bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Wearing Lower Body Compression Garments During a Cycling Performance Test
Authors: Driller Matthew W. , Halson Shona L.
Published: August 2016

Purpose:

Compression garments have been commonly used in a medical setting as a method to promote blood flow. Increases in blood flow during exercise may aid in the delivery of oxygen to the exercising muscles and, subsequently, enhance performance. The aim of the current study was to investigate the effect of wearing lower body compression garments during a cycling test.

Methods:

Twelve highly trained cyclists (mean ± SD age 30 ± 6 y, mass 75.6 ± 5.8 kg, VO2peak 66.6 ± 3.4 mL · kg−1 · min−1) performed two 30-min cycling bouts on a cycle ergometer in a randomized, crossover design. During exercise, either full-length lower body compression garments (COMP) or above-knee cycling shorts (CON) were worn. Cycling bouts involved 15 min at a fixed workload (70% of VO2max power) followed by a 15-min time trial. Heart rate (HR) and blood lactate (BL) were measured during the fixed-intensity component of the cycling bout to determine the physiological effect of the garments. Calf girth (CG), thigh girth (TG) and perceived soreness (PS) were measured preexercise and postexercise.

Results:

COMP produced a trivial effect on mean power output (ES = .14) compared with CON (mean ± 95% CI 1.3 ±1.0). COMP was also associated with a lower HR during the fixed-workload section of the test (−2.6% ± 2.3%, ES = −.38). There were no differences between groups for BL, CG, TG, and PS.

Conclusion:

Wearing compression garments during cycling may result in trivial performance improvements of ~1% and may enhance oxygen delivery to the exercising muscles.
Is Gross Efficiency Lower at Acute Simulated Altitude Than at Sea Level?
Authors: Noordhof Dionne A. , Schoots Thijs , Hoekert Derk H. , de Koning Jos J.
Published: August 2016

Purpose:

The purpose of this study was to test the assumption that gross efficiency (GE) at sea level (SL) is representative of GE at altitude (AL). It was hypothesized that an increased cost of ventilation and heart rate, combined with a higher respiratory-exchange ratio, at AL might result in a decrease in GE.

Methods:

Trained men (N = 16) completed 2 maximal incremental tests and 2 GE tests, 1 at SL and 1 at an acute simulated AL of 1500 m (hypobaric chamber). GE was determined during submaximal exercise at 45%, 55%, and 65% of the altitude-specific power output attained at VO2max.

Results:

GE determined at the highest submaximal exercise intensity with a mean RER ≤1.0, matched for both conditions, was significantly lower at AL (AL 20.7% ± 1.1% and SL 21.4% ± 0.8%, t15 = 2.9, P < .05).

Conclusion:

These results demonstrate that moderate AL resulted in a significantly lower GE during cycling exercise than SL. However, it might be that the lower GE at AL is caused by the lower absolute exercise intensity.
The Reliability of a Rugby League Movement-Simulation Protocol Designed to Replicate the Performance of Interchanged Players
Authors: Waldron Mark , Highton Jamie , Twist Craig
Published: August 2016

Purpose:

This study assessed the reliability of a rugby league movement-simulation protocol, relative to interchanged players (RLMSP-i).

Methods:

Fifteen male participants completed 2 trials of the RLMSP-i, separated by 1 wk. The RLMSP-i comprised low- to moderate-intensity running, interspersed by high-intensity sprinting and tackling activity, based on global positioning system (GPS) data recorded during Super League performances.

Results:

The lowest coefficient of variation (CV ± 95% CI) was observed for total m/min during both interchange bout 1 (1.1% ± 0.2%) and bout 2 (1.0% ± 0.2%). The percentage of heart rate peak and ratings of perceived exertion demonstrated CVs of 1.2–2.0% and 2.9–3.5%, respectively. The poorest agreement between trials was found for blood lactate concentration (16.2% ± 2.8%). In no case was the CV smaller than the smallest worthwhile change, yet in every case the moderate changes were larger than the CV.

Conclusions:

The RLMSP-i’s reliability is sufficient to enable the detection of moderate changes in various performance and physiological measurements that accurately simulate some, but not all, aspects of rugby league matches.
Predictors of Fielding Performance in Professional Baseball Players
Authors: Mangine Gerald T. , Hoffman Jay R. , Vazquez Jose , Pichardo Napoleon , Fragala Maren S. , Stout Jeffrey R.
Published: August 2016

The ultimate zone-rating extrapolation (UZR/150) rates fielding performance by runs saved or cost within a zone of responsibility in comparison with the league average (150 games) for a position. Spring-training anthropometric and performance measures have been previously related to hitting performance; however, their relationships with fielding performance measures are unknown.

Purpose:

To examine the relationship between anthropometric and performance measurements on fielding performance in professional baseball players.

