bluuebunny/crossref_metadata_2025 huggingface dataset:
Wheelchair Tennis Match-Play Demands: Effect of Player Rank and Result
Authors: Sindall Paul , Lenton John P. , Tolfrey Keith , Cooper Rory A. , Oyster Michelle , Goosey-Tolfrey Victoria L.
Published: August 2016

Purpose:

To examine the heart-rate (HR) response and court-movement variables during wheelchair tennis match play for high- (HIGH) and low- (LOW) performance-ranked players. Analysis of physiological and movement-based responses during match play offers an insight into the demands of tennis, allowing practical recommendations to be made.

Methods:

Fourteen male open-class players were monitored during tournament match play. A data logger was used to record distance and speed. HR was recorded during match play.

Results:

Significant rank-by-result interactions revealed that HIGH winners covered more forward distance than HIGH losers (P< .05) and had higher average (P< .05) and minimum (P< .01) HRs than LOW winners. LOW losers had higher average (P< .01) and minimum (P< .001) HRs than LOW winners. Independent of result, a significant main effect for rank was identified for maximum (P< .001) and average (P< .001) speed and total (P< .001), reverse (P< .001), and forward-to-reverse (P< .001) distance, with higher values for HIGH. Independent of rank, losing players experienced higher minimum HRs (P< .05). Main effects for maximum HR and actual playing time were not significant. Average playing time was 52.0 (9.1) min.

Conclusions:

These data suggest that independent of rank, tennis players were active for sufficient time to confer health-enhancing effects. While the relative playing intensity is similar, HIGH players push faster and farther than LOW players. HIGH players are therefore more capable of responding to ball movement and the challenges of competitive match play. Adjustments to the sport may be required to encourage skill developmental in LOW players, who move at significantly lower speeds and cover less distance.
Factors That Affect Selection of Elite Women’s Sculling Crews
Authors: Lawton Trent W. , Cronin John B. , McGuigan Michael R.
Published: August 2016

Purpose:

There is no common theory on criteria to appropriately select crew rowers in pursuit of small performance gains. The purpose of this study was to establish whether anthropometry, rowing ergometry, or lower body strength were suitable criteria to identify differences between selected and nonselected sculling crews.

Method:

Twelve elite women performed a 2000-m ergometer time trial and a 5-repetition leg-press dynamometer test, were anthropometrically profiled, and participated in on-water national crew seat-racing trials. Log-transformed data were analyzed to compare percent (± SD) and standardized differences in group means (ES; ±90% confidence interval [CI]) between selected and nonselected oarswomen, with adjustments for body mass where appropriate.

Results:

Selected crew boats were 4.60% ± 0.02% faster and won by an average margin of 13.5 ± 0.7 s over 1500 m. There were no differences between crews on average in height, arm span, seated height, body mass, or 8-site skinfold sum (body fat). Difference in 2000-m ergometer times were also trivial (ES = 0.2, 90%CI = −0.6 to 1.1, P = .63); however, selected crews had moderately greater leg-press strength (ES = 1.1, 90%CI = 0.3−1.9, P = .03).

Conclusion:

Selected oarswomen with comparable anthropometry and 2000-m ergometer ability had greater lower body strength. Coaches of elite oarswomen might consider leg strength as part of crew-selection criteria, given acceptable on-water boatmanship and attainment of 2000-m ergometer benchmarks.
Bringing Light into the Dark: Effects of Compression Clothing on Performance and Recovery
Authors: Born Dennis-Peter , Sperlich Billy , Holmberg Hans-Christer
Published: August 2016

To assess original research addressing the effect of the application of compression clothing on sport performance and recovery after exercise, a computer-based literature research was performed in July 2011 using the electronic databases PubMed, MEDLINE, SPORTDiscus, and Web of Science. Studies examining the effect of compression clothing on endurance, strength and power, motor control, and physiological, psychological, and biomechanical parameters during or after exercise were included, and means and measures of variability of the outcome measures were recorded to estimate the effect size (Hedges g) and associated 95% confidence intervals for comparisons of experimental (compression) and control trials (noncompression). The characteristics of the compression clothing, participants, and study design were also extracted. The original research from peer-reviewed journals was examined using the Physiotherapy Evidence Database (PEDro) Scale. Results indicated small effect sizes for the application of compression clothing during exercise for shortduration sprints (10–60 m), vertical-jump height, extending time to exhaustion (such as running at VO2max or during incremental tests), and time-trial performance (3–60 min). When compression clothing was applied for recovery purposes after exercise, small to moderate effect sizes were observed in recovery of maximal strength and power, especially vertical-jump exercise; reductions in muscle swelling and perceived muscle pain; blood lactate removal; and increases in body temperature. These results suggest that the application of compression clothing may assist athletic performance and recovery in given situations with consideration of the effects magnitude and practical relevance.
The ACTN3 XX Genotype’s Underrepresentation in Japanese Elite Wrestlers
Authors: Kikuchi Naoki , Ueda Dai , Min Seok-ki , Nakazato Koichi , Igawa Shoji
Published: August 2016

Purpose:

To examine the relationship betweenACTN3polymorphisms and level of athletic performance in Japanese wrestlers.

