The margin for error when releasing the asymmetric bars for dismounts

It has previously been shown that male gymnasts using the "scooped" giant circling technique were able to flatten the path followed by their mass center, resulting in a larger margin for error when releasing the high bar (Hiley and Yeadon, 2003a). The circling technique prior to performing double layout somersault dismounts from the asymmetric bars in women's artistic gymnastics appears to be similar to the "traditional" technique used by some male gymnasts on the high bar. It was speculated that as a result the female gymnasts would have margins for error similar to those of male gymnasts who use the traditional technique. However, it is unclear how the technique of the female gymnasts is affected by the need to avoid the lower bar. A 4-segment planar simulation model of the gymnast and upper bar was used to determine the margins for error when releasing the bar for 9 double layout somersault dismounts at the Sydney 2000 Olympics. The elastic properties of the gymnast and bar were modeled using damped linear springs. Model parameters, primarily the inertia and spring parameters, were optimized to obtain a close match between simulated and actual performances in terms of rotation angle (1.2 degrees), bar displacement (0.011 m), and release velocities (<1%). Each matching simulation was used to determine the time window around the actual point of release for which the model had appropriate release parameters to complete the dismount successfully. The margins for error of the 9 female gymnasts (release window 43-102 ms) were comparable to those of the 3 male gymnasts using the traditional technique (release window 79-84 ms).     

Optimisation of high bar circling technique for consistent performance of a triple piked somersault dismount

The dismount from the high bar is one of the most spectacular skills performed in Men's Artistic Gymnastics. Hiley and Yeadon [2005. Maximal dismounts from high bar. Journal of Biomechanics 38, 2221-2227] optimised the technique in the backward giant circle prior to release using a computer simulation model to show that a gymnast could generate sufficient linear and angular momentum to perform a triple piked backward somersault dismount with a sufficiently large release window (the period of time during which the gymnast could release the bar and successfully complete the dismount). In the present study, it was found that when the timing of the actions at the hip and shoulder joints from the optimum simulation were perturbed by 30ms the resulting simulation could no longer meet the criteria for sufficient aerial rotation and release window. Since it is to be expected that a gymnast's technique can cope with small errors in timing for consistent performance, a requirement of robustness to timing perturbations should be included within the optimisation process. When the technique in the backward giant circle was optimised to be robust to 30ms perturbations, it was found that sufficient linear and angular momentum for a triple piked dismount could be achieved with a realistic release window.     

Maximal dismounts from high bar

In men's artistic gymnastics the triple straight somersault dismount from the high bar has yet to be performed in competition. The present study used a simulation model of a gymnast and the high bar apparatus (J. Appl. Biomech. 19(2003a) 119) to determine whether a gymnast could produce the required angular momentum and flight to complete a triple straight somersault dismount. Optimisations were carried out to maximise the margin for error in timing the bar release for a given number of straight somersaults in flight. The amount of rotation potential (number of straight somersaults) the model could produce whilst maintaining a realistic margin for error was determined. A simulation model of aerial movement (J. Biomech.23 (1990) 85) was used to find what would be possible with this amount of rotation potential. The model was able to produce sufficient angular momentum and time in the air to complete a triple straight somersault dismount. The margin for error when releasing the bar using the optimum technique was 28 ms, which is small when compared with the mean margin for error determined for high bar finalists at the 2000 Sydney Olympic Games (55 ms). Although the triple straight somersault dismount is theoretically possible, it would require close to maximum effort and precise timing of the release from the bar. However, when the model was required to have a realistic margin for error, it was able to produce sufficient angular momentum for a double twisting triple somersault dismount.     

Optimization of backward giant circle technique on the asymmetric bars

The release window for a given dismount from the asymmetric bars is the period of time within which release results in a successful dismount. Larger release windows are likely to be associated with more consistent performance because they allow a greater margin for error in timing the release. A computer simulation model was used to investigate optimum technique for maximizing release windows in asymmetric bars dismounts. The model comprised four rigid segments with the elastic properties of the gymnast and bar modeled using damped linear springs. Model parameters were optimized to obtain a close match between simulated and actual performances of three gymnasts in terms of rotation angle (1.5 degrees ), bar displacement (0.014 m), and release velocities (<1%). Three optimizations to maximize the release window were carried out for each gymnast involving no perturbations, 10-ms perturbations, and 20-ms perturbations in the timing of the shoulder and hip joint movements preceding release. It was found that the optimizations robust to 20-ms perturbations produced release windows similar to those of the actual performances whereas the windows for the unperturbed optimizations were up to twice as large. It is concluded that robustness considerations must be included in optimization studies in order to obtain realistic results and that elite performances are likely to be robust to timing perturbations of the order of 20 ms.     

