Search

Barn owls are effective hunters of small rodents. One hunting technique is a leap from the ground followed by a brief flight and a plummeting 'strike' onto an acoustically targeted - and potentially entirely hidden - prey. We used forceplate measurements to derive kinetics of the leap and strike. Leaping performance was similar to reported values for guinea fowl. This is likely achieved despite the owl's considerably smaller size because of its relatively long legs and use of wing upstroke. Strikes appear deliberately forceful: impulses could have been spread over larger periods during greater deflections of the centre of mass, as observed in leaping and an alighting landing measurement. The strike, despite forces around 150 times that of a mouse body weight, is not thought to be crucial to the kill; rather, forceful strikes may function primarily to enable rapid penetration of leaf litter or snow cover, allowing grasping of hidden prey. [ABSTRACT FROM AUTHOR]

When for a difficult real-world optimisation problem no good problem-specific algorithm is available often randomised search heuristics are used. They are hoped to deliver good solutions in acceptable time. The theoretical analysis usually concentrates on the average time needed to find an optimal or approximately optimal solution. This matches neither the application in practice nor the empirical analysis since usually optimal solutions are not known and even if found cannot be recognised. More often the algorithms are stopped after some time. This motivates a theoretical analysis to concentrate on the quality of the best solution obtained after a pre-specified number of function evaluations called budget. Using this perspective two simple randomised search heuristics, random local search and the (1+1) evolutionary algorithm, are analysed on some well-known example problems. Upper and lower bounds on the expected quality of a solution for a fixed budget of function evaluations are proven. The analysis shows novel and challenging problems in the study of randomised search heuristics. It demonstrates the potential of this shift in perspective from expected run time to expected solution quality. [ABSTRACT FROM AUTHOR]

This study sought to lend experimental support to the theoretical influence of force-velocity (F-v) mechanical profile on jumping performance independently from the effect of maximal power output (Pmax). 48 high-level athletes (soccer players, sprinters, rugby players) performed maximal squat jumps with additional loads from 0 to 100 % of body mass. During each jump, mean force, velocity and power output were obtained using a simple computation method based on flight time, and then used to determine individual linear F-v relationships and Pmax values. Actual and optimal F-v profiles were computed for each subject to quantify mechanical F-v imbalance. A multiple regression analysis showed, with a high-adjustment quality (r² = 0.931, P < 0.001, SEE = 0.015 m), significant contributions of P max , F-v imbalance and lower limb extension range (hpo) to explain interindividual differences in jumping performance (P < 0.001) with positive regression coefficients for Pmax and hpo and a negative one for F-v imbalance. This experimentally supports that ballistic performance depends, in addition to Pmax, on the F–v profile of lower limbs. This adds support to the actual existence of an individual optimal F-v profile that maximizes jumping performance, a F-v imbalance being associated to a lower performance. These results have potential strong applications in the field of strength and conditioning. [ABSTRACT FROM AUTHOR]

Dorsiflexion sport shoes aim to increase jumping capacity and speed by means of a lower position of the heel in comparison with the forefoot, favouring additional stretching of the ankle plantar flexors. In previous studies, contradictory results have been found on the benefits of using this type of shoe. With the aim of comparing a dorsiflexion sport shoe model (DF) with a conventional sport shoe (CS), 41 participants performed a countermovement jump (CMJ) test and an agility test (MAT) with both models of shoe. There were no significant differences in the jump test [CS=35.3 cm (6.4) and DF=35.6 cm (6.4), P>0.05]. In the agility test, the conventional shoe obtained better results than the model with dorsiflexion with regard to time taken to complete the circuit [CS=6236 ms (540) and DF=6377 ms (507), P<0.05)]. In spite of producing pre-stretching of the plantar muscles, the DF sport shoes were not effective for improving either jump power or agility in a specific test. [ABSTRACT FROM AUTHOR]

During running, muscles of the lower limb act like a linear spring bouncing on the ground. When approaching an obstacle, the overall stiffness of this leg-spring system (kleg) is modified during the two steps preceding the jump to enhance the movement of the center of mass of the body while leaping the obstacle. The aim of the present study is to understand how kleg is modified during the running steps preceding the jump. Since kleg depends on the joint torsional stiffness and on the leg geometry, we analyzed the changes in these two parameters in eight subjects approaching and leaping a 0.65 m-high barrier at 15 km h-1. Ground reaction force (F) was measured during 5-6 steps preceding the obstacle using force platform and the lower limb movements were recorded by camera. From these data, the net muscular moment (Mj), the angular displacement (θj) and the lever arm of F were evaluated at the hip, knee and ankle. At the level of the hip, the Mj-θj relation shows that muscles are not acting like torsional springs. At the level of the knee and ankle, the Mj-θj relation shows that muscles are acting like torsional springs: as compared to steady-state running, the torsional stiffness kj decreases from ~1/3 two contacts before the obstacle, and increases from ~2/3 during the last contact. These modifications in kj reflect in changes in the magnitude of F but also to changes in the leg geometry, i.e. in the lever arms of F. [ABSTRACT FROM AUTHOR]