Methods:

The control group consisted of 243 healthy Japanese individuals. The authors divided 135 wrestlers into 3 groups based on their results in national or international competitions. They classified as elite 24 wrestlers who had placed in the top 8 in a world championship or participated in Olympic games, 28 wrestlers who had participated in world championships or become champions in Japan’s national championships were classified as subelite, and 83 wrestlers were classified as national (N-W, ie, national-level wrestler). In addition, the authors combined the elite and subelite to form the classification international-level wrestlers (I-W).

Results:

The frequency of the null X allele and the XX genotype were significantly lower in the I-W group than in the control group. However, there was no significant difference inACTN3genotype or allele frequency between the N-W and control groups. The frequency of theACTN3XX genotype in the elite groups was lower than that of all groups, and a linear tendency was observed betweenACTN3XX genotype and athletic status.

Conclusions:

In conclusion, the data indicated thatACTN3polymorphisms were related to athletic performance in Japanese wrestlers.
The Gender Gap in Sport Performance: Equity Influences Equality
Authors: Capranica Laura , Piacentini Maria Francesca , Halson Shona , Myburgh Kathryn H. , Ogasawara Etsuko , Millard-Stafford Mindy
Published: August 2016

Sport is recognized as playing a relevant societal role to promote education, health, intercultural dialogue, and the individual development, regardless of an individual’s gender, race, age, ability, religion, political affiliation, sexual orientation, and socioeconomic background. Yet, it was not until the 2012 Summer Olympic Games in London that every country’s delegation included a female competitor. The gender gap in sport, although closing, remains, due to biological differences affecting performance, but it is also influenced by reduced opportunity and sociopolitical factors that influence full female participation across a range of sports around the world. Until the cultural environment is equitable, scientific discussion related to physiological differences using methods that examine progression in male and female world-record performances is limited. This commentary is intended to provide a forum to discuss issues underlying gender differences in sport performance from a global perspective and acknowledge the influence of cultural and sociopolitical factors that continue to ultimately affect female performance.
Designing a Warm-Up Protocol for Elite Bob-Skeleton Athletes
Authors: Cook Christian , Holdcroft Danny , Drawer Scott , Kilduff Liam P.
Published: August 2016

Purpose:

To investigate how different warm-ups influenced subsequent sled-pull sprint performance in Olympic-level bob-skeleton athletes as part of their preparation for the 2010 Winter Olympics.

Methods:

Three female and 3 male athletes performed 5 different randomized warm-ups of differing intensities, durations, and timing relative to subsequent testing, each 2 days apart, all repeated twice. After warm-ups, testing on a sledpull sprint over 20 m, 3 repeats 3 min apart, took place.

Results:

Performance testing showed improvement (P < .001, ES > 1.2) with both increasing intensity of warm-up and closeness of completion to testing, with 20-m sled sprinting being 0.1–0.25 s faster in higher-intensity protocols performed near testing In addition, supplementing the warm-ups by wearing of a light survival coat resulted in further performance improvement (P = .000, ES 1.8).

Conclusions:

Changing timing and intensity of warm-up and using an ancillary passive heat-retention device improved sprint performance in Olympic-level bob-skeleton athletes. Subsequent adoption of these on the competitive circuit was associated with a seasonal improvement in push times and was ultimately implemented in the 2010 Winter Olympics.
Effectiveness of Water Immersion on Postmatch Recovery in Elite Professional Footballers
Authors: Elias George P. , Wyckelsma Victoria L. , Varley Matthew C. , McKenna Michael J. , Aughey Robert J.
Published: August 2016

Purpose:

The efficacy of a single exposure to 14 min of contrast water therapy (CWT) or cold-water immersion (COLD) on recovery postmatch in elite professional footballers was investigated.

Method:

Twenty-four elite footballers participated in a match followed by 1 of 3 recovery interventions. Recovery was monitored for 48 h postmatch. Repeat-sprint ability (6 × 20-m), static and countermovement jump performance, perceived soreness, and fatigue were measured prematch and immediately, 24 h, and 48 h after the match. Soreness and fatigue were also measured 1 h postmatch. Postmatch, players were randomly assigned to complete passive recovery (PAS; n = 8), COLD (n = 8), or CWT (n = 8).

Results:

Immediately postmatch, all groups exhibited similar psychometric and performance decrements, which persisted for 48 h only in the PAS group. Repeatsprinting performance remained slower at 24 and 48 h for PAS (3.9% and 2.0%) and CWT (1.6% and 0.9%) but was restored by COLD (0.2% and 0.0%). Soreness after 48 h was most effectively attenuated by COLD (ES 0.59 ± 0.10) but remained elevated for CWT (ES 2.39 ± 0.29) and PAS (ES 4.01 ± 0.97). Similarly, COLD more successfully reduced fatigue after 48 h (ES 1.02 ± 0.72) than did CWT (ES 1.22 ± 0.38) and PAS (ES 1.91 ± 0.67). Declines in static and countermovement jump were ameliorated best by COLD.

