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).     

Serum cortisol concentration and testosterone to cortisol ratio in elite prepubescent male gymnasts during training.

Serum cortisol concentrations and testosterone:cortisol concentration ratios of eight prepubescent elite male gymnasts (mean age 10 years 11 months) and 11 controls (mean age 11 years 1 month) were examined during 5 consecutive training days. During this period, the gymnasts trained 3 h each day with moderate intensity mobility, strength and skill exercises while the controls were relatively sedentary. Blood samples were taken from all the boys in both groups before (1630 hours) and 30 min after (2000 hours) training on 4 days. Serum cortisol concentrations of the gymnasts were not significantly different from those of the controls throughout the experiment. Serum cortisol concentrations of both groups were significantly larger (P < 0.05) at 1630 hours than at 2000 hours, indicating that cortisol secretion followed the typical adult circadian change, seemingly unaltered by training. However, there was a significant decrease (P < 0.05) in the testosterone:cortisol ratio of the gymnasts when compared with controls from day 1 to day 3. After a rest on day 4 the testosterone: cortisol ratio of the gymnasts significantly increased (P < 0.05) but the ratio of the control group also increased indicating that there may have been some day-to-day change by factor(s) other than training. The most obvious factor which may have accounted for the unresponsiveness of serum cortisol concentration to the gymnastics training was that the exercise intensity was too low. However, several days of the training seemed to reduce the anabolic to catabolic balance but further experiments are needed to confirm this finding.     

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.     

Robotics-based synthesis of human motion

The synthesis of human motion is a complex procedure that involves accurate reconstruction of movement sequences, modeling of musculoskeletal kinematics, dynamics and actuation, and characterization of reliable performance criteria. Many of these processes have much in common with the problems found in robotics research. Task-based methods used in robotics may be leveraged to provide novel musculoskeletal modeling methods and physiologically accurate performance predictions. In this paper, we present (i) a new method for the real-time reconstruction of human motion trajectories using direct marker tracking, (ii) a task-driven muscular effort minimization criterion and (iii) new human performance metrics for dynamic characterization of athletic skills. Dynamic motion reconstruction is achieved through the control of a simulated human model to follow the captured marker trajectories in real-time. The operational space control and real-time simulation provide human dynamics at any configuration of the performance. A new criteria of muscular effort minimization has been introduced to analyze human static postures. Extensive motion capture experiments were conducted to validate the new minimization criterion. Finally, new human performance metrics were introduced to study in details an athletic skill. These metrics include the effort expenditure and the feasible set of operational space accelerations during the performance of the skill. The dynamic characterization takes into account skeletal kinematics as well as muscle routing kinematics and force generating capacities. The developments draw upon an advanced musculoskeletal modeling platform and a task-oriented framework for the effective integration of biomechanics and robotics methods.     

EVALUATION OF WINE COMPETITION JUDGE PERFORMANCE USING PRINCIPAL COMPONENT SIMILARITY ANALYSIS

Principal component similarity (PCS) analysis was used to evaluate judge performance from a wine competition. Data were analyzed for five international judges and seven wine makers, for 42 white, 30 red and 25 specialty wines, using a 20-point quality scoring system. Principal similarity plots were used to group judges according to judging 'style' and to identify outliers, for each wine category. Judge groupings were consistent when three different references were used; however, the most interpretable PCS plot was obtained when the overall mean-judge-score was used as the reference. Results from PCS were compared to principal component analysis (PCA). PCS analysis allowed the information from all significant principal components to be graphically represented in two dimensions and was more successful in classifying judges than plots based on the first three principal components. The technique of PCS is an important complement to existing methodologies, and can provide wine competition coordinators with an objective technique for judge evaluation and selection.     

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).     

Effect of hip flexibility on optimal stalder performances on high bar

In the optimisation of sports movements using computer simulation models, the joint actuators must be constrained in order to obtain realistic results. In models of a gymnast, the main constraint used in previous studies was maximum voluntary active joint torque. In the stalder, gymnasts reach their maximal hip flexion under the bar. The purpose of this study was to introduce a model of passive torque to assess the effect of the gymnast's flexibility on the technique of the straddled stalder. A three-dimensional kinematics driven simulation model was developed. The kinematics of the shoulder flexion, hip flexion and hip abduction were optimised to minimise torques for four hip flexion flexibilities: 100°, 110°, 120° and 130°. With decreased flexibility, the piked posture period is shorter and occurs later. Moreover the peaks of shoulder and hip torques increase. Gymnasts with low hip flexibility need to be stronger to achieve a stalder; hip flexibility should be considered by coaches before teaching this skill.     

