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Abstract: The purpose of this study was to investigate the interaction between elastic energy utilization and the time available for active state development during countermovement, and to determine the contributions of these factors in enhancing work output from a quantitative standpoint. Especially, we focused on the effect of length variation of the series elastic element (SEE) and the speed of active state development. A Hill-type model of the muscle tendon complex (MTC) was constructed. A range of SEE lengths (between 0.625 and 10 times the optimal length of the contractile element) and a range of active state development rates were investigated. Forward dynamics simulations were performed to evaluate the causal factors for the gain in height during concentric (CO) and countermovement (CM) conditions. Simulated outputs suggested that the contribution of the time available for active state development was larger than the contribution of elastic energy utilization for a shorter SEE muscle. On the other hand, the contribution of the elastic energy utilization was larger for a longer SEE muscle. Additionally, the work output of the SEE in CM was considerably augmented due to increasing the speed of active state development. As results, two main findings were obtained. First, a quantitative discussion was developed regarding how the elastic energy utilization and the time available for active state development are contributing within the work enhancing mechanism. Second, it was found that elastic energy utilization and the time available for active state development have a synergistic effect during countermovement. [Copyright &y& Elsevier]

Arm swing during a jump can enhance performance. This study examined the mechanisms via which arm swing contributes to maximum vertical jump height. Two mechanisms have been proposed to explain how jump height can be increased by arm swing: production of additional energy or slow leg extension which may permit muscles to work on a more favorable region of the force-velocity curve. A simulation model of the vertical jump and an induced energy analysis were used to determine the contribution of each of these mechanisms. The results from the model suggest that both mechanisms for the role of arm swing in enhancing jump performance are at play. Arm swing did slow the hip extensors allowing for more force production from these muscles. The work done and the energy induced in the vertical direction by these muscles were greater in the jump simulated with arm swing. However, these increases were not sufficient to explain the entire improvement in jumping performance. The shoulder musculature generated a considerable amount of work and energy induced and is directly responsible for approximately one-third of the performance enhancement associated with arm swing. [ABSTRACT FROM AUTHOR]

Abstract: A model for option pricing of fractional version of the Merton model with ‘Hurst exponent’ being in is established with transaction costs. In particular, for the minimal price of an option under transaction costs is obtained, which displays that the timestep and the ‘Hurst exponent’ play an important role in option pricing with transaction costs. [Copyright &y& Elsevier]

The article reports on research conducted to examine the fatigue pattern of elite female soccer players after competitive games. Researchers evaluated 23 players from the Danish women Premier League. They found that the type of fatigue that occurs after a female soccer game caused marked impairment in intense intermittent exercise and repeated sprint performance but did not affect vertical jump performance.

This study aimed to determine simultaneously the effects of plyometric training on the passive stiffness of the ankle joint musculo-articular complex, the gastrocnemii muscle–tendon complex (MTC) and the Achilles tendon in order to assess possible local adaptations of elastic properties. Seventeen subjects were divided into a trained (TG) group and a control (CG) group. They were tested before and after 8 weeks of a plyometric training period. The ankle joint range of motion (RoM), the global musculo-articular passive stiffness of the ankle joint, the maximal passive stiffness of gastrocnemii and the stiffness of the Achilles tendon during isometric plantar flexion were determined. A significant increase in the jump performances of TG relative to CG was found (squat jumps: +17.6%, P=0.008; reactive jumps: +19.8%, P=0.001). No significant effect of plyometric training was observed in the ankle joint RoM, musculo-articular passive stiffness of the ankle joint or Achilles tendon stiffness ( P>0.05). In contrast, the maximal passive stiffness of gastrocnemii of TG increased after plyometric training relative to CG (+33.3%, P=0.001). Thus, a specific adaptation of the gastrocnemii MTC occurred after plyometric training, without affecting the global passive musculo-articular stiffness of the ankle joint. [ABSTRACT FROM AUTHOR]

The article focuses on research conducted to examine the strength, power, and anthropometric contributors to vertical jump performances that are considered specific to volleyball success by examining changes across 12 months of training in elite volleyball players. Researchers evaluated 20 male elite volleyball players. They found that stretch-shortening cycle performance and the ability to tolerate high stretch loads are critical to improving jumping performance.

Differentiated means are defined in order to find formulas for jumps of distributions. We analyze two types of jumps occurring in the notions of distributional jump behavior and symmetric jump behavior. We start by defining what we call Riesz differentiated means for numerical series, then the differentiated means are extended to distributional evaluations for the Schwartz class of tempered distributions. The jumps of tempered distributions are completely determined by the differentiated means of the Fourier transform. We also find formulas for the jumps in terms of the asymptotic behavior of partial derivatives of harmonic representations and harmonic conjugate functions. Applications to Fourier series are given. [ABSTRACT FROM AUTHOR]

The article reports on research conducted to investigate the physiologic demands, physiologic characteristics, and jumping ability of different playing positions in elite male volleyball players. Researchers evaluated 142 players. They found that larger jumping and landing demands were placed on taller and heavier players in the middle position.