Conclusions:

An elite professional football match results in prolonged physical and psychometric deficits for 48 h. COLD was more successful at restoring physical performance and psychometric measures than CWT, with PAS being the poorest.
Effects of Electrostimulation Therapy on Recovery From Acute Team-Sport Activity
Authors: Finberg Matthew , Braham Rebecca , Goodman Carmel , Gregory Peter , Peeling Peter
Published: August 2016

Purpose:

To assess the efficacy of a 1-off electrostimulation treatment as a recovery modality from acute teamsport exercise, directly comparing the benefits to contrast water therapy.

Methods:

Ten moderately trained male athletes completed a simulated team-game circuit (STGC). At the conclusion of exercise, participants then completed a 30-min recovery modality of either electrostimulation therapy (EST), contrast water therapy (CWT), or a passive resting control condition (CON). Twenty-four hours later, participants were required to complete a modified STGC as a measure of next-day performance. Venous blood samples were collected preexercise and 3 and 24 h postexercise. Blood samples were analyzed for circulating levels of interleukin-6 (IL-6) and C-reactive protein (CRP).

Results:

The EST trial resulted in significantly faster sprint times during the 24-h postrecovery than with CON (P < .05), with no significant differences recorded between EST and CWT or between CWT and CON (P > .05). There were no differences in IL-6 or CRP across all trials. Finally, the perception of recovery was significantly greater in the EST trial than in the CWT and CON (P < .05).

Conclusions:

These results suggest that a 1-off treatment with EST may be beneficial to perceptual recovery, which may enhance next-day performance.
Rapidity of Response to Hypoxic Conditions During Exercise
Authors: Harris Kayla B. Henslin , Foster Carl , de Koning Jos J. , Dodge Christopher , Wright Glenn A. , Porcari John P.
Published: August 2016

Previous studies have found decreases in arterial oxygen saturation to be temporally linked to reductions in power output (PO) during time-trial (TT) exercise. The purpose of this study was to determine whether preexercise desaturation (estimated from pulse oximetry [SpO2]), via normobaric hypoxia, would change the pattern of PO during a TT.

Purpose:

The authors tested the hypothesis that the starting PO of a TT would be reduced in the EARLY trial secondary to a reduced SpO2 but would not be reduced in LATE until ~30 s after the start of the TT.

Methods:

Eight trained cyclists/triathletes (4 male, 4 female) performed 3 randomly ordered 3-km TTs while breathing either room air (CONTROL) or hypoxic air administered 3 min before the start of the TT (EARLY) or at the beginning of the TT (LATE).

Results:

There was no effect of hypoxia on PO during the first 0.3 km of either the EARLY or the LATE trial compared with CONTROL, although there was a significant decrease in pre-TT SpO2 in EARLY vs CONTROL and LATE. The time for PO to decrease was ~40 s after the start of the TT in both EARLY and LATE.

Conclusions:

The results support the strong effect of the preexercise template on the pattern of PO during simulated competition and suggest that reductions in SpO2 are not direct signals to decrease PO.
Performance Analysis of a World-Class Sprinter During Cycling Grand Tours
Authors: Menaspà Paolo , Abbiss Chris R. , Martin David T.
Published: August 2016

This investigation describes the sprint performances of the highest internationally ranked professional male road sprint cyclist during the 2008–2011 Grand Tours. Sprint stages were classified as won, lost, or dropped from the front bunch before the sprint. Thirty-one stages were video-analyzed for average speed of the last km, sprint duration, position in the bunch, and number of teammates at 60, 30, and 15 s remaining. Race distance, total elevation gain (TEG), and average speed of 45 stages were determined. Head-to-head performances against the 2nd–5th most successful professional sprint cyclists were also reviewed. In the 52 Grand Tour sprint stages the subject started, he won 30 (58%), lost 15 (29%), was dropped in 6 (12%), and had 1 crash. Position in the bunch was closer to the front and the number of team members was significantly higher in won than in lost at 60, 30, and 15 s remaining (P < .05). The sprint duration was not different between won and lost (11.3 ± 1.7 and 10.4 ± 3.2 s). TEG was significantly higher in dropped (1089 ± 465 m) than in won and lost (574 ± 394 and 601 ± 423 m, P < .05). The ability to finish the race with the front bunch was lower (77%) than that of other successful sprinters (89%). However, the subject was highly successful, winning over 60% of contested stages, while his competitors won less than 15%. This investigation explores methodology that can be used to describe important aspects of road sprint cycling and supports the concept that tactical aspects of sprinting can relate to performance outcomes.
An Analysis of Pacing Profiles of World-Class Racewalkers
Authors: Hanley Brian
Published: August 2016

Purpose:

The aim of this study was to describe the pacing profiles used by racewalkers competing in IAAF World Championships.

Methods:

The times for each 5-km segment were obtained for 225 men competing over 20 km, 214 women competing over 20 km, and 232 men competing over 50 km, of whom 49 did not finish. Athletes were grouped based on finishing position (for medalists) or finishing time.

Results:

Different pacing profiles were used by athletes grouped by finishing time, with 20-km medalists using negative pacing and those finishing within 5% of the winning time matching the medalists’ early pace but failing to maintain it. Lower-placed 20-km athletes tended to start more quickly relative to personal-best pace and experienced significant decreases in pace later. Across all competitions, the fastest finishers started the slowest relative to previous best performance. All 50-km athletes slowed toward the finish, but lower-placed finishers tended to decrease pace earlier (with up to 60% of the race remaining). After halfway in the 50-km, 8 of the 15 athletes who had a 5-km split more than 15% slower than the previous split dropped out.

