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An experimental and analytical study of impact forces during human jumping.

Impact forces during landing in dismounts from the horizontal bar onto regulation gymnastic mats and in jumping from a height of 0.45 m onto a hard surface were measured. A two degree-of-freedom dynamic model was developed to predict the forces in landing on the hard surface. The periods of the two peaks that can be identified from experimental data were used in the determination of the system parameters. The peak forces recorded in gymnasts' landing ranged from 8.2 to 11.6 times the body weight. Maximum forces in jumping from 0.45 m, which ranged from 5.0 to 7.0 times the body weight, were accurately predicted by the model.

Biomechanical Phenomena↗

Maximising somersault rotation in tumbling.

Performing complex somersaulting skills during the flight phase of tumbling requires the generation of linear and angular momenta during the approach and takeoff phases. This paper investigates how approach characteristics and takeoff technique affect performance with a view to maximising somersault rotation in tumbling. A five-segment planar simulation model, customised to an elite gymnast, was used to produce a simulation which closely matched a recorded performance of a double layout somersault by the elite gymnast. Three optimisations were carried out to maximise somersault rotation with different sets of initial conditions. Using the same initial linear and angular momentum as the double layout somersault and varying the joint torque activation timings allowed a double straight somersault to be performed with 19% more rotation potential than the actual performance. Increasing the approach velocity to a realistic maximum of 7 ms(-1) resulted in a 42% reduction in rotation potential when the activation timings were unchanged but allowed a triple layout somersault to be performed with an increase of 31% in rotation potential when activation timings were re-optimised. Increasing also the initial angular momentum to a realistic maximum resulted in a 4% reduction in rotation potential when the activation timings were unchanged but allowed a triple straight somersault to be performed with a further increase of 9% in rotation potential when activation timings were re-optimised. It is concluded that the limiting factor to maximising somersault rotation is the ability to generate high linear and angular velocities during the approach phase coupled with the ability to adopt consonant activation timings during the takeoff phase.

Computer Simulation↗

Strategies in preflight for an optimal Yurchenko layout vault.

An optimal Yurchenko layout vault of an elite female gymnast was identified by Koh et al. [2003. A predicted optimal performance of the Yurchenko layout vault in women's artistic gymnastics. Journal of Applied Biomechanics 19, 187-204] to require a combination of an increased body angle at horse contact and increased angular momentum for postflight than was recorded experimentally. However, the individual effect of each of these variables to producing the optimal vault is not known. The purpose of the study was to determine an appropriate strategy to teaching the optimal Yurchenko layout vault. Separate optimisations were carried out to investigate how each of these variables would change in order to produce the optimal vault identified by Koh et al. (2003). A combined optimal parameter selection and optimal control approach was used. The results suggest that when the body angle of attack at horse impact was kept low, pre-flight angular momentum had to be increased, with further gains during horse impact, to produce an optimal vault. This strategy of increasing solely the level of angular momentum needed for optimum postflight may not be attainable realistically. On the other hand, employing a larger body angle of attack required an increase in angular momentum during impact but which was attainable. Both optimisations show that increasing the vertical CM horse takeoff velocity is essential for postflight height and distance. The strategy to enhance performance should thus focus on maintaining an appropriate CM pre-flight velocity, a high level of angular momentum during pre-flight and to contact the horse with a large body angle of attack.

Adult↗

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-humanbody 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%.

Algorithms↗

The effect of falling height on muscle activity and foot motion during landings.

The aims of this study were: (a) to examine the effect of falling height on the kinematics of the tibiotalar, talonavicular and calcaneocuboid joints and (b) to study the influence of falling height on the muscle activity of the leg during landings. Six female gymnasts (height: 1.63 +/- 0.04 m, weight: 58.21 +/- 3.46 kg) participated in this study. All six gymnasts carried out barefoot landings, falling from 1.0, 1.5 and 2.0 m height onto a mat. Three genlocked digital high speed video cameras (250 Hz) captured the motion of the left shank and foot. Surface electromyography (EMG) was used to measure muscle activity (1000 Hz) from five muscles (gastrocnemius medialis, tibialis anterior, peroneus longus, vastus lateralis and hamstrings) of the left leg. The kinematics of the tibiotalar, talonavicular and calcaneocuboid joints were studied. The lower-leg and the foot were modelled by means of a multi-body system, comprising seven rigid bodies. The falling height does not show any influence on the kinematics neither of the tibiotalar nor of the talonavicular joints during landing. The eversion at the calcaneocuboid joint increases with increasing falling height. When augmenting falling height, the myoelectric activity of the muscles of the lower limb increases as well during the pre-activation phase as during the landing itself. The muscles of the lower extremities are capable of stabilizing the tibiotalar and the talonavicular joints actively, restricting their maximal motion by means of a higher activation before and after touchdown. Maximal eversion at the calcaneocuboid joint increases about 52% when landing from 2.0 m.

