bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of Using Magnetic Resonance Elastography to Study the Effect of Aging on Shear Modulus of Skeletal Muscle
Authors: Domire Zachary J. , McCullough Matthew B. , Chen Qingshan , An Kai-Nan
Published: August 2016

A common complication associated with aging is the stiffening of skeletal muscles. The purpose of this study was to determine the ability of magnetic resonance elastography (MRE) to study this phenomenon in vivo. Twenty female subjects were included in the study with an age range of 50 to 70 years. Shear modulus was calculated for the tibialis anterior of each subject. There was not a significant relationship between age and shear modulus. However, three subjects had abnormally high values and were among the oldest subjects tested. There was a significant relationship between age and tissue stiffness homogeneity. More research is needed to determine whether the changes seen here are reflective of increased tissue cross-linking or related to reduced muscle quality. However, MRE shows promise as a tool to study aging-related muscle stiffness changes or to evaluate treatments to counteract these changes.
Effects of Bat Grip on Baseball Hitting Kinematics
Authors: Escamilla Rafael F. , Fleisig Glenn S. , DeRenne Coop , Taylor Marcus K. , Moorman Claude T. , Imamura Rodney , Barakatt Edward , Andrews James R.
Published: August 2016

A motion system collected 120-Hz data from 14 baseball adult hitters using normal and choke-up bat grips. Six swings were digitized for each hitter, and temporal and kinematic parameters were calculated. Compared with a normal grip, the choke-up grip resulted in 1) less time during stride phase and swing; 2) the upper torso more opened at lead foot contact; 3) the pelvis more closed and less bat linear velocity at bat-ball contact; 4) less range of motion of the upper torso and pelvis during swing; 5) greater elbow flexion at lead foot contact; and 6) greater peak right elbow extension angular velocity. The decreased time during the stride phase when using a choke-up grip implies that hitters quicken their stride when they choke up. Less swing time duration and less upper torso and pelvis rotation range of motion using the choke-up grip supports the belief of many coaches and players that using a choke-up grip results in a “quicker” swing. However, the belief that using a choke-up grip leads to a faster moving bat was not supported by the results of this study.
Errors in Force Generation and Changes in Controlling Patterns Following Agonist Muscle Fatigue
Authors: Huang Yi-Ming , Chang Ya-Ju , Hsu Miao-Ju , Chen Chia-Ling , Fang Chia-Ying , Wong Alice May-Kuen
Published: August 2016

The purpose of this study was to evaluate whether agonist muscle fatigue changed the coactivation time and the co-contraction magnitude of the agonist and antagonist muscle, and if the agonist muscle fatigue produced bias (constant error: CE) and inconsistency (variable error: VE) of the force. Subjects are 10 healthy people and one person with impaired proprioception. EMG and force for fast (0.19 ± 0.06 s) and slow (1.20 ± 0.44 s) targeted isometric dorsiflexions were recorded before and after fatigue of the dorsiflexors. The results revealed that the coactivation time increased after fatigue only in the slow contractions but the co-contraction magnitude did not change. The postfatigue increment of the CE was greater in the fast contractions than in the slow ones. We conclude that the postfatigue compensatory strategy can reduce the fatigue-induced bias. The change of muscles activation level after fatigue might be under the influence of the common drive. Impaired proprioception is a possible cause of the fatigue-related increase in bias and inconsistency.
Gait Dynamics on a Cross-Slope Walking Surface
Authors: Dixon Philippe C. , Pearsall David J.
Published: August 2016

The purpose of this study was to determine the effect of cross-slope on gait dynamics. Ten young adult males walked barefoot along an inclinable walkway. Ground reaction forces (GRFs), lower-limb joint kinematics, global pelvis orientation, functional leg-length, and joint reaction moments (JRMs) were measured. Statistical analyses revealed differences across limbs (up-slope [US] and down-slope [DS]) and inclinations (level; 0°; and cross-sloped, 6°). Adaptations included increases of nearly 300% in mediolateral GRFs (p < .001), functional shortening the US-limb and elongation of the DS-limb (p < .001), reduced step width (p = .024), asymmetrical changes in sagittal kinematics and JRM, and numerous pronounced coronal plane differences including increased US-hip adduction (and adductor moment) and decreased DS-hip adduction (and adductor moment). Data suggests that modest cross-slopes can induce substantial asymmetrical changes in gait dynamics and may represent a physical obstacle to populations with restricted mobility.
Influence of the Volume and Density Functions Within Geometric Models for Estimating Trunk Inertial Parameters
Authors: Wicke Jason , Dumas Genevieve A.
Published: August 2016

The geometric method combines a volume and a density function to estimate body segment parameters and has the best opportunity for developing the most accurate models. In the trunk, there are many different tissues that greatly differ in density (e.g., bone versus lung). Thus, the density function for the trunk must be particularly sensitive to capture this diversity, such that accurate inertial estimates are possible. Three different models were used to test this hypothesis by estimating trunk inertial parameters of 25 female and 24 male college-aged participants. The outcome of this study indicates that the inertial estimates for the upper and lower trunk are most sensitive to the volume function and not very sensitive to the density function. Although it appears that the uniform density function has a greater influence on inertial estimates in the lower trunk region than in the upper trunk region, this is likely due to the (overestimated) density value used. When geometric models are used to estimate body segment parameters, care must be taken in choosing a model that can accurately estimate segment volumes. Researchers wanting to develop accurate geometric models should focus on the volume function, especially in unique populations (e.g., pregnant or obese individuals).
Kinematic Characteristics of the Ski Jump Inrun: A 10-Year Longitudinal Study
Authors: Janura Miroslav , Cabell Lee , Elfmark Milan , Vaverka František
Published: August 2016

