Effect of the upper limbs muscles activity on the mechanical energy gain in pole vaulting

The shoulder muscles are highly solicited in pole vaulting and may afford energy gain. The objective of this study was to determine the bilateral muscle activity of the upper-limbs to explain the actions performed by the vaulter to bend the pole and store elastic energy. Seven experienced athletes performed 5-10 vaults which were recorded using two video cameras (50Hz). The mechanical energy of the centre of gravity (CG) was computed, while surface electromyographic (EMG) profiles were recorded from 5 muscles bilateral: deltoideus, infraspinatus, biceps brachii, triceps, and latissimus dorsi muscles. The level of intensity from EMG profile was retained in four sub phases between take-off (TO1) and complete pole straightening (PS). The athletes had a mean mechanical energy gain of 22% throughout the pole vault, while the intensities of deltoideus, biceps brachii, and latissimus dorsi muscles were sub phases-dependent (p<0.05). Stabilizing the glenohumeral joint (increase of deltoideus and biceps brachii activity) and applying a pole bending torque (increase of latissimus dorsi activity) required specific muscle activation. The gain in mechanical energy of the vaulter could be linked to an increase in muscle activation, especially from latissimusdorsi muscles.     

Influence of the moment exerted by the athlete on the pole in pole-vaulting performance

Current studies on pole-vaulting focus mostly on energy transfer data [Ekevad, M., Lundberg, B., 1995. Simulation of "smart" pole vaulting. Journal of Biomechanics 28, 1079-1090; Ekevad, M., Lundberg, B., 1997. Influence of pole length and stiffness on the energy conversion in pole-vaulting. Journal of Biomechanics, 30, 259-264; Linthorne, N.P., 2000. Energy loss in the pole vault take-off and the advantage of the flexible pole. Sports Engineering 3, 205-218; Schade, F., Arampatzis, A., Bruggemann, G.P., 2006. Reproducibility of energy parameters in the pole vault. Journal of Biomechanics 39, 146-147.] and often fail to take into account the actions exerted on the pole [Arampatzis, Schade, Bruggemann, 2004. Effect of the pole-human body interaction on pole-vaulting performance. Journal of Biomechanics 37, 1353-1360]. The present study integrates the 3D kinematics data of the athlete but also the actions measured at the end of the pole in the planting box and on the track during the last stride before take-off. It proposes a mechanical model allowing determination of the pole-vaulter's actions on the pole. The model is based on a global mechanical approach. The pole-vaulter's action on his upper and lower hand is concentrated on one middle point to solve the dynamics problem. The model was applied to seven experienced pole-vaulters. The force and the moment exerted on the pole by the pole-vaulter during the last stride before take off and during jump stage, were calculated. This analysis of the compressive force and bending moment for seven pole-vaulters helps to highlight the impact of the moment in the performance. The conclusion is confirmed by an additional comparative study carried out on two pole-vaulters, with comparable morphologies and performing with the same pole.     

Mechanical power and segmental contribution to force impulses in long jump take-off.

Changes in total mechanical work, its partitioning into different energy states, mechanical power, force-time characteristics, force impulses of body segments and mass center's pathway characteristics during long jump take-off were investigated on four national and six ordinary level athletes. Both cinematographic and force-platform techniques were used. The data showed that the national level jumpers had higher run-up and higher take-off (release) velocities in horizontal and vertical directions. In addition, they were able to utilize efficiently the elastic energy stored in the leg extensor muscles at take-off impact. This was seen in high support leg eccentric and concentric forces, which were produced in short contact times. The ordinary level athletes had greater variability in the investigated attributes, and they reached their maximum length of jumps in many different ways. Cinematically the greatest difference between the subject groups was observed in the timing of the various body segment movements. In better athletes all the body parts (arms, trunk, and legs) had decelerating horizontal impulses, but in all ordinary level athletes the horizontal impulse of the swing leg was accelerating during take-off.     

