reported criterion threshold inferring specific biomechanical limitations. Downward exertions were limited by elbow strength, wherea pulling exertions were often limited by balance along the anterior-posterior axis. No specific limitations wer identified for medial exertions.
The Computational Fluid Dynamics Study of Orientation Effects of Oar Blade
Authors: Laurent Alexandra , Rouard Annie , Mantha Vishveshwar R. , Marinho Daniel A. , Silva Antonio J. , Rouboa Abel I.
Published: August 2016

The distribution of pressure coefficient formed when the fluid contacts with the kayak oar blade is not been studied extensively. The CFD technique was employed to calculate pressure coefficient distribution on the front and rear faces of oar blade resulting from the numerical resolution equations of the flow around the oar blade in the steady flow conditions (4 m/s) for three angular orientations of the oar (45°, 90°, 135°) with main flow. A three-dimensional (3D) geometric model of oar blade was modeled and the kappa-epsilon turbulence model was applied to compute the flow around the oar. The main results reported that, under steady state flow conditions, the drag coefficient (Cd= 2.01 for 4 m/s) at 90° orientation has the similar evolution for the different oar blade orientation to the direction of the flow. This is valid when the orientation of the blade is perpendicular to the direction of the flow. Results indicated that the angle of oar strongly influenced the Cdwith maximum values for 90° angle of the oar. Moreover, the distribution of the pressure is different for the internal and external edges depending upon oar angle. Finally, the difference of negative pressure coefficient Cpin the rear side and the positive Cpin the front side, contributes toward propulsive force. The results indicate that CFD can be considered an interesting new approach for pressure coefficient calculation on kayak oar blade. The CFD approach could be a useful tool to evaluate the effects of different blade designs on the oar forces and consequently on the boat propulsion contributing toward the design improvement in future oar models. The dependence of variation of pressure coefficient on the angular position of oar with respect to flow direction gives valuable dynamic information, which can be used during training for kayak competition.
Changes of Postural Steadiness Following Use of Prefabricated Orthotic Insoles
Authors: Bateni Hamid
Published: August 2016

Orthoses are designed to assist a malaligned foot in adapting to the environment and reduce the frequency of injury. Literature is divided on the benefits of orthotics insoles for postural stability. The current study was conducted to determine the effect of prefabricated orthotic arch supports on postural stabilization. Twelve healthy young adults participated in this study and were tested with and without prefabricated orthotics. Different variables were computed from movement of center of pressure (COP) during orthotic use as suggested in the literature. The mean position of COP was significantly shifted forward and toward the dominant side. Neither the COP movement nor the velocity changes following the use of orthotics revealed significant differences. Mediolateral range of COP movement and the 95% confidence circle area of sway was significantly reduced (P = .022 and 0.048 respectively), but changes in 95% confidence circle and ellipse areas of fractal dimension were not significant (P = .053 and P = .057 respectively). In conclusion, orthotic insoles significantly improved postural sway initially by reducing mediolateral range of postural sway and 95% confidence circle area of sway at the cost of increased fractal dimension area variables and power.
A Comparison of Treadmill and Overground Walking Effects on Step Cycle Asymmetry in Young and Older Individuals
Authors: Nagano Hanatsu , Begg Rezaul K. , Sparrow William A. , Taylor Simon
Published: August 2016

Although lower limb strength becomes asymmetrical with age, past studies of aging effects on gait biomechanics have usually analyzed only one limb. This experiment measured how aging and treadmill surface influenced both dominant and nondominant step parameters in older (mean 74.0 y) and young participants (mean 21.9 y). Step-cycle parameters were obtained from 3-dimensional position/time data during preferred-speed walking for 40 trials along a 10 m walkway and for 10 minutes of treadmill walking. Walking speed (young 1.23 m/s, older 1.24 m/s) and step velocity for the two age groups were similar in overground walking but older adults showed significantly slower walking speed (young 1.26 m/s, older 1.05 m/s) and step velocity on the treadmill due to reduced step length and prolonged step time. Older adults had shorter step length than young adults and both groups reduced step length on the treadmill. Step velocity and length of older adults’ dominant limb was asymmetrically larger. Older adults increased the proportion of double support in step time when treadmill walking. This adaptation combined with reduced step velocity and length may preserve balance. The results suggest that bilateral analyses should be employed to accurately describe asymmetric features of gait especially for older adults.
Scapula Kinematics Differ by Body Mass Index
Authors: Gupta Miti , Dashottar Amitabh , Borstad John D.
Published: August 2016