Conclusions:

The negative pacing profile used by 20-km medalists required the ability to start fast and maintain this pace, and similarly paced training may be beneficial in race preparation. Over 50 km, the tactic of starting slower than personal-best pace was generally less risky; nonetheless, any chosen pacing strategy should be based on individual strengths.
Impact of Several Matches in a Day on Physical Performance in Rugby Sevens Referees
Authors: Suarez-Arrones Luis , Núñez Javier , Munguía-Izquierdo Diego , Portillo Javier , Mendez-Villanueva Alberto
Published: August 2016

Purpose:

To examine the effects of several matches per day on running performance and cardiovascular stress in referees during a national Rugby Sevens championship.

Methods:

Seven referees, who refereed 3 matches/day, were monitored by GPS during 21 matches.

Results:

Referees’ movement patterns were relatively stable from the 1st to the 2nd match, although a substantial decrease was observed in the 2nd match for maximal and average sprint distance. A substantial decrease in the number of sprints, maximal speed, walking, distance covered at medium intensity, total and >14 km/h distance covered per minute was observed in the 3rd match in comparison with the 2nd. Compared with the 1st match, in the 3rd game referees showed a substantial decrease in maximal and average sprint distance, total walking at medium intensity, distance covered >14 km/h, and high-intensity running distance. Referees exhibited a substantial decrease in average heart rate (HR), percentage of time at >70%HRmax, and percentage of time at >90%HRmax in the 2nd match compared with the 1st. Referees’ HR responses were relatively stable from the 2nd to the 3rd match except for the HR zones of 71–80%HRmax and 81–90%HRmax and performance-efficiency index (Effindex). Substantial differences were observed in the 3rd match compared with the 1st in average HR, 81–90%HRmax, >90%HRmax, and Effindex.

Conclusion:

This study provides evidence of reduced overall running performance and pronounced reduction in high-intensity running performance during the last match in Rugby Sevens referees refereeing 3 matches in the same day.
Effect of Running Speed and Aerobic Dance Jump Height on Vertical Ground Reaction Forces
Authors: Ricard Mark D. , Veatch Steve
Published: August 2016

Aerobic dance movement sequences are similar to running in repetitive frequency. The purpose of this study was to compare ground reaction force variables in aerobic dance and running. Five female subjects performed 10 trials of five running speeds (2.4–4.0 ± 0.4 m/s) and five heights (0–8 ± 0.2 cm) of front knee lift aerobic dance steps on an AMTI force plate (1000 Hz). First peak impact force, peak loading rate, high-frequency impulse, and 50-ms impulse increased with increased running speed and jumping height. Time to first peak impact force decreased as running speed and jumping height increased. Although first peak impact forces resulting from airborne aerobic dance movements (1.96–2.62 BW) were greater than first peak impact forces in running (1.30–2.01 BW), running compared to aerobic dance resulted in shorter time to first peak impact force and higher values for loading rate, high-frequency impulse, and 50-ms impulse. When compared to aerobic dance, running exhibits smaller peak vertical forces but higher loading rates and vertical impulses.
Impact Probability Distribution, Sweet Spot, and the Concept of an Effective Power Region in Tennis Rackets
Authors: Hatze Herbert
Published: August 2016

A two-dimensional impact probability density distribution for tennis rackets has been established. It was found that the center of this distribution, and therefore the most likely candidate for a preferred impact center, is the nodal point of the fundamental transverse vibration mode. It is suggested that the node be defined as the sweet spot and the location of maximum restitution as the power spot. The concept of an effective power region centered at the sweet spot and accounting for both the decreasing impact probabilities around the sweet spot and the global restitution function has been introduced. About 78% of all impacts fall within this region, which is therefore truly representative of the power transfer characteristics of a racket. It has been found that high-quality rackets have an effective power area in excess of 100 cm2.
A Biomechanical Analysis of the Last Stride, Touchdown, and Takeoff Characteristics of the Men's Long Jump
Authors: Lees Adrian , Graham-Smith Philip , Fowler Neil
Published: August 2016

This study was concerned with the measurement of performance variables from competitors in the men's long jump final of the World Student Games held in Sheffield, England, in July 1991. Several performances of 10 finalists were recorded on cine film at 100 Hz. Resulting sagittal plane kinematic data were obtained for the last stride, touchdown, and takeoff for a total of 27 jumps. It was confirmed that takeoff velocity was a function of touchdown velocity, and that there was an increase in vertical velocity at the expense of a reduction of horizontal velocity. It was concluded that there was evidence for mechanisms which may be termed mechanical, biomechanical, and muscular. The former relates to the generation of vertical velocity by the body pivoting over the base of support during the compression phase, and a lifting of the arms and free leg during the lift phase; the second is the elastic reutilization of energy; and the third is the contribution by concentric muscular contraction.
Small Effects in Running
Authors: Behncke Horst
Published: August 2016