Reproducibility of energy parameters in the pole vault

The purpose of this study was to analyze the reproducibility of kinematic, dynamometric and derived mechanical energy parameters in the pole vault as a main precondition for the practical applicability of the concept of energy exchange in the pole vault. A total of 46 vaults of six experienced vaulters were analyzed. On the basis of 3D kinematic data of the athlete and the pole and ground reaction forces measured at the end of the pole in the planting box the reproducibility of parameters that describe the energy transfer into the pole and the energy exchange between the athlete and the pole during the vault was proofed. Intraclass correlation, mean root mean square and the coefficient of variance were determined, additionally the Wilcoxon Test was applied. Parameters of the athlete's 3D total mechanical energy, e.g. initial energy and final energy, and the pole energy (maximum pole energy, energy of the pole due to compressive force and bending moment) were highly reproducible. The distribution of the energy transferred into the pole due to compressive force and bending moment, the same as the energy gain of the vaulter-pole system during the vault, which indicates the strategy of interacting with the pole, were also reproducible. With this the concept of energy exchange in the pole vault can be used to analyze the impact of training interventions, changes in movement pattern respectively, on the vaulters performance during different phases of the vault. The analysis of one trial of an athlete should be sufficient to identify changes in the athlete's interaction with the elastic pole.     

Effect of the pole--human body interaction on pole vaulting performance

The purposes of this study were: (a) to examine the interactions between the athlete and the pole and the possibility for the athlete to take advantage of the pole's elasticity by means of muscular work and (b) to develop performance criteria during the interaction between the athlete and the pole in pole vaulting. Six athletes performed 4-11 trials each, at 90% of their respective personal best performance. All trials were recorded using four synchronized, genlocked video cameras operating at 50 Hz. The ground reaction forces exerted on the bottom of the pole were measured using a planting box fixed on a force plate (1000 Hz). The interaction between athlete and pole may be split into two parts. During the first part, energy is transferred into the pole and the total energy of the athlete decreases. The difference between the energy decrease of the athlete and the pole energy is an indicator of the energy produced by the athletes by means of muscular work (criterion 1). During the second part of the interaction, energy is transferred back to the athlete and the total energy of the athlete increases. The difference between the returned pole energy and the amount of energy increase of the athlete defines criterion 2. In general, the function of the pole during the interaction is: (a) store part of the kinetic energy that the athlete achieved during the run up as strain energy and convert this strain energy into potential energy of the athlete, (b) allow the active system (athlete) to produce muscular work to increase the total energy potential.     

Pole vault performance for anthropometric variability via a dynamical optimal control model

Optimal performance of a dynamical pole vault process was modeled as a constrained nonlinear optimization problem. That is, given a vaulter's anthropomorphic data and approach speed, the vaulter chose a specific take-off angle, pole stiffness and gripping height in order to yield the greatest jumping height compromised by feasible bar-crossing velocities. The optimization problem was solved by nesting a technique of searching an input-to-output mapping arising from the vaulting trajectory and a method of nonlinear sequential quadratic programming (SQP). It was suggested from the optimization results that the body's weight has an important influence on the vaulting performance beside the vaulter's height and approach speed; the less skilled vaulter should gradually adopt a longer pole to improve the performance.     

Biological Jumping Mechanism Analysis and Modeling for Frog Robot

This paper presents a mechanical model of jumping robot based on the biological mechanism analysis of frog. By biological observation and kinematic analysis the frog jump is divided into take-offphase, aerial phase and landing phase. We find the similar trajectories of hindlimb joints during jump, the important effect of foot during take-off and the role of forelimb in supporting the body. Based on the observation, the frog jump is simplified and a mechanical model is put forward. The robot leg is represented by a 4-bar spring/linkage mechanism model, which has three Degrees of Freedom （DOF） at hip joint and one DOF （passive） at tarsometatarsal joint on the foot. The shoulder and elbow joints each has one DOF for the balancing function of arm. The ground reaction force of the model is analyzed and compared with that of frog during take-off. The results show that the model has the same advantages of low likelihood of premature lift-off and high efficiency as the frog. Analysis results and the model can be employed to develop and control a robot capable of mimicking the jumping behavior of frog.     