Methods:

Body mass, lean body mass (LBM), grip strength, 10-yd sprint, proagility, and vertical-jump mean (VJMP) and peak power (VJPP) were collected during spring training over the course of 5 seasons (2007–2011) for professional corner infielders (CI; n = 17, fielding opportunities = 420.7 ± 307.1), middle infielders (MI; n = 14, fielding opportunities = 497.3 ± 259.1), and outfielders (OF; n = 16, fielding opportunities = 227.9 ± 70.9). The relationships between these data and regular-season (100-opportunity minimum) fielding statistics were examined using Pearson correlation coefficients, while stepwise regression identified the single best predictor of UZR/150.

Results:

Significant correlations (P < .05) were observed between UZR/150 and body mass (r = .364), LBM (r = .396), VJPP (r = .397), and VJMP (r = .405). Of these variables, stepwise regression indicated VJMP (R = .405, SEE = 14.441, P = .005) as the single best predictor for all players, although the addition of proagility performance strengthened (R = .496, SEE = 13.865, P = .002) predictive ability by 8.3%. The best predictor for UZR/150 was body mass for CI (R = .519, SEE = 15.364, P = .033) and MI (R = .672, SEE = 12.331, P = .009), while proagility time was the best predictor for OF (R = .514, SEE = 8.850, P = .042).

Conclusions:

Spring-training measurements of VJMP and proagility time may predict the defensive run value of a player over the course of a professional baseball season.
Compression Garments: No Enhancement of High-Intensity Exercise in Hot Radiant Conditions
Authors: Barwood Martin J. , Corbett Jo , Feeney John , Hannaford Paul , Henderson Dan , Jones Ian , Kirke Jade
Published: August 2016

Purpose:

To establish the thermal and performance effects of wearing a lower-body graduated compression garment (GCG) in a hot environment (35.2°C ± 0.1°C) with a representative radiant heat load (~800 W/m2) in contrast to a control (running shorts) and sham condition (a compression garment 1 size larger than that recommended by the manufacturer), with the latter included to establish any placebo effect.

Method:

Eight participants (mean ± SD; age 21 ± 2 y, height 1.77 ± 0.06 m, mass 72.8 ± 7.1 kg, surface area, 1.89 ± 0.10 m2) completed 3 treadmill tests at a fixed speed for 15 min followed by a self-paced 5-km time trial. Performance (completion time) and pacing (split time), thermal responses (aural, skin, and mean body temperature, cardiac frequency), and perceptual responses (rating of perceived exertion [RPE], thermal sensation, thermal comfort) were measured.

Results:

Performance in the compression group was not different than in either sham or control at any stage (P > .05); completion time 26.08 ± 4.08, 26.05 ± 3.27, and 25.18 ± 3.15 min, respectively. At the end of the 5-km time trial, RPE was not different; it was 19 ± 1 across conditions. In general, thermal and perceptual responses were not different, although the radiant heat load increased site-specific skin temperature (quadriceps) in the garment conditions.

Conclusion:

GCG did not enhance performance in a hot environment with a representative radiant heat load. The sham treatment did not benefit perception. GCG provided no evidence of performance enhancement.
The Effect of Physiology and Hydration Beliefs on Race Behavior and Postrace Sodium in 161-km Ultramarathon Finishers
Authors: Winger James M. , Hoffman Martin D. , Hew-Butler Tamara D. , Stuempfle Kristin J. , Dugas Jonathan P. , Fogard Kevin , Dugas Lara R.
Published: August 2016

Purpose:

To determine if beliefs about physiology and rehydration affect ultramarathon runners’ hydration behaviors or if these beliefs increase the risk for exercise-associated hyponatremia (EAH).

Methods:

Participants of the 2011 161-km Western States Endurance Run completed a prerace questionnaire, prerace and postrace body-mass measurements, and postrace assessment of serum sodium ([Na+]).

Results:

Of 310 finishers, 309 (99.7%) completed the prerace questionnaire and 207 (67%) underwent postrace blood studies. Twelve (5.8%) finishers had asymptomatic EAH ([Na+] range 131–134 mmol/L). The most common hydration plan (43.1%) was drinking according to schedule, and these runners did so to replace fluid lost when sweating (100%) and to avoid dehydration (81.2%). Prerace drinking plan was not associated with postrace [Na+] or the development of postrace hyponatremia. There also were no group differences between those with and those without EAH for any other variables including planned energy intake or knowledge of fluid balance. Runners not planning to drink to thirst trended toward more influence from advertisements (P= .056) and were significantly more influenced by scientific organizations (P= .043) than runners with other drinking plans. Finally, runners who believe that EAH is caused by excessive drinking adopted a lower-volume drinking plan (P= .005), while runners who believe that EAH is caused by sodium loss via sweating reported more common use of sodium supplementation during the race (P= .017).

Conclusions:

Beliefs regarding the causes of EAH alter race behaviors including drinking plan and sodium supplementation but do not appear to affect the likelihood of developing EAH during a 161-km ultramarathon.
Effect of Dietary Antioxidants, Training, and Performance Correlates on Antioxidant Status in Competitive Rowers
Authors: Braakhuis Andrea J. , Hopkins Will G. , Lowe Timothy E.
Published: August 2016

The beneficial effects of exercise and a healthy diet are well documented in the general population but poorly understood in elite athletes. Previous research in subelite athletes suggests that regular training and an antioxidant-rich diet enhance antioxidant defenses but not performance.