The influence of altitude, wind, and track curvature is studied on the basis of a simple biomechanical model. The results are compared with some data from the Olympic Games in Tokyo, Munich, and Mexico City. The influence of these factors is found to be considerably larger than the current precision in the measurement of records.
The Dynamics of Springboards
Authors: Kooi Bob W. , Kuipers Max
Published: August 2016

The maneuvers of a competition diver on a springboard before takeoff may serve to maximize the height of the flight phase. To simplify analysis, it is often assumed that the diver performs motions at the top of a single degree-of-freedom (DOF) system, usually consisting of one mass and one linear spring. This system is expected to simulate the behavior of the board sufficiently. In this paper we propose a new single DOF system approximating the effects of a board with passable accuracy. This model is applied to three types of springboards to obtain numerical values for their virtual masses at the tip.
Construction of a High-Pass Digital Filter from a Low-Pass Digital Filter
Authors: Murphy Stephen D. , Robertson D. Gordon E.
Published: August 2016

To remove low-frequency noise from data such as DC-bias from electromyo-grams (EMGs) or drift from force transducers, a high-pass filter was constructed from a low-pass filter of known characteristics. A summary of the necessary steps required to transform the low-pass digital were developed. Contaminated EMG and force platform data were used to test the filter. The high-pass filter successfully removed the low-frequency noise from the EMG signals. The high-pass filter was then cascaded with the low-pass filter to produce a band-pass filter to enable simultaneous high- and low-frequency noise reduction.
Angular Momentum and Performance in the Triple Jump: A Cross-Sectional Analysis
Authors: Yu Bing , Hay James G.
Published: August 2016

The purposes of this study were (a) to determine the magnitude of the angular momentum elite triple jumpers possess during each of the three phases of a triple jump, and (b) to identify those components of the angular momentum that are closely related to the actual distance of the triple jump. Angular momentum about each of three orthogonal axes at the takeoff of each of the last stride, hop, step, and jump was computed from the smoothed 3-D coordinate data of 21 body landmarks and joint centers and normalized to body mass (mb) and standing height (hb). Linear and nonlinear regression analyses were conducted to examine the relationships between angular momenta and actual distance. The results suggested that the estimated optimum magnitude of this side-somersaulting angular momentum is 0.0069 mb hb2 kg · m2 · s-1 toward the side of the free leg, that the side-somersaulting angular momentum needed at the takeoff of the step should be obtained during the support phase of the hop; and that the change in the side-somersaulting angular momentum during the support phase of the step should be minimized.
A New Method for Continuous Recording of Trunk Postures while Playing Golf
Authors: Derksen José C. , van Riel Marcel P. , Snijders Chris J.
Published: August 2016

In this paper a new method for the registration of trunk movements is presented. With this method, called the Portable Posture Registration Set (PPRS), movements can be recorded continuously over a long period of time. The purpose of this study was to test whether the PPRS can be applied in golf. A pilot study using 4 male golfers demonstrated that qualitative and quantitative data on trunk movements in golf can be collected with the PPRS. The inclination of the trunk proved to be large (40–45°) in all swings tested, resulting in a considerable load on the back. The contribution of torsion to the spinal load was relatively small, especially in the putt, which showed very little movement in the transverse and frontal planes. However, putting accounted for most of the total spinal load in playing a course. Even when playing a round of 18 holes, subjects did not experience any hindrance or discomfort from the sensors or the recorder. This method seems to offer new possibilities in the biomechanical study of trunk movement in golf.
Three-Dimensional Evaluation of the Kinematic Release Parameters for Javelin Throwers of Different Skill Levels
Authors: Bartlett Roger , Müller Erich , Lindinger Stefan , Brunner Fritz , Morriss Calvin
Published: August 2016

This study compared three-dimensional release parameters and important features of the throwing technique for male javelin throwers of three different skill levels (elite, club, novice), recorded using three-dimensional cine or video. As expected, significant differences (p < .01) in throw distances and release speeds were found between all three groups. The only other release parameter for which a significant difference was found (between club and novice groups) was the yaw angle. The increase in release speed with increasing skill across the groups may be attributable in part to greater run-up speeds. Also important were significantly greater peak speeds of the throwing shoulder, elbow, and hand during the delivery stride for the elite group compared to the other groups. Significantly longer acceleration paths at the start of the delivery stride and a delay in elbow flexion until after final foot strike for the elite throwers were also important in generating greater release speeds.
Takeoff Characteristics of Single and Double Axel Figure Skating Jumps
Authors: Albert Wayne J. , Miller Doris I.
Published: August 2016

Takeoff kinematics of axel jumps were determined from a spatial analysis of singles and doubles performed by 16 figure skaters. The takeoff was divided into glide, transition, and pivot phases. During the glide, horizontal speed remained constant, vertical velocity was slightly negative, and over half the angular momentum for flight was generated. In the transition, skaters gained considerable vertical velocity from tangential motion by rotating about the long axis of the blade, Initially this reduced the angle of the support leg with respect to the vertical while the blade ran in the direction of progression. Most skaters continued to gain vertical velocity by angling the blade to the direction of progression (skidding) and rotating up and forward, still about the blade's long axis. There was little angular momentum gain, and forward speed decreased significantly. In the pivot, skaters rocked forward onto the toe picks losing horizontal speed, vertical velocity, and angular momentum.
Obesity: Effects on Gait in an Osteoarthritic Population
Authors: Messier Stephen P. , Ettinger Walter H. , Doyle Thomas E. , Morgan Timothy , James Margaret K. , O'Toole Mary L. , Burns Robert
Published: August 2016