The planthopper insect Issus produces one of the fastest and most powerful jumps of any insect. The jump is powered by large muscles that are found in its thorax and that, in other insects, contribute to both flying and walking movements. These muscles were therefore analysed by transmission electron microscopy to determine whether they have the properties of fast-acting muscle used in flying or those of more slowly acting muscle used in walking. The muscle fibres are arranged in a parallel bundle that inserts onto an umbrella-shaped tendon. The individual fibres have a diameter of about 70 μm and are subdivided into myofibrils a few micrometres in diameter. No variation in ultrastructure was observed in various fibres taken from different parts of the muscle. The sarcomeres are about 15 μm long and the A bands about 10 μm long. The Z lines are poorly aligned within a myofibril. Mitochondrial profiles are sparse and are close to the Z lines. Each thick filament is surrounded by 10-12 thin filaments and the registration of these arrays of filaments is irregular. Synaptic boutons from the two excitatory motor neurons to the muscle fibres are characterised by accumulations of ~60 translucent 40-nm-diameter vesicle profiles per section, corresponding to an estimated 220 vesicles, within a 0.5-μm hemisphere at a presynaptic density. All ultrastructural features conform to those of slow muscle and thus suggest that the muscle is capable of slow sustained contractions in keeping with its known actions during jumping. A fast and powerful movement is thus generated by a slow muscle. [ABSTRACT FROM AUTHOR]

The article discusses a study of the impact of static stretching on explosive performance which indicates that static stretching can impair explosive performance for at least 24 hours. Topics include dynamic stretching, sprint ability, long-jump performances, stretching protocols, and the testing of soccer players.

The purpose of this investigation was to examine the effects of in-season plyometric training program on power and agility performance in young male basketball players. Twenty intermediate basketball players (age 20.1 ± 1.3 years; height 181.1 ± 8.5 cm; body mass 78.8 ± 5 kg) from Division I province team volunteered to participate in this study and were randomly divided into two groups: plyometric training (PL; n = 10) and control group (CG; n = 10). Plyometric training took place twice weekly for 6 weeks including three sets of 15 repetitions of depth jump (from 45-cm box height), vertical jump, and standing long jump, in addition to regular basketball practice of the team. Vertical jump (VJ), standing long jump (SLJ), 4 × 9-m shuttle run, agility t test (ATT), and Illinois Agility Test (IAT) were measured at pre- and post-training. The PL group showed significant improvement ( P < 0.05) in VJ (10.21 ± 2.72 cm), SLJ (21.15 ± 8.10 cm), 4 × 9-m shuttle run (0.62 ± 0.28 s), ATT (1.16 ± 0.57 s), and IAT (1.17 ± 0.65 s) after a 6-week training period and compared to CG. It can be concluded that a 6-week in-season plyometric training program has positive effects for improving power and agility performance in young male basketball players and this study provides support for coaches and basketball players who use this training method during competitive phase. [ABSTRACT FROM AUTHOR]

The generalized double exponential distribution is proposed by combining the asymmetric and biased double exponential distributions, which could fully disclose the features of bias, asymmetry, and steep-peak and heavy tails in financial markets. By referencing to the KDJ model, the generalized double exponential jump diffusion model (GDED-KDJ) is proposed and analyzed. Taking into account the heteroskedasticity and volatility jump, and the double jump diffusion model proposed by Eraker, we further extend the GDED-KDJ to the generalized double exponential double-jump diffusion model, i.e., GDED-SVIJ model. Then, we analyze the features of the new model, such as the general, biased, asymmetric and steep-peak and heavy tails, which also present its superiority. Also, we study the conditions likelihood function and MCMC iterative algorithm of the new model. At last, by the empirical study about three metal futures in SHEF, the feasibility and superiority of the new model are showed and proved. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with a family of balanced implicit methods with linear interpolation for the stochastic pantograph equations with jumps. In this paper, the strong mean-square convergence theory is established for the numerical solutions of the system. It is shown that the balanced implicit methods, which are fully implicit methods, give strong convergence rate of at least 1/2. For a linear scalar test equation, the balanced implicit methods are shown to capture the mean-square stability for all sufficiently small time-steps under appropriate conditions. Furthermore, weak variants are also considered and their mean-square stability analyzed. Several numerical experiments are given for illustration and show that the fully implicit methods are superior to those of the explicit methods in terms of mean-square stabilities. [Copyright &y& Elsevier]

The article discusses a study which was aimed to investigate the impact of wearing shoes inducing moderate dorsiflexion on neuromuscular fatigue induced by volleyball exercises involving multiple stretch-shortening cycles. The study concluded that acute moderate dorsiflexion had no effect on jumping performance and neuromuscular fatigue in unfamiliarized trained subjects.