The athlete’s inrun position affects the outcome for take-off in ski jumping. The purpose of this study was to examine the kinematic parameters between skiers’ adjacent body segments during their first straight path of the inrun. Elite ski jumpers participated in the study at the World Cup events in Innsbruck, Austria, during the years 1992 through 2001. A video image was taken at a right angle to the tracks of the K-110 (meter) jumping hill. Kinematic data were collected from the lower extremities and trunk of the athletes. Findings indicated that jumpers had diminished ankle and knee joint angles and increased trunk and hip angles over the 10 years. In recent years, the best athletes achieved a further length of their jumps, while they experienced slower inrun average velocity. These results are perhaps explained by several possible contributing factors, such as new technique of the jumper’s body kinematics, advancements in equipment technology, and somatotype of the jumpers.
The Influence of Seat Configuration on Maximal Average Crank Power during Pedaling: A Simulation Study
Authors: Rankin Jeffery W. , Neptune Richard R.
Published: August 2016

Manipulating seat configuration (i.e., seat tube angle, seat height and pelvic orientation) alters the bicycle-rider geometry, which influences lower extremity muscle kinematics and ultimately muscle force and power generation during pedaling. Previous studies have sought to identify the optimal configuration, but isolating the effects of specific variables on rider performance from the confounding effect of rider adaptation makes such studies challenging. Of particular interest is the influence of seat tube angle on rider performance, as seat tube angle varies across riding disciplines (e.g., road racers vs. triathletes). The goals of the current study were to use muscle-actuated forward dynamics simulations of pedaling to 1) identify the overall optimal seat configuration that produces maximum crank power and 2) systematically vary seat tube angle to assess how it influences maximum crank power. The simulations showed that a seat height of 0.76 m (or 102% greater than trochanter height), seat tube angle of 85.1 deg, and pelvic orientation of 20.5 deg placed the major power-producing muscles on more favorable regions of the intrinsic force-length-velocity relationships to generate a maximum average crank power of 981 W. However, seat tube angle had little influence on crank power, with maximal values varying at most by 1% across a wide range of seat tube angles (65 to 110 deg). The similar power values across the wide range of seat tube angles were the result of nearly identical joint kinematics, which occurred using a similar optimal seat height and pelvic orientation while systematically shifting the pedal angle with increasing seat tube angles.
Gender and Foot Orthotic Device Effect on Frontal Plane Hip Motion During Landing From a Vertical Jump
Authors: Jenkins Walter L. , Williams D.S. , Bevil Brandon , Stanley Sara , Blemker Michael , Taylor Drue , O’Brien Kevin
Published: August 2016

Excessive hip motion has been linked to lower extremity pathology. Foot orthoses are commonly used to control motion within lower extremity joints when lower extremity pathology and dysfunction are present. Few studies have investigated the effect of foot orthoses on hip angular kinematics during functional activities. Eighteen females and 18 males performed a vertical jump with and without a prefabricated foot orthoses to determine the biomechanical effect of foot orthoses on hip kinematics when landing from a jump. Data collection included three-dimensional motion analysis of the lower extremity. Paired t tests were performed to determine if differences existed within genders with and without foot orthoses. At the hip joint, there was significantly less hip adduction motion in the foot orthoses condition as compared with the no foot orthoses condition in females (p < .05). There were no differences between foot orthoses conditions in males. Females appear to have a different proximal response to foot orthoses when landing from a forward jump than males.
A Three-Dimensional Analysis of Finger and Bow String Movements During the Release in Archery
Authors: Horsak Brian , Heller Mario
Published: August 2016

The aim of this paper was to examine finger and bow string movements during archery by investigating a top Austrian athlete (FITA score = 1233) under laboratory conditions. Maximum lateral bow string deflection and angular displacements for index, third, and ring fingers between the full draw position and the end of the release were quantified using a motion tracking system. Stepwise multiple regression analyses were used to determine whether bow string deflection and finger movements are predictive for scoring. Joint ranges of motion during the shot itself were large in the proximal and distal interphalangeal joints, and much smaller in the metacarpophalangeal joints. Contrary to our expectations, greater deflection leads to higher scores (R2 = .18, p < .001) and the distal interphalangeal joint of the third finger weakly predicts the deflection (R2 = .11, p < .014). More variability in the joint angles of the third finger was found in bad shots than in good shots. Findings in this study let presume that maximum lateral bow string deflection does not adversely affect the archer’s performance.
Flap Irritation Phenomenon (FLIP): Etiology of Chronic Tenosynovitis After Finger Pulley Rupture
Authors: Schöffl Isabelle , Baier Thomas , Schöffl Volker
Published: August 2016