The intention of this case study was to analyze a sport artifact sold in the Costa Rican market, the Skyrunner®, from the biomechanical and physiological point of view. For it, the biomechanics and physiological differences are studied when the Skyrunner® is and is not used. A man (20 years, 1.67 m, 55 kg) was the case of study. The analysis of the biomechanical variables was made by means of a force platform, with which the vertical force was obtained, the height, the jump flight time, vertical impulse and duration of the impulse phase. For the measurement of the physiological variables a metabolic car was used to evaluate the power consumption while the subject was exercised in an endless band during the heating, the exercise and the phase of recovery. In general, the use of the Skyrunner® caused a greater cost of energy that can be attributed to the requirement of mechanisms of balance and muscular tension that entail an important cost of energy. The height of the jumps with Skyrunner® was greater by 50%, although the vertical impulse was nearly 15% less. The time of impulse was 27.5% the time of a normal jump and forces were generated almost three times greater. This denotes the great mechanical efficiency of the system that is able to keep and use greater amount of elastic energy accumulated in the structure, in comparison with that produced by the legs in an isolated form. [ABSTRACT FROM AUTHOR]

Abstract: The objective of the present experiment was to determine the implications of prenatal undernutrition on the behaviour of juvenile lambs. Dams of one group (C) were fed 100% of the recommended requirements throughout pregnancy, while those of two other groups were fed 50% of the control nutrient allowance during the first 30 days of pregnancy (R1) or 50% of the control nutrient allowance from days 31–100 of pregnancy (R2). Between 2 and 5 months old, behaviour of lambs was tested by the implementation of 2 types of test: isolation and novelty. There were no statistical differences between lamb treatments in escape behaviour and heart rates during isolation test, or the latency to approach a novel or a familiar object in the novelty test in tests conducted at 2, 3, 4 and 5 months of age. Male lambs showed a tendency of turning to the right-hand side of the test pen, irrespective of treatment group, between the age of 2 and 5 months old. A greater proportion of C compared to R1 males turned right at the age of 2 and 5 months old (P <0.05). Significant differences concerning laterality were found also between C and R1 female lambs at the age of 2 and 4 months old (P <0.001), between C and R2 male lambs at the age of 2 months old (P <0.05), between C and R2 female lambs at the age of 4 and 5 months old (P <0.01), between R1 and R2 male lambs at the age of 2 and 5 months old (P <0.05) and between R1 and R2 female lambs at the age of 2 months old (P <0.001). It is concluded that prenatal undernutrition during different periods of pregnancy had no effect on fear-related behaviour, but effect on laterality at the early stages of lamb age between 2 and 5 months old. [Copyright &y& Elsevier]

The article presents a study on the impact of training on the power-, force- and velocity-time curves of the countermovement jump (CMJ). Results revealed significant differences in peak performance variables, such as peak power, force and velocity, between jumpers and nonjumpers. Jumpers and nonjumpers were also observed to have differences throughout the power-, force-, velocity- and displacement-time curves of the CMJ.

The article reports on the power performance of elite Australian Rules Football (ARF) among football players. This study measured variables showing the significance of performance in peak power output. The effects of training and informing adjustments among twelve members of the ARF team were studied and recorded.

The authors performed an experiment in which participants (N = 24) made judgments about maximum jump and reachability on ground surfaces with different elastic properties: sand and a trampoline. Participants performed judgments in two conditions: (a) while standing and after having recently jumped on the surface in question and (b) while standing on a third control surface, eliminating haptic exploration of the surface in question. There was a high correlation between perceived maximum reachable height and actual maximum reachable height in all conditions. Judging performance on the basis of visual and haptic exploration of ground surface information was slightly overestimated, whereas performance on the basis of visual information alone was underestimated and variable for the different surfaces. The authors discuss possible causes for the observed errors. They emphasize that there is a considerable nonvisual aspect to the nature of the information specifying affordances for overhead reach and jumping and that perceptual performance is degraded when spontaneous exploratory movement is restricted. [ABSTRACT FROM AUTHOR]

Background: Ballet and modern dance are jump-intensive activities, but little is known about the incidence of anterior cruciate ligament (ACL) injuries among dancers. Hypothesis: Rigorous jump and balance training has been shown in some prospective studies to significantly reduce ACL injury rates among athletes. Dancers advance to the professional level only after having achieved virtuosic jump and balance technique. Therefore, dancers on the elite level may be at relatively low risk for ACL injury. Study Design: Descriptive epidemiology study. Methods: Dance exposure, injuries, and injury conditions were systematically recorded at 4 dance organizations over 5 years. Select neuromuscular and psychometric variables were compared between and within ACL-injured and noninjured dancers. Results: Of 298 dancers, 12 experienced an ACL injury over the 5-year period. The incidence of ACL injury was 0.009 per 1000 exposures. Landing from a jump onto 1 leg was the mechanism of injury in 92% of cases. Incidence was not statistically different between gender or dance groups, although women modern dancers had a 3 to 5 times greater relative risk than women ballet dancers and men dancers. No difference between ACL-injured and noninjured dancers emerged with regard to race, oral contraceptive use, or select musculoskeletal measures. Conclusion: Dancers suffer considerably fewer ACL injuries than athletes participating in team ball sports. The training dancers undertake to perfect lower extremity alignment, jump, and balance skills may serve to protect them against ACL injury. Anterior cruciate ligament injuries happened most often late in the day and season, suggesting an effect of fatigue. [ABSTRACT FROM AUTHOR]