• No study has been investigated on the mechanisms of new peak and jump in the grain-beam system. • The concept of dynamic mass of the complicated grain-beam system is put forward, realizing the decoupling of mass, stiffness, and damping of the system and does not require complex calculation. • We confirm the size effect of frequency-dependent characteristics of the system. • The negative mass mainly observed in artificial metamaterial is first discovered in a grain-beam system. • We simplify the grain-beam as a two-degree-of-freedom vibration absorber to rationalise the occurrence of new peak caused by the frequency-dependent negative mass. We experimentally investigated the dynamic properties of a grain-beam coupling system and theoretically examined the mechanisms of new peak and jump. The dynamic mass of an excited beam buried in the grains was introduced to identify the equivalent stiffness, damping, and mass of the system. The dependence of the dynamic mass and amplitude on the excitation frequency was determined to analyse these dynamic parameters through sweeping frequency experiments under a constant force amplitude. The negative mass mainly observed in artificial metamaterials was first discovered in a grain-beam system and rationalised using a dynamic absorber model. We analysed the dynamic parameters of the system under various conditions (layer depth, force amplitude, and particle size). We found that frequency-dependent characteristics generated new peaks and jump phenomena. (I) The negative equivalent mass induced the appearance of new peaks below the first-order natural frequency of the beam. (II) The abrupt decrease in the equivalent mass, stiffness, and damping corresponded to jumps higher than the natural frequency. [Display omitted] [ABSTRACT FROM AUTHOR]

In this article, we present a new open-source tool for algebraic modeling and mathematical optimization. We begin by distilling the main gaps within the existing algebraic modeling languages and tools (varying performance, limited cross-compatibility, complex syntax, and different solver, feature, and problem type support). Later, we propose a state-of-the-art web-based tool (WebAML and Optimization System) for algebraic modeling languages and mathematical optimization. The tool does not require specific algebraic language knowledge, allows solving problems using different solvers, and utilizes the best characteristics of existing algebraic modeling languages. We also provide clear extension points and ideas on how we could further improve such a tool. [ABSTRACT FROM AUTHOR]

X. L. Shi and W. Wang [12] studied the question on determination of jumps for functions via conjugate convolution operators. In the present paper a different way to calculate jumps is discussed. We show that derivative convolution operators can be used to determine jumps for functions. Furthurmore, we point out that the assumption ' ϕ is even' in Shi-Wang's theorem can be removed. [ABSTRACT FROM AUTHOR]

Abstract: The dynamic quantification of jump ability is useful for sports performance evaluation. We developed a force measurement system using the Wii Balance Board (WBB). This study was conducted to validate the system in comparison with a laboratory-grade force plate (FP). For a static validation, weights of 10–180kg were put progressively on the WBB put on the FP. The vertical component of the ground reaction force (vGRF) was measured using both devices and compared. For the dynamic validation, 10 subjects without lower limb pathology participated in the study and performed vertical jumping twice on the WBB on the FP. The range of analysis was set from the landing after the first jump to taking off of the second jump. The peak values during the landing phase and jumping phase were obtained and the force–time integral (force impulse) was measured. The relations of the values measured using each device were compared using Pearson''s correlation coefficient test and Bland–Altman plots (BAP). Significant correlation (P <.01, r =.99) was found between the values of both devices in the static and the dynamic test. Examination of the BAP revealed a proportion error in the landing phase and showed no relation in the jumping phase between the difference and the mean in the dynamic test. The WBB detects the vGRF in the jumping phase with high precision. [Copyright &y& Elsevier]

The present study aimed to quantify the intensity of lower extremity plyometric exercises by determining joint mechanical output. Ten men (age, 27.3 ± 4.1 years; height, 173.6 ± 5.4 cm; weight, 69.4 ± 6.0 kg; 1-repetition maximum [1RM] load in back squat 118.5 ± 12.0 kg) performed the following seven plyometric exercises: two-foot ankle hop, repeated squat jump, double-leg hop, depth jumps from 30 and 60 cm, and single-leg and double-leg tuck jumps. Mechanical output variables (torque, angular impulse, power, and work) at the lower limb joints were determined using inverse-dynamics analysis. For all measured variables, ANOVA revealed significant main effects of exercise type for all joints (P < 0.05) along with significant interactions between joint and exercise (P < 0.01), indicating that the influence of exercise type on mechanical output varied among joints. Paired comparisons revealed that there were marked differences in mechanical output at the ankle and hip joints; most of the variables at the ankle joint were greatest for two-foot ankle hop and tuck jumps, while most hip joint variables were greatest for repeated squat jump or double-leg hop. The present results indicate the necessity for determining mechanical output for each joint when evaluating the intensity of plyometric exercises. [ABSTRACT FROM AUTHOR]

