Wolfram Müller

Current status of body composition assessment in sport: review and position statement on behalf of the ad hoc research working group on body composition health and performance, under the auspices of the I.O.C. Medical Commission.

Quantifying human body composition has played an important role in monitoring all athlete performance and training regimens, but especially so in gravitational, weight class and aesthetic sports wherein the tissue composition of the body profoundly affects performance or adjudication. Over the past century, a myriad of techniques and equations have been proposed, but all have some inherent problems, whether in measurement methodology or in the assumptions they make. To date, there is no universally applicable criterion or ‘gold standard’ methodology for body composition assessment. Having considered issues of accuracy, repeatability and utility, the multi-component model might be employed as a performance or selection criterion, provided the selected model accounts for variability in the density of fat-free mass in its computation. However, when profiling change in interventions, single methods whose raw data are surrogates for body composition (with the notable exception of the body mass index) remain useful.

How to minimise the health risks to athletes who compete in weight-sensitive sports review and position statement on behalf of the Ad Hoc Research Working Group on Body Composition, Health and Performance, under the auspices of the IOC Medical Commission

A focus on low body weight and body fat content, combined with regulations in some weight-sensitive sports, are considered risk factors for extreme dieting, eating disorders (EDs) and related health consequences among athletes. At present there are, from a health perspective, no generally accepted optimum values for body weight or percentage of fat mass in different sports and there is no ‘gold standard’ method for body composition assessment in athletes. On the basis of health considerations as well as performance, medical support teams should know how to approach elite athletes who seek to achieve an unrealistic body composition and how to prevent restrictive eating practices from developing into an ED. In addition, these teams must know when to raise the alarm and how to advice athletes who are affected by extreme dieting or clinical EDs. However, there is no consensus on when athletes struggling with extreme dieting or EDs should be referred for specialist medical treatment or removed from competition. Based on the present review, we conclude that there is a need for (1) sport-specific and gender-specific preventive programmes, (2) criteria for raising alarm and ‘does not start’ (DNS) for athletes with EDs and (3) modifications to the regulations in some sports. Further, the key areas for research identified include the development of standard methods for body composition assessment in elite athletes; screening measures for EDs among athletes; development and testing of prevention programmes; investigating the short and long-term effects of extreme dieting; and EDs on health and performance.

Determinants of ski-jump performance and implications for health, safety and fairness.

Ski jumping puts high demands on the athlete’s ability to control posture and movement. The athlete has to solve extremely difficult optimization problems. These implicit decisions and the resulting control manoeuvres can be understood by means of computer simulations. Computer simulations based on wind tunnel input data can identify the determinants for high performance and answer many questions of training methods, safety and health, role of weight, fairness, optimized hill design, sport development, and changes to the regulations.Each of the performance determinants has to be seen in the context of all others in order to understand its importance; the predominant factors are: high in-run velocity, high momentum perpendicular to the ramp at take-off due to the jump and the lift force, accurate timing of the take-off with respect to the ramp edge, appropriate angular momentum at take-off in order to obtain an aerodynamically advantageous and stable flight position as soon as possible, choice of advantageous body and equipment configurations during the entire flight in order to obtain optimum lift and drag values, and the ability to control the flight stability.Wind blowing up the hill increases the jump length dramatically and decreases the landing velocity, which eases the landing, and vice versa for wind from behind. Improvements to reduce unfairness due to changing wind are urgently needed. The current practice of the judges to reduce the score when the athlete has to perform body movements in order to counteract dangerous gusts is irrational. The athletes should rather be rewarded and not punished for their ability to handle such dangerous situations.For the quantification of underweight it is suggested to use the mass index: MI = 0.28m/s2 (where m is the jumper mass and s is the sitting height), which indirectly considers the individual leg length. The MI formula is similar to the body mass index (BMI) formula: the height is replaced by the sitting height s and a factor of 0.28 effects that the MI is equal to the BMI for persons with average leg length. The classification of underweight is not only a question of the cut-off point, as much it is a question of the measure for relative bodyweight used.Low weight is one of the performance determinants; however, it should be considered that very low weight can cause severe performance setbacks due to decreased jumping force, general weakness, reduced ability to cope with pressure, and increased susceptibility for diseases. In the past, several cases of anorexia nervosa among ski jumpers had come to light. The development toward extremely low weight was stopped in 2004 by new Fédération Internationale de Ski ski-jumping regulations, which relate relative body mass to maximum ski length. The 2006/7 and 2008/9 seasons showed that light athletes who had to use skis with just 142% of their height could still win competitions. A further increase of the borderline weight is being discussed. The current regulations are based on the well known BMI; the use of the MI instead of the BMI should be explored in future studies.