Abstract: The purposes of this study were to quantify and compare how arm swing and countermovement affect lower extremity torque and work during vertical jumping and to gain insight into the mechanisms that enable the arm swing and countermovement to increase jump height. Five participants maximally performed two types of vertical squat jumps with (SJA) and without (SJ) an arm swing and two types of countermovement vertical jumps with (CJA) and without (CJ) an arm swing. The participants jumped from a force platform and all performances were videotaped with a high-speed video camera (200Hz). Jump heights, joint torques and work were calculated by combining kinematic and kinetic data. It was found that of the four jumping conditions, the participants jumped highest when they used an arm swing with countermovement (i.e., CJA). The increase of the countermovement jump height with an arm swing is the result of the increase of the lower extremity work. In the hip joint, the increase in torque caused by the countermovement predominantly occurred at the beginning of the propulsion phase, while the increase in torque caused by the arm swing occurred in the rest of the propulsion phase. A key finding of our study is that arm swing and countermovement have independent effects on lower extremity work, and their effects are additive in CJA to produce greater jump height. [Copyright &y& Elsevier]

The article presents a study which examined the impact of anaerobic fitness on basketball players. It also aims to analyze the effect of game rule changes implemented in 2000 on the physiological factors of success in basketball. It involved eight elite male players and eight average-level players, who conducted seven tests, including vertical jump, sprint and isokinetic testing of the knee extensors. Results have shown that elite players achieve better performances than average players.

The article discusses a study to examine the potential strength, power and anthropometric contributors to vertical jump performances that are specific to the success of volleyball players. A correlation and regression analysis was performed to assess the relationship among strength, power and anthropometric variables. The results of the study demonstrate that stretch shortening cycle performance and the ability to tolerate high stretch loads.

In this study, we compared the kinematic variables of the split triple twist with those of the split double twist to help coaches and scientists understand these landmark pair skating skills. High-speed video was taken during the pair short and free programmes at the 2002 Salt Lake City Winter Olympics and the 2003 International Skating Union Grand Prix Finals. Three-dimensional analyses of 14 split double twists and 15 split triple twists from eleven pairs were completed. In spite of considerable variability in the performance variables among the pairs, the main difference between the split double twists and split triple twists was an increase in rotational rate. While eight of the eleven pairs relied primarily on an increased rotational rate to complete the split triple twist, three pairs employed a combined strategy of increased rotational rate and increased flight time due predominantly to delayed or lower catches. These results were similar to observations of jumps in singles skating for which the extra rotation is typically due to an increase in rotational velocity; increases in flight time come primarily from delayed landings as opposed to additional height during flight. Combining an increase in flight time and rotational rate may be a good strategy for completing the split triple twist in pair skating. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to compare the injury patterns and incidence of snowboarding and ski boarding injuries with that of alpine skiing in 2000 to 2005, as there are few previous studies comparing these 3 sports, especially in Asia. Hypothesis: The injury patterns are different among the 3 snow sports. Study Design: Descriptive epidemiology study. Methods: The subjects were alpine skiers (1240 cases), snowboarders (2220 cases), and ski boarders (132 cases) who were injured in 2 ski resorts located in Niigata prefecture in Japan and visited the authors' clinics in these ski resorts between 2000 and 2005. On visiting the clinics, patients completed a questionnaire reviewing the circumstances surrounding the injury event, and physicians documented the diagnosis. Results: The injury rate, which was based on all purchased lift tickets, in snowboarding decreased gradually, although it was still 2 times higher than that of alpine skiing. Snowboarding and ski boarding had a higher fracture and dislocation rate. Both sports also had a 4 times higher rate of injuries because of jumping. The characteristics of ski boarding were a lower head and neck injury rate and collision injury rate than those of the other 2 snow sports, as well as a 2 times higher rate of fractures compared with alpine skiing injuries and a 1.4 times higher incidence than that of snowboarding injuries. Of the fractures caused by ski boarding accidents, 39.6% affected the lower leg bones. Conclusion: Injury prevention strategies should focus on jumps for snowboarders and ski boarders. [ABSTRACT FROM AUTHOR]