When leaping an obstacle, the runner increases the vertical velocity of his/her centre of mass (COM) at takeoff to augment the amplitude and duration of the aerial phase over it. This study analyses the modification of the bouncing mechanism of running when approaching a barrier. The forces exerted by the feet on the ground are measured by a 13-m-long force platform during the four to nine running steps preceding the jump over a 0.45- to 0.85-m-high barrier, at an approaching speed between 9 and 21 km h. The movements of the COM are evaluated by time-integration of the forces and the stiffness of the bouncing system by computer simulation. The running mechanism is modified during the two steps preceding the barrier. During the contact period, two steps before the barrier, the leg-spring stiffness decreases; consequently, the COM is lowered and accelerated forward. Then during the contact period preceding the obstacle, the leg-spring stiffness increases and the COM is raised and accelerated upwards, whereas its forward velocity is reduced. During this phase, the leg-spring acts like a pole, which stores elastic energy and changes the direction of the velocity vector to release this energy in a vertical direction. At high speeds, this storage-release mechanism of elastic energy is sufficient to provide the energy necessary to leap the obstacle. On the contrary, at low speeds, the amount of elastic energy stored and released in the leg-spring is not sufficient to jump over the obstacle and additional positive muscular work must be done. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the relationship between somatotype, muscle torque, maximal power output and height of rise of the body mass centre measured in akimbo counter movement jump (ACMJ), counter movement jump (CMJ) and spike jump (SPJ), and power output measured in maximal cycle ergometer exercise bouts in female volleyball players. Fourteen players participated in the study. Somatotype was determined using the Heath-Carter method. Maximal muscle torque was measured under static conditions. Power output was measured in 5 maximal cycle ergometer exercise bouts, 10 s each, at increasing external loads equal to 2.5, 5.0, 7.5, 10.0 and 12.5% of body weight (BW). All jump trials (ACMJ, SPJ and CMJ) were performed on a force plate. The mean somatotype of volleyball players was: 4.9-3.5-2.5. The value of the sum of muscle torque of the left upper extremities was significantly correlated only with mesomorphic component. Mesomorphic and ectomorphic components correlated significantly with values of maximal power measured during ACMJ and CMJ. Power output measured in maximal cycle ergometer exercise bouts at increasing external loads equal to 2.5, 5.0 and 7.5% of BW was significantly correlated with endomorphy, mesomorphy and ectomorphy. [ABSTRACT FROM AUTHOR]

The article discusses a study of the benefits of plyometric training methods in cricket players, focusing on changes in performance in intermittent shuttle running in simulated cricket innings and the mechanical properties of the Achilles tendon. Subjects were evaluated for sprint times and countermovement and squat jumping before and after an 8 week plyometric training regimen, as well as monitoring of the strength and elasticity of the Achilles tendon using dynamometry and ultrasonography.

The article describes a study of the correlation between jumping event performance and running performance at various race distances by college track and field athletes. Subjects were evaluated in a triple long jump and sprint, middle-distance, or long-distance running. The results indicate that high jump performance correlated strongest with sprint running and suggest that improvements in lower body muscle power from jump training produced faster race times.

Abstract: Positive results are proved here about the ability of balanced methods to reproduce the asymptotic stability of the stochastic differential equation with jumps. Balanced methods including strong balanced methods and weak balanced methods, which possess implicitness in the diffusion term, have the potential to overcome some of the numerical instabilities that are often experienced when using the explicit methods. The paper shows that the asymptotic stability for stochastic jump-diffusion differential equations is inherited by the two kinds of balanced methods with sufficiently small stepsizes. Some numerical experiments included in the paper illustrate the theoretical results. [Copyright &y& Elsevier]

A startling auditory stimulus (SAS) causes a faster execution of voluntary actions when applied together with the imperative signal in reaction time tasks (the StartReact effect). However, speeding up reaction time may not be the best strategy in all tasks. After a self-initiated fall, the program for landing has to be time-locked to foot contact to avoid damage, and therefore advanced execution of the program would not be convenient. We examined the effects of SAS on the landing motor program in 8 healthy subjects that were requested to let themselves fall from platforms either 50 or 80 cm high at the perception of a visual imperative signal and land on specific targets. In trials at random, SAS was applied either together with the imperative signal (SASIS) or at an appropriate prelanding time (SASPL). As expected, the latency of takeoff was significantly shortened in SASIS trials. On the contrary, the timing of foot contact was not significantly different for SASPL compared with control trials. No changes were observed in the size of the electromyograph bursts in the two experimental conditions with respect to the control condition. Our results indicate that the landing program after a self-initiated fall may in part be organized at the time of takeoff and involve precise information on timing of muscle activation. Once launched, the program is protected against interferences by external inputs. [ABSTRACT FROM AUTHOR]

Plyometric training is commonly used to improve athletic performance; however, it is unclear how each component of the muscle-tendon complex (MTC) is affected by this intervention. The effects of 14 weeks of plyometric training on the passive stiffness of the gastrocnemii muscles and Achilles tendon was determined simultaneously to assess possible local adaptations of elastic properties. The passive force-length relationship of the gastrocnemii MTC and elongation of the gastrocnemii muscles were determined using ultrasonography during passive cyclic stretching in 19 subjects divided into trained ( n = 9) and control ( n = 10) groups. An upward trend in stiffness of the gastrocnemii MTC ( P = 0.09) and a significant increase in the intrinsic gastrocnemii muscle stiffness were found ( P < 0.05). In contrast, no significant change in gastrocnemii tendon stiffness, or in muscle and tendon geometry, was determined ( P > 0.05). Considering the lack of change in gastrocnemii muscle geometry, the change in the gastrocnemii muscle stiffness may be mainly due to a change in the intrinsic mechanical properties of the muscular tissues. [ABSTRACT FROM AUTHOR]

The article reports on research which was conducted to examine the anthropometric, vertical jump, and strength quality changes over two years in a group of national team volleyball players. Researchers evaluated 14 players. After evaluating the players for two years researchers concluded that elite male volleyball players can improve leanness and power, which contribute to improvements in vertical jump.

