Optimal distance from the implement to the axis of rotation in hammer and discus throws.

It is a well-known fact that a dramatic improvement in the range of any projective throw can be achieved by increasing the release velocity. In this paper a simple model of a competitor with an implement (hammer or discus) in the turns is considered. The thrower is regarded as a rigid body, and the implement as a point mass. The transverse velocity component of the implement at the release moment is maximized. For finding the optimal distance of the implement from the axis of rotation optimal control theory is applied. According to the proposed model, the optimal hammer throwing technique requires constant and maximal distance of the implement from the axis of rotation, followed by the rapid shortening of the distance immediately prior to the release. In the discus throw, however, this shortening is useless.     

Simulation of javelin flight using experimental aerodynamic data

This paper discusses computer simulation of the differential equations which describe javelin dynamics in flight. It is shown that the use of experimental aerodynamic forces and moments in the equations is preferable to theoretical approximations for these forces and moments which have been used in previous studies. An example which is characteristic of a good throw is presented and analyzed and many interesting features of the trajectory are pointed out.     

Optimal javelin trajectories

A companion paper has treated computer simulation of javelin flight using measured lift, drag and pitching moments. In the present paper we present, categorize and discuss the relative significance of various initial conditions in such a simulation. Since the differential equations describing flight are autonomous, the eventual javelin range and entry angle are unique functions of the initial conditions. A series of successively less constrained optimum solutions is defined, the last of which is the global optimum javelin trajectory. Sensitivities of these trajectories to perturbations from the optima and their implications for throwers are discussed. Finally, we investigate the effects of some design and environmental parameters on optimal initial conditions and trajectories.     

A kinematic study of center of mass motions in the hammer throw

Eight highly-skilled hammer throwers were studied using film analysis procedures. The location and velocity of the center of mass (c.m.) of each thrower, hammer and thrower-hammer system were calculated. The vertical component of motion of all three c.m.s followed cyclic patterns with one fluctuation per turn. The fluctuation of the c.m. of the thrower was ahead of that of the hammer by approximately a third of a cycle, and this made the periods of upward vertical acceleration of the system c.m. coincide approximately with the double-support phases. In the horizontal direction, the c.m.s of the thrower and of the hammer followed roughly trochoid patterns as a result of the combination of rotation with forward displacement across the throwing circle. Their rotations were out of synchrony by approximate synchrony with the hammer, or an essentially straight trajectory. The results of this study suggest that the investigation of the hammer throw might be facilitated by the use of a quasi-inertial non-rotating reference frame that follows the general motion of the system c.m. while ignoring its fluctuations within each turn.     

Modelling the wave movement of a multisegment biomechanical system

Modeling of wave motion of human body's multi-segment biomechanical system by examination of forced transverse oscillations of one-dimensional bar system with distributed parameters is performed in javelin throwing. Energy flow value under different changes of model parameters is investigated. The experimental data showing wave front motion and transformation of spectral density of oscillations from segment to segment of the thrower's body are discussed. Share of the energy transferred along the body's segments in the total energy of javelin release is 70-72 per cent according to theoretical estimates for concrete model parameters, and 63-75 per cent according to the experimental data for 8 attempts.     

A three-dimensional analysis of overarm throwing in experienced handball players

The aim of this study was to investigate the contribution of upper extremity, trunk, and lower extremity movements in overarm throwing in team handball. In total, 11 joint movements during the throw were analyzed. The analysis consists of maximal angles, angles at ball release, and maximal angular velocities of the joint movements and their timing during the throw. Only the elbow angle (extension movement range) and the level of internal rotation velocity of the shoulder at ball release showed a significant relationship with the throwing performance. Also, a significant correlation was found for the timing of the maximal pelvis angle with ball velocity, indicating that better throwers started to rotate their pelvis forward earlier during the throw. No other significant correlations were found, indicating that the role of the trunk and lower limb are of minor importance for team handball players.     

A comparison of kinematics between overarm throwing with 20% underweight, regular, and 20% overweight balls

The aim of this study was to compare the kinematics in throwing with a regular weighted handball with 20% lighter and heavier balls in female experienced handball players. In total, eight joint movements during the throw were analyzed. The analysis consisted of maximal angles, angles at ball release, and maximal angular velocities of the joint movements and their timings during the throw. Results on 24 experienced female team handball players (mean age 18.2 ± 2.1 years) showed that the difference in ball weight affected the maximal ball velocity. The difference in ball release velocity was probably a result of the significant differences in kinematics of the major contributors to overarm throwing: elbow extension and internal rotation of the shoulder. These were altered when changing the ball weight, which resulted in differences in ball release velocity.     