The biomechanical changes due to increased arm mass in individuals with high body mass index (BMI) may lead to altered scapular motions at the shoulder joint. Scapula kinematic alterations are often associated with shoulder pain and pathology, and if present in overweight or obese individuals could impact shoulder health. The purpose of this study was to examine if scapula biomechanics differ between groups separated by BMI. Three-dimensional scapula kinematic data during arm elevation were collected on 41 subjects, and then compared between higher BMI (BMI ≥ 27; n = 10) and lower BMI (BMI ≤ 23; n = 10) individuals, both with and without holding a 1.36 kg (3 lb) weight. Data were analyzed with a mixed-model ANOVA with Group and Elevation Angle the between- and within-subject factors, respectively. The higher BMI group had significantly greater scapula upward rotation than the lower BMI group at 120° for both the unweighted and weighted tasks. Individuals with higher BMI in this study had altered scapulothoracic movement, which may be a strategy to better manage increased arm mass. With increased scapula upward rotation also reported in groups with rotator cuff tears, this study supports the potential link between high BMI, kinematics, and rotator cuff pathology.
The Interday Reliability of Ankle, Knee, Leg, and Vertical Musculoskeletal Stiffness During Hopping and Overground Running
Authors: Joseph Corey W. , Bradshaw Elizabeth J. , Kemp Justin , Clark Ross A.
Published: August 2016

A number of methods are used to measure lower extremity musculoskeletal stiffness, but there is a paucity of research examining the reliability of these techniques. Therefore, we investigated the reliability of vertical, leg, knee, and ankle stiffness during overground running and hopping in 20 active men. Participants were required to run on a 10 m overground runway at 3.83 m/s (actual; 3.35 ± 0.12 m/s) and to hop in place at 2.2 Hz (actual; 2.37 ± 0.03 Hz), and at a self-selected frequency (actual; 2.05 ± 0.12 Hz) and at 2.2 Hz (actual; 2.39 ± 0.04 Hz). Reliability was determined using the intraclass correlation coefficient, coefficient of variation, mean differences, and Cohen’s effect sizes. There was good reliability for vertical stiffness, moderate reliability for leg stiffness, and poor reliability for knee and ankle stiffness during the running task. Similar results were observed during the 2.2 Hz hopping tasks, with good reliability displayed for vertical stiffness and poor reliability for ankle and knee stiffness. In conclusion, our results suggest that vertical stiffness is a reliable measure when running at 3.83 m/s and hopping at 2.2 Hz.
Foot Forces Induced Through Tai Chi Push-Hand Exercises
Authors: Wong Shiu Hong , Ji Tianjian , Hong Youlian , Fok Siu Lun , Wang Lin
Published: August 2016

The low impact forces of Tai Chi push-hand exercises may be particularly suited for older people and for those with arthritis; however, the biomechanics of push-hand exercises have not previously been reported. This paper examines the ground reaction forces (GRFs) and plantar force distributions during Tai Chi push-hand exercises in a stationary stance with and without an opponent. Ten male Tai Chi practitioners participated in the study. The GRFs of each foot were measured in three perpendicular directions using two force plates (Kistler). The plantar force distribution of each foot was measured concurrently using an insole sensor system (Novel). The results showed that the average maximum vertical GRF of each foot was not more than 88% ± 6.1% of the body weight and the sum of the vertical forces (103% ± 1.4%) generated by the two feet approximately equals the body weight at any one time. The horizontal GRFs generated by the two feet were in the opposite directions and the measured mean peak values were not more than 12% ± 2.8% and 17% ± 4.3% of the body weight in the medio-lateral and antero-posterior directions respectively. Among the nine plantar areas, the toes sustained the greatest plantar force. This study indicates that push-hand exercises generate lower vertical forces than those induced by walking, bouncing, jumping and Tai Chi gait, and that the greatest plantar force is located in the toe area, which may have an important application in balance training particularly for older adults.
Relationship Between Muscle Architecture and Joint Performance During Concentric Contractions in Humans
Authors: Wakahara Taku , Kanehisa Hiroaki , Kawakami Yasuo , Fukunaga Tetsuo , Yanai Toshimasa
Published: August 2016

The purpose of this study was to examine the relationship between muscle architecture of the triceps brachii (TB) and joint performance during concentric elbow extensions. Twenty-two men performed maximal isometric and concentric elbow extensions against various loads. Joint torque and angular velocity during concentric contractions were measured, and joint power was calculated. Muscle length, cross-sectional areas, and volume of TB were measured from magnetic resonance images. Pennation angle (PA) of TB at rest was determined by ultrasonography. The PA was significantly correlated with the maximal isometric torque (r = .471), but not to the torque normalized by muscle volume (r = .312). A significant correlation was found between PA and the angular velocity at 0 kg load (r = .563), even when the angular velocity was normalized by the muscle length (r = .536). The PA was significantly correlated with the maximal joint power (r = .519), but not with the power normalized by muscle volume (r = .393). These results suggest that PA has a positive influence on the muscle shortening velocity during an unloaded movement, but does not have a significant influence on the maximum power generation in untrained men.
Abdomen-Thigh Contact During Forward Reaching Tasks in Obese Individuals
Authors: Singh Bhupinder , Brown Thomas D. , Callaghan John J. , Yack H. John
Published: August 2016