Abstract: Two of the most common gait patterns in children with spastic diplegic cerebral palsy (CP) are termed ‘crouch gait’ and ‘jump gait’. While outcomes of surgical interventions designed to improve functional mobility are generally positive, many children displaying these gait patterns show minimal or no improvement post-surgery. A poor response to treatment may be partially attributable to incorrect interpretations of muscle function. Computational techniques that assess muscle function may help address this issue, but before studying specific surgeries, the gait patterns themselves must be better understood. The aim of this study was to identify differences in lower-limb muscle function when comparing crouch, jump and able-bodied gait patterns by quantifying the potential of lower-limb muscles to accelerate the body''s center of mass. A muscle''s potential acceleration was defined as the acceleration induced by a unit of muscle force. Dynamic simulations of walking using musculoskeletal models were developed for eight children with crouch gait, ten with jump gait, and ten controls. There were significant differences (p <0.05) in muscle potential accelerations between crouch and able-bodied gait patterns, and between jump and able-bodied gait patterns, for most of the major muscles of the hip, knee, and ankle. One important outcome was the identification of the significantly reduced potential of gluteus medius to extend the hip in both crouch gait and jump gait. Potential acceleration analyses appear to be suitable for evaluating differences between common gait patterns and may also be applied to study the effects of surgical treatments. The results of such studies may lead to improved treatment outcomes for individuals with impaired mobility. [Copyright &y& Elsevier]

We give a characterization of piecewise C 1 class P-homeomorphism f of the circle with irrational rotation number and finitely many break points which is piecewise C 1 conjugate to a C 1-diffeomorphism. The following properties are equivalent:  (i) f is conjugate to a C 1-diffeomorphism of the circle by a piecewise C 1-homeomorphism. (ii) The product of jumps of f in the break points contained in a same orbit is trivial. (iii) f is conjugate to a C 1-diffeomorphism of the circle by a piecewise linear (PL)-homeomorphism or a piecewise quadratic homeomorphism. For a PL-homeomorphism f having the property (ii): f is conjugate to a rotation either by a PL-homeomorphism or by a piecewise analytic homeomorphism. [ABSTRACT FROM PUBLISHER]

The dynamic behaviors of an Atomic Force Microscope are of interest, and variously unpredictable phenomena are experimentally measured. In practical measurements, researchers have proposed many methods for avoiding these uncertainties. However, causes of these phenomena are still hard to demonstrate in simulation. To demonstrate these phenomena, this paper claims the tip-jump motion is a predictable process, and the jumping kinetic energy results in different nonlinear phenomena. It emphasizes the variation in the eigenvalues of an AFM with tip-sample distance. This requirement ensures the phase transformations from one associated with the oscillation mode to one associated with the tip-jump/sample-contact mode. Also, multi-modal analysis was utilized to ensure the modal transformation in varying tip-sample distances. In the presented model, oscillations with various tip-sample distances and with various excitation frequencies and amplitudes were compared. The results reveal that the tip-jump motion separates the oscillation orbit into two regions, and the jumping kinetic energy, comparing with the superficial potential energy, leads the oscillation to be bistable or intermittent. The sample contact condition associates to bifurcation and chaos. Additionally, the jumping is a strong motion that occurs before the tip-sample contacts, and this motion signal can replace the sample-contact-signal to avoid destroying the sample. [ABSTRACT FROM AUTHOR]

Abstract: We derive a Floyd–Hoare logic for non-local jumps and mutable higher-order procedural variables from a formulæ-as-types notion of control for classical logic. A key contribution of this work is the design of an imperative dependent type system for Hoare triples, which corresponds to classical logic, but where the famous consequence rule is admissible. Moreover, we prove that this system is complete for a reasonable notion of validity for Hoare judgments. [Copyright &y& Elsevier]

We prove that the conjugate convolution operators can be used to calculate jumps for functions. Our results generalize the theorems established by He and Shi. Furthermore, by using Lukács and Móricz's idea, we solve an open question posed by Shi and Hu. [ABSTRACT FROM AUTHOR]

The article discusses the changes in performance indicators related to strength and the development of speed-strength in the transitioning of volleyball players from junior to senior national team. An overview of the study conducted to professional players who played at the world championships, World Cup, and senior continental championships is provided. It explores aspects of the training for counter movement vertical jumps (CMVJ) and spike jump (SPJ).

Numerous volatility-based derivative products have been engineered in recent years. This has led to interest in constructing conditional predictive densities and confidence intervals for integrated volatility. In this article we propose nonparametric estimators of the aforementioned quantities, based on model-free volatility estimators. We establish consistency and asymptotic normality for the feasible estimators and study their finite-sample properties through a Monte Carlo experiment. Finally, using data from the New York Stock Exchange, we provide an empirical application to volatility directional predictability. [ABSTRACT FROM AUTHOR]

The article presents a study which determined the relationship between functional movement screen and athletic performance capabilities of golfers. The researchers investigated the sport-specific performance of the golfers from the National Collegiate Athletic Association (NCAA) with focus on sprint time, agility, and club head velocity. The study found that repetition maximum squat strength appeared to be a good indicator of athletic performance.