Abstract: Background: Patellofemoral pain is commonly associated with lower extremity joint rotations that decrease retropatellar contact area and subsequently increase retropatellar stress during weightbearing activities. People with patellofemoral pain are thought to be capable of avoiding such harmful mechanics during activities with low external demands. However, this may not be possible during more demanding activities. The purpose of this study was to analyze lower extremity mechanics in females with and without patellofemoral pain during three different activities. Specifically, we sought to determine if differences between groups increase with increasingly demanding activities. Methods: 20 females with patellofemoral pain and 20 healthy female controls performed single leg squats, running, and repetitive single leg jumps as their three-dimensional lower extremity mechanics were recorded. Transverse and frontal plane hip and knee kinematics were compared between groups for all activities. Findings: Differences in the variables of interest between groups did not generally depend on the nature of the activity. The patellofemoral pain group performed all three activities with 4.3° greater knee external rotation (P =0.06), 3.5° greater hip adduction (P =0.012), and 3.9° decreased hip internal rotation with respect to the control group (P =0.01). Interpretation: These results suggest that females with patellofemoral pain do not employ different mechanics as demand of the activity increases. Rather, females with patellofemoral pain seem to demonstrate similar abnormal lower extremity mechanics across a variety of activities. [Copyright &y& Elsevier]

On having investigated the differences of physical performance between boys and girls, one thinks that the biological differences are too small and cannot produce so many advantages to the males on the women. In the childhood the physical aptitudes are practically equal in both sexes. When in the classes of physical Education the motive performance is compared between the males and the women, the males overcome the girls in the jumps in high place and in length, in the races and in the skills with balls like that also like in almost all the games and sports, of the same way, the women overcome the males in activities of ritmic, pace and dance and there do not exist biological or physiological reasons in order that this happens, therefore there will be necessary to look for the reason of these differences in other variables. On this search it treats this article. [ABSTRACT FROM AUTHOR]

Improvements in coordination and technical sports must be considered among the key components of training in every sports, the most receptive adaptability skills are expressed in the youth age. By administering tests explosive force in three different periods, the study intends to verify if a minivolley protocol training for six weeks on two groups of young players of different ages can improve capabilities and coordination through the teaching of basic technical disciplines so that the can consequently improve explosive power of the lower and upper limbs. The results show a marked improvement in performance, both in jump and in putting, of trained groups between the initial test and post-test training protocol. The final test, performed thirty days after the end of training protocol, shows a pattern not consistent in performance. [ABSTRACT FROM AUTHOR]

Aim: To quantify the global changes in anaerobic fitness (operationalized as power and speed test performance) of children and adolescents. Methods: Following an extensive review of the literature, 32 studies examining secular changes in power and speed test performance of children and adolescents were analysed. Performance changes were calculated at the country × age × sex × test level using weighted least-squares regression, and were expressed as a percentage of the weighted mean value for all data points in the regression. Negative values indicated performance declines, and positive values indicated improvements. Results: Changes in power ( n=20 802 925) and speed ( n=28 320 308) test performance were calculated for 6–19 year olds from 27 countries and five geographical regions, for the period 1958–2003. Overall, power and speed test performances improved at +0.03% and +0.04% per annum, respectively. Performance changes were remarkably similar for boys and girls, and children and adolescents, and somewhat similar for different geographical regions, and high and low income economies. The pattern of change was reasonably consistent over time. Conclusion: The relative stability in anaerobic fitness test performances in recent decades could be due to the negating effects of increases in fat mass and fat-free mass on anaerobic performance. [ABSTRACT FROM AUTHOR]

Rodent-associated Bartonella species are generally host-specific parasites in North America. Here evidence that Bartonella species can ‘jump’ between host species is presented. Northern grasshopper mice and other rodents were trapped in the western USA. A study of Bartonella infection in grasshopper mice demonstrated a high prevalence that varied from 25% to 90% by location. Bartonella infection was detected in other rodent species with a high prevalence as well. Sequence analyses of gltA identified 29 Bartonella variants in rodents, 10 of which were obtained from grasshopper mice. Among these 10, only six variants were specific to grasshopper mice, whereas four were identical to variants specific to deer mice or 13-lined ground squirrels. Fourteen of 90 sequenced isolates obtained from grasshopper mice were strains found more commonly in other rodent species and were apparently acquired from these animals. The ecological behavior of grasshopper mice may explain the occurrence of Bartonella strains in occasional hosts. The observed rate at which Bartonella jumps from a donor host species to the grasshopper mouse was directly proportional to a metric of donor host density and to the prevalence of Bartonella in the donor host, and inversely proportional to the same parameters for the grasshopper mouse. [ABSTRACT FROM AUTHOR]

For representatives of sport games are very important components of physical abilities -- spring and rate of psychomotoric reaction. For the following sportsman's especially important is the rate of psychomotoric reaction, which defines reaction to the constantly changing ambience, similar to the sport action. Testing system, which simulates the situation of sports game, was created in the department of Informatics and biomechanics of LKKA. This system allows estimating the physical capabilities of player -- spring and the speed of psychomotoric reaction. The speed of psychomotoric reaction is evaluated by making the jump-up. The influence of the height of jump-up on the spring and speed of reaction of sportsman is investigated. Considering the results of experiments and statistical analysis some recommendations are given and conclusions withdrawn. [ABSTRACT FROM AUTHOR]