Biomechanical Phenomena↗

A 7-year study on risks and costs of knee injuries in male and female youth participants in 12 sports.

Knee injuries are common and account in various sports for 15-50% of all sports injuries. The cost of knee injuries is therefore a large part of the cost for medical care of sports injuries. Furthermore, the risk of acquiring a knee injury during sports is considered higher for females than for males. The nationwide organization "Youth and Sports" represents the major source of organized sports and recreation for Swiss youth and engages annually around 370000 participants in the age group of 14 to 20 years. The purpose of this study was to combine data on knee injuries from two sources, the first being data on the exposure to risk found in the activity registration in "Youth and Sports" and the second injuries with their associated costs resulting from the activities and filed at the Swiss Military Insurance. This allowed calculation of knee injury incidences, to compare risks between males and females and to estimate the costs of medical treatment. The study comprises 3864 knee injuries from 12 sports during 7 years. Females were significantly more at risk in six sports: alpinism, downhill skiing, gymnastics, volleyball, basketball and team handball. The incidences of knee injuries and of cruciate ligament injuries in particular, together with the costs per hour of participation, all displayed the same sports as the top five for both females and males: ice hockey, team handball, soccer, downhill skiing and basketball. Female alpinism and gymnastics had also high rankings. Knee injuries comprised 10% of all injuries in males and 13% in females, but their proportional contribution to the costs per hour of participation was 27% and 33%, respectively. From this study it can be concluded that females were significantly more at risk for knee injuries than males in six sports and that knee injuries accounted for a high proportion of the costs of medical treatment.

Adolescent↗

Sports-related spinal cord injury in Japan (from the nationwide spinal cord injury registry between 1990 and 1992).

The Injury Prevention Committee of the Japan Medical Society of Paraplegia (JMSoP) conducted a nationwide epidemiological survey on spinal cord injury (SCI) using postal questionnaires for 3 years periods from 1990 to 1992, and the annual incidence of the spinal cord injury was estimated as 40.2 per million. From this registry, we investigated SCI related to sports activities. In 3 years, 528 patients were registered and 374 of them had neurological deficits. The incidence was 1.95 per million per annum. Mean age at injury was 28.5 years (10-77), and 88.1% of the patients were males. Diving was the commonest cause of SCI (21.6%), which was followed by skiing (13.4%), football including rugby, American football and soccer (12.7%), sky sports (7.0%), judo (6.8%) and gymnastics (6.6%). Mean age at injury was higher than 30 years in skiing (38.6 years) and sky sports (38.2 years). Cervical injury was predominant in all but sky sports and accounted for 83.5% of SCI. Motor complete paralysis was reported in 35.0% of the patients. Bony injury was observed in 55.9% of the patients; most of the patients who sustained the SCI in diving and sky sports had bony injury, and no bony injury was detected in more than a half of the patients who sustained injuries in skiing, judo or gymnastics. Although the percentage of sports-related SCI was small in the present study as compared to the data from previous reports, it is not difficult to imagine the increase in the number of sports-related SCI. We have launched an injury prevention campaign and are planning to conduct a similar study in future to evaluate the effect of the campaign as well as the changes in the incidence and pattern of SCI.

Adolescent↗

Arthroscopic treatment of osteochondritis dissecans of the capitellum: Report of 5 female athletes.