Purpose:

To investigate whether habitual diet and/or exercise (training status or performance) affect antioxidant status in elite athletes.

Methods:

Antioxidant blood biomarkers were assessed before and after a 30-min ergometer time trial in 28 male and 34 female rowers. The antioxidant blood biomarkers included ascorbic acid, uric acid, total antioxidant capacity (TAC), erythrocyte- superoxide dismutase, glutathione peroxidase (GPx), and catalase. Rowers completed a 7-d food diary and an antioxidant-intake questionnaire. Effects of diet, training, and performance on resting biomarkers were assessed with Pearson correlations, and their effect on exercise-induced changes in blood biomarkers was assessed by a method of standardization.

Results:

With the exception of GPx, there were small to moderate increases with exercise for all markers. Blood resting TAC had a small correlation with total antioxidant intake (correlation .29; 90% confidence limits, ±.27), and the exercise-induced change in TAC had a trivial to small association with dietary antioxidant intake from vitamin C (standardized effect .19; ±.22), vegetables (.20; ±.23), and vitamin A (.25; ±.27). Most other dietary intakes had trivial associations with antioxidant biomarkers. Years of training had a small inverse correlation with TAC (−.32; ±.19) and a small association with the exercise-induced change in TAC (.27; ±.24).

Conclusion:

Training status correlates more strongly with antioxidant status than diet does.
Men Cross America Faster Than Women—The “Race Across America” From 1982 to 2012
Authors: Rüst Christoph Alexander , Knechtle Beat , Rosemann Thomas , Lepers Romuald
Published: August 2016

Purpose:

The sex difference in ultraendurance performance has been investigated in swimmers, runners, and triathletes but not in cyclists. The purpose of this study was to examine the sex difference in the longest ultracycling race in the world, the Race Across America (RAAM).

Methods:

Cycling speed of female and male finishers in the RAAM between 1982 and 2012 was compared.

Results:

A total of 452 athletes including 404 men (89.4%) and 48 women (10.6%) finished. Mean cycling speed was 19.4 ± 2.0 km/h for men and 17.5 ± 2.0 km/h for women. Men were riding 1.9 ± 2.0 km/h (10.9%) faster than women. The fastest cycling speed ever was 24.77 km/h for men and 21.27 km/h for women, with a sex difference of 14.2%. Between 1982 and 2012, cycling speed was 22.7 ± 1.1 km/h for the annual fastest men and 18.4 ± 1.6 km/h for the annual fastest women, with an unchanged sex difference of 19.4% ± 7.3% (P > .05). For the annual top 3 men, cycling speed was 21.8 ± 0.9 km/h with no change across years (P > .05). The annual top 3 women achieved a cycling speed of 16.6 ± 1.0 km/h with no change over time (P > .05). The sex difference of 24.6% ± 3.0% showed no change across years (P > .05).

Conclusions:

In the last 30 y, men crossed America faster than women, and it seems unlikely that women will overtop men in the near future in the RAAM. However, the sex difference was only 14–15% among top competitors. Future studies need to analyze anthropometric, psychological, and physiological characteristics of successful female and male ultracyclists.
Validity and Reliability of a 1500-m Lap-Time Collection Method Using Public Videos
Authors: Mytton Graham J. , Archer David T. , Thompson Kevin G. , Renfree Andrew , Gibson Alan St Clair
Published: August 2016

The collection of retrospective lap times from video footage is a potentially useful research tool to analyze the pacing strategies in any number of competitive events. The aim of this study was to validate a novel method of obtaining running split-time data from publically available video footage. Videos of the 1500-m men’s final from the 2004 and 2008 Olympics, 2005 and 2009 World Championships, and 2010 European Championships were obtained from the YouTube Web site, and split times were collected from all competitors using frame-by-frame playback. The typical error of video split times ranged between 0.02 s and 0.11 s for the 4 laps when compared with official split times. Video finishing times were also similar to official finishing times (typical error of 0.04 s). The method was shown to be highly reliable with a typical error of 0.02 s when the same video was analyzed on 2 occasions separated by 8 mo. Video data of track races are widely available; however, camera angles are not always perpendicular to the start/finish line, and some slower athletes may cross the line after the camera has panned away. Nevertheless, the typical errors reported here show that when appropriate camera angles are available this method is both valid and reliable.
Increased Lean Mass with Reduced Fat Mass in an Elite Female Cyclist Returning to Competition: Case Study
Authors: Haakonssen Eric C. , Martin David T. , Burke Louise M. , Jenkins David G.
Published: August 2016