Dynamics of human flight on skis: improvements in safety and fairness in ski jumping

This study of ski jumping includes three areas of research: Wind tunnel measurements with world class athletes in various flight positions, field measurements during the World Championships in Ski Flying 1994 in Planica (Slovenia) and a highly reliable mapping of ski jumping to a computable simulation model. The results explain the effects of equipment, flight style changes, the reason for the enhanced tumbling risk and high gust sensitivity observed. Consequences can be drawn for changes to the FIS regulations, the design of jumping hills and training methods. The internationally induced anorexia of the athletes could be prohibited by a new ski length regulation. Women jumpers could become a real competitive threat.

Body composition for health and performance: a survey of body composition assessment practice carried out by the Ad Hoc Research Working Group on Body Composition, Health and Performance under the auspices of the IOC Medical Commission

Background Successful performers in weight-sensitive sports are characterised by low body mass (BM) and fat content. This often requires chronic energy restriction and acute weight loss practices. Aim To evaluate current use of body composition (BC) assessment methods and identify problems and solutions with current BC approaches. Methods A 40-item survey was developed, including demographic and content questions related to BC assessment. The survey was electronically distributed among international sporting organisations. Frequencies and χ2 analyses were computed. Results 216 responses were received, from 33 countries, representing various institutions, sports and competitive levels. Of the sample, 86% of respondents currently assess BC, most frequently using skinfolds (International Society for the Advancement of Kinanthropometry (ISAK): 50%; non-ISAK, conventional: 40%; both: 28%), dual energy X-ray absorptiometry (38%), bioelectrical impedance (29%), air displacement plethysmography (17%) and hydrostatic weighing (10%). Of those using skinfolds, more at the international level used ISAK, whereas conventional approaches were more reported at regional/national level (p=0.006). The sport dietitian/nutritionist (57%) and physiologist/sports scientist (54%) were most frequently the professionals assessing BC, followed by MDs and athletic trainers, with some reporting coaches (5%). 36% of 116 respondents assessed hydration status and more (64%) did so at international than regional/national level (36%, p=0.028). Of 125 participants answering the question of whether they thought that BC assessment raised problems, 69% said ‘yes’, with most providing ideas for solutions. Conclusions Results show high use of BC assessment but also a lack of standardisation and widespread perception of problems related to BM and BC in sport. Future work should emphasise standardisation with appropriate training opportunities and more research on BC and performance.

Body composition in sport: a comparison of a novel ultrasound imaging technique to measure subcutaneous fat tissue compared with skinfold measurement

Background Extremely low weight and rapid changes in weight and body composition have become major concerns in many sports, but sufficiently accurate field methods for body composition assessment in athletes are missing. This study aimed to explore the use of ultrasound methods for assessment of body fat content in athletes. Methods 19 female athletes (stature: 1.67(±0.06) m, weight: 59.6(±7.6) kg; age: 19.5(±3.3) years) were investigated by three observers using a novel ultrasound method for thickness measurement of uncompressed subcutaneous adipose tissue and of embedded structures. Two observers also measured skinfold thickness at eight International Society for the Advancement of Kinanthrometry (ISAK) sites; mean skinfold values were compared to mean subcutaneous adipose tissue thicknesses measured by ultrasound. Interobserver reliability of imaging and evaluation obtained by this ultrasound technique: intraclass correlation coefficient ICC=0.968 (95% CI 0.957 to 0.977); evaluation of given images: ICC=0.997 (0.993 to 0.999). Results Skinfold compared to ultrasound thickness showed that compressibility of subcutaneous adipose tissue depends largely on the site and the person: regression slopes ranged from 0.61 (biceps) to 1.59 (thigh) and CIs were large. Limits of agreement ranged from 2.6 to 8.6 mm. Regression lines did not intercept the skinfold axis at zero because of the skin thickness being included in the skinfold. The four ISAK trunk sites caused ultrasound imaging problems in 13 of 152 sites (8 ISAK sites, 19 athletes). Conclusions The ultrasound method allows measurement of uncompressed subcutaneous adipose tissue thickness with an accuracy of 0.1–0.5 mm, depending on the probe frequency. Compressibility of the skinfold depends on the anatomical site, and skin thickness varies by a factor of two. This inevitably limits the skinfold methods for body fat estimation. Ultrasound accuracy for subcutaneous adipose tissue measurement is limited by the plasticity of fat and furrowed tissue borders. Comparative US measurements show that skinfold measurements do not allow accurate assessment of subcutaneous adipose tissue thickness.