After a pulley rupture, most climbers regain the full function of their previously uninjured fingers. However, in some cases of pulley rupture, a persistent inflammation of the tendon sheath is observed. In this study, 16 cadaver fingers were loaded until pulley rupture and then studied for the rupturing mechanism. In addition, two patients with this pathology were investigated using ultrasound and MRI, and received surgery. In 13 fingers, a rupture of one or several pulleys occurred and almost always at the medial or lateral insertion. In one finger, a capsizing of the pulley underneath the intact tendon sheath was observed, leading to an avulsion between tendon and tendon sheath. A similar pathology was observed in the ultrasound imaging, in MRI, and during surgery in two patients with prolonged recovery after minor pulley rupture. In cases of prolonged tenosynovitis after minor pulley rupture, a capsizing of the pulley stump is probably the cause for constant friction leading to inflammation. In those cases, a surgical removal of the remaining pulley stump and sometimes a pulley repair may be necessary.
Pedaling Asymmetries in Cyclists With Unilateral Transtibial Amputation: Effect of Prosthetic Foot Stiffness
Authors: Childers W. Lee , Kistenberg Robert S. , Gregor Robert J.
Published: August 2016

Cyclists with unilateral transtibial amputation (CTA) provide a unique model to study integration of the neuromuscular and bicycle systems while having the option to modify this integration via the properties of the prosthesis. This study included eight CTA and nine intact cyclists. The cyclists pedaled on a stationary bicycle with instrumented force pedals. The CTA group pedaled with a stiff or flexible prosthetic foot during a simulated time trial and a low difficulty condition. During the time trial condition, pedaling with the flexible foot resulted in force and work asymmetries of 11.4% and 30.5%, the stiff foot displayed 11.1% and 21.7%, and the intact group displayed 4.3% and 4.2%, respectively. Similar trends were shown in the low difficulty condition. These data suggest foot stiffness has an effect on cycling symmetry in amputees.
Walking on High Heels Changes Muscle Activity and the Dynamics of Human Walking Significantly
Authors: Simonsen Erik B. , Svendsen Morten B. , Nørreslet Andreas , Baldvinsson Henrik K. , Heilskov-Hansen Thomas , Larsen Peter K. , Alkjær Tine , Henriksen Marius
Published: August 2016

The aim of the study was to investigate the distribution of net joint moments in the lower extremities during walking on high-heeled shoes compared with barefooted walking at identical speed. Fourteen female subjects walked at 4 km/h across three force platforms while they were filmed by five digital video cameras operating at 50 frames/second. Both barefooted walking and walking on high-heeled shoes (heel height: 9 cm) were recorded. Net joint moments were calculated by 3D inverse dynamics. EMG was recorded from eight leg muscles. The knee extensor moment peak in the first half of the stance phase was doubled when walking on high heels. The knee joint angle showed that high-heeled walking caused the subjects to flex the knee joint significantly more in the first half of the stance phase. In the frontal plane a significant increase was observed in the knee joint abductor moment and the hip joint abductor moment. Several EMG parameters increased significantly when walking on high-heels. The results indicate a large increase in bone-on-bone forces in the knee joint directly caused by the increased knee joint extensor moment during high-heeled walking, which may explain the observed higher incidence of osteoarthritis in the knee joint in women as compared with men.
A Comparison of Algorithms for Body-Worn Sensor-Based Spatiotemporal Gait Parameters to the GAITRite Electronic Walkway
Authors: Greene Barry R. , Foran Timothy G. , McGrath Denise , Doheny Emer P. , Burns Adrian , Caulfield Brian
Published: August 2016

This study compares the performance of algorithms for body-worn sensors used with a spatiotemporal gait analysis platform to the GAITRite electronic walkway. The mean error in detection time (true error) for heel strike and toe-off was 33.9 ± 10.4 ms and 3.8 ± 28.7 ms, respectively. The ICC for temporal parameters step, stride, swing and stance time was found to be greater than 0.84, indicating good agreement. Similarly, for spatial gait parameters—stride length and velocity—the ICC was found to be greater than 0.88. Results show good to excellent concurrent validity in spatiotemporal gait parameters, at three different walking speeds (best agreement observed at normal walking speed). The reported algorithms for body-worn sensors are comparable to the GAITRite electronic walkway for measurement of spatiotemporal gait parameters in healthy subjects.
Musculoskeletal Attenuation of Impact Shock in Response to Knee Angle Manipulation
Authors: Edwards W. Brent , Derrick Timothy R. , Hamill Joseph
Published: August 2016

Shock waves resulting from the foot-ground impact are attenuated by biological tissues within the body. It has been suggested that the primary site for shock attenuation is the knee joint. The purpose of this study was to determine if knee flexion affects the filtering characteristics of the musculoskeletal system in response to impacts. Impacts were delivered to 10 participants during inline skating on a treadmill at 2.0 m/s. Four knee angle conditions (0, 10, 20, and 30 degrees) were investigated using real-time visual feedback of motion capture data. Shock attenuation between the leg and head was determined using accelerometry. The cutoff frequency of the body was determined by progressive filtering of the leg acceleration until differences between head acceleration and filtered leg acceleration were minimized. A nonlinear increase in shock attenuation (p < .001) and a nonlinear decrease in the cutoff frequency of the body (p < .001) were observed as the knee became more flexed. These results suggest that the knee joint acts as a low-pass filter allowing greater shock attenuation with increased knee flexion. Flexing the knee may shift the shock-attenuating responsibilities away from passive biological tissue toward active muscular contraction.
Comparison of Four Reconstructive Methods for Diaphyseal Defects of the Humerus After Tumor Resection
Authors: Sakellariou Vasileios I. , Mavrogenis Andreas F. , Babis George C. , Soucacos Panayiotis N. , Magnissalis Evangelos A. , Papagelopoulos Panayiotis J.
Published: August 2016