Take-Off Time of the First Generation of the Overwintering Small Brown Planthopper,Laodelphax striatellus in the Temperate Zone in East Asia

Overseas migration of the small brown planthopper, Laodelphax striatellus (Fallén), occurs during the winter wheat harvest season in East Asia. Knowing the take-off time of emigrating L. striatellus is crucial for predicting such migrations with a simulation technique because winds, carriers of migratory insects, change continuously. Several methods were used in China and Japan from late May to early June 2012 and again in 2013 to identify the precise timing of take-off. These methods included: a tow net trap mounted to a pole at 10 m above the ground, a helicopter-towed net trap, and a canopy trap (which also had video monitoring) set over wheat plants. Laodelphax striatellus emigrated from wheat fields mainly in the early evening, before dusk. The insects also emigrated during the daytime but rarely emigrated at dawn, showing a pattern that is unlike the bimodal emigration at dusk and dawn of two other rice planthoppers, the brown planthopper, Nilaparvata lugens (Stål), and the white-backed planthopper, Sogatella furcifera (Horváth). There was no significant difference in the temporal pattern of take-off behavior between females and males of Japanese L. striatellus populations.     

Comparison of lower limb kinetics,kinematics and muscle activation during drop jumping under shod and barefoot conditions

This study was to investigate the acute effects of wearing shoes on lower limb kinetics, kinematics and muscle activation during a drop jump. Eighteen healthy men performed a drop jump under barefoot and shod conditions. Vertical ground reaction force (GRF) was measured on a force plate during the contact phase of a drop jump, and GRF valuables were calculated for each condition. The angles of the knee and ankle joints, and the foot strike angle (the angle between the plantar surface of the foot and the ground during ground contact) as well as the electromyography of 7 muscles were measured. The shod condition showed a significant larger first peak GRF, longer time to first peak GRF from the initial ground contact and lower initial loading rate than the barefoot condition. The shod condition showed a significant larger ankle joint angle at initial ground contact, smaller knee joint angle between the second peak GRF and take-off as well as smaller foot strike angle at both initial ground contact and take-off than the barefoot condition. There were significant correlations between relative differences in ankle joint at the initial ground contact and relative differences in the initial loading rate. The muscle activity of all muscles during foot ground contact did not differ between two conditions; however, in the shod condition, muscle activation of 150 ms before foot ground contact was significantly higher in the rectus femoris, whereas it was lower in the biceps femoris and tibialis anterior muscles than the barefoot condition. These results indicate that wearing shoes alternates the GRF variables at initial ground contact, joint kinematics at the ground contact and muscle activation before foot ground contact during a drop jump, suggesting that the effects of wearing shoes on drop jump training differ from being barefoot.     

Influence of different approaches for calculating the athlete's mechanical energy on energetic parameters in the pole vault

The purposes of this study were as follows: (1) To determine the differences between two- and three-dimensionally calculated energy of the athlete in the pole vault. (2) To determine the differences between CM energy and total body energy. (3) To examine the influence of these different approaches of calculating the athlete's energy on energetic parameter values during the pole vault. Kinematic data were gathered during the pole vault final of the track and field world championships in 1997. Two video cameras (50Hz) covered the last step of the approach including the pole plant and 2 cameras covered the pole phase up to bar clearance, respectively. Twenty successful jumps were analysed. The characteristics of the energy development is similar for the different approaches. Initial energy, energy at maximum pole bend and energy at pole release (primary parameters) show significant differences (p<0.05). The findings indicate that rotatory movements and movements relative to the CM have a larger influence on the primary parameters than movements apart from the main plane of movement. For analysing the energy exchange between the athlete and the elastic implement pole only the differences among the secondary parameters (initial energy minus energy at maximum pole bend, final energy minus energy at maximum pole bend) are needed (Arampatzis et al., 1997 Biomechanical Research Project at the Vth World Championships in Athletics, Athens 1997: Preliminary Report. New Studies in Athletics 13, 66-69). For those parameters the relative differences between the calculation approaches range only between 1.47 and 0.04%. This indicates that the influence of the different approaches for calculating the athlete's energy on the analysis of energy exchange is negligible.     