Body composition in a female road cyclist was measured using dual-energy X-ray absorptiometry (5 occasions) and anthropometry (10 occasions) at the start of the season (Dec to Mar), during a period of chronic fatigue associated with poor weight management (Jun to Aug), and in the following months of recovery and retraining (Aug to Nov). Dietary manipulation involved a modest reduction in energy availability to 30–40 kcal · kg fat-free mass−1 · d−1 and an increased intake of high-quality protein, particularly after training (20 g). Through the retraining period, total body mass decreased (−2.82 kg), lean mass increased (+0.88 kg), and fat mass decreased (−3.47 kg). Hemoglobin mass increased by 58.7 g (8.4%). Maximal aerobic- and anaerobic-power outputs were returned to within 2% of preseason values. The presented case shows that through a subtle energy restriction associated with increased protein intake and sufficient energy intake during training, fat mass can be reduced with simultaneous increases in lean mass, performance gains, and improved health.
A Kinematic Profile of Skills in Professional Basketball Players
Authors: McClay Irene S. , Robinson John R. , Andriacchi Thomas P. , Frederick Edward C. , Gross Ted , Martin Philip , Valiant Gordon , Williams Keith R. , Cavanagh Peter R.
Published: August 2016

Overuse injuries are common in basketball. To gain insight into their etiology and relationship to mechanics, researchers and clinicians need an understanding of the normal biomechanics of the sport. This study was undertaken with this goal in mind. Lower extremity joint kinematics and structural parameters were collected from 24 players from five professional basketball teams as they performed maneuvers typical of their sport. The results indicated that certain common moves such as the layup landing resulted in knee flexion velocities almost double those seen during the landing phase of running. Lateral movements such as cutting and shuffling placed the foot in extreme positions of supination. Both of these findings have implications for injuries common to basketball such as patellar tendinitis and ankle sprains. It is hoped that this information will initiate a database for normal lower extremity kinematics during basketball and lead to a greater understanding of the relationship of lower extremity movement patterns and injury.
In-Shoe Pressure Distribution for Running in Various Types of Footwear
Authors: Hennig Ewald M. , Milani Thomas L.
Published: August 2016

Discrete pressure sensors were used to examine the influence of shoe construction on the local forces under the foot. Measurements were performed at eight locations under the feet of 22 subjects wearing 19 different models of running shoes. Mechanical properties of shoe soles were assessed with an impacter device. Pressure distribution, ground reaction force, and acceleration data were collected simultaneously during running at 3.3 m/s. Early lateral loading of the rearfoot was followed by increasing medial forefoot loads. In the later phase of pushoff the load was almost entirely carried by the first metatarsal head and the hallux. Substantial differences in plantar foot pressures and relative loads among shoe models indicated that footwear construction has a substantial influence on the loading behavior of the foot during ground contact. Finally, the chosen sensor locations under the foot were found to be adequate to estimate the vertical ground reaction force.
A New Force Plate Design Incorporating Octagonal Strain Rings
Authors: Hull Maury L. , Brewer Richard , Hawkins David
Published: August 2016

This paper reports on the design, fabrication, and performance evaluation of a new force plate. The force plate is unique in that it can be manufactured “in house” using conventional machine tools for substantially lower cost than commercially available units. To achieve these attributes, the force plate embodies four octagonal strain ring sensing elements that are instrumented with conventional strain gauges. Strain gauge signals are amplified by simple signal conditioning circuits with a low component count. Despite the simplicity of the design, a calibration and accuracy check revealed root mean squared errors of 14 N for the vertical force component and less than 11 N for the horizontal force components.
Desirable Gliding Styles and Techniques in Ski Jumping
Authors: Jin Hiroshi , Shimizu Shunsuke , Watanuki Tadaharu , Kubota Hirotoshi , Kobayashi Kazutoshi
Published: August 2016

Desirable flight styles and techniques in ski jumping were calculated on the basis of the new aerodynamic force data for three styles: classic style, V style, and flat V style. In the V style and flat V style two skis are in a herringbone position in the frontal plane, whereas in the classic style the skis are parallel Flat V style is more flat in the sagittal plane than V Style. The most effective style was the flat V style if a ski jumper model did not change style during the gliding phase, which was the late part of flight phase (distance was 110 m). If the model changed flight style, the model that changed from classic style to V style at 1.3 s after takeoff or from flat V style to V style at 1.6 s could achieve 112.5 m. In addition, forward initial angular velocity was a positive factor to increase distance; in particular, the distance for the V style was sensitive to initial angular velocity.
A Video Technique for Obtaining 3-D Coordinates in Alpine Skiing
Authors: Nachbauer Werner , Kaps Peter , Nigg Benno , Brunner Fritz , Lutz Alexander , Obkircher Günter , Mössner Martin
Published: August 2016

A video technique to obtain 3-D data in an Alpine skiing competition was investigated. The flight and landing phases of a jump were recorded during the 1994 Olympic combined downhill race. A direct linear transformation (DLT) implementation was applied, which computes the DLT parameters for each video image of each camera separately. As a consequence, one is able to pan and tilt the cameras and zoom the lenses. The problem of distributing control points in the large object space could be solved satisfactorily. The method proved to be suitable for obtaining 3-D data with reasonable accuracy, which is even sufficient for inverse dynamics. The computed resultant knee joint forces and moments compare well with results reported by other authors.
Prediction of Human Segment Inertias during Pregnancy
Authors: Jensen Robert K. , Treitz Tina , Doucet Sylvie
Published: August 2016

