because observed behavior is the result of interactions between environmental factors and genes during the extended period of development. Therefore, to better understand expert and exceptional performance, we must require that the account specify the different environmental factors that could selectively promote and facilitate the achievement of such performance. In addition, recent research on expert performance and expertise (Chi, Glaser, & Farr, 1988; Ericsson & Smith, 1991a) has shown that important characteristics of experts' superior performance are acquired through experience and that the effect of practice on performance is larger than earlier believed possible. For this reason, an account of exceptional performance must specify the environmental circumstances, such as the duration and structure of activities, and necessary minimal biological attributes that lead to the acquisition of such characteristics and a corresponding level of performance. An account that explains how a majority of individuals can attain a given level of expert performance might seem inherently unable to explain the exceptional performance of only a small number of individuals. However, if such an empirical account could be empirically supported, then the extreme characteristics of experts could be viewed as having been acquired through learning and adaptation, and studies of expert performance could provide unique insights into the possibilities and limits of change in cognitive capacities and bodily functions. In this article we propose a theoretical framework that explains expert performance in terms of acquired characteristics resulting from extended deliberate practice and that limits the role of innate (inherited) characteristics to general levels of activity and emotionality. We provide empirical support from two new studies and from already published evidence on expert performance in many different domains.

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The role of deliberate practice in the acquisition of expert performance.

To revise 1998 recommendations on childhood obesity, an Expert Committee, comprised of representatives from 15 professional organizations, appointed experienced scientists and clinicians to 3 writing groups to review the literature and recommend approaches to prevention, assessment, and treatment. Because effective strategies remain poorly defined, the writing groups used both available evidence and expert opinion to develop the recommendations. Primary care providers should universally assess children for obesity risk to improve early identification of elevated BMI, medical risks, and unhealthy eating and physical activity habits. Providers can provide obesity prevention messages for most children and suggest weight control interventions for those with excess weight. The writing groups also recommend changing office systems so that they support efforts to address the problem. BMI should be calculated and plotted at least annually, and the classification should be integrated with other information such as growth pattern, familial obesity, and medical risks to assess the child’s obesity risk. For prevention, the recommendations include both specific eating and physical activity behaviors, which are likely to promote maintenance of healthy weight, but also the use of patient-centered counseling techniques such as motivational interviewing, which helps families identify their own motivation for making change. For assessment, the recommendations include methods to screen for current medical conditions and for future risks, and methods to assess diet and physical activity behaviors. For treatment, the recommendations propose 4 stages of obesity care; the first is brief counseling that can be delivered in a health care office, and subsequent stages require more time and resources. The appropriateness of higher stages is influenced by a patient’s age and degree of excess weight. These recommendations recognize the importance of social and environmental change to reduce the obesity epidemic but also identify ways healthcare providers and health care systems can be part of broader efforts.

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Expert Committee Recommendations Regarding the Prevention, Assessment, and Treatment of Child and Adolescent Overweight and Obesity: Summary Report

Purpose: The range of variability between individuals of the same chronological age (CA) in somatic and biological maturity is large and especially accentuated around the adolescent growth spurt. Maturity assessment is an important consideration when dealing with adolescents, from both a research perspective and youth sports stratification. A noninvasive, practical method predicting years from peak height velocity (a maturity offset value) by using anthropometric variables is developed in one sample and cross-validated in two different samples. Methods: Gender specific multiple regression equations were calculated on a sample of 152 Canadian children aged 8-16 yr (79 boys; 73 girls) who were followed through adolescence from 1991 to 1997, The equations included three somatic dimensions (height, sitting height, and leg length), CA, and their interactions. The equations were cross-validated on a Combined sample of Canadian (71 boys, 40 girls measured from 1964 through 1973) and Flemish children (50 boys, 48 girls measured from 1985 through 1999). Results: The coefficient of determination (R2) for the boys' model was 0.92 and for the girls' model 0.91 the SEEs were 0.49 and 0.50, respectively, Mean difference between actual and predicted maturity offset for the verification samples was 0.24 (SD 0.65) yr in boys and 0,001 (SD 0.68) yr in girls. Conclusion: Although the cross-validation meets statistical standards or acceptance, caution 1, warranted with regard to implementation. It is recommended that maturity offset be considered as a categorical rather than a continuous assessment. Nevertheless, the equations presented are a reliable, noninvasive and a practical solution for the measure of biological maturity for matching adolescent athletes.