The purpose of our study was to examine the association between obesity and gait mechanics in older adults with knee osteoarthritis (OA). Subjects were 101 older adults (25 males and 76 females) with knee OA. High-speed video analysis and a force platform were used to record sagittal view lower extremity kinematic data and ground reaction forces. Increased body mass index (BMI) was significantly related to both decreases in walking velocity and knee maximum extension. There were no significant relationships between BMI and any of the hip or ankle kinematic variables. BMI was directly related to vertical force minimum and maximum values, vertical impulse, and loading rate. Increases in braking and propulsive forces were significantly correlated with increased BMI. Maximum medially and laterally directed ground reaction forces were positively correlated with BMI. Our results suggests that, in subjects with knee OA, obesity is associated with an alteration in gait.
Supramaximal Activation Increases Motor Unit Velocity of Unloaded Shortening
Authors: Nelson Arnold G.
Published: August 2016

It has been shown that the rate of tension generation (dP/dt) continues to increase with increasing stimulation rates, even after maximal tetanic tension has been achieved. Since dP/dt is directly proportional to unloaded shortening velocity, it was questioned whether supramaximal stimulation rates would increase shortening velocity. To test the relationship of velocity and stimulation rate, slack tests were performed on motor units isolated in the rat soleus muscles. For each motor unit tested, two slack tests were performed at two different stimulation rates: one rate yielded a maximal tetanic tension with a "slow" dP/dt (PO) and the other rate yielded a maximal tetanic tension with a "fast" dP/dt (RG). The two stimulation rates (PO and RG) had significantly different effects (p < .05) on motor unit shortening velocity, with the RG rate yielding a shortening velocity greater than that of PO by an average of 13 ± 6%. This suggests that rate coding could be used to grade motor unit power production by grading force production and/or shortening velocity.
Effects of the Method of Body Segment Parameter Estimation on Airborne Angular Momentum
Authors: Kwon Young-Hoo
Published: August 2016

Ten body segment parameter (BSP) estimation methods were selected to compute the BSPs of 3 collegiate male gymnasts: cadaver-based methods (Group C, 4 methods), mass scanning-based methods (Group M, 4 methods) and geometric methods (Group G, 2 methods). Angular momenta of nine double somersault with full twist H-bar dismounts performed by the 3 gymnasts were computed. Each trial was processed 10 times using 10 sets of BSPs obtained from the estimation methods. Intergroup and intermethod comparisons of the airborne angular momenta were made. It was concluded that the method of BSP estimation affected the magnitude of airborne angular momentum but did not affect the magnitude of angular momentum fluctuation during the airborne phase.
Methods for Determining Hip Movement in Seated Cycling and Their Effect on Kinematics and Kinetics
Authors: Neptune Richard R. , Hull Maury L.
Published: August 2016

In a previous paper (Neptune & Hull, 1995), a new video-based method (ASIS) for locating the hip joint center (HJC) in seated cycling was shown to be more accurate than tracking a marker placed over the superior aspect of the greater trochanter (TRO). The main goal of the present study was to see if the conclusions presented in Neptune and Hull (1995) may be applied to other cyclists. Lower limb kinematic and pedal force data were collected from 7 cyclists at nine combinations of pedaling rate and work rate. ASIS produced significantly different hip joint movement patterns than TRO, which resulted in significantly different power and work calculations developed by the intersegmental hip joint force, at all combinations except one. A significant quadratic trend was evident as a function of pedaling rate, and a significant linear trend was evident for work rate. At naturally preferred pedaling rates (~90 rpm) and lower work rates (<225 W), the hip joint movement was minimum. Under these conditions, the fixed hip assumption is least prone to error.
Accuracy of Human Limb Moment of Inertia Estimations and Their influence on Resultant Joint Moments
Authors: Challis John H.
Published: August 2016

Segmental moment of inertia values, which are often required to perform mechanical analyses of human movement, are commonly computed using statistical models based on cadaver data. Two sets of equations for estimating human limb moments of inertia were evaluated: linear multivariable equations and nonlinear equations. Equation coefficients for both sets of equations were determined using the cadaver data of Chandler et al. (1975). A cross-validation procedure was used to circumvent the problem of model evaluation when there is limited data with which to develop and evaluate the model. Moment of inertia values for the longitudinal axes were predicted with similar degrees of accuracy with either set of equations, while for the transverse axes the nonlinear equations were superior. An evaluation of the influence of the accuracy of moment of inertia estimates on resultant joint moments for three activities showed that the influence of these errors was generally small.
Reconstructing Digital Signals Using Shannon's Sampling Theorem
Authors: Hamill Joseph , Caldwell Graham E. , Derrick Timothy R.
Published: August 2016