During seated forward reaching tasks in obese individuals, excessive abdominal tissue can come into contact with the anterior thigh. This soft tissue apposition acts as a mechanical restriction, altering functional biomechanics at the hip, and causing difficulty in certain daily activities such as bending down, or picking up objects from the floor. The purpose of the study was to investigate the contact forces and associated moments exerted by the abdomen on the thigh during seated forward-reaching tasks in adult obese individuals. Ten healthy subjects (age 58.1 ± 4.4) with elevated BMI (39.04 ± 5.02) participated in the study. Contact pressures between the abdomen and thigh were measured using a Tekscan Conformat pressure-mapping sensor during forward-reaching tasks. Kinematic and force plate data were obtained using an infrared motion capture system. The mean abdomen-thigh contact force was 10.17 ± 5.18% of body weight, ranging from 57.8 N to 200 N. Net extensor moment at the hip decreased by mean 16.5 ± 6.44% after accounting for the moment generated by abdomen-thigh tissue contact. In obese individuals, abdomen-thigh contact decreases the net moment at the hip joint during seated forward-reaching activities. This phenomenon should be taken into consideration for accurate biomechanical modeling in these individuals.
A Work-Loop Method for Characterizing Leg Function During Sagittal Plane Movements
Authors: Maykranz Daniel , Grimmer Sten , Seyfarth Andre
Published: August 2016

The work-loop method is frequently used to determine the mechanical work performed by a system, for instance, when analyzing muscles or describing the work balance at the joint level. While for these examples usually only one-dimensional movements are investigated, for two- or three-dimensional movements, such as leg function during walking and running, the work-loop has to be adapted. In this paper, we present an analytical derivation that extends the work-loop method to two-dimensional sagittal plane movements. Three effects contribute to the mechanical work of the leg: (1) forces directed along the leg axis, (2) forces acting perpendicular to the leg axis, and (3) a shift of the center of pressure (COP) during stance. These three contributors to the mechanical work performed can be interpreted as three general tasks of the leg. To demonstrate the new work-loop method, we analyzed experimental data on hopping, running and walking. The results indicate that the proposed new generalized work-loop concept is suitable for describing the overall mechanical work performed on the COM during stance with energy consistent net work balances. Depending on the type of gait, specific contributions of each work term were found that characterize leg function during locomotion.
The Relationship Between Hamstring Muscle Extensibility and Spinal Postures Varies with the Degree of Knee Extension
Authors: Muyor José M. , López-Miñarro Pedro A. , Alacid Fernando
Published: August 2016

The aim was to determine the relationship between hamstring muscle extensibility and sagittal spinal curvatures and pelvic tilt in cyclists while adopting several postures. A total of 75 male cyclists were recruited for this study (34.79 ± 9.46 years). Thoracic and lumbar spine and pelvic tilt were randomly measured using a Spinal Mouse. Hamstring muscle extensibility was determined in both legs by a passive knee extension test. Low relationships were found between hamstring muscle extensibility and spinal parameters (thoracic and lumbar curvature, and pelvic tilt) in standing, slumped sitting, and on the bicycle (r = .19; P > .05). Significant but low relationships were found in maximal trunk flexion with knees flexed (r = .29; P < .05). In addition, in the sit-and-reach test, low and statistically significant relationships were found between hamstring muscle extensibility for thoracic spine (r = –.23; P = .01) and (r = .37; P = .001) for pelvic tilt. In conclusion, hamstring muscle extensibility has a significant relationship in maximal trunk flexion postures with knees flexed and extended, but there are no relationships while standing or on the bicycle postures.
Differences in Spring-Mass Characteristics Between One- and Two-Legged Hopping
Authors: Hobara Hiroaki , Kobayashi Yoshiyuki , Kato Emika , Ogata Toru
Published: August 2016