The purpose of this study was to develop prediction equations to estimate mass, radius to the center of mass (CM), and principal moments of the segments during pregnancy. Nonlinear regression equations were determined for the lower trunk, upper trunk, and thigh. The third sampling month of a longitudinal study was used (Sample 1, n = 15). The nonlinear regressions were then used to predict segment inertias above and below the third sampling month (Sample 2, the remaining 74 measurements). For the remaining segments, body mass and segment lengths were used as predictor variables for mass, radius to CM, and radius of gyration about the centroidal axes. The remaining seven segments did not change substantially during pregnancy, and the means of the repeated measures were used for the simple linear regressions. Eighteen of the 28 regressions and all of the CM regressions were significant. With pregnant subjects it is recommended that these regressions be used if application of the elliptical cylinder model is not possible.
The Effect of Body Position and Number of Supports on Wall Reaction Forces in Rock Climbing
Authors: Quaine Franck , Martin Luc , Blanchi Jean-Pierre
Published: August 2016

This manuscript describes three-dimensional force data collected during postural shifts performed by individuals simulating rock-climbing skills. Starting from a quadrupedal vertical posture, 6 expert climbers had to release their right-hand holds and maintain the tripedal posture for a few seconds. The vertical and contact forces (lateral and anteroposterior forces) applied on the holds were analyzed in two positions: an “imposed” position (the trunk far from the supporting wall) and an “optimized” position (the trunk close to the wall and lower contact forces at the holds). The tripedal postures performed in the two positions were achieved by the same pattern of vertical and contact forces exerted by the limbs on the holds. In the optimized position, the transfer of the forces was less extensive than in the imposed position, so that the forces were exerted primarily on the ipsilateral hold. Moreover, a link between the contact force values and the couple due to body weight with respect to the feet was shown.
Hydrodynamic Characteristics of Competitive Swimmers of Different Genders and Performance Levels
Authors: Kolmogorov Sergei V. , Rumyantseva Olga A. , Gordon Brian J. , Cappaert Jane M.
Published: August 2016

The purpose of this study was to describe the hydrodynamic characteristics of the four strokes by gender and performance level. Active drag during maximal swimming was measured in each of the four swimming strokes (freestyle, butterfly, backstroke, and breaststroke) on males and females of varying ability levels using the perturbation method developed by Kolmogorov and Duplisheva (1992). Active drag (FDa), the hydrodynamic coefficient (CxDa), and total external mechanical power output (Pto) were calculated at each swimmer's maximal swimming velocity. There were complex, nonlinear relationships between maximum swimming velocity and the three hydrodynamic indicators. The four swimming strokes were ranked in order of resistance based on the three hydrodynamic indicators. The order, from least to most resistance, was (1) freestyle, (2) backstroke, butterfly, (3) breaststroke. No statistical difference was seen between the backstroke and butterfly. Within each stroke, the most important factor for reducing active drag appeared to be individual biomechanical technique.
The Use of Surface Electromyography in Biomechanics
Authors: De Luca Carlo J.
Published: August 2016

This lecture explores the various uses of surface electromyography in the field of biomechanics. Three groups of applications are considered: those involving the activation timing of muscles, the force/EMG signal relationship, and the use of the EMG signal as a fatigue index. Technical considerations for recording the EMG signal with maximal fidelity are reviewed, and a compendium of all known factors that affect the information contained in the EMG signal is presented. Questions are posed to guide the practitioner in the proper use of surface electromyography. Sixteen recommendations are made regarding the proper detection, analysis, and interpretation of the EMG signal and measured force. Sixteen outstanding problems that present the greatest challenges to the advancement of surface electromyography are put forward for consideration. Finally, a plea is made for arriving at an international agreement on procedures commonly used in electromyography and biomechanics.
Three-Dimensional Dynamic Analysis of Wheelchair Propulsion
Authors: Rodgers Mary M. , Tummarakota Srinivas , Lieh Junghsen
Published: August 2016

A three-dimensional (3-D) inverse dynamic model of wheelchair propulsion was developed using the Newton-Euler method based on body coordinate systems. With this model, the arm was assumed to be three rigid segments (hand, forearm, and upper arm) connected by the wrist, elbow, and shoulder joints. A symbolic method was adopted to generate the equations of motion. The model was used to compute the joint forces and moments based on the inputs obtained from a 3-D motion analysis system, which included an instrumented wheelchair, video cameras, and a data acquisition system. The linear displacements of markers placed on the joints were measured and differentiated to obtain their velocities and accelerations. Three-dimensional contact forces and moments from hand to handrim were measured and used to calculate joint forces and moments of the segments.
The Relationship between Free Limb Motions and Performance in the Triple Jump
Authors: Yu Bing , Andrews James G.
Published: August 2016