Researchers must be cognizant of the frequency content of analog signals that they are collecting. Knowing the frequency content allows the researcher to determine the minimum sampling frequency of the data (Nyquist critical frequency), ensuring that the digital data will have all of the frequency characteristics of the original signal. The Nyquist critical frequency is 2 times greater than the highest frequency in the signal. When sampled at a rate above the Nyquist, the digital data will contain all of the frequency characteristics of the original signal but may not present a correct time-series representation of the signal. In this paper, an algorithm known as Shannon's Sampling Theorem is presented that correctly reconstructs the time-series profile of any signal sampled above the Nyquist critical frequency. This method is superior to polynomial or spline interpolation techniques in that it can reconstruct peak values found in the original signal but missing from the sampled data time-series.
Photocell Contact Mat: A New Instrument to Measure Contact and Flight Times in Running
Authors: Viitasalo Jukka T. , Luhtanen Pekka , Mononen Harri V. , Norvapalo Kare , Paavolainen Leena , Salonen Matti
Published: August 2016

A new instrument, the photocell contact mat (PCM), was developed to measure ground contact time and flight time as well as step and stride frequency as a function of running time or running distance. The purpose of this study was to evaluate the validity and accuracy of PCM measurements against simultaneous force platform measurements. Effects of striking pattern (sprinter or long-distance), running velocity, and height of the PCM from ground level on the contact parameters were analyzed. One male sprint runner and one male distance (marathon) runner volunteered as subjects. The time difference between the PCM and force platform determinations linearly increased as a function of the PCM height and decreased as a function of running velocity (except for the lowest 10 mm PCM height). The low coefficients of variation found between corrected PCM contact times and force platform contact times suggested that the PCM is an accurate instrument to measure ground contact times.
Changes in Resultant Pedal Reaction Forces Due to Ankle Immobilization during Pedaling
Authors: Pierson-Carey Cheryl D. , Brown David A. , Dairaghi Christine A.
Published: August 2016

The purpose of this study was to determine the effects of limiting ankle motion on pedal forces. Sixteen adults pedaled an instrumented ergometer against constant cadence and frictional load while wearing hinged braces. Ankle motion was limited under four randomly assigned conditions: both braces unlocked (UL), only the preferred leg (PL) brace locked, only the nonpreferred leg (NPL) brace locked, and braces on both legs (BL) locked. Measurements of pedal force, crank, and pedal angles were sampled at 200/s for 20 s. With both braces locked, resultant force mean magnitude decreased during the downstroke, due to reduced radial crank force. Asymmetry between PL and NPL decreased during the power phase when only PL was braced but increased when only NPL was braced. It was concluded that constrained ankle motion, as may occur with ankle injury or hemiplegia, reduces the ability to transmit power during the downstroke while enhancing ability during the upstroke.
Relationship between Knee Joint Torque, Velocity, and Muscle Activation: Considerations for Musculoskeletal Modeling
Authors: Hawkins David , Smeulders Mark
Published: August 2016

The purpose of this study was to determine if the Hill model, used to describe the force-velocity relationship for isolated tetanically stimulated muscle, could be modified and used to describe the torque-velocity behavior of the knee for maximally and submaximally stimulated quadriceps and hamstrings muscles. Fourteen subjects performed both knee flexion and extension movements at 100%, 70%, and 40% of maximum isometric effort. For each effort level, the knee was allowed to move against resistances equal to 75%, 50%, 25%, and 0% of the specified effort level. An electrogoniometer quantified knee angle. Knee velocity was determined by numerically differentiating the joint angle data. Torque-velocity-activation (or effort level) data were determined for each trial. Model parameters were determined to give the best fit to the data for each subject. Average parameter values were determined for each gender and for the entire group. The modified Hill-type model accurately described the relationship between torque, velocity, and muscle activation level for subject-specific parameters but not for parameters averaged across genders or the entire group.
The Influence of Heal Lift Manipulation on Sagittal Plane Kinematics in Running
Authors: Dixon Sharon J. , Kerwin David G.
Published: August 2016

In this study sagittal plane joint angles of the lower extremity were used to obtain an indication of the influence of heel lift manipulation on Achilles tendon strain in running. The influence of increased heel lift on lower extremity kinematics was investigated for 8 heel striking subjects. With increased heel lift, all subjects demonstrated reductions in peak ankle dorsi-flexion and consistent values of peak knee flexion, indicating that there were reductions in peak Achilles tendon strain. Group analysis demonstrated that the reductions in peak ankle angle were statistically significant (p < .01). Typically, subjects also demonstrated adjustments in initial ankle angle, whereby the amount of ankle dorsi-flexion at initial ground contact was reduced with increased heel lift. Group mean data indicated that a 15-mm heel lift resulted in a mean decrease in initial ankle dorsi-flexion of 3.9°, while peak ankle dorsi-flexion was also reduced by 3.9°. It is suggested that the initial ankle angle adjustment acted to maintain a similar range of ankle joint movement in the period from initial ground contact to peak ankle dorsi-flexion across heel lift conditions. The distinct behavior of one subject, who demonstrated an increased ankle dorsi-flexion at ground impact, has highlighted the importance of considering single subject results in studies of footwear variation in running.
An Investigation of the Relationship between Hip Extension Torque, Hip Extension Velocity, and Muscle Activation
Authors: Hawkins David , Smeulders Mark
Published: August 2016