We discuss determination of jumps for functions with generalized bounded variation. The questions are motivated by A. Gelb and E. Tadmor [1], F. Móricz [5] and [6] and Q. L. Shi and X. L. Shi [7]. Corollary 1 improves the results proved in B. I. Golubov [2] and G. Kvernadze [3]. [ABSTRACT FROM AUTHOR]

The aim of this study was to establish the anthropometric and physiological profiles of young nonelite soccer players according to their playing position, and to determine their relevance for the selection process. Two hundred forty-one male soccer players who were members of the Getxo Arenas Club (Bizkaia) participated in this study. Players, age 17.31 (± 2.64) years, range 14-21 years, were classified into the following groups: forwards (n = 56), midfielders (n = 79), defenders (n = 77), and goalkeepers (n = 29). Anthropometric variables of participants (height, weight, body mass index, 6 skinfolds, 4 diameters, and 3 perimeters) were measured. Also, their somatotype and body composition (weights and percentages of fat, bone, and muscle) were calculated. Participants performed the Astrand test to estimate their absolute and relative O2max, an endurance test, sprint tests (30 meters flat and 30 meters with 10 cones) and 3 jump tests (squat jump, counter movement jump and drop jump). Forwards were the leanest, presenting the highest percentage of muscle. They were the best performers in all the physiological tests, including endurance, velocity, agility, and power. In contrast, goalkeepers were found to be the tallest and the heaviest players. They also had the largest fat skinfolds and the highest fat percentage, but their aerobic capacity was the lowest. In the selection process, agility and the jump tests were the most discriminating for forwards. In contrast, agility, height, and endurance were the key factors for midfielders. The defenders group was characterized by a lower quantity of fat. Thus, we may conclude that anthropometric and physiological differences exist among soccer players who play in different positions. These differences fit with their different workload in a game. Therefore, training programs should include specific sessions for each positional role. [ABSTRACT FROM AUTHOR]

Jumping is an important locomotor behaviour used by many animals. The power required to perform a jump is supplied by skeletal muscle. The mechanical properties of skeletal muscle, including the power it can produce, are determined by its composition, which in turn reflects trade-offs between the differing tasks performed by the muscle. Recent studies suggest that muscles used for jumping are relatively fast compared with other limb muscles. As animals get bigger absolute jump performance tends to increase, but recent evidence suggests that adult jump performance may be relatively independent of body size. As body size increases the relative shortening velocity of muscle decreases, whereas normalised power output remains relatively constant. However, the relative shortening velocity of the fastest muscle fibre types appears to remain relatively constant over a large body size range of species. It appears likely that in many species during jumping, other factors are compensating for, or allowing for, uncoupling of jumping performance from size-related changes in the mechanical properties of muscle. In some species smaller absolute body size is compensated for by rapid development of locomotor morphology to attain high locomotor performance early in life. Smaller animal species also appear to rely more heavily on elastic storage mechanisms to amplify the power output available from skeletal muscle. Adaptations involving increased relative hindlimb length and relative mass of jumping muscles, and beneficial alteration of the origin and/or insertion of jumping muscles, have all been found to improve animal jump performance. However, further integrative studies are needed to provide conclusive evidence of which morphological and physiological adaptations are the most important in enhancing jump performance. [ABSTRACT FROM AUTHOR]

The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch–shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90° of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle–tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles. [ABSTRACT FROM AUTHOR]

Abstract: Bubble motion is the primary means of inducing particle motion in fluidised beds. The objective of this study is to link bubble motion to the particle motion. The technique used is positron emission particle tracking (PEPT), which enables a single particle tracer to be tracked in milliseconds and in 3D movement. Features investigated include particle velocity and particle “jump” behaviour. [Copyright &y& Elsevier]

We describe crawling and jumping by a soft robot. Locomotion over rough terrain has been achieved mainly by rigid body systems including crawlers and leg mechanisms. This paper presents an alternative method, one that employs deformation. First, we describe the principle of crawling and jumping as performed through deformation of a robot body. Second, in a physical simulation, we investigate the feasibility of the approach. Next, we show experimentally that a prototype of a circular soft robot can crawl and jump. Finally, we describe crawling and jumping performed by a spherical deformable robot. [ABSTRACT FROM AUTHOR]

Spring is an integral physical ability, which depends on other physical abilities: strength, velocity, coordination. The aim of this work is to prove, referring to theoretical assumptions and experimental data, that spring as a physical ability has dual expression. In some cases it is important to a sportsman to jump high, no matter how long it takes to make a spring; in other cases it is important to him to reach the same altitude as quickly as possible. In the first case the height of jump, determined by take-off force impulse, is what matters, in the second case the time of jump, determined by dynamic force, which determines the time of movement, is important. 14 members of Lithuanian juniors' handball team have been examined. They have performed three jumps each on the force platform without an amortizing squat. We have estimated the take-off time tats, time of darting in the air tlėk, velocity at the moment of the abruption off support v0, body mass center's (MC) maximum raise off the ground (hMC), average take-off force (Fvid), absolute dynamic force (dF/dt)max and relative dynamic force (R). Founding our and other authors' research data on theoretical presumptions we may state that: a) the height of jump does not depend on dynamic force, but does depend on force impulse; b) the time of jump depends on dynamic force; c) spring as human physical ability must be defined not only by height of jump, but also by speed of jump. These two aspects of jump, different in qualitative terms, reflect different speed-strength characteristics; d) the most appropriate measure for estimating spring as complex human physical ability is relative power of jump. [ABSTRACT FROM AUTHOR]