The purpose of this study was to investigate relationships between free limb motions and triple jump performance. The subjects were 13 elite male triple jumpers. Three-dimensional videographic data were collected using a direct linear transformation technique with panning cameras. Changes in the velocity of the whole body center of gravity (G), changes in the whole body angular momentum about G, changes in the velocity of G due to free limb motions, and changes in the whole body angular momentum about G due to free limb motions were determined for each of the three support phases. Free limb motions were associated with decreases in the forward horizontal velocity of G and increases in the vertical velocity of G and significantly influenced changes of the corresponding velocity components of G when the changes were large. The free limb motions also created some angular momentum components about G during each support phase but did not significantly influence the changes of the corresponding angular momentum components of the whole body. Neither the changes in the three velocity components of G nor the changes in the three angular momentum components of the whole body about G due to free limb motions were significantly related to the actual distance of the triple jump.
A Comparison of the Kinetic and Kinematic Characteristics of Plyometric Drop-Jump and Pendulum Exercises
Authors: Fowler Neil E. , Lees Adrian
Published: August 2016

The aim of this study was to compare the kinetic and kinematic characteristics of plyometric drop-jump and pendulum exercises. Exercises were filmed (100 Hz) from the sagittal view and manually digitized; the data were smoothed and differentiated using cross-validated quintic splines. Ground reaction force data were sampled using a Kistler force platform sampling at 500 Hz. Differences between movement amplitudes and coordination strategies were assessed using t tests and conjugate cross-correlations. Pendulum exercises involved a greater range of motion at the ankle and knee but less motion at the hip joint than drop-jumps. Although different in absolute terms, the exercises used a similar coordination strategy. Drop-jumps resulted in greater peak vertical ground reaction forces than the pendulum exercises although the latter involved a greater net impulse. The similarity between the movement patterns for the two modes of exercise led to the conclusion that pendulum exercises offer a training stimulus similar to that of drop-jumps.
The Influence of Heel Lift Manipulation on Achilles Tendon Loading in Running
Authors: Dixon Sharon J. , Kerwin David G.
Published: August 2016

In this study, a modeling method was developed to estimate Achilles tendon forces in running. Owing to the common use of heel lift devices in the treatment of Achilles tendon injury, we investigated the influence of increased heel lift on Achilles tendon loading. The hypothesis was that heel lift manipulation can influence maximum Achilles tendon force. Responses to heel lift variation were found to differ among 3 elite runners demonstrating distinct running styles. A rearfoot and a midfoot striker demonstrated significant increases in maximum Achilles tendon force with increased heel lift, whereas a forefoot striker demonstrated no changes in maximum Achilles tendon force values with heel lift manipulation (p< .05). Analysis of the factors contributing to the observed changes in maximum Achilles tendon force highlighted the influence of the moment arm of ground reaction force and the moment arm of the Achilles tendon about the ankle joint center. The finding that increased heel lift may increase maximum Achilles tendon force suggests that caution is advised in the routine use of this intervention. The different responses to heel lift increase between subjects highlight the importance of classifying subjects based on running style.
Precision of the Estimation of Human Limb Inertial Parameters
Authors: Challis John H.
Published: August 2016

Repeat measurements were made by 2 operators on a group of 50 physically active subjects (age, 20.7 years ± 1.8; males: height 1.780 m ± 0.043. mass, 78.09 kg ± 9.30; females: height. 1.680 m ± 0.064. mass. 66.67 kg ± 6.67) to determine the precision with which the subjects' limb segment inertial parameters could be estimated. Segmental inertial parameters were determined using 3 techniques. 2 of which involved modeling segments as geometric solids, and a 3rd which used the equations of Zatsiorsky et al. (1990). Precisions were high for all 3 techniques, with little difference between inter- and intra-operator precisions. The lowest precisions were obtained for the hands and feet. For these segments the use of repeat measures to improve precision is recommended. These results imply that with similarly trained measurers, comparison of inertial parameters determined using the same protocol but obtained by different operators is appropriate, and that it is viable to have 2 measurers taking measurements on the same subject to accelerate data collection.
Specificity and Plasticity of Mammalian Skeletal Muscles
Authors: Herzog Walter , Koh Timothy , Hasler Evelyne , Leonard Tim
Published: August 2016

We hypothesize that the neuromuscular system is designed to function effectively in accomplishing everyday movement tasks. Since everyday movement tasks may vary substantially in terms of speed and resistance, we speculate that agonistic muscles contribute differently to varying movement tasks such that the mechanical, structural, and physiological properties of the system are optimized at all times. We further hypothesize that a mechanical perturbation to the musculoskeletal system, such as the loss of an important joint ligament or the change of a muscle’s line of action, causes an adaptation of the system aimed at reestablishing effective function. Here. we demonstrate how the specificity of the cat ankle extensors is used to accommodate different locomotor tasks. We then illustrate how the loss of an important ligament in the cat knee leads to neuromuscular adaptation. Finally, we discuss the adaptability of skeletal muscle following an intervention that changes a muscle’s line of action, moment arm, and excursion.
Timing of Lower Extremity Motions during Barefoot and Shod Running at Three Velocities
Authors: De Wit Brigit , De Clercq Dirk
Published: August 2016