The purpose of this study was to determine if the characteristic Hill model, used to describe me force–velocity relationship for isolated tetanically stimulated muscle, could be modified and used to describe me torque–velocity behavior of me hip for maximally and submaximally stimulated hip extensor muscles. Fourteen subjects performed hip extension movements at effort levels of 100%, 70%, and 40% of a maximum isometric effort. A solenoid provided isometric resistance to hip extension. Once the desired effort level was achieved, as indicated by me isometric force, the solenoid released and me hip moved against an opposing elastic resistance equal to 75%, 50%, 25%, and 0% of the specified effort level. An electrogoniometer quantified hip angle. Hip velocity was determined by numerically differentiating the angle data. Torque-velocity-activation (or effort level) data were determined for each trial. Model parameters were determined to give me best fit to the data for each subject. Average parameter values were determined for each gender and for the entire group. The modified Hill-type model, Tm = (Tmax · A − K1 · ω)/(K2 · ω + 1), accurately describes me relationship between joint torque (Tm), maximum isometric joint torque (Tmax), joint velocity (ω), and muscle activation level (A) for subject-specific parameters (K1 and K2), but not for parameters averaged across genders or the entire group. Values for Tmax, K1, and K2 ranged from 90 to 385 Nm, 6.1 to 47.9 Nms, and 0.030 to 0.716 s, respectively.
Torques Produced by Different Compartments of the Rabbit Masseter Muscle
Authors: English Arthur W. , Carrasco Dario I. , Widmer Charles G.
Published: August 2016

Intramuscular microstimulation was used to evaluate the mechanical properties of 6 different neuromuscular compartments of four adult rabbit masseter muscles. Single compartment stimulation was verified by simultaneous multichannel electromyo-graphic recordings. A multi-axis force-moment sensor was used to measure evoked reaction forces at the mandibular symphysis, and these records were used to determine the magnitude and directions of the torques produced about the ipsilateral temoromandibular joint. The magnitude of the resultant torque vector differed between compartments. The most superficial compartments of the superficial masseter (MSSla, MSSlp) produced the largest torques, and compartments of the superficial masseter lying more caudal, such as MSS3, produced the smallest torques. The rise time of this vector was shortest for the posterior deep masseter (MPPo) compartment and longest for compartment MSSla. The directions of the torque vectors of different compartments varied considerably. Torque vectors of deep compartments such as MPPo, and the pars reflexa of the superficial masseter (MSPR) produced significant yaw torques toward the working masseter but very small lingual roll torques. Torque vectors from superficial compartments such as MSSI contain larger lingual roll components and smaller working yaw components. These observations are consistent with the hypothesis that neuromuscular compartments of the rabbit masseter muscle form output elements in the neural control of masticatory movements.
Whole-Body Momentum during Gait: A Preliminary Study of Non-Fallers and Frequent Fallers
Authors: Simoneau Guy C. , Krebs David E.
Published: August 2016

The importance of momentum in compensating for elderly individuals’ strength deficits to achieve activities of daily living, such as rising from a chair has been demonstrated in earlier studies. Here we present a case-control study of three healthy “non-fallers” and two “frequent fallers.” All 5 elders were community-living and were tested in the gait laboratory. A four-camera Selspot system was used to obtain whole-body momentum from an 11-segment kinematic model. Ground reaction forces and kinematics were used to calculate lower extremity joint moments. With the exception of the whole-body’s angular momentum about the vertical axis, linear and angular momenta during gait were minimum during mid-single limb support and maximum near heel contact. Whole-body momentum values for individuals with a history of falls were similar to those measured in non-fallers. However, subjects with a history of falls had between 17 and 37% smaller maximum ankle and knee torque values than the subjects without a history of falls during ambulation, A comprehensive description of whole-body linear and angular momenta during steady-state gait in older individuals is presented. While whole-body momentum characteristics and magnitude were similar between fallers and non-fallers. the consequences of the lesser torque values in the fallers’ knees and ankles to generate and control this momentum warrant further investigation.
Validity and Reliability of a Kinematic Device for Measuring the Force Developed during Squatting
Authors: Rahmani Abderrehmane , Dalleau Georges , Viale Fabrice , Hautier Christophe A. , Lacour Jean-René
Published: August 2016

This study determined the validity and reliability of the kinematic device developed by Bosco et al. (1995) by comparing its peak force, peak velocity, and peak power measurements to data obtained simultaneously with a force platform placed under the subject’s feet. Fifteen international downhill skiers performed maximal half-squats on a guided barbell with masses of 60–180 kg. The coefficient of correlation (r) between the two peak forces (r = 0.85–0.95, p < .001), the two peak velocities (r = 0.74–0.91, p < .001), and the two peak powers (r = 0.85–0.95, p < .001) indicated that the kinematic device measurements were valid. The trial-to-trial reliability of half-squat exercises measured by the kinematic device gave an intraclass coefficient of correlation (CR) of: 0.70-0.90 for peak force, 0.62-0.90 for peak velocity, and 0.57-0.91 for peak power. There were no statistical differences between the two trials. The standard error of the means (SEM%) was less than 5% for peak force, less than 4% for peak velocity, and less than 7% for power. The high CR and low SEM% indicate that the kinematic device is reliable. The movement recorded by the kinematic device accurately described the action measured by the force platform.