The biomechanics of leaping in gibbons

Gibbons are skilled brachiators but they are also highly capable leapers, crossing distances in excess of 10 m in the wild. Despite this impressive performance capability, no detailed biomechanical studies of leaping in gibbons have been undertaken to date. We measured ground reaction forces and derived kinematic parameters from high-speed videos during gibbon leaps in a captive zoo environment. We identified four distinct leap types defined by the number of feet used during take-off and the orientation of the trunk, orthograde single-footed, orthograde two-footed, orthograde squat, and pronograde single-footed leaps. The center of mass trajectories of three of the four leap types were broadly similar, with the pronograde single-footed leaps exhibiting less vertical displacement of the center of mass than the other three types. Mechanical energy at take-off was similar in all four leap types. The ratio of kinetic energy to mechanical energy was highest in pronograde single-footed leaps and similar in the other three leap types. The highest mechanical work and power were generated during orthograde squat leaps. Take-off angle decreased with take-off velocity and the hind limbs showed a proximal to distal extension sequence during take-off. In the forelimbs, the shoulder joints were always flexed at take-off, while the kinematics of the distal joints (elbow and wrist joints) were variable between leaps. It is possible that gibbons may utilize more metabolically expensive orthograde squat leaps when a safe landing is uncertain, while more rapid (less expensive) pronograde single-footed leaps might be used during bouts of rapid locomotion when a safe landing is more certain.     

Understanding how an arm swing enhances performance in the vertical jump

This investigation was conducted to examine the various theories that have been proposed to explain the enhancement of jumping performance when using an arm swing compared to when no arm swing is used. Twenty adult males were asked to perform a series of maximal vertical jumps while using an arm swing and again while holding their arms by their sides. Force, motion and electromyographical data were recorded during each performance. Participants jumped higher (0.086 m) in the arm swing compared to the no-arm swing condition and was due to increased height (28%) and velocity (72%) of the center of mass at take-off. The increased height at take-off was due to the elevation of the arm segments. The increased velocity of take-off stemmed from a complex series of events which allowed the arms to build up energy early in the jump and transfer it to the rest of the body during the later stages of the jump. This energy came from the shoulder and elbow joints as well as from extra work done at the hip. This energy was used to (i) increase the kinetic and potential energy of the arms at take-off, (ii) store and release energy from the muscles and tendons around the ankle, knee and hip joint, and (iii) ‘pull’ on the body through an upward force acting on the trunk at the shoulder. It was concluded that none of the prevailing theories exclusively explains the enhanced performance in the arm swing jump, but rather the enhanced performance is based on several mechanisms operating together.     

Changes in states of commitment of single animal pole blastomeres of Xenopus laevis

The experiments described in this paper were designed to compare the normal fates of animal pole blastomeres of Xenopus laevis with their state of commitment. Single animal pole blastomeres were labeled with a lineage marker and transplanted into the blastocoels of host embryos of different stages. The distribution of labeled daughter cells in the tadpole reflects the state of commitment of the parent cell at the time of transplantation. It is known that cells from the animal pole of the early blastula normally contribute predominantly to ectoderm with a small, but significant, contribution to the mesoderm. We show that on transplantation to the blastocoels of late blastula host embryos these blastomeres are pluripotent, contributing to all three germ layers. At later stages the normal fate of these cells becomes restricted solely to ectoderm and concomitantly the proportion of pluripotent cells is reduced, although the results depend upon the stage of the host embryo. Blastomeres from late blastula donors transplanted to mid gastrulae contribute solely to ectoderm in 34% of cases; however, in earlier hosts, when the vegetal hemisphere cells have "mesoderm inducing" or "vegetalizing" activity, late blastula animal pole blastomeres contribute to mesoderm and endoderm rather than ectoderm. Thus during the blastula stage animal pole cells pass from pluripotency to a labile state of commitment to ectoderm.     