The management of osteochondritis dissecans of the capitellum of the adolescent elbow is still controversial. We report on 5 cases of female high-level athletes aged from 10 to 19 years (4 gymnasts, 1 waterpolo player). All these athletes had a symptomatic osteochondritis dissecans of the capitellum, which was treated arthroscopically in all cases. Follow-up time averaged 5 months (1 to 6.5 months). During the arthroscopy, loose osteochondral fragments of the capitellum and radial head were removed, and the defect was debrided. Thorough evaluation of the anterior and posterior joint including the olecranon fossa was performed. One of the 5 patients had a loose body requiring arthroscopic removal. Within 6 months after surgery, all except 1 elbow, the elbow with a loose body, regained maximum range of motion. Two patients returned to a high level of gymnastics and 1 was considering return. The short-term results of this treatment suggest that arthroscopic debridement of the loose osteochondral fragments provides a good result.

Adolescent↗

Relationship between muscle fiber pennation and force generation capability in Olympic athletes.

The thickness (TBmt) and fiber pennation angle (TBpen) of triceps brachii as well as isokinetic force developed during elbow extension were measured in Olympic athletes to investigate the relationship between muscle fiber pennation and force generation capability. The subjects were male members of the 1996 Japanese Olympic team who competed in seven different events; 9 wrestlers, 16 soccer players, 11 sprinters, 5 judo athletes, 7 gymnasts, 9 rowers and 18 baseball players. The TBmt and TBpen, measured by a B-mode ultrasound, ranged between 29 mm and 50 mm and between 11 degrees and 30 degrees, respectively, and on average were larger in the judo athletes, wrestlers and gymnasts compared to the other groups. A significant correlation (r=0.580, p < 0.05) was found between TPpen and TBmt per unit of the upper arm length, and so the observed event-related differences in TBpen tended to reflect the differences in TBmt. The isokinetic forces relative to the cross-sectional area (CSA) estimated from TBmt, measured at two constant velocities of 1.05 rad/s (F1.05/CSA) and 3.14 rad/s (F3.14/ CSA), were negatively correlated to the CSA; r=-0.617 (p < 0.05) for F1.05/CSA and r=-0.635 (p < 0.05) for F3.14/CSA. In addition, low but significant negative correlations existed between TBpen and both F1.05/CSA (r=-0.365, p < 0.05) and F3.14/ CSA (r=-0.336, p <0.05). Even when the effect of TBpen was statistically normalized, the F1.05/CSA and F3.14/CSA were still negatively correlated to the CSA, r=-0.530 (p < 0.05) for F1.05/ CSA and r=-0.561 (p < 0.05) for F3.14/CSA. Therefore, at least in the Olympic athletes tested in this study, the magnitude of the pennation angles reflects muscle size, but it does not seem to be a factor that explains extensively the lower F/CSA in athletes with large muscle size.

Adult↗

Apolipoprotein and lipid profiles in young female athletes.

The apolipoprotein and lipid profiles were investigated in 22 female gymnasts, 20 girl swimmers, and 12 controls. The average age of all groups was about 12 years, and the girls were matched for sexual development, i.e., breast development stage m = 1 or m = 2. The gymnasts appeared to have the highest level of HDL cholesterol and the highest HDL cholesterol / total cholesterol, HDL cholesterol / LDL cholesterol and HDL cholesterol/apo A-I ratios in comparison to both the swimmers and the control group. The swimmers had the highest level of apo A-I, but a lipid profile similar to that of the controls. It is concluded that in children, as in adults, regular physical activity affects the lipid and apolipoprotein profiles. In addition, it appears that the apolipoproteins discriminate between trained and nontrained subjects as well as (apo B) or better (apo A-I) than the lipid components of the corresponding lipoproteins (LDL cholesterol or HDL cholesterol).

Anthropometry↗

Muscle mass of competitive male athletes.