Mechanical energetic processes during the giant swing exercise before dismounts and flight elements on the high bar and the uneven parallel bars.

The purposes of this study were as follows: (1) To study the energy exchange between the body of the gymnast and the high bar and uneven parallel bars during forward and backward giant swings. (2) To examine the differences between the mechanical energy produced and the mechanical energy absorbed by the muscles during forward and backward giant swings on the high bar and the uneven parallel bars. The data were gathered during the gymnastic world championships in 1994. The experimental set up consisted of two video cameras (50 Hz) and two force measurement bars (500 Hz). A total of 101 giant swings before dismounts and flight elements performed by 33 male and 34 female gymnasts were analyzed. There are characteristically two main phases during forward and backward giant swings before dismounts and flight elements. During the first phase energy is transferred from the gymnast's body into the bar. During this phase of the backward giant swing the energy of the system decreases because the amount of energy decrease of the gymnast's body is more than the energy transferred into the high bar. An exception can be seen during the giant swings in which the gymnast used the power technique. During forward giant swings the energy of the system increases during the first phase. This occurs through active flexion of the hipjoint which produced the extra muscular energy. During the second phase energy is transferred from the bar back into the gymnast's body whose total energy increases. An increase in the energy of the system can only be achieved through muscular work. During the second phase of the backward giant swing the energy of the system increases. The forward giant swings performed on the uneven parallel bars showed a large energy loss during this phase. The energy deficit seen during the first phase of the backward giant swing can be improved by using the power technique. To achieve this the athlete must be in a bent position at the start of the giant swing exercise. Through extension at the shoulder and hip joints muscular energy can be put into the system.     

Mechanical energetic processes during the giant swing before the Tkatchev exercise

The goal of this study was to examine the possibility of the utilization of high bar and uneven parallel bar elasticity by the gymnasts through muscular work during the giant swing before the Tkatchev exercise on the high bar or uneven parallel bars. The performances were gathered during the Gymnastic World Championship in 1994. The set up consisted of two video cameras (50Hz) and two force measuring bars (500Hz). Twenty giant swings before the Tkatchev exercise, nine giant swings before the Tkatchev exercise after Tkatchev on the high bar and 15 giant swings before the Tkatchev exercise on the uneven parallel bars were analyzed. The giant swings were performed by 20 male and 15 female gymnasts. There are three phases during the giant swing exercise before the Tkatchev in which the systems (high bar-human body) total energy can be changed. During the first phase, energy is transferred from the gymnast's body into the bar. A clearly effective use of the bar's elasticity during the first phase could not be found. During the second phase, energy is transferred from the bar's back into the gymnast's body whose total energy increases. An increase in the energy of the system can only be achieved through muscular work. During the second phase of the various giant swing techniques no significant (p<0.05) difference in the energy increase through muscular work could be found. During the third phase, energy is once again produced by the gymnast through extension at the hip and shoulder joints.     

Optimised performance of the backward longswing on rings

Many elite gymnasts perform the straight arm backward longswing on rings in competition. Since points are deducted if gymnasts possess motion on completion of the movement, the ability to successfully perform the longswing to a stationary final handstand is of great importance. Sprigings et al. (1998) found that for a longswing initiated from a still handstand the optimum performance of an inelastic planar simulation model resulted in a residual swing of more than 3 degrees in the final handstand.For the present study, a three-dimensional simulation model of a gymnast swinging on rings, incorporating lateral arm movements used by gymnasts and mandatory apparatus elasticity, was used to investigate the possibility of performing a backward longswing initiated and completed in handstands with minimal swing. Root mean square differences between the actual and simulated performances for the orientations of the gymnast and rings cables, the combined cable tension and the extension of the gymnast were 3.2 degrees, 1.0 degrees, 270N and 0.05m respectively.The optimised simulated performance initiated from a handstand with 2.1 degrees of swing and using realistic changes to the gymnast's technique resulted in 0.6 degrees of residual swing in the final handstand. The sensitivity of the backward longswing to perturbations in the technique used for the optimised performance was determined. For a final handstand with minimal residual swing (2 degrees) the changes in body configuration must be timed to within 15 ms while a delay of 30 ms will result in considerable residual swing (7 degrees).     