Early warning signals (EWS) of regime shifts are challenging in cases where the true natural-data-generating process is uncertain. Nonparametric drift-diffusion-jump models address this problem by fitting a general model that can approximate a wide range of data- generating processes. Drift measures the local rate of change. Diffusion measures relatively small shocks that occur at each time step. Jumps are large intermittent shocks. Total variance combines the contributions of diffusion and jumps. Nonparametric methods are well suited to emerging technology for automated, high-frequency sensors. Total. variance is the most precisely measured indicator. Jump intensity appears to be a useful.EWS. Estimates of the drift are highly uncertain unless long time series with many regime shifts are available. EWS computed from drift estimates (such as autocorrelation coefficients or return rates) have low precision and should be used with caution. Nonetheless, in the current state of knowledge, it is premature to disregard any potential EWS. [ABSTRACT FROM AUTHOR]

Removing noise from signals which are piecewise constant (PWC) is a challenging signal processing problem that arises in many practical scientific and engineering contexts. In the first paper (part I) of this series of two, we presented background theory building on results from the image processing community to show that the majority of these algorithms, and more proposed in the wider literature, are each associated with a special case of a generalized functional, that, when minimized, solves the PWC denoising problem. It shows how the minimizer can be obtained by a range of computational solver algorithms. In this second paper (part II), using this understanding developed in part I, we introduce several novel PWC denoising methods, which, for example, combine the global behaviour of mean shift clustering with the local smoothing of total variation diffusion, and show example solver algorithms for these new methods. Comparisons between these methods are performed on synthetic and real signals, revealing that our new methods have a useful role to play. Finally, overlaps between the generalized methods of these two papers and others such as wavelet shrinkage, hidden Markov models, and piecewise smooth filtering are touched on. [ABSTRACT FROM AUTHOR]

Removing noise from piecewise constant (PWC) signals is a challenging signal processing problem arising in many practical contexts. For example, in exploration geosciences, noisy drill hole records need to be separated into stratigraphic zones, and in biophysics, jumps between molecular dwell states have to be extracted from noisy fluorescence microscopy signals. Many PWC denoising methods exist, including total variation regularization, mean shift clustering, stepwise jump placement, running medians, convex clustering shrinkage and bilateral filtering; conventional linear signal processing methods are fundamentally unsuited. This paper (part I, the first of two) shows that most of these methods are associated with a special case of a generalized functional, minimized to achieve PWC denoising. The minimizer can be obtained by diverse solver algorithms, including stepwise jump placement, convex programming, finite differences, iterated running medians, least angle regression, regularization path following and coordinate descent. In the second paper, part II, we introduce novel PWC denoising methods, and comparisons between these methods performed on synthetic and real signals, showing that the new understanding of the problem gained in part I leads to new methods that have a useful role to play. [ABSTRACT FROM AUTHOR]

In this article, we implement the Variance Ratio test to study on the intraday serial correlation of Shenzhen component index return series. The empirical research indicates significant positive serial correlation in China's stock market. For a better understanding of the dynamics of intraday serial correlation in China's stock market, we first investigate the presence of autocorrelation mode of serial correlation. Then, we construct the VR-HAR-RV and VR-HAR-RV-CJ models to explore the links between serial correlation and volatility. We find both the VR-HAR-RV and VR-HAR-RV-CJ models can partially explain the links between serial correlation and volatility, but the VR-HAR-RV-CJ model is more powerful than the VR-HAR-RV model. [ABSTRACT FROM AUTHOR]

Introduction: Basketball is a sport that is characterized by the predominance of anaerobic metabolism in providing energy with the importance of power on the different fundamentals, especially in the ability of jump. With intermittent actions in the game, the production of fatigue and decline in athletes' performance is a factor to be investigated. Objective: the objective of the study was to analyze vertical jumps of basketball athletes, playing in different quarters and positions, in two matches. Methods: Study participants were 11 male athletes (age 22.8 ± 3.7 years, body mass 94.15 ± 13.9 kg, height of 196 ± 9.1 cm) in different positions and evaluation of explosive strength of lower limbs was performed with the technique of Counter Movement Jump with the help of arms. he players were evaluated at the beginning of the match and at the end of all quarters. For data analysis we used mean and standard deviation, the Kruskal-Wallis test for normality, Student's T for paired data, comparing the positions. Results: he main results of the jumps indicates to the homogeneity of the initial data for all quarters of the game in both matches and in relation to the playing time and participation, the guards shown significant differences (p <0 , 05) at the jumps evaluated at the second and third quarter, of game 2 and 1, respectively. Conclusion: he results are in accordance with findings of other studies, implying that the lack of fatigue in lower limbs in the act of jumping could be linked to the physiological responses and the number of jumps during the matches. [ABSTRACT FROM AUTHOR]