Local versus global optimal sports techniques in a group of athletes

Various optimization algorithms have been used to achieve optimal control of sports movements. Nevertheless, no local or global optimization algorithm could be the most effective for solving all optimal control problems. This study aims at comparing local and global optimal solutions in a multistart gradient-based optimization by considering actual repetitive performances of a group of athletes performing a transition move on the uneven bars. Twenty-four trials by eight national-level female gymnasts were recorded using a motion capture system, and then multistart sequential quadratic programming optimizations were performed to obtain global optimal, local optimal and suboptimal solutions. The multistart approach combined with a gradient-based algorithm did not often find the local solution to be the best and proposed several other solutions including global optimal and suboptimal techniques. The qualitative change between actual and optimal techniques provided three directions for training: to increase hip flexion–abduction, to transfer leg and arm angular momentum to the trunk and to straighten hand path to the bar.     

Evaluation of performance criteria for simulation of submaximal steady-state cycling using a forward dynamic model.

The objectives of this study were twofold. The first was to develop a forward dynamic model of cycling and an optimization framework to simulate pedaling during submaximal steady-state cycling conditions. The second was to use the model and framework to identify the kinetic, kinematic, and muscle timing quantities that should be included in a performance criterion to reproduce natural pedaling mechanics best during these pedaling conditions. To make this identification, kinetic and kinematic data were collected from 6 subjects who pedaled at 90 rpm and 225 W. Intersegmental joint moments were computed using an inverse dynamics technique and the muscle excitation onset and offset were taken from electromyographic (EMG) data collected previously (Neptune et al., 1997). Average cycles and their standard deviations for the various quantities were used to describe normal pedaling mechanics. The model of the bicycle-rider system was driven by 15 muscle actuators per leg. The optimization framework determined both the timing and magnitude of the muscle excitations to simulate pedaling at 90 rpm and 225 W. Using the model and optimization framework, seven performance criteria were evaluated. The criterion that included all of the kinematic and kinetic quantities combined with the EMG timing was the most successful in replicating the experimental data. The close agreement between the simulation results and the experimentally collected kinetic, kinematic, and EMG data gives confidence in the model to investigate individual muscle coordination during submaximal steady-state pedaling conditions from a theoretical perspective, which to date has only been performed experimentally.     

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.     

A New Cyclic Scheduling Algorithm for Flexible Manufacturing Systems

Flexible manufacturing system control is an NP-hard problem. A cyclic approach has been demonstrated to be adequate for an infinite scheduling problem because of maximal throughput reachability. However, it is not the only optimization criterion in general. In this article we consider the minimization of the work in process (WIP) as an economical and productivity factor. We propose a new cyclic scheduling algorithm giving the maximal throughput (a hard constraint) while minimizing WIP. This algorithm is based on progressive operations placing. A controlled beam search approach has been developed to determine at each step the schedule of the next operations. After presenting the main principles of the algorithm, we compare our approach to several most known cyclic scheduling algorithms using a significant existing example from the literature.     

Effects of biomotor structures on performance of competitive gymnastics elements in elementary school male sixth-graders

In order to identify the biomotor systems that determine performance of competitive gymnastics elements in elementary school male sixth-graders, factor structures of morphological characteristics and basic motor abilities were determined first, followed by relations of the morphological-motor system factors obtained with a set of criterion variables evaluating specific motor skills in competitive gymnastics in 110 male children aged 12 years +/- 3 months. Factor analysis of 17 morphological measures produced three morphological factors: factor of mesoectoendomorphy (general morphological factor) and factor of pronounced endomorphy, i.e. excessive adipose tissue, along with low skeleton longitudinality. Factor analysis of 16 motor variables yielded four motor factors: factor of general motoricity; factor integrating leg flexibility and arm explosiveness; factor juxtaposing body flexibility and repetitive leg strength; and factor predominantly defining leg movement frequency. Three significant canonical correlations, i.e. linear combinations, explained the association between the set of six latent variables of the morphological and basic motor system, and five variables assessing the knowledge in competitive gymnastics. The first canonical linear combination was based on the favorable and predominant impact of the general motor factor (a system integrating leg explosiveness, whole body coordination, relative arm and trunk strength, and arm movement frequency), along with unfavorable effect of morphological factors on the gymnastics elements performance, squat vault and handstand in particular The relation of the second pair of canonical factors pointed to the effects of leg flexibility and arm explosiveness on the cartwheel and backward pullover mount performance, whereas the relation of the third pair of canonical factors showed a favorable impact of the general morphological factor and leg movement frequency regulator on the forward shoulderkip from increase, cartwheel and handstand performance.     