The recent publication of the first validated equation for the estimation of muscle mass (MM) in men has made possible a comparison of MM in athletes from different sports. Limb girths and skinfold thicknesses were measured in 62 male athletes (aged 17-38 years) and 13 non-athletic males (aged 22-36 years). The MM (g) was calculated from the equation MM = S(0.0553 Gt2 + 0.0987 Gf2 + 0.0331 Gc2)-2445, where S is stature, Gt is the mid-thigh girth corrected for the front thigh skinfold thickness, Gc is the maximum calf girth corrected for the calf skinfold thickness and Gf is the uncorrected maximum forearm girth (all in cm). The athletes were classified as gymnasts (n = 10), basketball players (n = 10), body-builders (n = 10), track and field power athletes (n = 12), track and field long sprinters (n = 10) or distance runners (n = 10). The MM means ranged from 38.4 kg for the distance runners to 58.7 kg for the body-builders. Both body-builders and basketball players had significantly greater MM than gymnasts, long sprinters, non-athletic males and distance runners (P < 0.01). Also, MM was greater in track and field power athletes than in distance runners (P < 0.05). The MM as a percentage of body mass (%MM) ranged from 56.5% in the non-athletic group to 65.1% in the body-builders; body-builders scored higher than basketball players (P < 0.05), distance runners (P < 0.01) and the non-athletic group (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗

Intensity and direction dimensions of competitive state anxiety and relationships with performance.

This study examined relationships between intensity and direction dimensions of competitive state anxiety, and also relationships with beam performance in a sample of female gymnasts. The 48 gymnasts, whose ages ranged from 14 to 16 years, competed in a beam competition and were divided, via the median split technique, into poor performance and good performance groups. All the subjects completed a modified version of the Competitive State Anxiety Inventory-2 (CSAI-2) 10 min prior to performance. This inventory included the original intensity scale plus a direction scale in which subjects rated the degree to which the experienced intensity of each symptom was either facilitative of debilitative to subsequent beam performance. Analyses of variance showed no significant group differences on any of the CSAI-2 sub-component intensity scores, or on somatic anxiety and self-confidence direction scores. However, the good performance group reported their cognitive anxiety intensity as being more facilitating and less debilitating to performance than the poor performance group. Stepwise multiple-regression analyses showed that the only significant predictor of beam performance was self-confidence intensity. These findings support the proposal that sports performers' directional perceptions of their anxiety symptoms may provide further understanding of the competitive state anxiety response, and also emphasize the importance of self-confidence in predicting performance.

Adolescent↗

Specificity of learning and dynamic balance.

Contrary to a strict specificity of learning position, Robertson, Collins, Elliott, and Starkes (1994) have reported that the balance beam performance of expert gymnasts is less affected by the withdrawal of vision than is the performance of novice gymnasts. In this study, we employed a training paradigm in order to exercise complete control over the sensory conditions under which a dynamic balance beam task was acquired. Novice participants were trained either with or without vision to walk across a balance beam as quickly as possible and later tested in the other vision condition. Although participants improved more in the condition in which they trained, practice in one sensory condition did not negatively affect performance in a different sensory circumstance. The finding that vision was still extremely important after 5 days of practice is problematic for models of motor learning that propose a progression with learning from closed-loop to open-loop control.

Adult↗

Role of joint torques generated in an optimised Yurchenko layout vault.

The purpose of the study was to quantify the muscle torques required in the performance of an optimised Yurchenko layout vault based on a five-segment rigid link model and using input data from an elite female gymnast. At impact, the wrist torque trajectory indicated an extension-flexion action while the shoulder was characterised by extension. The approximate 100 Nm (wrist flexor) and 125 Nm (shoulder extensor) respective peak torque magnitudes indicated that the impact action is not passive in nature. The contribution of joint torques to the adjoining segments was apportioned to the relative components namely; centripetal, gravity and net joint torque components. Despite the presence of both large wrist and shoulder joint torques, the net turning effect on the upper limb and hand segments about their centre of mass (CM) was small. The principal role of the upper limb joint torques was therefore to effect the appropriate joint motions and to support the weight of the gymnast. The performance of the optimum vault was primarily the result of the interplay between the centripetal and the net joint torque components at the wrist, hip and shoulder joints. This has implications to the performer in that successful execution of the vault is principally concerned with the ability to create a high angular momentum for horse impact and to then apply an appropriate level of joint torques that will make optimal use of the initial kinetic condition.

Algorithms↗

Biomechanical similarities of progressions for the longswing on high bar.