Modelling analysis and prediction of women javelin throw results in the years 1946 – 2013

The main goals of our study of the women’s javelin throw were twofold:. first, to analyse the dynamics of female javelin throw results variability as a function of time (time period 1946-2014), second, to create a predictive model of the results during the upcoming 4 years. The study material consisted of databases covering the female track and field events obtained from the International Association of Athletics Federations. Prior to predicting the magnitude of results change dynamics in the time to follow, the adjustment of trend function to empirical data was tested using the coefficients of convergence. Phase II of the investigation consisted of the construction of predictive models. The greatest decreases in result indexes were noted in 2000 (9.4%), 2005-2006 (8.7%) and 2009 (7.4%). The trend increase was only noted in the years 2006-2008. In general, until 1998 the mean result improved by 54.6% (100% - results of 1946) whereas from 1999 through 2011 the result only increased by 1.3%. Based on data and results variability analysis it might be presumed that, in the nearest future (2015-2018), results variability will increase by approximately 9.7%. Percent improvement of javelin throw distance calculated on the basis of the 1999 raw input data is 1.4% (end of 2014).     

Dependence of release variables in the shot put

When the shot is released above a horizontal plane, range from this point depends on release height, speed and angle. Measured distance is the sum of this range and horizontal distance of the release point from the throwing circle edge. Optimal release conditions can be calculated only if the dependence of release velocity on other variables, due to thrower limitations, is known. Experiments on two shot-putters investigated the hypothesis that there are constraint relationships among these four release parameters. A variable scaling scheme, using measurement of impact point and the known magnitude of g, corrected 2D data from one camera for out-of-plane motion and yielded accurate estimates of release parameters. Multivariate regression analyses determined approximate constraint surfaces limiting performance. Achievable release speed decreases with increasing release angle at about 1.7(m/s)/rad and decreases with increasing release height at about 0.8(m/s)/m, with only small differences in sensitivities between the throwers. Horizontal release distance also decreases with increasing release angle at about 1.7m/rad and increases with increasing release height at about 1.3m/m, again with only small differences between the two throwers. Optimal release conditions producing maximum range for a particular athlete can be determined using similar constraints for that athlete.     

Muscle-contraction properties in overarm throwing movements

On the basis of dynamic and kinematic data, this study identifies the type of muscle contraction in unloaded overarm throwing movements. An unloaded throw or nearly unloaded throw is defined as the throw in which the external resistance is too small (e.g., the team handball, baseball, and water polo throws as well as the tennis and badminton smashes). A special arm-force-measuring apparatus was constructed to imitate an overarm throw. Forty-two subjects were placed into 3 groups: untrained subjects, weight-trained athletes, and team handball players. The measured parameters included the velocity of the initial movement, the release velocity, the velocity of the first 50 milliseconds of the concentric phase, the force value at the moment of deceleration of the initial movement, and the impulse values during the eccentric and concentric phases of the test movement. Statistically significant higher values of the above parameters (p < 0.05) were determined in that test at which the initial speed of movement was higher. Also, the correlation coefficients of the parameters of the initial phase of the throw movement were very high (p < 0.001), especially the parameters related with the movement's first 50 milliseconds. The results support the thesis that the stretch-shortening cycle is the type of muscle contraction in unloaded overarm throws. Furthermore, it is possible to increase the throw velocity by increasing the velocity of the initial movement (i.e., by provoking higher inertia forces).     

Shoulder muscle activity during pushing, pulling, elevation and overhead throw.

PURPOSE: The aim of this study was to compare the muscle activity of recreational athletes and professional javelin throwers during pull, push, and elevation of upper extremities and during overhead throw. SCOPE: Nine professional javelin throwers and 16 recreational athletes without shoulder problems were studied. Signals were recorded by surface EMG from eight different muscles. The results obtained from the muscles of upper extremities of throwers were compared with those of recreational athletes. CONCLUSION: The different neuromuscular control of professional throwers caused a more profitable muscle activity. Differences during the overhead throw were more significant. The deltoid muscle and rotator cuff of recreational athletes showed stronger activity than those of throwers during pull, push and elevation. The deltoid muscle and the rotator cuff of professional throwers showed stronger activity during overhead throw. Studying the detailed characteristics of muscle activity pattern (differences in length of activity periods, MVC% of muscles and time broadness among peak muscle activities in percent of total time of a movement cycle) may provide a basis for better understanding improved performance and help in planning proper rehabilitation protocol.     