Integral dose based inverse optimization objective function promises lower toxicity in head-and-neck

PurposeThe voxels in a CT data sets contain density information. Besides its use in dose calculation density has no other application in modern radiotherapy treatment planning. This work introduces the use of density information by integral dose minimization in radiotherapy treatment planning for head-and-neck squamous cell carcinoma (HNSCC).Materials and methodsEighteen HNSCC cases were studied. For each case two intensity modulated radiotherapy (IMRT) plans were created: one based on dose-volume (DV) optimization, and one based on integral dose minimization (Energy hereafter) inverse optimization. The target objective functions in both optimization schemes were specified in terms of minimum, maximum, and uniform doses, while the organs at risk (OAR) objectives were specified in terms of DV- and Energy-objectives respectively. Commonly used dosimetric measures were applied to assess the performance of Energy-based optimization. In addition, generalized equivalent uniform doses (gEUDs) were evaluated. Statistical analyses were performed to estimate the performance of this novel inverse optimization paradigm.ResultsEnergy-based inverse optimization resulted in lower OAR doses for equivalent target doses and isodose coverage. The statistical tests showed dose reduction to the OARs with Energy-based optimization ranging from ∼2% to ∼15%.ConclusionsIntegral dose minimization based inverse optimization for HNSCC promises lower doses to nearby OARs. For comparable therapeutic effect the incorporation of density information into the optimization cost function allows reduction in the normal tissue doses and possibly in the risk and the severity of treatment related toxicities.     

INVESTIGATION OF THE DUAL-PAIR METHOD AS A POSSIBLE ALTERNATIVE TO THE TRIANGLE AND SAME-DIFFERENT TESTS

Previous experiments have shown that the same-different test, because of its more suitable cognitive strategy and lower memory requirements, is a more powerful and sensitive alternative to the triangle and duo-trio tests. This project describes an experiment conducted in order to investigate ways to improve further the performance of the same-different test. Three protocols were compared using orange flavored beverages and 24 judges: the same-different method, the triangle test and the dual-pair paradigm. The latter protocol could improve the same-different's performance by preventing the spontaneous variations of the judges'τ criterion. While no significant differences were detected among the d' values obtained with each procedure, a trend was observed for the same-different and dual-pair test to be slightly more sensitive (higher d' values) than the triangle test. Since the same-different test is statistically more powerful, it is a preferable choice over the triangle, duo-trio and dual-pair tests.     

What has transcranial magnetic stimulation taught us about neural adaptations to strength training? A brief review

The evidence for neural mechanisms underpinning rapid strength increases has been investigated and discussed for over 30 years using indirect methods, such as surface electromyography, with inferences made toward the nervous system. Alternatively, electrical stimulation techniques such as the Hoffman reflex, volitional wave, and maximal wave have provided evidence of central nervous system changes at the spinal level. For 25 years, the technique of transcranial magnetic stimulation (TMS) has allowed for noninvasive supraspinal measurement of the human nervous system in a number of areas such as fatigue, skill acquisition, clinical neurophysiology, and neurology. However, it has only been within the last decade that this technique has been used to assess neural changes after strength training. The aim of this brief review is to provide an overview of TMS, discuss specific strength training studies that have investigated changes, after short-term strength training in healthy populations in upper and lower limbs, and conclude with further research suggestions and the application of this knowledge for the strength and conditioning coach.     