This study investigates the timing differences between subtalar and knee joint movement of 9 male subjects while running barefoot and shod at three velocities. An alternative approach is used by dividing the pronation curve into 3 phases. Consequently, the timing of the maximum pronation phase was evaluated, not just the event of the maximum pronation value. Statistical differences were tested using the General Linear Method and paired t tests (p £.05), The extension of the knee starts both barefoot and shod significantly earlier than the resupination phase. Individual analysis shows that a larger time discrepancy between knee extension and the end of pronation mainly depends on the presence of bimodal pronation curves. The relative time differences significantly diminish with increased running velocity. Results suggest that by using this alternative approach, more detailed and useful information is available to describe the lime relationship between flexion-extension of the knee and pro-supination.
Finger Coordination and Bilateral Deficit during Two-Hand Force Production Tasks Performed by Right-Handed Subjects
Authors: Li Sheng , Danion Frederic , Latash Mark L. , Li Zong-Ming , Zatsiorsky Vladimir M.
Published: August 2016

One purpose of the present study was to compare indices of finger coordination during force production by the fingers of the right hand and of the left hand. The other purpose was to study the relation between the phenomena of force deficit during multifinger one-hand tasks and of bilateral force deficit during two-hand tasks. Thirteen healthy right-handed subjects performed maximal voluntary force production tasks with different finger combinations involving fingers of one hand or of both hands together. Fingers of the left hand demonstrated lower peak forces, higher indices of finger enslaving, and similar indices of force deficit. Significant bilateral effects during force production by fingers of both hands acting in parallel were seen only during tasks involving different fingers or finger groups in the two hands (asymmetrical tasks). The bilateral deficit effects were more pronounced in the hand whose fingers generated higher forces. These findings suggest a generalization of an earlier introduced principle of minimization of secondary moments. They also may be interpreted as suggesting that bilateral force deficit is task-specific and may reflect certain optimization principles.
On Variability and Stability in Human Movement
Authors: van Emmerik Richard E.A. , van Wegen Erwin E.H.
Published: August 2016

Current research in biology and physiology has unequivocally demonstrated the significance of variability for the optimal functioning of healthy and adaptable systems. Different pathologies are characterized by reductions in complexity of organization, often signified by loss of variability and adaptability. It is argued that the traditional perspective on biology in general and movement science in particular that tended to associate noise and variability with performance decrements and pathology is no longer tenable. Tools and methodologies that have emerged from the dynamical systems perspective to coordination and control are discussed in the context of postural control and transitions in interlimb coordination and locomotion. First, it is shown that variability can play a functional role in the detection and exploration of stability boundaries during balance control. Second, pattern transitions are characterized by increased variability in movement coordination dynamics. Under conditions of movement pathologies, such as in Parkinson’s disease, reductions in variability in coordination dynamics clearly identify movement coordination and transition problems so characteristic for these patients. It is concluded that the relation between variability and stability is complex and that variability cannot be equated with instability without knowledge of the underlying movement dynamics.
The Variability in Running Gait Caused by Force Plate Targeting
Authors: Challis John H.
Published: August 2016

This study examined the influence of force plate targeting, via stride length adjustments, on the magnitude and consistency of ground reaction force and segment angle profiles of the stance phase of human running. Seven male subjects (height, 1.77 m ± 0.081; mass, 72.4 kg ± 7.52; age range, 23 to 32 years) were asked to run at a mean velocity of 3.2 m · s–1 under three conditions (normal, short, and long strides). Four trials were completed for each condition. For each trial, the ground reaction forces were measured and the orientations of the foot, shank, and thigh computed. There were no statistically significant differences (p > .05) between the coefficients of variation of ground reaction force and segment angle profiles under the three conditions, so these profiles were produced consistently. Peak active vertical ground reaction forces, their timings, and segment angles at foot off were not significantly different across conditions. In contrast, significant differences between conditions were found for peak vertical impact forces and their timings, and for the three lower limb segment angles at the start of force plate contact. These results have implications for human gait studies, which require subjects to target the force plate. Targeting may be acceptable depending on the variables to be analyzed.
Effects of Neuromuscular Strength Training on Vertical Jumping Performance— A Computer Simulation Study
Authors: Nagano Akinori , Gerritsen Karin G.M.
Published: August 2016

The purpose of this study was twofold: (a) to systematically investigate the effect of altering specific neuromuscular parameters on maximum vertical jump height, and (b) to systematically investigate the effect of strengthening specific muscle groups on maximum vertical jump height. A two-dimensional musculoskeletal model which consisted of four rigid segments, three joints, and six Hill-type muscle models, representing the six major muscles and muscle groups in the lower extremity that contribute to jumping performance, was trained systematically. Maximum isometric muscle force, maximum muscle shortening velocity, and maximum muscle activation, which were manipulated to simulate the effects of strength training, all had substantial effects on jumping performance. Part of the increase in jumping performance could be explained solely by the interaction between the three neuromuscular parameters. It appeared that the most effective way to improve jumping performance was to train the knee extensors among all lower extremity muscles. For the model to fully benefit from any training effects of the neuromuscular system, it was necessary to continue to reoptimize the muscle coordination, in particular after the strength training sessions that focused on increasing maximum isometric muscle force.
Lower Extremity Kinematic and Kinetic Differences in Runners with High and Low Arches
Authors: Williams Dorsey S. , McClay Irene S. , Hamill Joseph , Buchanan Thomas S.
Published: August 2016