Although many athletic activities and plyometric training methods involve both unilateral and bilateral movement, little is known about differences in the leg stiffness (Kleg) experienced during one-legged hopping (OLH) and two-legged hopping (TLH) in place. The purpose of this study was to investigate the effect of hopping frequencies on differences inKlegduring OLH and TLH. Using a spring-mass model and data collected from 17 participants during OLH and TLH at frequencies of 2.0, 2.5, and 3.0 Hz,Klegwas calculated as the ratio of maximal ground reaction force (Fpeak) to the maximum center of mass displacement (ΔCOM) at the middle of the stance phase measured from vertical ground reaction force. BothKlegandFpeakwere found to be significantly greater during TLH than OLH at all frequencies, but type of hopping was not found to have a significant effect on ΔCOM. These results suggest thatKlegis different between OLH and TLH at a given hopping frequency and differences inKlegduring OLH and TLH are mainly associated with differences inFpeakbut not ΔCOM.
Maximal Physiological Responses to Deep-Water and Treadmill Running in Young and Older Women
Authors: Chu Kelly S. , Rhodes Edward C. , Taunton Jack E. , Martin Alan D.
Published: August 2016

The purpose of this study was to assess the difference in maximal physiological responses between an acute bout of deep-water running (DWR) and treadmill running (TMR) in young and older adults. Participants were 9 young and 9 older women who performed maximal DWR and TMR tests. Maximal measures included oxygen consumption (VO2max), heart rate (HRmax), ventilation (VE), respiratory-exchange ratio (RER), and blood lactate (BLac). The young women exhibited higher VO2max, HRmax, VE, and BLac than did the older women for both exercise conditions (p < .05). Lower VO2max and HRmax values were observed with DWR for both age groups (p < .05). No significant differences were found for VE, RER, and BLac in either group between exercise conditions, nor a significant interaction between exercise conditions or ages for any of the variables measured. The data suggest that although older adults exhibit lower maximal metabolic responses, differences between DWR and TMR responses occur irrespective of age.
Accelerated Decline in Running Performance in a Master Runner with a History of a Large Volume of Training and Racing
Authors: Lambert Mike I. , Bryer Lise , Hampson David B. , Nobbs Les , Rapolthy Andrea M. , Taliep M. Sharhidd , Viljoen L. Wayne
Published: August 2016

The aim of this study was to measure the change in running performance in a runner from age 27–64 years. During this time the runner had a history of high-volume training and racing. The change in his average running speed over 10-, 21.1-, 42.2-, and 90-km races was compared with the changes in the age-group records for each distance. He trained an average of 4,051 ± 1,762 km/year and ran 16,604 km during races. His training load reached a peak of 7,596 km/year at the age of 33. His rate of decline in running performance was higher than the expected age decline at 47 years for 10-km, 47 years for 21.1-km, 40 years for the 42.2-km, and 48 years for 90-km races. Decreases in performance with increasing age could be explained by reduced training volume, or, alternatively, high volumes of training and racing might accelerate the normal age-related decrements in running performance.
Physical-Fitness Declines in Older Japanese Adults
Authors: Demura Shinichi , Minami Masaki , Nagasawa Yoshinori , Tada Nobuhiko , Matsuzawa Jinzaburo , Sato Susumu
Published: August 2016

This cross-sectional study determined physical-fitness levels of more than 1,000 Japanese older men and women, including 338 participants who were 75 years of age and older. Each participant performed 11 tests representing 4 domains of functioning (muscular, joint, neural, and respiratory). Two-way ANOVA was used to examine gender and age differences for each variable. Performance on every test decreased with advancing age, but the declines did not occur at a uniform rate. In addition, men and women did not decline at the same rate for each variable. Although leg strength, balance ability, and reaction time did not decline until after the age of 65, they exhibited the steepest decline of all the variables after age 75. These findings suggest that significant declines in physical fitness occur with advancing age, especially those that are related to mobility and risk for falls.
Leisure-Time Activity among Older U.S. Women in Relation to Hormone-Replacement-Therapy Initiation
Authors: Andersen Ross E. , Crespo Carlos J. , Franckowiak Shawn C. , Walston Jeremy D.
Published: August 2016

Hormone-replacement therapy (HRT) and physical activity are both related to aging and health. U.S. minorities are more likely to be inactive and less likely to initiate HRT than are non-Hispanic White women. The purpose of this investigation was to examine the relationship of race and HRT use with physical inactivity among older women (60+ years). The authors used data from 3,479 women who had participated in the Third National Health and Nutrition Examination Survey (NHANES III), conducted in 1988-1994. NHANES III included an in-person interview and a medical examination. The prevalence of physical inactivity among women who reported ever having used HRT was 28.5% (CI 22.9–34.1%), compared with 40.0% (CI 35.9–44.1%) among those who had never used HRT. Mexican American and non-Hispanic Black women reported higher levels of inactivity than did non-Hispanic White women across HRT-use categories. To promote successful aging, physicians should educate postmenopausal women on the possible health benefits of HRT combined with an active lifestyle.