A mathematical high bar–human body model for analysing and interpreting mechanical-energetic processes on the high bar

The aims of this study were:

1. To study the transfer of energy between the high bar and the gymnast.

2. To develop criteria from the utilisation of high bar elasticity and the utilisation of muscle capacity to assess the effectiveness of a movement solution.

3. To study the influence of varying segment movement upon release parameters.

For these purposes a model of the human body attached to the high bar (high bar–human body model) was developed. The human body was modelled using a 15-segment body system. The joint-beam element method (superelement) was employed for modelling the high bar. A superelement consists of four rigid segments connected by joints (two Cardan joints and one rotational–translational joint) and springs (seven rotation springs and one tension–compression spring). The high bar was modelled using three superelements. The input data required for the high bar–human body model were collected with video-kinematographic (50 Hz) and dynamometric (500 Hz) techniques. Masses and moments of inertia of the 15 segments were calculated using the data from the Zatsiorsky et al. (1984) model. There are two major phases characteristic of the giant swing prior to dismounts from the high bar. In the first phase the gymnast attempts to supply energy to the high bar–human body system through muscle activity and to store this energy in the high bar. The difference between the energy transferred to the high bar and the reduction in the total energy of the body could be adopted as a criterion for the utilisation of high bar elasticity. The energy previously transferred into the high bar is returned to the body during the second phase. An advantageous increase in total body energy at the end of the exercise could only be obtained through muscle energy supply. An index characterising the utilisation of muscle capacity was developed out of the difference between the increase in total body energy and the energy returned from the high bar. A delayed and initially slow but even reduction of hip and shoulder angles provided more advantageous release conditions. The total body energy could be improved by up to 15%, the vertical CM release velocity by up to 10% and the angular momentum by up to 35%.     

A 7 year pollen profile of major Olympic Games venues in Sydney, Australia

The year 2000 Olympic and Paralympic Games heldin Sydney, Australia were unique in the historyof the Games because they were staged in theearly to mid spring. This led to the concernthat pollen-sensitive athletes may havesignificant problems with allergic symptomstriggered by pollen exposure and that this mayhave compromised their ability to attain theirbest performance. Unfortunately, there was nosystematic pollen count data available for thecity of Sydney up until this time so thepurpose of this study was to obtain a profileof the pattern and type of pollens in theregion so that Olympic team managers andmedical staff could be adequately advised andable to prepare allergic athletes for anyexposures encountered while training andcompeting.We performed pollen monitoring of three majorOlympic venues over the six years before theGames to provide a profile of the mostprevalent species appearing over the spring.The pollen counts obtained at the major siteswere extremely high over the periods oftraining and competition. Tree pollens appearedfrom late July, peaking in August andSeptember, whilst grass pollens appeared fromSeptember and peaked in mid October. Arelatively small number of pollen varietiescomprise the majority of the pollen count.     

Sport for tall.

Eight new events (handball, basketball, and six rowing events) were introduced for women in the Olympic Games at Montreal in 1976. Of 187 women rowers who competed at Montreal, none was shorter than the mean height (162 cm, 64 in) of women aged 18-24 in the United States. In team events only two out of 250 participants were shorter than the reference mean. Even among the tall, it was the taller participants who won medals. What does the slogan "Sport for All" mean in this context? Moreover, the physical size required of champion rowers and basketball players is not to be found in some Asian, African, and Latin American populations. International contests in many such events therefore seem to be at variance with the first charter of the Olympic Games. An independent reviewing body is urgently needed to examine the merits of man made rules in many sporting contests.     

Smoke Rings: Towards a Comprehensive Tobacco Free Policy for the Olympic Games

Background

The tobacco industry has long sought affiliation with major sporting events, including the Olympic Games, for marketing, advertising and promotion purposes. Since 1988, each Olympic Games has adopted a tobacco-free policy. Limited study of the effectiveness of the smoke-free policy has been undertaken to date, with none examining the tobacco industry’s involvement with the Olympics or use of the Olympic brand.