Body composition in sport: interobserver reliability of a novel ultrasound measure of subcutaneous fat tissue

Background Very low body mass, extreme mass changes, and extremely low per cent body fat are becoming increasingly common in many sports, but sufficiently reliable and accurate field methods for body composition assessment in athletes are missing. Methods Nineteen female athletes were investigated (mean (SD) age: 19.5 (±3.3) years; body mass: 59.6 (±7.6) kg; height: 1.674 (±0.056) m; BMI: 21.3 (±2.3) kg/m2). Three observers applied diagnostic B-mode-ultrasound (US) combined with the evaluation software for subcutaneous adipose tissue measurements at eight ISAK sites (International Society for the Advancement of Kinanthrometry). Regression and reliability analyses are presented. Results US measurements and evaluation of subcutaneous adipose tissue (SAT) thicknesses (including fibrous structures: Dincluded; n=378) resulted in an SE of estimate SEE=0.60 mm, R2=0.98 (p<0.001), limit of agreement LOA=1.18, ICC=0.968 (0.957–0.977). Similar values were found for Dexcluded: SEE=0.68 mm, R2=0.97 (p<0.001). Dincluded at individual ISAK sites: at biceps, R2=0.87 and intraclass-correlation coefficient ICC=0.811 were lowest and SEE=0.79 mm was highest. Values at all other sites ranged from R2: 0.94–0.99, SEE: 0.42–0.65 mm, and ICC: 0.917–0.985. Interobserver coefficients ranged from 0.92 to 0.99, except for biceps (0.74, 0.83 and 0.87). Evaluations of 20 randomly selected US images by three observers (Dincluded) resulted in: SEE=0.15 mm, R2=0.998(p<0.001), ICC=0.997 (0.993, 0999). Conclusions Subject to optimal choice of sites and certain standardisations, US can offer a highly reliable field method for measurement of uncompressed thickness of the SAT. High accuracy and high reliability of measurement, as obtained with this US approach, are essential for protection of the athlete’s health and also for optimising performance.

Subcutaneous fat patterning in athletes: selection of appropriate sites and standardisation of a novel ultrasound measurement technique: ad hoc working group on body composition, health and performance, under the auspices of the IOC Medical Commission

Background Precise and accurate field methods for body composition analyses in athletes are needed urgently. Aim Standardisation of a novel ultrasound (US) technique for accurate and reliable measurement of subcutaneous adipose tissue (SAT). Methods Three observers captured US images of uncompressed SAT in 12 athletes and applied a semiautomatic evaluation algorithm for multiple SAT measurements. Results Eight new sites are recommended: upper abdomen, lower abdomen, erector spinae, distal triceps, brachioradialis, lateral thigh, front thigh, medial calf. Obtainable accuracy was 0.2 mm (18 MHz probe; speed of sound: 1450 m/s). Reliability of SAT thickness sums (N=36): R2=0.998, SEE=0.55 mm, ICC (95% CI) 0.998 (0.994 to 0.999); observer differences from their mean: 95% of the SAT thickness sums were within ±1 mm (sums of SAT thicknesses ranged from 10 to 50 mm). Embedded fibrous tissues were also measured. Conclusions A minimum of eight sites is suggested to accommodate inter-individual differences in SAT patterning. All sites overlie muscle with a clearly visible fascia, which eases the acquisition of clear images and the marking of these sites takes only a few minutes. This US method reaches the fundamental accuracy and precision limits for SAT measurements given by tissue plasticity and furrowed borders, provided the measurers are trained appropriately.

The need for a novel approach to measure body composition: is ultrasound an answer?

Body composition is an important determinant of health and performance. In ‘weight-sensitive sports’, among which are aesthetic sports, weight class sports and gravitational sports (in which body weight influences performance), many athletes use extreme methods to reduce weight rapidly or maintain a low body weight in order to gain a competitive advantage. As a consequence, athletes with very low bodyweight, extreme weight changes due to dehydration or eating disorders, extremely low body fat content, or insufficient bone mineral density are encountered with increasing frequency in many sports.1–5 In weight-sensitive sports, low bodyweight should be seen as only one possible performance factor among others. A deliberately induced underweight condition or short-term weight reduction may lead to severe medical problems, and loss of tissue can cause disastrous performance setbacks due to decreased muscle strength, general weakness, increased susceptibility to illness and reduced ability to cope with pressure: in extreme cases, athletes may develop a clinical eating disorder which is accompanied by severe mental and physical effects that may prove fatal.1 ,6 ,7 The health of the athlete is a precondition for optimum performance. Adipose tissue functions as an endocrine organ and is important in terms of health; it is not just ‘ballast’, as might be …

Dynamic force measurements for a high bar using 3D motion capturing.

The displacement of a calibrated horizontal bar is used as a measure for forces acting on the bar itself during dynamic performances in artistic gymnastics. The high bar is loaded with known forces and the displacement is monitored by means of a Vicon motion capturing system. The calibration results are fitted according to the Euler-Bernoulli beam theory. After calibration, forces can straightforwardly be measured by multiplication of the bar displacement with the determined fit parameter. This approach is also able to account for non-central force application (two hands on the bar) and the effect of the bars inertia. Uncertainties in measured forces are assessed to be +/-25 N plus an additional 1% for the unknown weight distribution between the two hands.