The objective of the current study was to compare quantitative data on the biomechanical analysis of different techniques for fixation of intercalary bone defects of the humerus, by means of consistently applied methodology on composite models. A total of 25 humeral specimens of composite models were used. An intercalary defect was created and reconstructed using plates, intramedullary nails, external fixators and segmental prosthetic implants. The specimens were loaded under axial compression, four-point bending and torsion within the linear elastic region. Modular segmental implants and intramedullary nails were able to compensate significantly greater amounts of compressive loads compared to locking plates and external fixators. However, in flexion and torsion, the modular segmental implants and the external fixators were significantly better load-bearing devices compared to the intramedullary nails and plates. Early mobilization of the upper limb in patients with diaphyseal bone defects of the humerus could probably be more safe and tolerable when reconstructed with modular segmental implants.
Gross Efficiency and Cycling Economy Are Higher in the Field as Compared with on an Axiom Stationary Ergometer
Authors: Bertucci William M. , Betik Andrew C. , Duc Sebastien , Grappe Frederic
Published: August 2016

This study was designed to examine the biomechanical and physiological responses between cycling on the Axiom stationary ergometer (Axiom, Elite, Fontaniva, Italy) vs. field conditions for both uphill and level ground cycling. Nine cyclists performed cycling bouts in the laboratory on an Axiom stationary ergometer and on their personal road bikes in actual road cycling conditions in the field with three pedaling cadences during uphill and level cycling. Gross efficiency and cycling economy were lower (–10%) for the Axiom stationary ergometer compared with the field. The preferred pedaling cadence was higher for the Axiom stationary ergometer conditions compared with the field conditions only for uphill cycling. Our data suggests that simulated cycling using the Axiom stationary ergometer differs from actual cycling in the field. These results should be taken into account notably for improving the precision of the model of cycling performance, and when it is necessary to compare two cycling test conditions (field/laboratory, using different ergometers).
Next-Generation Low-Cost Motion Capture Systems Can Provide Comparable Spatial Accuracy to High-End Systems
Authors: Thewlis Dominic , Bishop Chris , Daniell Nathan , Paul Gunther
Published: August 2016

The objective quantification of three-dimensional kinematics during different functional and occupational tasks is now more in demand than ever. The introduction of new generation of low-cost passive motion capture systems from a number of manufacturers has made this technology accessible for teaching, clinical practice and in small/medium industry. Despite the attractive nature of these systems, their accuracy remains unproved in independent tests. We assessed static linear accuracy, dynamic linear accuracy and compared gait kinematics from a Vicon MX-f20 system to a Natural Point OptiTrack system. In all experiments data were sampled simultaneously. We identified both systems perform excellently in linear accuracy tests with absolute errors not exceeding 1%. In gait data there was again strong agreement between the two systems in sagittal and coronal plane kinematics. Transverse plane kinematics differed by up to 3° at the knee and hip, which we attributed to the impact of soft tissue artifact accelerations on the data. We suggest that low-cost systems are comparably accurate to their high-end competitors and offer a platform with accuracy acceptable in research for laboratories with a limited budget.
Effects of Medially Wedged Foot Orthoses on Knee and Hip Joint Running Mechanics in Females With and Without Patellofemoral Pain Syndrome
Authors: Boldt Andrew R. , Willson John D. , Barrios Joaquin A. , Kernozek Thomas W.
Published: August 2016

We examined the effects of medially wedged foot orthoses on knee and hip joint mechanics during running in females with and without patellofemoral pain syndrome (PFPS). We also tested if these effects depend on standing calcaneal eversion angle. Twenty female runners with and without PFPS participated. Knee and hip joint transverse and frontal plane peak angle, excursion, and peak internal knee and hip abduction moment were calculated while running with and without a 6° full-length medially wedged foot orthoses. Separate 3-factor mixed ANOVAs (group [PFPS, control] x condition [medial wedge, no medial wedge] x standing calcaneal angle [everted, neutral, inverted]) were used to test the effect of medially wedged orthoses on each dependent variable. Knee abduction moment increased 3% (P= .03) and hip adduction excursion decreased 0.6° (P< .01) using medially wedged foot orthoses. No significant group x condition or calcaneal angle x condition effects were observed. The addition of medially wedged foot orthoses to standardized running shoes had minimal effect on knee and hip joint mechanics during running thought to be associated with the etiology or exacerbation of PFPS symptoms. These effects did not appear to depend on injury status or standing calcaneal posture.
Gender Differences in Trunk and Pelvic Kinematics During Prolonged Ergometer Rowing in Adolescents
Authors: Ng Leo , Campbell Amity , Burnett Angus , O’Sullivan Peter
Published: August 2016