Based on specificity of training and biomechanical analysis, the aim of this study was to develop a method to rank selected progressions for learning the longswing on high bar. Four members of the Men's National Gymnastics Squad were recorded (50 Hz) performing three series of five longswings and eight progressions. Real world co-ordinates from the digitized data were determined using two-dimensional direct linear transformation. Biomechanical similarity between the functional phases of the longswing and the corresponding phases of the progressions were calculated. The functional phases were described as a hyperextension to flexion of the hip and hyperflexion to extension of the shoulder joints as the gymnast passed underneath the bar. Using a combined score of 'Difference' and movement 'Variability' a 'Specificity score' was calculated for hip and shoulder angular displacements and velocities. An overall score based on the average of the four scores provided a ranked list of progressions based on their similarity to the target skill. The progression that showed the greatest similarity to the biomechanics of the longswing, and was therefore ranked first, was the chalked bar pendulum swing. The least similar progression, and, therefore, eighth ranked, was the chalked bar bent knee longswing. The hip kinematics were found to contribute most to the overall differences because the performance requirements of these progressions emphasize an increase in hip flexion during the ascending phase. The method described provides a means to quantify and rank progressions based on their kinematic similarity to the longswing.

Adult↗

Somatosensory-evoked potentials in athletes.

We measured somatosensory-evoked potentials in athletes to determine whether there were differences in somatosensory pathways related to sports performance or training. Seven sedentary subjects, 10 endurance runners, and seven elite gymnasts of similar height and weight were investigated. Peak latencies and amplitudes were measured of P9, P11, P13/14, N20, P25, and N30 waves, following electrical stimulation of the median nerve at the wrist. Central and peripheral conduction speeds of the sensory pathway were calculated. The subjects also completed a simple reaction test to a visual stimulus. There were no significant differences between the groups in any of the attributes we measured. The was a positive correlation between years of training undergone and the amplitude of N20, a negative correlation between the amplitudes of P11 and P13/14 and the number of hours of training undertaken per week, and a positive correlation between the amplitude of N30 and the simple visual reaction time. We conclude that the gymnasts, runners and sedentary subjects had no differences in somatosensory pathways, as measured using standard clinical procedures for evaluating somatosensory-evoked potentials.

Adult↗

Stress fracture in the world class athlete: a case study.

Stress fracture presents a difficult problem in the high performance, world-class athlete. Competitive demands provide little tolerance for, or agreement with, prolonged periods of rest which are the first line of conservative treatment methods. The use of a specifically programmed, pulsed, low-intensity ultrasound device to shorten the time of healing was investigated in a well-known gymnast with an Olympic deadline. Prior animal, in vitro, and clinical studies had established the safety and effectiveness of this device in fractures. The location of the stress injury was in the mid-tibia which is considered to present the greatest challenge to an early healing result. The low-intensity ultrasound device was prescribed for daily use at home. At 3 wk after the start of low-intensity ultrasound, the stress fracture responded well and the patient was allowed use of tumble track, trampoline, and to do some weight-bearing activities, such as jumping in the pool and loading-type activities. At 4.5 wk, the patient progressed to full workout activities and participated in a trial meet for the Olympics. At 6 wk, the patient's participation in the women's gymnastic team event was a factor in the United States receiving a gold medal.

Adolescent↗

School achievement and school adaptation in children in relation to CNS development as assessed by a complex reaction time measured on school entry--a follow-up.

Schoolchildren aged seven years underwent a complex reaction time (CRT) measurement and were followed up regarding language achievements and performance in gymnastics during the nine years of compulsory school. An analysis was made of the correlation between school results and CRT findings. In grade 3, there were large differences in psychomotor development between children with fast and slow CRT in both sexes. Only minor differences in school achievement were seen between girls in different CRT groups. Among the boys, however, many with a slow CRT were considered handicapped in language development, with dyslexia as the most important problem in addition to poor motoricity. They left compulsory school with poor results in Swedish, their native language, and gymnastics, and with a certificate that may reduce their changes of future studies and employment. The boys in general were inferior to the girls. The slow CRT boys, who were mainly considered to be developmentally delayed, also carried a risk of social maladjustment. It would appear to be important that psychophysical maturity receives attention at school, in addition to emotional and social factors. The school health services have an important responsibility in this respect.

Achievement↗