Plyometric jumping performances of male and female gymnasts from different heights

The objective of this study was to investigate and compare the factors influencing plyometric jumping performance between well-trained gymnasts and a control group. Seventy-six gymnasts and 91 moderately active subjects volunteered to participate in this study. Drop jumps (DJ) were performed from 20-, 40-, 60-, 80-, and 100-cm heights. Flight time (FT) and contact time (CT) were recorded using contact mat. Flight time to contact time (FC) ratio and Bosco expression (BE) were calculated. Male gymnasts scored similar FT to their controls, whereas female gymnasts had significantly longer FT compared with their peers. The gymnasts obtained significantly shorter CT than their control groups, whereas their FC ratios were significantly higher and increased when the height of the drops was close to 60 cm. Moreover, gymnasts' BE was greater in comparison to their respective control groups independent of the drop height. The height of the drop that produced the best FC ratio and BE varied between the groups. The best performances were obtained between 40- and 60-cm drop height for both groups. Female control group showed a trend toward a continuing decline with the increase of the drop height. The best gymnasts (finalists at World Championships) obtained their best performance at 80-cm drop. Flight time is the less discriminating factor distinguishing gymnasts' DJ performances. Considering CT, FC, and BE results all together could better profile the gymnasts rather than taken separately. Bosco expression was shown to be more sensitive to the increase in FT; we suggest BE as the best criteria to assess the appropriate drop height for plyometric training purposes in gymnasts as it has been significantly correlated to FT.     

Landing from different heights: Biomechanical and neuromuscular strategies in trained gymnasts and untrained prepubescent girls

The purpose of this study was to examine the biomechanics of the lower limb, during landing in female prepubertal gymnasts and prepubertal untrained girls, aged 9–12 years. Ten healthy participants were included in each group and performed five landings from 20, 40, and 60 cm. Kinematics, ground reaction forces (GRF) and electromyogram (EMG) from the lateral gastrocnemius, tibialis anterior, and vastus lateralis are presented. Gymnasts had higher vertical GRF and shorter braking phase during landing. Compared to untrained girls, gymnasts exhibited for all examined drop heights more knee flexion before and at ground contact, but less knee flexion at maximum knee flexion position. Especially when increasing drop heights the gymnasts activated their examined muscles earlier, and generally they had higher pre- and post landing EMG amplitudes normalized to the peak EMG at 60 cm drop height. Furthermore, gymnasts had lower antagonist EMG for the tibialis anterior compared to untrained girls, especially when landing from higher heights. It is concluded that the landing strategy preferred by gymnasts is influenced by long-term and specialized training and induces a stiffer landing pattern. This could have implications in injury prevention, which requires further investigation.     

VARIATION IN SENSORY CONCEPTUAL STRUCTURE: AN INVESTIGATION INVOLVING THE SORTING OF ODOR STIMULI

Judges sorted forty-three odor stimuli into groupings of conceptual similarity, repeating the task over several sessions. There was little between-judges consistency in conceptual structure inferred from the sorting patterns and little within-judges consistency over sessions. The latter suggests that 'one time' sorting experiments would give different results on repetition. In a second experiment, the effect of prior categorization experience on subsequent categorical learning was examined. Naive judges and judges from the first study performed further sortings to see whether they could be induced to sort into a chosen set of perfumery categories. Various cues were given: category names, exemplar stimuli, numbers of stimuli within each category and finally the 'correct' answers. Increasing the cues increased the tendency to sort according to the a priori plan but complete success was not achieved. Judges who had previously sorted the stimuli according to their own conceptual structure, found the a priori perfumery structure harder to learn than naive judges.     

Total work rate of breathing optimization in CO-2 inhalation and exercise.

The hypothesis that respiratory frequency and the relative durations of inspiration and expiration are regulated according to a total cycle work rate minimization criterion was explored. Effects of negative work performed by the respiratory muscles and dead space variation as a function of tidal volume were included in a formulation which yielded a theoretically predictable optimal frequency and relative duration of inspiration and expiration at all levels of ventilation. Predicted cycle characteristics based on measured mechanical parameters were compared with data taken during CO-2 inhalation (3 and 5%) and moderate exercise (MRR = 3 and 6) in three normal human subjects. No major difference in breathing pattern was observed between CO-2 inhalation and exercise. Results suggest that conditions for minimization of total cycle work rate are achieved asympototically as the level of ventilation rises above the resting level. At rest and at low levels of hyperpnea complete work rate optimization is not achieved.