One of the main problems in effective model theory is to find an appropriate information complexity measure of the algebraic structures in the sense of computability. Unlike the commonly used degrees of structures, the structure degree measure is total. We introduce and study the jump operation for structure degrees. We prove that it has all natural jump properties (including jump inversion theorem, theorem of Ash), which show that our definition is relevant. We study the relation between the structure degree jump (in the sense of Soskov) and the jump degrees of a structure (in the sense of Jockusch) and give necessary and sufficient conditions for their existence in the terms of structure degrees. We show some properties, distinguishing the structure degrees from the enumeration degrees. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies a class of stochastic delay differential equations with jumps (SDDEJs). Explicit solutions can hardly be obtained for the SDDEJs. Appropriate numerical approximation schemes such as the Euler scheme are needed to apply SDDEJs in practice or to study their properties. In this paper, it is proved that the Euler approximation solutions converge to the analytic solution for SDDEJs under weaker conditions than the linear growth condition and global Lipschitz condition. An example is given for illustration. [Copyright &y& Elsevier]

ABSTRACT: Two case studies are presented involving fatal falls of adult females from a height. One involved a launch at low speed from a balcony, and one involved a launch at high speed from the top of a cliff. Crime scene evidence obtained on the balcony itself provided a strong indication of homicide, but subsequent investigation showed that the fall was accidental. No crime scene evidence was obtained for the cliff fall since the fall initially appeared to be just another suicide from a popular suicide spot. Subsequent investigations indicated homicide based on measurements of cliff height, horizontal distance to the impact, and available runup distance, plus measurements of possible run, jump, and throw speeds. It was found that a female weighing 61 kg (134 lb) can be thrown at speeds up to 4.85 m/s by a strong male, more than enough to account for the estimated launch speed (4.5 m/s). Given the available 4.0 m runup distance, it was found that women of better than average rather than elite athletic ability can dive at speeds of about 3.5 m/s or jump feet first at speeds of about 4.0 m/s, both being less than the estimated launch speed. The decedent had no athletic ability and landed head first after falling through a height of 29 m. [ABSTRACT FROM AUTHOR]

Abstract: Introduction. – This study explored concentric and eccentric profile of knee musculature in a jumpers population. Relationships between isokinetic assessment and field tests performances have also been explored. Materials. – Jumpers population presented higher knee flexors performances in concentric and eccentric mode and superior knee extensors strength in eccentric. Significant correlations between isokinetics and field tests results were exclusively observed with athletes quadriceps performances. A very high correlation (r =0.93) was found between the second bound relative performance of the ten multijumps test and eccentric quadriceps relative peak torque. Conclusion. – Jumpers training may favour a specific muscular development. The knee extensors eccentric strength may be a major factor in the athletic performance. [Copyright &y& Elsevier]

Background: Spike effectiveness represents a determining element in volleyball. To compete at a high level, the player must, in particular, produce a spike characterized by a high ball velocity. Hypothesis: Some muscular and physical features could influence ball velocity during the volleyball spike. Study Design: Descriptive laboratory study. Methods: A total of 19 male volleyball players from the 2 highest Belgian national divisions underwent an isokinetic assessment of the dominant shoulder and elbow. Ball velocity performance (radar gun) during a spike test, morphological feature, and jump capacity (ergo jump) of the player were measured. We tested the relationship between the isokinetic parameters or physical features and field performances represented by spike velocity. We also compared first-division and second-division player data. Results: Spike velocity correlated significantly with strength performance of the dominant shoulder (internal rotators) and of the dominant elbow (flexors and extensors) in the concentric mode. Negative correlations were established with the concentric external rotator on internal rotator ratio at 400 deg/s and with the mixed ratio (external rotator at 60 deg/s in the eccentric mode on internal rotator at 240 deg/s in the concentric mode). Positive correlations appeared with both the volleyball players' jump capacity and body mass index. First-division players differed from second-division players by higher ball velocity and increased jump capacity. Conclusion: Some specific strength and physical characteristics correlated significantly with spike performance in high-level volleyball practice. Clinical Relevance: Our results could provide useful information for training management and propose some reflections on injury prevention. [ABSTRACT FROM AUTHOR]

The authors compared leg stiffness (K(VERT)), muscle activation, and joint movement patterns between 11 men and 10 women during hopping. Physically active and healthy men and women performed continuous 2-legged hopping at their preferred rate and at 3.0 Hz. Compared with men, women demonstrated decreased K(VERT); however, after the authors normalized for body mass, gender differences in K(VERT) were eliminated. In comparison with men, women also demonstrated increased quadriceps and soleus activity, as well as greater quadriceps-to-hamstrings coactivation ratios. There were no significant gender differences for joint movement patterns (p>.05). The relationship between the observed gender differences in muscle recruitment and the increased risk of anterior cruciate ligament injury in women requires further study. [ABSTRACT FROM AUTHOR]