The neural and cognitive correlates of aimed throwing in chimpanzees: a magnetic resonance image and behavioural study on a unique form of social tool use

It has been hypothesized that neurological adaptations associated with evolutionary selection for throwing may have served as a precursor for the emergence of language and speech in early hominins. Although there are reports of individual differences in aimed throwing in wild and captive apes, to date there has not been a single study that has examined the potential neuroanatomical correlates of this very unique tool-use behaviour in non-human primates. In this study, we examined whether differences in the ratio of white (WM) to grey matter (GM) were evident in the homologue to Broca's area as well as the motor-hand area of the precentral gyrus (termed the KNOB) in chimpanzees that reliably throw compared with those that do not. We found that the proportion of WM in Broca's homologue and the KNOB was significantly higher in subjects that reliably throw compared with those that do not. We further found that asymmetries in WM within both brain regions were larger in the hemisphere contralateral to the chimpanzee's preferred throwing hand. We also found that chimpanzees that reliably throw show significantly better communication abilities than chimpanzees that do not. These results suggest that chimpanzees that have learned to throw have developed greater cortical connectivity between primary motor cortex and the Broca's area homologue. It is suggested that during hominin evolution, after the split between the lines leading to chimpanzees and humans, there was intense selection on increased motor skills associated with throwing and that this potentially formed the foundation for left hemisphere specialization associated with language and speech found in modern humans.     

Effect of different training programs on the velocity of overarm throwing: a brief review

Throwing velocity in overarm throwing is of major importance in sports like baseball, team handball, javelin, and water polo. The purpose of this literature review was to give an overview of the effect of different training programs on the throwing velocity in overarm throwing, provide a theoretical framework that explains findings, and give some practical applications based on these findings. The training studies were divided into 4 categories: (a) specific resistance training with an overload of velocity, (b) specific resistance training with an overload of force, (c) specific resistance training with a combination of overload of force and velocity, and (d) general resistance training according to the overload of force. Each category is presented and discussed.     

Validity and reliability of the medicine ball throw for kindergarten children

The purpose of this study was to establish validity and reliability evidence for the medicine ball throw test for kindergarten students, an underrepresented group in the literature. The subjects were 105 students, 5-7 years old, BMI 17.44 +/- 3.17 kg x m(-2), 43% female and 57% male. Intraclass correlation coefficients (ICCs) were used to examine reliability, and Pearson correlation coefficients and a paired t-test were used to examine validity. To accomplish this, the kindergarten students completed the medicine ball throw test on two different days and the modified pull-up test, the "criterion" measure, on another day. For the medicine ball throw, each student sat on the floor before throwing the medicine ball forward like a chest pass three times. The medicine ball throw was highly reliable both within 1 day (ICCs = 0.93 and 0.94 for day 1 and day 2, respectively) and across 2 days (ICC = 0.88), with all reliability estimates over the acceptable level of 0.80. The medicine ball throw scores were positively related with height (r = 0.34) and weight (r = 0.34), and there was a significant difference between the 5-year-old group (mean +/- SD; 111.78 +/- 34.93) and the 6-year-old group (135.60 +/- 39.77), t = -3.23, p = 0.002, which supports correlational and known-difference evidence of validity for the medicine ball throw test. Even though no correlation was found between the medicine ball throw test and the modified pull-up test, r = -0.04, other forms of validity evidence (i.e., known-difference and correlational) were apparent. In conclusion, the medicine ball throw test seems to be a valid and reliable measure of upper-body strength for kindergarten children.     

The uniquely human capacity to throw evolved from a non-throwing primate: an evolutionary dissociation between action and perception

Humans are uniquely endowed with the ability to engage in accurate, high-momentum throwing. Underlying this ability is a unique morphological adaptation that enables the characteristic rotation of the arm and pelvis. What is unknown is whether the psychological mechanisms that accompany the act of throwing are also uniquely human. Here we explore this problem by asking whether free-ranging rhesus monkeys (Macaca mulatta), which lack both the morphological and neural structures to throw, nonetheless recognize the functional properties of throwing. Rhesus not only understand that human throwing represents a threat, but that some aspects of a throwing event are more relevant than others; specifically, rhesus are sensitive to the kinematics, direction and speed of the rotating arm, the direction of the thrower's eye gaze and the object thrown. These results suggest that the capacity to throw did not coevolve with psychological mechanisms that accompany throwing; rather, this capacity may have built upon pre-existing perceptual processes. These results are consistent with a growing body of work showing that non-human animals often exhibit perceptual competencies that do not show up in their motor responses, suggesting evolutionary dissociations between the systems of perception that provide understanding of the world and those that mediate action on the world.     