The trunk and pelvis kinematics of 20 healthy male and female adolescent rowers were recorded during an ergometer trial using an electromagnetic tracking system (Fastrak). The kinematics of each drive phase were collected during the 1st and 20th minute, respectively. The mean and range of the kinematics, stroke rate and stroke length were compared between genders and over time. Male rowers postured their pelvis with more posterior tilt and their thoracic spine in more flexion than female rowers (P < .05). Both genders postured their pelvis in more posterior pelvic rotation and upper trunk in more flexion over time. Male rowers were found to have a significantly shorter drive phase than female rowers (P = .001). Differences in trunk and pelvic kinematics between adolescent male and female rowers suggest potentially various mechanisms for biomechanical stress. Assessment and training of rowers should take gender differences into consideration.
The Effect of Jump-Landing Directions on Dynamic Stability
Authors: Liu Kathy , Heise Gary D.
Published: August 2016

Dynamic stability is often measured by time to stabilization (TTS), which is calculated from the dwindling fluctuations of ground reaction force (GRF) components over time. Common protocols of dynamic stability research have involved forward or vertical jumps, neglecting different jump-landing directions. Therefore, the purpose of the present investigation was to examine the influence of different jump-landing directions on TTS. Twenty healthy participants (9 male, 11 female; age = 28 ± 4 y; body mass = 73.3 ± 21.5 kg; body height = 173.4 ± 10.5 cm) completed the Multi-Directional Dynamic Stability Protocol hopping tasks from four different directions—forward, lateral, medial, and backward—landing single-legged onto the force plate. TTS was calculated for each component of the GRF (ap = anterior-posterior; ml = medial-lateral; v = vertical) and was based on a sequential averaging technique. All TTS measures showed a statistically significant main effect for jump-landing direction. TTSml showed significantly longer times for landings from the medial and lateral directions (medial: 4.10 ± 0.21 s, lateral: 4.24 ± 0.15 s, forward: 1.48 ± 0.59 s, backward: 1.42 ± 0.37 s), whereas TTSap showed significantly longer times for landings from the forward and backward directions (forward: 4.53 ± 0.17 s, backward: 4.34 0.35 s, medial: 1.18 ± 0.49 s, lateral: 1.11 ± 0.43 s). TTSv showed a significantly shorter time for the forward direction compared with all other landing directions (forward: 2.62 ± 0.31 s, backward: 2.82 ± 0.29 s, medial: 2.91 ± 0.31 s, lateral: 2.86 ± 0.32 s). Based on these results, multiple jump-landing directions should be considered when assessing dynamic stability.
The Effect of Arm Action on the Vertical Jump Performance in Children and Adult Females
Authors: Floría Pablo , Harrison Andrew J.
Published: August 2016

The aim of this study was to evaluate the effect of age on the use of arm swing in the vertical jump. Counter-movement jumps with arms (CMJA) and without arms (CMJ) performed by 36 girls and 20 adult females were examined using force platform analysis. The data were analyzed to determine differences between groups and between types of jump. The analysis of the data indicated that the arm action increased the jump height in both groups, although the increase was greater in children than adults (22.6% and 18.7% respectively; P < .05). This difference in jump height was due to a combination of a greater increase of the height at take-off in children compared with adults (40.6% and 21.6% respectively; P < .05) with no differences in the increase of the flight height. This increase in height of take-off was accompanied by an increase in the distance of propulsion in CMJA compared with CMJ (0.25 m and 0.23 m respectively; P < .05). The results suggested that children take advantage of the action of the arms in vertical jump differently than adults. The children improved their jump height by increasing height at take-off whereas the adults improved by increasing the flight height.
The Relationship Between Different Body Mass Index Categories and Chair Rise Performance in Adult Women
Authors: Schmid Stefan , Armand Stéphane , Pataky Zoltan , Golay Alain , Allet Lara
Published: August 2016

An important prerequisite to carry out daily activities is the sit-to-stand movement. However, in obese people, this movement is characterized by altered biomechanics, which might lead to daily life activity impairments. The aim of this study was to investigate whether there are differences in kinetic and kinematic variables between three different BMI categories when performing a specific sit-to-stand test. Thirty-six adult women (BMI = 17–45 kg/m2) performed the sit-to stand test five times consecutively and as quickly as possible. Analyses of variance were used to determine differences between three BMI groups (normal or overweight: BMI < 30 kg/m2; obese: 30 ≤ BMI < 35; severely obese: BMI ≥ 35). Peak and mean vertical sacrum velocity indicated a decrease in severely obese subjects. Obese and severely obese individuals did not show higher fatigue over the five consecutive movements. Peak force and rate of force development decreased in normal or overweight subjects. The ability to successfully complete the test decreased with a higher BMI, probably due to a reduced ability to rapidly generate a high force.
Effect of Heel Construction on Muscular Control Potential of the Ankle Joint in Running
Authors: Willwacher Steffen , Potthast Wolfgang , Konrad Markus , Brüggemann Gert-Peter
Published: August 2016