Methods and Findings

A comparison of the contents of Olympic tobacco-free policies from 1988 to 2014 was carried out by searching the websites of the IOC and host NOCs. The specific tobacco control measures adopted for each Games were compiled and compared with measures recommended by the WHO Tobacco Free Sports Initiative and Article 13 of the Framework Convention on Tobacco Control (FCTC). This was supported by semi-structured interviews of key informants involved with the adoption of tobacco-free policies for selected games. To understand the industry’s interests in the Olympics, the Legacy Tobacco Documents Library (http://legacy.library.ucsf.edu) was systematically searched between June 2013 and August 2014. Company websites, secondary sources and media reports were also searched to triangulate the above data sources.This paper finds that, while most direct associations between tobacco and the Olympics have been prohibited since 1988, a variety of indirect associations undermine the Olympic tobacco-free policy. This is due to variation in the scope of tobacco-free policies, limited jurisdiction and continued efforts by the industry to be associated with Olympic ideals.

Conclusions

The paper concludes that, compatible with the IOC’s commitment to promoting healthy lifestyles, a comprehensive tobacco-free policy with standardized and binding measures should be adopted by the International Olympic Committee and all national Olympic committees.     

On the organizing role of nonmuscular forces during performance of a giant circle in gymnastics

Five elite gymnasts performed giant circles on the high bar under different conditions of loading (without and with 6-kg loads attached to the shoulders, waist or ankles). Comparing the gymnasts' kinematic pattern of movement with that of a triple-pendulum moving under the sole influence of nonmuscular forces revealed qualitative similarities, including the adoption of an arched position during the downswing and a piked position during the upswing. The structuring role of nonmuscular forces in the organization of movement was further reinforced by the results of an inverse dynamics analysis, assessing the contributions of gravitational, inertial and muscular components to the net joint torques. Adding loads at the level of the shoulders, waist or ankles systematically influenced movement kinematics and net joint torques. However, with the loads attached at the level of the shoulders or waist, the load-induced changes in gravitational and inertial torques provided the required increase in net joint torque, thereby allowing the muscular torques to remain unchanged. With the loads attached at the level of the ankles, this was no longer the case and the gymnasts increased the muscular torques at the shoulder and hip joints. Together, these results demonstrate that expert gymnasts skillfully exploit the operative nonmuscular forces, employing muscle force only in the capacity of complementary forces needed to perform the task.     

The citius end: world records progression announces the completion of a brief ultra-physiological quest

World records (WR) in sports illustrate the ultimate expression of human integrated muscle biology, through speed or strength performances. Analysis and prediction of man's physiological boundaries in sports and impact of external (historical or environmental) conditions on WR occurrence are subject to scientific controversy. Based on the analysis of 3263 WR established for all quantifiable official contests since the first Olympic Games, we show here that WR progression rate follows a piecewise exponential decaying pattern with very high accuracy (mean adjusted r(2) values = 0.91+/-0.08 (s.d.)). Starting at 75% of their estimated asymptotic values in 1896, WR have now reached 99%, and, present conditions prevailing, half of all WR will not be improved by more than 0,05% in 2027. Our model, which may be used to compare future athletic performances or assess the impact of international antidoping policies, forecasts that human species' physiological frontiers will be reached in one generation. This will have an impact on the future conditions of athlete training and on the organization of competitions. It may also alter the Olympic motto and spirit.     

Patterns of anterior and posterior muscle chain interactions during high performance long-hang elements in gymnastics

In a prior study with high level gymnasts we could demonstrate that the neuromuscular activation pattern during the “whip-like” leg acceleration phases (LAP) in accelerating movement sequences on high bar, primarily runs in a consecutive succession from the bar (punctum fixum) to the legs (punctum mobile). The current study presents how the neuromuscular activation is represented during movement sequences that immediately follow the LAP by the antagonist muscle chain to generate an effective transfer of momentum for performing specific elements, based on the energy generated by the preceding LAP. Thirteen high level gymnasts were assessed by surface electromyography during high performance elements on high bar and parallel bars. The results show that the neuromuscular succession runs primarily from punctum mobile towards punctum fixum for generating the transfer of momentum. Additionally, further principles of neuromuscular interactions between the anterior and posterior muscle chain during such movement sequences are presented. The findings complement the understanding of neuromuscular activation patterns during rotational movements around fixed axes and will help to form the basis of more direct and better teaching methods regarding earlier optimization and facilitation of the motor learning process concerning fundamental movement requirements.     