This paper deals with the balanced methods which are implicit methods for stochastic differential equations with Poisson-driven jumps. It is shown that the balanced methods give a strong convergence rate of at least 1/2 and can preserve the linear mean-square stability with the sufficiently small stepsize. Weak variants are also considered and their mean-square stability analysed. Some numerical experiments are given to demonstrate the conclusions. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the acute effects of endurance exercise on jumping and kicking performance in young soccer players. Twenty-one top-class young soccer players (16.1±0.2 years) performed a countermovement jump test and a maximal instep soccer kick test before and after running for 20 min on a treadmill at 80% of their individual maximum heart rate. Two force platforms were used to obtain the following parameters during the countermovement jump: jump height, maximum power, maximum power relative to body mass, maximum vertical ground reaction force, maximum vertical ground reaction force relative to body mass, and maximum vertical ground reaction force applied to each leg. Maximum vertical ground reaction force and maximum vertical ground reaction force relative to body mass applied to the support leg during the kicks were also calculated with a force platform. The kicking motion was recorded using a three-dimensional motion-capture system. Maximum velocity of the ball, maximum linear velocity of the toe, ankle, knee and hip, and linear velocity of the toe at ball contact during the kicks were calculated. Non-significant differences were found in the parameters measured during the countermovement jump and the maximal instep soccer kick test before and after running, suggesting that the jumping and kicking performances of top-class young soccer players were not significantly affected after 20 min treadmill running at 80% of their individual maximum heart rate. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to analysis the GRF of vertical jumping to head a ball by male students who were suffering from flexible flat foot. Methods: A Total 600 male students participated in a public physical education class, test lines (Feiss test) and box mirror recognition parenthesis plantar, evaluated precision. After examination of 15 students with smooth feet from grades 2 and 3 with a mean age (73/22), height (60/174) and weight (87/69) as a group of people and number of floor flat foot with 15 students having a normal plantar arch, with a mean age (13/23), height (40/176) and weight (55/69) as a group of people were natural foot floor. Samples necessarily are not soccer. Subjects on the page of the Force (Force plate) had to jump and hit the head football peak at a height commensurate with each individual jump, jump and act did tick off. Day 3 foot jump right individuals' natural floor flat foot on the floor and individuals of different directions Kinetic was evaluated. Data obtained from independent t-test were analyzed Results & Findings: The results suggest a significant difference in kinetic patterns of vertical jumping of individuals with flat foot in vertical direction (P=0. 01), as well as in kinematics' pattern of total contact time of foot to ground in individuals with flat foot and normal foot (P=0.01). In the other directions (saggital and mediolateral) there were no significant differences between two groups of test subjects (P=0.05). Discussion and conclusion: In general, the results of this study shows that the values of ground reaction forces in vertical direction are higher in individuals with flat foot compared to those with normal foot; moreover there is difference between the total contact time to ground of foot among individuals with flat foot and those with normal foot. [ABSTRACT FROM AUTHOR]

We investigated the association of the angiotensin converting enzyme gene (ACE) insertion/deletion (I/D) polymorphism, alone or in combination with the α-actinin-3 gene (ACTN3) R577X polymorphism, with jumping (vertical squat and counter-movement jump tests) and sprint ability (30 m dash) in non-athletic, healthy young adults [N = 281 (214 male), mean (SD) age 21 (2) years]. We did not observe any effect of the ACE I/D polymorphism on study phenotypes. We repeated the analyses separately in men and women and the results did not materially change. Likewise, the mean estimates of the study phenotypes were similar in subjects with the genotype combinations ACE II + ID and ACTN3 XX or ACE DD and ACTN3 RR + RX. We found no association between the ACE DD and ACTN3 RR + RX genotype combination and performance (≥90th of the sex-specific percentile). In summary, though the ACE I/D polymorphism is a strong candidate to modulate some exercise-related phenotypes or athletic performance status, this polymorphism, alone or in combination with the ACTN3 R577X polymorphism, does not seem to exert a major influence in the muscle 'explosive' power of young healthy adults, as assessed during multi-joint exercise tests. [ABSTRACT FROM AUTHOR]

Ballistic accelerations of a limb or the whole body require special joint mechanisms in many animals. Specialized joints can be moved by stereotypic or variable motor control during motor patterns with and without ballistic components. As a model of variable motor control, the specialized femur-tibia (knee) joints of cricket (Acheta domesticus) hindlegs were studied during ballistic kicking, jumping and swimming and in non-ballistic walking. In this joint the tendons of the antagonistic flexor and the extensor muscles attach at different distances from the pivot and the opposed lever arms form an angle of 120 deg. A 10:1 ratio of their effective lever arms at full knee flexion helps to prepare for most ballistic extensions: the tension of the extensor can reach its peak while it is restrained by flexor co-contraction. In kicks, preparatory flexion is rapid and the co-contraction terminates just before knee extensions. Therefore, mainly the stored tension of the extensor muscle accelerates the small mass of the tibia. Jumps are prepared with slower extensor-flexor co-contractions that flex both knees simultaneously and then halt to rotate both legs outward to a near horizontal level. From there, catapult extension of both knees accelerates the body, supported by continued high frequency motor activity to their tibia extensor muscles during the ongoing push-off from the substrate. Premature extension of one knee instantly takes load from the lagging leg that extends and catches up, which finally results in a straight jump. In swimming, synchronous ballistic power strokes of both hindlegs drive the tibiae on a ventral-to-posterior trajectory through the water, well coordinated with the swimming patterns of all legs. In walking, running and climbing the steps of the hindlegs range between 45deg flexion and l25deg extension and use non-ballistic, alternating activity of knee flexor and extensor muscles. Steep climbing requires longer bursts from the extensor tibiae muscles when they support the extended hindlegs against gravity forces when the body hangs over. All ballistic movements of cricket knees are elicited by a basic but variable motor pattern: knee flexions by co-contraction of the antagonists prepare catapult extensions with speeds and forces as required in the different behaviours. [ABSTRACT FROM AUTHOR]