The purpose of this study was to investigate the effect of heel construction on ankle joint mechanics during the early stance phase of running. Kinematic and kinetic parameters (ankle joint angles, angular velocities and joint moments, lever arms of ground reaction force, triceps surae muscle tendon unit lengths, and rates of muscle tendon unit length change) were calculated from 19 male subjects running at 3.3 m/s in shoes with different heel constructions. Increasing heel height and posterior wedging amplified initial plantar flexion velocity and range. The potential for a muscle to control the movement of a joint depends upon its ability to produce joint moments. Runners in this study showed decreased external eversion moments and an increase in eversion range. Maximum eversion angles were not significantly affected by shoe conditions. Without considerable tendon prestretch, joint moment generation potentials of triceps surae and deep plantar flexors might be inhibited due to rapid plantar flexion based on the force–velocity relationship. It could be speculated that increasing ankle inversion at heel strike could be a strategy to keep maximum eversion angles inside an adequate range, if joint moment generation potentials of deep plantar flexors are inhibited due to rapid plantar flexion.
Effect of BMI on Knee Joint Torques in Ergometer Rowing
Authors: Roemer Karen , Hortobagyi Tibor , Richter Chris , Munoz-Maldonado Yolanda , Hamilton Stephanie
Published: August 2016

Although an authoritative panel recommended the use of ergometer rowing as a non-weight-bearing form of exercise for obese adults, the biomechanical characterization of ergometer rowing is strikingly absent. We examined the interaction between body mass index (BMI) relative to the lower extremity biomechanics during rowing in 10 normal weight (BMI 18–25), 10 overweight (BMI 25–30 kg·m−2), and 10 obese (BMI > 30 kg·m−2) participants. The results showed that BMI affects joint kinematics and primarily knee joint kinetics. The data revealed that high BMI leads to unfavorable knee joint torques, implying increased loads of the medial compartment in the knee joint that could be avoided by allowing more variable foot positioning on future designs of rowing ergometers.
Extrinsic Feedback and the Learning of Kinetic Patterns in Cycling
Authors: Broker Jeffrey P. , Gregor Robert J. , Schmidt Richard A.
Published: August 2016

This study evaluated the retention of a cycling kinetic pattern using two different feedback schedules and evaluated the potential for feedback dependency in a continuous-task learning environment. Eighteen inexperienced cyclists rode a racing bicycle mounted to a fixed-fork Velodyne Trainer, with pedal forces monitored by dual piezoelectric transducers. Subjects received right-pedal shear force feedback and a criterion pattern emphasizing “effective” shear. Concurrent feedback (CFB) subjects received concurrent feedback 140 ms after the completion of every other revolution, while summary feedback (SFB) subjects received averaged feedback between trials. All subjects performed 10 retention trials without feedback 1 week later. Both groups improved significantly during practice, and performance decay in retention was negligible. Group differences during all phases were not significant. High CFB group proficiency in retention indicated that the detrimental aspects of frequent feedback were not significant. High SFB proficiency in retention suggests that large changes in kinetic patterning are achievable with relatively few feedback presentations.
A Panning Videographic Technique to Obtain Selected Kinematic Characteristics of the Strides in Sprint Hurdling
Authors: Chow John W.
Published: August 2016

This paper describes a panning videographic technique for measuring stride lengths and horizontal velocities of strides over an entire hurdle race. The technique requires that tapes of alternate black and white sections be placed at the inside border of the inside lane and the outside border of the outside lane of a track as spatial reference and that a vertical reference be videotaped when it is erected at different locations within the track. The stride lengths and horizontal velocities obtained with the panning technique were compared with the corresponding values that were obtained with conventional stationary camera techniques. The results indicate that if three panning cameras are used to cover the entire hurdle race, the average absolute errors in stride length and horizontal velocity are 0.07 m and 0.15 m/s, respectively. Such errors are considered acceptable for some applications. Certain properties of the panning technique are discussed.
Physical Activity, Psychological Well-Being, and Mood State in Elderly Women
Authors: Nieman David C. , Warren Beverly J. , Dotson Ruth G. , Butterworth Diane E. , Henson Dru A.
Published: August 2016

The relationship between cardiorespiratory exercise and psychological well-being and mood state was studied in elderly women. Thirty-two sedentary Caucasian women 67 to 85 years of age were randomly assigned to either a walking or an attention-placebo control group; 30 completed all phases of the study. Intervention groups exercised 30 to 40 minutes 5 days a week for 12 weeks, with the walking group training at 60% heart rate reserve and the control group engaging in mild range-of-motion and flexibility movements that kept their heart rates close to resting levels. In a separate analysis, 12 highly conditioned elderly women 65 to 84 years of age who were active in endurance competitions were recruited at baseline for cross-sectional comparisons. At baseline they exhibited superior scores on the profile of mood states (POMS) and general well-being (GWB) schedule. Twelve weeks of moderate cardiorespiratory exercise improved the VO2max of the sedentary subjects 12.6% but did not result in improvement in POMS or GWB scores greater than those of the attention-placebo control group.
Perceived Barriers to Physical Activity among Older Australians
Authors: Booth Michael L. , Bauman Adrian , Owen Neville
Published: August 2016