去叶时间对半干旱草原植物养分回收和干草生产的影响

去叶时间对半干旱草原植物养分回收和干草生产的影响 养分回收是植物养分保存的重要策略,其对环境和管理变化的响应关系到生态系统的养分循环和生产。去叶(刈割)是影响草地植物养分回收和生产的重要途径,而去叶时间的影响尚不清楚。本研究以内蒙古典型草原生态系统为对象,设置早期去叶(生物量高峰期之前)、峰期去叶(生物量高峰期)、晚期去叶(养分回收开始后)和不去叶(对照)四个处理,探讨了去叶时间对植物养分回收和生产的影响。通过测定植物物种和群落水平氮(N)和磷(P)回收特征,量化了植物N、P回收通量以及凋落物归还通量和干草输出通量,并评估了不同去叶时间处理下割草草地系统干草产量和质量。研究结果显示,峰期和晚期去叶降低植物群落N、P回收度,而早期去叶则对二者无影响;不同去叶时间处理下植物N、P回收效率相对稳定,仅晚期去叶降低N回收效率。峰期和晚期去叶降低植物群落N、P回收通量和凋落物N、P归还通量,而早期去叶并不影响这些参数。去叶时间降低植物群落养分回收通量,但未改变植物根系养分储存,说明根系养分吸收增加可补偿养分回收通量的降低。草地干草产量和质量在峰期去叶处理下最高,晚期去叶处理下最低。本研究结果为割草草地生态系统养分循环提供了新见解,通过调整刈割时间可以平衡草原的保护与生产,在植物生物量高峰期之前割草可实现保护和可持续生产的双重目标。     

The jump as a fast mode of locomotion in arboreal and terrestrial biotopes

The jump is always used for locomotion. For its execution in arboreal and terrestrial biotopes the requirements are of somewhat different nature. In an arboreal biotope the jump is characterized by a rapid progression through discontinuous substrates and the ability to take off from a small area and a secure landing on a spot. This requires well coordinated movements in all phases of the jump. On the ground, the jump is less frequent and often used for crossing obstacles or gaps. In primates both variants can be observed. In order to relate the details of locomotor behaviour to a certain environment, the biomechanics of jumping are analyzed in five primate species: The three mainly arboreal prosimian species Galago moholi, the smallest and most specialized leaper of all, Galago garnettii, a medium-sized bushbaby with some capacities for jumping, and Lemur catta also with some abilities to jump. The two simian species, Macaca fuscata and Homo sapiens, are usually terrestrial and have good jumping capacities, although not in terms of quantity. The investigation is based on high-speed motion analyses (100-500 frames/second) and the synchronized records of a force-plate from which all subjects had to jump off. On the basis of the results two kinds of jumping can be distinguished: standing and running jumps. The three prosimian species perform standing jumps. Dorsiflexion of their tails compensates ventrally oriented rotational moments of the trunk during body extension at take-off. The upward arm swing yields an overall increase in take-off velocity without additional muscular force exerted by the legs. The main difference among the species are the high relative forces in the small Galago moholi (up to 13 times body weight) as compared to the larger G. garnettii (8.5 times body weight) and the even larger Lemur catta (4.5 times body weight). In Homo sapiens the standing jump is characterized by an extensive arm swing backward, which is then followed by a forward and upward movement. The velocity at take-off is much smaller if compared to the prosimians. The running jump in Macaca fuscata is always preceded by at least one gallop cycle. The body assumes a ball shape at the beginning of the actual take-off. This is advantageous for rotating the body into a position in which the trunk axis is in line with the direction of movement. The tail of the Japanese macaque is too short to compensate the trunk's lift exerted on the hip region by the extending hindlimbs.(ABSTRACT TRUNCATED AT 400 WORDS)     

The specialized locomotory apparatus of the freshwater hatchetfish family Gasteropelecidae

High-speed video (200 frames/second) and kinematic analysis of the specialized locomotion of the Gasteropelecidae reveal a take-off mechanism from water to air with highly stereotyped components: a bilateral pectoral fin abduction and a C-start. With variations in timing between components of the take-off mechanism, a wide range of trajectories, all consistent with projectile motion, can be elicited. Correlated with studies of pectoral and caudal osteology and myology, the analysis indicates that active flight in the gasteropelecids is unlikely. Rather, the mechanism produces a jump, a modified startle response, achieved through the activation of powerful abductor muscles through the Mauthner mediated cell complex.     