Neuromuscular onset succession of high level gymnasts during dynamic leg acceleration phases on high bar

In several athletic disciplines there is evidence that for generating the most effective acceleration of a specific body part the transfer of momentum should run in a “whip-like” consecutive succession of body parts towards the segment which shall be accelerated most effectively (e.g. the arm in throwing disciplines). This study investigated the question how this relates to the succession of neuromuscular activation to induce such “whip like” leg acceleration in sports like gymnastics with changed conditions concerning the body position and momentary rotational axis of movements (e.g. performing giant swings on high bar). The study demonstrates that during different long hang elements, performed by 12 high level gymnasts, the succession of the neuromuscular activation runs primarily from the bar (punctum fixum) towards the legs (punctum mobile). This demonstrates that the frequently used teaching instruction, first to accelerate the legs for a successful realization of such movements, according to a high level kinematic output, is contradictory to the neuromuscular input patterns, being used in high level athletes, realizing these skills with high efficiency.Based on these findings new approaches could be developed for more direct and more adequate teaching methods regarding to an earlier optimization and facilitation of fundamental movement requirements.     

Spatial consistency of circle on the pedagogic pommel horse: influence of expertise

Gymnastics is a closed-skill sport, and the repeatability of a specific technique is accepted as a valuable indicator of a performer's level of expertise. The circle movement, defined as a gyrating movement in the horizontal plane, is a key component of all contemporary pommel horse exercises. The aims of this study were to determine the spatial consistency of the circle movement and to assess the influence of expertise on the repeatability of this skill performed on the pedagogic pommel horse. Six expert gymnasts and six nonexperts performed 10 circles on this apparatus. A 3-dimensional analysis system recorded the trajectories of 6 markers fixed on the right and left ankles, hips, and shoulders. The spatiotemporal consistency was assessed by the SD of the marker trajectories during the circle sequence. The results showed that the shoulder and trajectories were more consistent than the ankle trajectory (P < 0.05); the marker trajectories were less consistent in the sagittal plane (P < 0.05); and the expert gymnasts showed better repeatability of the ankle trajectory than the nonexpert gymnasts did (P < 0.05). In this context, the use of the SD of the ankle trajectory during the circle sequence could be an interesting tool for trainers to quantify objectively the positional errors of the legs during circular swings and to measure the improvement in movements after specific training.     

Restoration of abdominal wall integrity as a salvage procedure in difficult recurrent abdominal wall hernias using a method of wide myofascial release

The management of primary and recurrent giant incisional hernias remains a complex and frustrating challenge even with multiple alloplastic and autogenous closure options. The purpose of this study was to develop a reconstructive technique of restoring abdominal wall integrity to a subcategory of patients, who have failed initial hernia therapy, by performing superior and lateral myofascial release. Over a 1.5-year period, 10 patients with previously unsuccessful treatment of abdominal wall hernias, using either primary repair or placement of synthetic material, were studied. The patients had either recurrence of the hernia or complications such as infections requiring removal of synthetic material. The hernias were not able to be treated with standard primary closure techniques or synthetic material. The average defect size was 19 x 9 cm. Each patient underwent wide lysis of bowel adhesions releasing the posterior abdominal wall fascia to the posterior axillary line, subcutaneous release of the anterior abdominal wall fascia to a similar level, and complete removal of any synthetic material (if present). The abdominal domain was reestablished by releasing the laterally retracted abdominal wall. The amount of available abdominal wall tissue was increased by wide release of the cephalic abdominal wall fascia overlying the costal margin and the external oblique fascia and muscle laterally. If needed, partial thickness of the internal oblique muscle and its anterior fascia were also released laterally to perform a tension-free primary closure of the defect. All repairs were closed with satisfactory functional and aesthetic results. All alloplastic material was removed. Fascial release was limited so as to close only the hernia defect without tension. No significant release of the rectus sheath and muscle was needed. Good, dynamic muscle function was noted postoperatively. All repairs have remained intact, and no further abdominal wall hernias have been noted on follow-up.     