We study a class of stochastic integral equations with jumps under non-Lipschitz conditions. We use the method of Euler approximations to obtain the existence of the solution and give some sufficient conditions for the strong uniqueness. [ABSTRACT FROM AUTHOR]

Purpose. Despite concerns elicited by the injury-rate statistics for skateboarding, the literature has been silent on biomechanical factors that might be causing or exacerbating these injuries. To help fill this void, we sought to describe the kinetic characteristics of landing from a rail slide, one of the more high-risk, albeit common, maneuvers practiced by skateboarders. Methods. Twelve top-amateur or professional skateboarders (BW = 688 ± 89 N) performed rail slide maneuvers down a steep handrail before landing on a force plate. We recorded ground reaction force (GRF) data whether the subjects landed successfully (L) on their skateboards, or, bailed-out (BO), i.e. landed on their feet. Results. Vertical GRF (VGRF) during L had an initial peak, due to skateboard contact, immediately followed by a set of impact peaks (mean = 7.98 ± 1.32 (SD) BW) representing landing on the board. BO showed a VGRF impact peak rising to a significantly higher (P < 0.05) mean of 12.09 ± 2.63 BW. Conclusions. These data suggest that the skateboard provides significant shock attenuation. However, because BO landings are frequent, the relatively high peak ground reaction forces are a cause for concern. Given the musculoskeletal immaturity of typical skateboarders, clinicians should be aware of these high impact forces, and footwear manufacturers should explore ways to reduce peak pressures, and high impact and shear forces in the heel, forefoot, and toe box. [ABSTRACT FROM AUTHOR]

The article discusses the athletic performance's adaptations after ballistic power exercise versus heavy strength training. It presents implication of different exercises and training stimuli to the changes in the force-velocity relationship, jump mechanics, muscle architecture, and neural activation. It depicts the different long-term and short-term benefits of ballistic training and strength training. It focuses on the performance improvement due to neuromuscular adaptations using various heavy physical training.

The article discusses the research findings in determining the implication of strength to the magnitude of performance improvement and the driving adaptation of mechanisms to ballistic power training. It presents the methodology of the study from categorizing the participants by their strength using one-repetition maximum-to-body mass ration (IRM/BM), and the training of the group and its assessment. It reports that strength level do not influence the magnitude of improvements after ballistic power training.

Abstract: Locusts respond to the images of approaching (looming) objects with responses that include gliding while in flight and jumping while standing. For both of these responses there is good evidence that the DCMD neuron (descending contralateral movement detector), which carries spike trains from the brain to the thoracic ganglia, is involved. Sudden glides during flight, which cause a rapid loss of height, are last-chance manoeuvres without prior preparation. Jumps from standing require preparation over several tens of milliseconds because of the need to store muscle-derived energy in a catapult-like mechanism. Locusts’ DCMD neurons respond selectively to looming stimuli, and make connections with some motor neurons and interneurons known to be involved in flying and jumping. For glides, a burst of high-frequency DCMD spikes is a key trigger. For jumping, a similar burst can influence timing, but neither the DCMD nor any other single interneuron has been shown to be essential for triggering any stage in preparation or take-off. Responses by the DCMD to looming stimuli can alter in different behavioural contexts: in a flying locust, arousal ensures a high level of both DCMD responsiveness and glide occurrence; and there are significant differences in DCMD activity between locusts in the gregarious and the solitarious phase. [Copyright &y& Elsevier]

The article presents the results of a study which investigated the impact of weight training on basketball player performance. An overview of related previous research is provided, along with details of the experimental protocol, which involved half squats in a Smith machine. It was found that strength training produced improved running and jumping ability.

Abstract: Imitative behavior underlaid by perception and action links during children’s development in complex locomotor skills has been the object of relatively few studies. In order to explore children’s motor coordination modes, 130 children divided into five age groups from 3.5 to 7.5years were instructed to imitate jumping tasks in spontaneous motor situation and in various imitative contexts by an adult providing verbal orders and gestural demonstrations. Their conformity to the model, stability and variability scores were coded from a video analysis when they performed jumps with obstacles. To evaluate their postural-motor control level, the durations of the preparatory phase and jumping flights were also timed. Results showed that all age groups generated the demonstrator’s goal but not necessarily the same coordination modes of jumping. In imitation with temporal proximity, the model helped the youngest age groups to adopt his coordination modes and stabilized only the oldest age groups’ performances starting from 5.5years old, without effect on learning imitation. Differences between the youngest and oldest children in the jump duration suggested that the reproduction of a complex motor activity such as jumping with a one foot take-off would require resolution and adjustment of main postural stability. [Copyright &y& Elsevier]