Oskar anchoring restricts pole plasm formation to the posterior of the Drosophila oocyte

Localization of the maternal determinant Oskar at the posterior pole of Drosophila melanogaster oocyte provides the positional information for pole plasm formation. Spatial control of Oskar expression is achieved through the tight coupling of mRNA localization to translational control, such that only posterior-localized oskar mRNA is translated, producing the two Oskar isoforms Long Osk and Short Osk. We present evidence that this coupling is not sufficient to restrict Oskar to the posterior pole of the oocyte. We show that Long Osk anchors both oskar mRNA and Short Osk, the isoform active in pole plasm assembly, at the posterior pole. In the absence of anchoring by Long Osk, Short Osk disperses into the bulk cytoplasm during late oogenesis, impairing pole cell formation in the embryo. In addition, the pool of untethered Short Osk causes anteroposterior patterning defects, owing to the dispersion of pole plasm and its abdomen-inducing activity throughout the oocyte. We show that the N-terminal extension of Long Osk is necessary but not sufficient for posterior anchoring, arguing for multiple docking elements in Oskar. This study reveals cortical anchoring of the posterior determinant Oskar as a crucial step in pole plasm assembly and restriction, required for proper development of Drosophila melanogaster.     

Scaling and jumping: gravity loses grip on small jumpers

There are several ways to quantify jumping performance, a common definition being the height gained by the body's centre of mass (CM) in the airborne phase. Under this definition, jump height is determined by take-off velocity. According to the existing literature on jumping and scaling, take-off velocity, and hence jumping performance is independent of size because the energy that differently sized geometrically scaled jumpers can generate with their muscles is proportional to their mass. In this article it is shown, based on a simple energy balance, that it is incorrect to presume that jump height does not depend on size. Contrary to common belief, size as such has does have an effect on take-off velocity, putting small jumpers at a mechanical advantage, as is shown analytically. To quantify the effect of size on take-off velocity, a generic jumper model was scaled geometrically and evaluated numerically. While a 70-kg jumper took off at 2.65 m/s and raised its CM by 0.36 m after take-off, a perfectly geometrically similar jumper of 0.7 g reached a take-off velocity of 3.46 m/s and raised its CM by 0.61 m. The reason for the better performance of small jumpers is their higher efficacy in transforming the energy generated by the actuators into energy due to vertical velocity of the CM. Considering the ecological and evolutionary relevance of different definitions of jump height, size-dependent efficacy might explain why habitual jumping is especially prominent among small animals such as insects.     

Influence of leg stiffness and its effect on myodynamic jumping performance.

The purposes of this study are: a) to examine the possibility of influencing the leg stiffness through instructions given to the subjects and b) to determine the effect of the leg stiffness on the mechanical power and take-off velocity during the drop jumps. A total of 15 athletes performed a series of drop jumps from heights of 20, 40 and 60 cm. The instructions given to the subjects were a) "jump as high as you can" and b) "jump high a little faster than your previous jump". The jumps were performed at each height until the athlete could not achieve a shorter ground contact time. The ground reaction forces were measured using a "Kistler" force plate (1000 Hz). The athletes body positions were recorded using a high speed (250 Hz) video camera. EMG was used to measure muscle activity in five leg muscles. The data was divided into 5 groups where group 1 was made up of the longest ground contact times of each athlete and group 5 the shortest. The leg and ankle stiffness values were higher when the contact times were shorter. This means that by influencing contact time through verbal instructions it is possible to control leg stiffness. Maximum center of mass take-off velocity the can be achieved with different levels of leg stiffness. The mechanical power acting on the human body during the positive phase of the drop jumps had the highest values in group 3. This means that there is an optimum stiffness value for the lower extremities to maximize mechanical power.     

Effect of sex hormones on neuromuscular control patterns during landing.

The purpose of the study was to investigate the effects of sex hormones across menstrual cycle phases on lower extremity neuromuscular control patterns during the landing phase of a drop jump. A repeated-measures design was utilized to examine sex hormone effects in 26 recreationally active eumenorrheic women. Varus/valgus knee angle and EMG activity from six lower extremity muscles were recorded during three drop jumps from a 50 cm platform in each phase of the menstrual cycle. Blood assays verified sex hormone levels and cycle phase. The semitendinosus muscle exhibited onset delays (p0.006) relative to ground contact during the luteal phase, and demonstrated a significant (p0.05) difference between early and late follicular phases. Muscle timing differences between the gluteus maximus and semitendinosus were decreased (p0.05) in the luteal compared to early follicular phases. These results suggest a different co-contractive behavior between the gluteus maximus and semitendinosus, signifying a shift in neuromuscular control patterns. It appears that female recreational athletes utilize a different neuromuscular control pattern for performing a drop jump sequence when estrogen levels are high (luteal phase) compared to when they are low (early follicular phase).