On the basis of the principles of geometric scaling, maximum vertical-jump height should decrease in an approximately linear fashion with increasing mass. To test this prediction, a group of 10 male subjects performed maximum vertical jumps with masses up to 22.7 kg strapped to their trunks. The results from these jumps indicated that jump height did scale on an individual basis in a linear fashion. A computer simulation model of jumping was developed that permitted the examination of a greater range of masses than was possible experimentally. The simulations also support the trend of linear scaling, but do replicate the decrement expected based on geometric scaling principles. Experimental and simulation model results provide evidence for a linear decrement in subject maximum vertical-jump height with increasing mass, which is relevant information for athletes aiming to increase their body mass or performing jump training while carrying additional mass. [ABSTRACT FROM AUTHOR]

In Auchenorrhyncha, jumping is achieved by metathoracic muscles which are inserted into the trochanter of the hind leg. The synchronisation of movements of the hind legs is a difficult problem, as the leg extension that produces the jump occurs in less than 1 ms. Even slight asynchrony could potentially result in failure of a jump. Both the synchronisation of the movements of a pair of jumping legs, and their stabilisation during a jump, seem to be important problems for small jumping insects.The present study was performed in order to clarify some questions of the functional morphology of the leafhopper jumping mechanism. It is based on skeleton–muscle reconstruction, high-speed video recordings, transmission (TEM) and scanning electron microscopic (SEM) investigations of the cuticle, together with 3D inverse-kinematic modelling of angles and working zones of hind leg joints of cicada Cercopis vulnerata (Cercopidae). The complete extension of the hind leg takes less than 1 ms, which suggests that the jump is powered not only by the muscle system, but also by an elastic spring. Histological staining and fluorescence microscopy showed resilin-bearing structures, responsible for elastic energy storage, in the pleural area of the metathorax.Synchronisation of hind leg movements may be aided by microtrichia fields that are located on the medial surface of each hind coxa. In Auchenorrhyncha, hind coxae are rounded in their anterior and lateral parts, whereas medial parts are planar, and contact each other over a rather large area. The inverse-kinematic model of propulsive leg movements was used to draw the surface outlined by the medial surface of the coxa, during the jump movement. This is a cone surface, faced with its bulged-in side, medially. Surfaces outlined by the movements of both right and left coxae overlap in their anterior and posterior positions. In both extreme positions, coxae are presumably connected to each other by coupled microtrichia fields. Thus, in extreme positions, both coxae can be moved synchronously. [Copyright &y& Elsevier]

The aim of this study was to identify the anthropometric and physical prerequisites for high difficulty floor tumbling and vaulting. Twenty 8-14 year old female talent-selected gymnasts performed handstand push-offs, and single and multiple Jumps on a portable Kistler force plate. The force curves were analysed using Kistler and Excel software to obtain peak displacement, peak take-off force, and power. The gymnasts were also assessed for sprinting, with and without vaulting, and standing broad jump performances. Video footage from the vault take-off was analysed using Video Expert II software to obtain the horizontal and vertical take-off velocities. Each gymnast's best vault starting score, three best floor tumbling skills, and anthropometric characteristics were recorded. Statistical analysis included one-way analysis of variance (ANOVA) to examine the effect of age (8-10 years, 11-12 years, 13-14 years) on the performance measures and linear regression analysis with performance start score for vault or best floor tumbling score as the outcome variable. The best regression model for indicating vaulting talent had, as predictor variables, resultant velocity at take-off from the board, squat jump power, and average power during the last five jumps in the continuous bent-leg jump series. The best regression model for indicating floor tumbling ability had, as predictor variables, age, vault running velocity, and reduced ground contact time in a handstand push-off. [ABSTRACT FROM AUTHOR]

This laboratory exercise is designed to provide an understanding of the mechanical concept of impulse as it applies to human movement and athletic performance. Students compare jumps performed with and without handheld weights. Contrary to initial expectation, jump distance is increased with moderate additional weights. This was familiar to Ancient Greek athletes where “halteres” were a part of the original Olympic jumping sports. The effectiveness of this laboratory was assessed with a prelab questionnaire evaluating understanding of the concepts relevant to jumping mechanics and a postlab questionnaire assessing understanding of the same principles in the context of a different but mechanically analogous circumstance, that of throwing. Results indicate that understanding improved significantly as a result of participation in the laboratory exercise. [ABSTRACT FROM AUTHOR]

We continue research on machine-oracle modelling of second-order arithmetic. The pulsating process described in [1, 2] is simulated using oracles of so-called autonomous hierarchies. The outcome is constructing a generalized constructive model for a fragment of second-order arithmetic described in [2]. [ABSTRACT FROM AUTHOR]