In a cross-sectional survey, older Australians (N = 402) were asked to report their physical activity habits and the 3 main barriers to more physical activity. Active and inactive men and women differed only in how many reported being sufficiently active or that their health was too poor to be more active. Six barriers were reported by more than 10% of inactive men and women: “already active enough,” “have an injury or disability,” “poor health,” “too old,” “don't have enough time,” and “I'm not the sporty type.” Insufficient time was identified by significantly fewer respondents as age increased. More respondents 65–70+ years old identified poor health as a barrier than did those 60–64. The proportion who had an injury or disability decreased from 60–64 to 65–69 and increased markedly among those 70+. Programs for older adults should take into account the age of the target group and the limitations imposed by poor health or disability.
Physical Activity and Cardiovascular Health in Aging Women: A Health-Promotion Perspective
Authors: Sawatzky Jo-Ann V. , Naimark Barbara J.
Published: August 2016

Cardiovascular disease is the leading cause of death in women. The purpose of this study was to explore the relationship between physical activity and other determinants of cardiovascular health in aging women from a health-promotion perspective. Participants (N = 206) completed a cardiovascular health-promotion profile, and various physical measures were recorded. The findings suggest that physically active aging women, especially those who exercise regularly or vigorously, have healthier cardiovascular profiles than do their less active counterparts. They were more likely to be members of a health and fitness facility, to be younger, and have higher socioeconomic status. Their diets were healthier, and their perception of their health status was more positive. Physical measures of cardiovascular health also decreased with increased levels of activity (p < .05). These findings validate physical activity promotion as an effective strategy to ameliorate the cardiovascular health profile of aging women. The study also lends support for population-based cardiovascular health-promotion strategies.
Future-Oriented Self-Perceptions and Exercise Behavior in Middle-Aged Women
Authors: Whaley Diane E.
Published: August 2016

Future-oriented self-perceptions, or possible selves (Markus & Nurius, 1986), represent how individuals think about their potential and their future. To explore the cognitive processes involved in the decision to exercise, the possible selves of 203 middle-aged women from a university community, representing a range of exercise behaviors, were examined. Comparisons were made of possible selves identified by participants across levels of exercise behavior, and the ability of possible selves to discriminate exercisers from nonexercisers was examined. Group differences were most evident in possible selves related to body image, with hoped-for and feared selves more likely to be described by inactive individuals than by their more active counterparts. The self-regulatory mechanisms of self-efficacy, outcome expectancy, and importance discriminated nonexercisers from exercisers, particularly long-term exercisers. Findings support the conclusion that possible selves related to exercise is a useful construct for examining the process of behavioral change and for planning future exercise interventions.
Components of Response Time as a Function of Age, Physical Activity, and Aerobic Fitness
Authors: Etnier Jennifer L. , Sibley Benjamin A. , Pomeroy Jeremy , Kao James C.
Published: August 2016

Research suggests that there are differences in response time (RespT) as a function of age but that aerobic fitness might have a facilitatory effect on RespT. This study was designed to examine this relationship while addressing methodological issues from past research. Men from 3 age groups completed speeded tasks, a physical activity questionnaire, and an aerobic-fitness test. Results indicated that age has a negative impact on RespT (specifically premotor time and movement time). The interaction of aerobic fitness by age was also a significant predictor of RespT (specifically movement time) such that aerobic fitness was positively related to speed of performance for older participants. It is concluded that aerobic fitness might serve a preservative function for speeded tasks in older adults.
Evaluation of Differences in Bone-Mineral Density in 51 Men Age 65–93 Years: A Cross-Sectional Study
Authors: Ballard Joyce E. , Wallace Lorraine S. , Holiday David B. , Herron Cassandra , Harrington Liberty L. , Mobbs Karen C. , Cussen Patricia
Published: August 2016

This study assessed differences in bone-mineral density (BMD) and lean and fat tissues between 5 age groups of White men age 65–93 years. Lean and fat tissues were measured with absorptiometry and anthropometry, and BMD, with dual-energy X-ray absorptiometry. Forearm, spinal, and femoralTscores were used to classify BMD as normal, osteopenic, or osteoporotic. A questionnaire evaluated previous physical activity, calcium intake, and bone fractures. Significantly lower values in body weight, lean tissue, and forearm BMD occurred in the older age groups. Significant, positive relationships were found between total lean tissue and radial, spinal, and hip BMDs. For the total group, osteopenic and osteoporoticTscores, respectively, were femoral neck 70.6% and 9.8%, radius 27.5% and 25.5%, and spine 25.5% and 7.8%. Differences in BMD values were found between levels of lifestyle factors (dietary calcium and history of previous fractures). In conclusion, elderly men should be encouraged to maintain adequate total lean tissue because of its association with BMD.
Age-Related Changes in Skeletal-Muscle Myosin Heavy-Chain Composition: Effect of Mechanical Loading
Authors: Pehme Ando , Alev Karin , Kaasik Priit , Seene Teet
Published: August 2016