High- and low-arched feet have long been thought to function differently. The purpose of this study was to investigate the relationship between arch structure and lower extremity mechanics in runners with extreme pes planus and pes cavus. It was hypothesized that low-arched individuals would exhibit an increased rearfoot eversion excursion, eversion/tibial internal rotation ratio, and increased angular velocity in rearfoot eversion when compared to high-arched runners. In addition, it was hypothesized that high-arched runners would exhibit greater vertical loading rates. Twenty high-arched and 20 low-arched runners with histories of running-related injuries were included in this study. Low-arched runners were found to have increased rearfoot eversion excursion, eversion to tibial internal rotation ratio, and rearfoot eversion velocity. High-arched runners had increased vertical loading rate when compared to low-arched runners. These results suggest that arch structure is associated with specific lower extremity kinematics and kinetics. Differences in these parameters may subsequently lead to differences in injury patterns in high-arched and low-arched runners.
Effects of Age on the Spinal Stretch Reflex
Authors: Mynark Richard G. , Koceja David M.
Published: August 2016

The spinal stretch reflex consists of a relatively simple neuronal network. The Ia afferent fiber of the muscle spindle communicates to the alpha motoneuron via a single synapse. This basic pathway has been studied extensively over the past century, yet considerable information continues to emerge concerning the manner in which this pathway adapts to aging. It is well accepted that the amplitude of the spinal stretch reflex declines with normal aging, and it is intuitively agreed that these changes have a detrimental impact on the motor output of aging individuals. Understanding the changes observed in the spinal stretch reflex pathway due to aging requires a recognition of the changes that can occur in each component of this spinal network. This review will address these changes by following the spinal stretch reflex from initiation to completion. The components that result in the sensory input to the motoneuron will be covered first, followed by a review of the physiological changes that can occur to the motoneuron soma that can affect the processing of the sensory input. The output of the motoneuron encompasses the remaining components from the motor axon itself, to the neuromuscular junction, and then to the characteristic changes in the muscle. Finally, the functional effect that these changes have on the reflex as a fundamental motor behavior will be addressed, especially in terms of its impact on posture and balance.
Two Methods for Estimating Tendinous Tissue Elongation during Human Movement
Authors: Finni Taija , Komi Paavo V.
Published: August 2016

During dynamic activities it is difficult to assess in vivo length changes in human tendon and aponeurosis. The present study compared the outcome of two methods during unilateral squat jump and drop jump performances of four volunteers. Tendinous tissue elongation of vastus lateralis muscle was estimated using either (a) direct measurement of in vivo fascicle length change and muscletendon length estimation (kinematic method), or (b) prediction using a quadratic force function in combination with direct tendon force measurement (force method). In the kinematic method the most critical measures contributing to the 10% uncertainty were the fascicle angle and fraction of the estimated fascicle length. The force method was most sensitive to resting length, with 1% error margin. Both methods predicted the same pattern of tendinous elongation because of the monotonic force/length relationship. The magnitude of length change, however, differed considerably between both methods. Based on the force method, the changes were only 20% (absolute values) or 30% (strain values) of those obtained with the kinematic method. On average, the maximum strains were 5% with the force method and 15% with the kinematic method. This difference can be explained by the fact that the kinematic method characterizes not only the changes in tendon length but also includes aponeurosis strain along the muscle belly. In addition, the kinematic method may be affected by non-uniform distribution of fascicle length change along the length of the muscle. When applying either method for estimating the patterns of tendon and tendinous tissue length changes during human locomotion, the given methodological considerations should be acknowledged.
Influence of Curve Sharpness on Torsional Loading of the Tibia in Running
Authors: Kawamoto Ryuji , Ishige Yusuke , Watarai Koji , Fukashiro Senshi
Published: August 2016

The purpose of this study was to test quantitatively the hypothesis that, as runners run along a more sharply curved track, greater torsional moments act on their tibiae. Six male participants were asked to run along a straight track and along counterclockwise curved tracks with turn radii of 15 m (gentle) and 5 m (sharp) at 3.5 m s–1. Data were collected using two high-speed cameras and force platforms. Each participant’s left (corresponding to the inside of the curves) foot and tibia were modeled as a system of coupled rigid bodies. For analysis, net axial moments acting on both ends of the tibia were calculated using free-body analysis. The torsional moment acting on the tibia was determined from the quasi-equilibrium balance of the tibial axial moments based on the assumption that the rate of change of the angular momentum about the tibial axis was negligible. The results showed that the torsional moments, which were in the direction of external rotational loading of the proximal tibiae, increased as the track curvature became sharper. Furthermore, the mean value of the maximum torsional moments, while running on a sharply curved track (28.5 Nm), was significantly higher than the values obtained while running on a straight track (11.0 Nm, p < .01) and on a gently curved track (12.2 Nm, p < .01). In conclusion, the present study has quantitatively confirmed that as runners run along a more sharply curved track, greater torsional moments act on their tibiae. The findings imply that athletes prone to tibial running injuries such as stress fractures should avoid repetitive running on sharply curved paths.