Validation of instrumentation to monitor dynamic performance of olympic weightlifters

The purpose of this study was to validate the accuracy and reliability of the Weightlifting Video Overlay System (WVOS) used by coaches and sport biomechanists at the United States Olympic Training Center. Static trials with the bar set at specific positions and dynamic trials of a power snatch were performed. Static and dynamic values obtained by the WVOS were compared with values obtained by tape measure and standard video kinematic analysis. Coordinate positions (horizontal [X] and vertical [Y]) were compared on both ends (left and right) of the bar. Absolute technical error of measurement between WVOS and kinematic values were calculated (0.97 cm [left X], 0.98 cm [right X], 0.88 cm [left Y], and 0.53 cm [right Y]) for the static data. Pearson correlations for all dynamic trials exceeded r = 0.88. The greatest discrepancies between the 2 measuring systems were found to occur when there was twisting of the bar during the performance. This error was probably due to the location on the bar where the coordinates were measured. The WVOS appears to provide accurate position information when compared with standard kinematics; however, care must be taken in evaluating position measurements if there is a significant amount of twisting in the movement. The WVOS appears to be reliable and valid within reasonable error limits for the determination of weightlifting movement technique.     

Timing accuracy in human throwing

This study examines the precision required in the timing of muscle activations and projectile release to hit a target of 20 cm in diameter oriented horizontally either 6 or 8 m away. Over-arm throws, constrained to the sagittal plane, were simulated using a muscle-actuated, two-segment model representing the forearm and hand plus projectile. The parameters defining the modeled muscles and the anthropometry were specific to two male subjects. An objective function specified that throws must be both fast and accurate. Once an optimal solution had been found, the sensitivity of these timings was investigated. The times of activation or release were changed and the simulation model re-run with the new timings, and it was determined whether the projectile would still have struck the target. For one set of simulations, to hit the target at 8 m, the optimal throw was achieved with a time delay between the onset of wrist activation and elbow extensor activation [Proximal-distal (PD) delay] of 49 ms and a release time of 83.4 ms. At this optimal point in the solution space, the launch window was 1.2 ms (assuming the original PD delay). The launch window was the time available within which the projectile must be released and still strike the target. The window during which the wrist flexors could be activated was 10. 41 ms (assuming the projectile was released at the pre-planned optimal time). The control scheme which required the least timing precision had a PD delay of 56 ms and a release time of 89.4 ms. Errors in timing could occur in activation and release simultaneously under this scheme, the timing windows were 4 ms in PD delay and 2.4 ms in release. Similar results were found for a second set of simulations. These simulations revealed the precise timings required in muscle activations and release required for fast accurate throws.     

A temporal window for lateralization of interaural time difference by barn owls

Summary Lateralization of interaural time difference by barn owls (Tyto alba) was studied in a dichotic masking experiment. Sound bursts consisted of two parts: binaurally time-shifted noise, termed the probe, was inserted between masking noise. The owls indicated that they detected and lateralized the time-shift in the probe by a head turn in the direction predicted from sign of the time-shift.The general characteristics of head turns in response to this stimulus was similar to the head turns elicited by free-field stimulation or to head turns in response to presentation of the probe alone.The owls could easily lateralize stimuli containing long probes. The number of correct turns decreased as probe duration decreased, demonstrating that the masking noise interfered with the owls' ability to lateralize the probe. The minimal probe duration that the animals could lateralize (minimal duration) became shorter as burst duration decreased. Minimal durations ranged from 1 ms to 15 ms for the two subjects and burst durations from 10 to 100 ms.These findings suggested that owls possess a temporal window. A fitting procedure proposed by Moore et al. (1988) was used to determine the shape of the temporal window. The fitting procedure showed that the shape of the owls' binaural temporal window could be described by the same algorithms as the human monaural temporal window. Thus, the temporal window is composed of a short time constant that determines the central part of the window, and a longer time constant that determines the shape at the skirts of the window.Abbreviations ERD equivalent rectangular duration - ILD interaural level difference - ITD interaural time difference - RSE relative signal energy - SNR signal-to-noise ratio