An assessment of maturity from anthropometric measurements.

OBJECTIVE: To study the relationship between percent body fat and body mass index (BMI) in different ethnic groups and to evaluate the validity of the BMI cut-off points for obesity. DESIGN: Meta analysis of literature data. SUBJECTS: Populations of American Blacks, Caucasians, Chinese, Ethiopians, Indonesians, Polynesians and Thais. MEASUREMENTS: Mean values of BMI, percent body fat, gender and age were adapted from original papers. RESULTS: The relationship between percent body fat and BMI differs in the ethnic groups studied. For the same level of body fat, age and gender, American Blacks have a 1.3 kg/m2 and Polynesians a 4.5 kg/m2 lower BMI compared to Caucasians. By contrast, in Chinese, Ethiopians, Indonesians and Thais BMIs are 1.9, 4.6, 3.2 and 2.9 kg/m2 lower compared to Caucasians, respectively. Slight differences in the relationship between percent body fat and BMI of American Caucasians and European Caucasians were also found. The differences found in the body fat/BMI relationship in different ethnic groups could be due to differences in energy balance as well as to differences in body build. CONCLUSIONS: The results show that the relationship between percent body fat and BMI is different among different ethnic groups. This should have public health implications for the definitions of BMI cut-off points for obesity, which would need to be population-specific.

Body mass index and percent body fat: a meta analysis among different ethnic groups.

The Wingate anaerobic test. An update on methodology, reliability and validity.

Introducing the Basics of Growth, Maturation, and Performance Age- and Sex-Associated Variation in Growth Age- and Sex-Associated Variation in Performance Biological Maturation Regulatory and Influencing Factors The Child in Physical Activity and Sport: Applications

Growth, Maturation, and Physical Activity

Reviewing the most widely used anaerobic test around the world - the Wingate anaerobic test - this text explains the methodological considerations, typical findings, and various applications of the test The text includes an introduction to the test and perspectives on how it compares with the other tests of anaerobic power; decribes the proper protocol, necessary equipment, obtainable measures, standardization process, and safety considerations during the test; summarizes research on the reliability, validity and sensitivity of the test; discusses factors to control or consider while performing the test; gives typical values of performance found with variuos groups of subjects; and provides suggestions for future research in anaerobic testing

The Wingate Anaerobic Test

Pediatric Sports Medicine for the Practitioner

The purpose of the present study was to define the optimal loads (OL) for eliciting maximal power-outputs (PO) in the leg and arm modes of the 30s Wingate Anaerobic Test (WAnT). Eighteen female and seventeen male physical education students, respectively 20.6 +/- 1.6 and 24.1 +/- 2.5 years old, volunteered to participate. In each of the total five sessions, the test was administered twice on a convertible, mechanically braked cycle-ergometer, once for the legs and once for the arms. The five randomized, evenly-spaced resistance loads ranged from 2.43 to 5.39 Joule per pedal revolution per kg body weight (B. W.) for the legs, and from 1.96 to 3.92 for the arms. The measured variables were mean (MP x kg-1) and peak PO as well as absolute and relative measures of fatigue. A parabola-fitting technique was employed to define the optimal loads from the MP x kg-1 data. The resulting OL were 5.04 and 5.13 Joule x Rev-1 x kg B.W.-1 in the leg and 2.82 and 3.52 in the arm tests for the women and men, respectively. OL were shown to depend on PO magnitude. However, within a two-load span (0.98 Joule x Rev-1 x kg B.W.-1) about the OL, MP x kg-1 did not vary by more than 1.4% in the leg and 2.2% in the arm tests. It is suggested that although the WAnT is rather insensitive to moderate variation in load assignment, improved results could be obtained by using the stated OL as guidelines that may be modified according to individual body build, composition, and, particularly, anaerobic fitness level.

Oded Bar-Or

Papers

Growth, Maturation, and Physical Activity

The Wingate anaerobic test. An update on methodology, reliability and validity.

The Wingate Anaerobic Test

Pediatric Sports Medicine for the Practitioner

Load optimization for the wingate anaerobic test