The purpose of this study was to investigate the effect of compensatory hypertrophy (CH), heavy-resistance exercise training (HRET), and simultaneous CH and HRET on fast-twitch skeletal-muscle myofibrillar-protein synthesis, myosin heavy-chain (MHC) turnover rate, and MHC-isoform composition in young and old rats. In young animals all treatments intensified myofibrillar-protein synthesis, whereas in old animals with CH protein synthesis remained unchanged. The relative content of MHC I and IID in plantaris muscle increases with age, and the relative content of MHC IIB decreases. HRET and simultaneous CH and HRET decreased the proportion of MHC IIB and IIA and increased that of MHC IID in young rat muscle. In old rat muscle, relative content of MHC IID decreased and that of MHC IIB increased. CH decreased relative content of MHC IIB in both age groups and of MHC IIA in old animals. Relative content of MHC IID increased in both groups, and of MHC IIA, in young animals. MHC in plantaris of young rats turned over much faster in all types of mechanical loading but in old rats only during HRET and its combination with CH.
The Effect of Habitual Exercise on Respiratory-Muscle Function in Older Adults
Authors: Watsford Mark L. , Murphy Aron J. , Pine Matthew J. , Coutts Aaron J.
Published: August 2016

Older adults’ participation in habitual exercise might be affected by alterations to respiratory mechanics such as decreased respiratory-muscle strength. This reduction can cause a decrease in efficiency of the ventilatory pump, potentially compromising exercise participation. This research examined the role of habitual exercise in respiratory-muscle function and the associated implications for exercise performance. Seventy-two healthy older adults (36 men, 64.9 ± 8.6 years, 177.2 ± 8.4 cm, 82.5 ± 11.9 kg; 36 women, 64.9 ± 9.5 years, 161.7 ± 6.4 cm, 61.6 ± 9.2 kg) undertook respiratory-function and walking-performance tests. Active men and women achieved higher scores than their inactive counterparts for all tests except spirometry, where no differences were evident. The results indicate that a significant amount of the elevated fitness level might be accounted for by increased endurance capacity of the inspiratory muscles. Inactive older individuals might be at risk for inadequate respiratory-muscle strength, so interventions should be considered.
Age-Related Changes in Maximal Power and Maximal Heart Rate Recorded during a Ramped Test in 114 Cyclists Age 15–73 Years
Authors: Balmer James , Potter Christopher R. , Bird Steve R. , Davison R.C. Richard
Published: August 2016

This study assessed age-related changes in power and heart rate in 114 competitive male cyclists age 15–73 years. Participants completed a maximal Kingcycle™ ergometer test with maximal ramped minute power (RMPmax, W) recorded as the highest average power during any 60 s and maximal heart rate (HRmax, beats/min) as the highest value during the test. From age 15 to 29 (n = 38) RMPmax increased by 7.2 W/year (r = .53, SE 49 W, p < .05). From age 30 to 73 (n = 78) RMPmax declined by 2.4 W/year (r = –.49, SE 49 W, p < .05). Heart rate decreased across the full age range by 0.66 beats · min–1 · year–1 (r = –.75, SE 9 beats/min, p < .05). Age accounted for only 25% of the variance in RMPmax but 56% in HRmax. RMPmax was shown to peak at age 30, then decline with age, whereas HRmax declined across the full age range.
The Effects of Physical Activity and Sedentary Behavior on Cognitive Health in Older Adults
Authors: Vance David E. , Wadley Virginia G. , Ball Karlene K. , Roenker Daniel L. , Rizzo Matthew
Published: August 2016

Physical activity has been shown to be positively associated with cognitive health, but the mechanisms underlying the benefits of physical activity on cognitive health are unclear. The present study simultaneously examined two hypotheses using structural equation modeling (SEM). The depression-reduction hypothesis states that depression suppresses cognitive ability and that physical activity alleviates dysphoric mood and thereby improves cognitive ability. The social-stimulation hypothesis posits that social contact, which is often facilitated by socially laden physical activities, improves cognitive functioning by stimulating the nervous system. Sedentary behavior in the absence of physical activity is expected to exert an inverse relationship on cognitive health through each of these hypotheses. Community-dwelling elders (N = 158) were administered a variety of measures of cognition, depression, social support, and physical activity. SEM techniques provided partial support for the social-stimulation hypothesis and depression-reduction hypothesis. Implications for treating depression and improving cognitive functioning are discussed.
Comparison of Two Methods of Measuring Physical Activity in South African Older Adults
Authors: Kolbe-Alexander Tracy L. , Lambert Estelle V. , Harkins Judith Biletnikoff , Ekelund Ulf
Published: August 2016

The aim of this study was to assess the validity and reliability of the Yale Physical Activity Survey (YPAS) and the short version of the International Physical Activity Questionnaire (IPAQ) in older South African adults. The YPAS includes measures of weekly energy expenditure (EE) for housework, yard work, caregiving, exercise, and recreation. The IPAQ measures total time and EE during vigorous and moderate activity, walking, and sitting. The instruments were administered twice for test–retest reliability (men, n = 52, 68 ± 5.4 years, and women, n = 70, 66 ± 5.8 years). Data for criterion validity were obtained from accelerometers. YPAS reliability ranged from r = .44 to.80 for men and r = .59 to .99 for women (p < .0001). IPAQ reliability was lower for men (r = .29 to .76) than for women (r = .46 to .77). Criterion validity of the YPAS was .31 to .54 for men and .26 to .29 for women. The YPAS and short IPAQ had comparable results for reliability and criterion validity.