During growth and maturation, the study of very brief high-intensity exercise has not received the same attention from researchers as, for instance, aerobic function. In anaerobic tasks or sports events such as sprint cycling, jumping or running, the children's performance is distinctly lower than that of adults. This partly reflects children's lesser ability to generate mechanical energy from chemical energy sources during short-term intensive activity. For many years, various attempts have been made to quantify the anaerobic energy yield in maximal-intensity exercise, but many assumptions have had to be made with respect to mechanical efficiency, lactate turnover, dilution space for lactate, and so on. During childhood and adolescence, direct measurements of the rate or capacity of anaerobic pathways for energy turnover presents several ethical and methodological difficulties. Thus, rather than measure energy supply, paediatric exercise scientists have concentrated on measuring short-term muscle power (STMP) by means of standardised tests. Previously, investigators have used various protocols such as short-term cycling power tests, vertical jump tests or running tests. Cycling ergometer tests are the most common. There is, however, no ideal test, and so it is important to acknowledge the limitations of each test. Progress has been made in assessing instantaneous cycling STMP from a single exercise bout. Several investigators have reported STMP increases with age and have suggested that late pubertal period may accentuate anaerobic glycolysis. Mass-related STMP was shown to increase dramatically during childhood and adolescence, whereas the corresponding increase in peak blood lactate was considerably lower. The latter results support the hypothesis that the difference observed between children and adolescents during STMP testing is more related to neuromuscular factors, hormonal factors and improved motor coordination, rather than being an indicator of reduced lactate-producing glycolysis mechanism. Evidence suggesting a causal link between the ability to generate lactate during exercise and sexual maturation is weak. Despite the majority of research being focused on short-term power output, the study of anaerobic function warrants more investigation. Spectacular progress is being made at the moment in the development of molecular biology tools that can be used in, for example, the genetic dissection of human performance phenotypes. Noninvasive power tools like magnetic resonance imaging and magnetic resonance spectroscopy are presently used to determine possible differences in phosphorus compounds between fast and slow fibre types. Undoubtedly these tools will lead to more information in the near future regarding STMP capabilities of the growing child.

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Our results provide the basis for a detailed prospective evaluation of autoimmunity and inflammation in the context of PIDs, with a view to accurately assessing these risks and describing the possible effect of medical intervention.

Few studies have investigated the impact of school-based physical activity interventions on anthropometric characteristics concomitantly with aerobic and anaerobic capacities in young children. The present study aimed to assess the effect of a 6-month physical activity program on body composition and physical fitness among primary schoolchildren. Four hundred fifty-seven children aged 6 to 10 years were randomly assigned to the intervention group (229 children) or observational group (228 children). Participants' height and weight were assessed, and obesity was determined using French reference curves for BMI. The sum of the four skinfolds and fat-free mass were determined. Ground tests were used to assess aerobic (20-m shuttle run test) and anaerobic (cycling peak power) fitness before and after a 6-month physical activity intervention. The anthropometric modifications obtained over the 6 months cannot be attributed to the intervention as the ANOVA revealed no group effect (intervention vs. group). However, anaerobic and aerobic fitness were significantly improved, thanks to the program in both lean and obese children. A 6-month school-based physical activity intervention in 6- to 10-year-old children did not yield positive anthropometric improvements, but appears effective in terms of aerobic and anaerobic physical fitness. Two physical activity sessions per week in addition to standard physical education classes in primary schoolchildren bring effective results for the prevention of childhood obesity.

Evans syndrome (ES) is a rare severe autoimmune disorder characterized by the combination of autoimmune hemolytic anemia and immune thrombocytopenia. In most cases, the underlying cause is unknown. We sought to identify genetic defects in pediatric ES (pES), based on a hypothesis of strong genetic determinism. In a national, prospective cohort of 203 patients with early-onset ES (median [range] age at last follow-up: 16.3 years ([1.2-41.0 years]) initiated in 2004, 80 nonselected consecutive individuals underwent genetic testing. The clinical data were analyzed as a function of the genetic findings. Fifty-two patients (65%) received a genetic diagnosis (the M+ group): 49 carried germline mutations and 3 carried somatic variants. Thirty-two (40%) had pathogenic mutations in 1 of 9 genes known to be involved in primary immunodeficiencies (TNFRSF6, CTLA4, STAT3, PIK3CD, CBL, ADAR1, LRBA, RAG1, and KRAS), whereas 20 patients (25%) carried probable pathogenic variants in 16 genes that had not previously been reported in the context of autoimmune disease. Lastly, no genetic abnormalities were found in the remaining 28 patients (35%, the M− group). The M+ group displayed more severe disease than the M− group, with a greater frequency of additional immunopathologic manifestations and a greater median number of lines of treatment. Six patients (all from the M+ group) died during the study. In conclusion, pES was potentially genetically determined in at least 65% of cases. Systematic, wide-ranging genetic screening should be offered in pES; the genetic findings have prognostic significance and may guide the choice of a targeted treatment.