Spontaneous use of sticks as tools by captive gorillas (Gorilla gorilla gorilla)

The present report describes the spontaneous use of sticks, as tools by young adult gorillas (Gorilla gorilla gorilla) in a social group at the San Diego Wild Animal Park, CA, USA. Three 8-year-old gorillas (one female and two males) threw sticks into the foliage of trees, which the gorillas could not climb due to electric wire, to knock down leaves and seeds. Two of the three gorillas selected sticks that were more suitable (i.e. longer or thicker sticks) for throwing. Moreover, they looked up at the target (i.e. the foliage of the tree) before throwing and grasped the stick at a position appropriate, for throwing (i. e. the end of the stick). They were more likely to throw sticks when particular adult group members were not nearby. These two gorillas also pulled branches of trees toward themselves by using sticks to capture them (branch-pulling), and one of these two beat a branch with a stick to knock down leaves and seeds (branch-beating). One of these two gorillas used much longer sticks for branch-pulling than for stick-throwing, indicating that he was capable of task-dependent selection of sticks. Analyzing the spontaneous use of sticks as tools by gorillas in captivity can lead to a better understanding of not only their cognitive ability but also of their social relationships which may otherwise be concealed.     

Throwing velocities, anthropometric characteristics, and efficacy indices of women's European water polo subchampions

Water polo is a team sport characterized by a high-intensity, intermittent activity, where technical and tactical aspect are of a great importance. For that reason, the main aim of this study was to define the anthropometrical characteristics, maximum isometric grip strength, training and competition throwing velocities, and the efficacy indices in female high-level water polo players. A second purpose was to examine the differences between the throwing velocities in training vs. European championships in the water polo female national team. Ten elite trained female water polo players participated in this study. Before the competitive phase of their season, the following measures were taken: standard anthropometry, static and dynamic training throwing velocities, and hand-grip dynamometry. In the competitive phase, efficacy indices, average and maximum throwing velocities from all the participants were also determined. Significant differences (p ≤ 0.05) were found between different training situations and different competitive throwing velocities. We concluded that elite female water polo players modify their throwing velocity depending if the throw is performed during training or competitive situation.     

升马唐种群生态及其田间密度调控指标的研究

 研究表明,马唐的生育期为62—111天,需>0℃积温1380—2716。其生殖生长阶段对季节的温度要求严,营养生长阶段宽,生育期长短主要靠营养生长期的长短来调节。马唐种子休眠期一般为150天,休眠期长短和解除休眠速率与种子贮藏条件关系密切,以恒温贮藏最快。种子发芽起点温度为15℃,60%种子发芽的有效积温平均为555.13℃。马唐种子发芽对光照要求不敏感。在农田7cm土层内的种子均能出苗,但以1—4cm层最佳。马唐的再生能力强,试验表明,凡是带有须根和幼芽的任何断节都能发生新的植株。通径分析结果表明,马唐是我国北方夏播粮田的主要杂草。马唐群体水平(x,株／m2)与夏玉米籽粒减产率(y,%)间呈以下关系模式：(1)y=0.1532x1-5574(x≤20株／m2) (2)y=-18.400+11.315lnx(x>20株／m2)与夏玉米共同生长日数对作物籽粒减产率呈以下关系模式：y=54.5956／1+89.7962e-0.1184x根据推算,在石家庄地区夏播玉米田,马唐的允许存在密度即生态经济阈值为5.8株／m2。     

The influence of an elastic tendon on the force producing capabilities of a muscle during dynamic movements

With increasing computer power, computer simulation of human movement has become a popular research tool. However, time to complete simulations can still be long even on powerful computers. One possibility for reducing simulation time, with models of musculo-skeletal system, is to simulate the muscle using a rigid tendon rather than the more realistic compliant tendon. This study examines the effect of tendon elasticity on muscle force output under different dynamic conditions. A single muscle, point mass model was used and simulations were performed varying the mass, the tendon length, the initial position, and the task. For simulations for relatively slow motion, as experienced for example in upper limb reaching motions or rising from a chair, tendon properties had little influence on muscle force, in contrast simulations of an explosive task similar to jumping or throwing tendon had a much larger effect.