The mobility of gas in foam in porous media depends both on an effective yield stress and on the drag of moving bubbles on pore walls. Previous modeling has split the effective gas viscosity into those two parts and solved for them separately. For the first time we present a dynamic model for the movement of bubbles through constricted tubes in 2D, accounting for the drag on lamellae along pore walls and the capillary forces that govern bubble shape in periodically constricted tubes. In the limit of slow flow rate, lamellae jump to asymmetric shapes even in radially symmetric pores, in agreement with Rossen [J. Colloid Interf. Sci. 136 (1990) 1; J. Colloid Interf. Sci. 136 (1990) 17; J. Colloid Interf. Sci. 136 (1990) 38; J. Colloid Interf. Sci. 139 (1990) 457]. The drag on the lamella increases the pressure gradient above the quasi-static limit by a factor scaling roughly as the 2/3 power of velocity, in agreement with Hirasaki and Lawson [SPE J. 25 (1985) 176]. At sufficiently high velocities, however, a symmetric jump replaces the asymmetric jump. In such cases unstable perturbations away from the symmetric shape have insufficient time to grow before the lamella settles into a symmetric shape on the other side of pore body. A lamella moving at a fast rate may require a lower pressure gradient than one moving more slowly, due to the disappearance of the asymmetric jump. Observations of lamella movement in glass pores support these predictions. [Copyright &y& Elsevier]

Purpose – The aim of this study is to appreciate the relation between sprint, jump and knee isokinetic torque in high-level soccer players.Methods – Twenty soccer players (first french national division) were evaluated by sprint and jump tests. Extensors and flexors isokinetic torque was measured by a Cybex Norm dynamometer. Relations between sprints, jumps and isokinetic peak torque were appreciated after correlation analysis.Results – Jumps are correlated with the extensors concentric peak torque at the speed of 180° s−1 when values were corrected by weight (Squat Jump: r = 0.507; Countermovement Jump: r = 0.649; Vertical Jump: r = 0.496). Sprints are correlated with the extensors concentric peak torque at the speed of 180° s−1 when values were corrected by weight (10 and 20 m fixed departure sprint: r = −0.427 and −0.548; 10 and 20 m thrown departure sprint: r = −0.406 and −0.480). Furthermore, sprints with fixed departure are conversely correlated with the flexors eccentric peak torque at the speed of 60° s−1 (r = 0.546 and 0.478) doubtless because a mechanism of knees protection.Conclusions – According to these causal relations, knee extensors and flexors strengthening is recommended for high-level soccer players with the aim of improving sprints and jumps. [Copyright &y& Elsevier]

The method of averaging is applied in this paper to deal with a primary resonance of a three circular plates torsion vibration system having cubic nonlinearities which is excited by a simple-harmonic excitation. Bifurcation equation of the steady state response is obtained and its singularity analysis is given. The results of theoretical analysis are shown to be in good agreement with experimental ones. [ABSTRACT FROM AUTHOR]

The article presents an experimental study that examines the suitability of the dynamometric horseshoe (DHS) for the recording of ground reaction forces (GRF) on ridden horses. In the study, a French trotter gelding in a DHS with four triaxial piezoelectric force sensors was ridden by an experienced rider and was allowed to perform various exercises. The findings reveal that the DHS is suitable for GRF recording during standard exercises on ridden horses, however, improvements are suggested.

The jump performance of locusts depends on several physiological and environmental factors. Few studies have examined the effects of different ground types on the jump performance of locusts. Here, mature adult locusts (Locusta migratoria manilensis) were examined using a custom-developed measuring system to test their jump performance (including postural features, kinematics, and reaction forces) on three types of ground (sand, soil, and wood). Significant differences were primarily observed in the elevation angle at take-off, the tibial angle at take-off, and the component of the mass-specific reaction force along the aft direction of the insect body between wood and the other two ground types (sand and soil). Slippage of the tarsus and insertion of the tibia were often observed when the locusts jumped on sand and soil, respectively. Nevertheless, comparisons of the different parameters of jump initiation (i.e., take-off speed and mass-specific kinetic energy) did not reveal any differences among the three types of ground, indicating that locusts were able to achieve robust jump performance on various substrates. This study provides insights into the biomechanical basis of the locust jump on different types of ground and enhances our understanding of the mechanism underlying the locust jump. [ABSTRACT FROM AUTHOR]

The long-range objective is to help the development of computational tools for all human movement on the ground and in the air. Movements that can be neurally and physiologically observed and measured contribute to unlocking the mysteries of the central nervous system (CNS). Medicine, science and engineering have successfully adopted minimal and reduced systems to understand the complexities of the human system and to offer effective solutions. The coordinate systems and the state variables the CNS utilizes are not well known. Movement in the air poses problems of dynamics, control, stability, coordination, maneuverability, landing and signal processing. Awareness of the states of the implement and how the CNS estimates these states from the available contact with it in the air is one challenge. It is assumed the head and the torso are held as one rigid body such that the angular velocities and accelerations, measured by the vestibular system, are the same as those of the torso. The vision system is not considered. [ABSTRACT FROM AUTHOR]