Effect of exercise training on energy expenditure, muscle volume, and maximal oxygen uptake in female adolescents.

OBJECTIVES: American female adolescents are at high risk of a physically inactive lifestyle that likely leads to health problems later in life. We hypothesized that a brief program of endurance exercise training in female adolescents would result in increased energy expenditure and quantifiable structural and functional adaptations. STUDY DESIGN: Forty-four high school girls (aged 15 to 17 years, none were elite athletes) enrolled in a 5-day per week anatomy class for 5 weeks and were randomly assigned to control (n = 22) and training groups. All subjects participated in a 2-hour daily teaching program. During the remaining time (2 hours), the training group members underwent endurance-type training and control group subjects participated in a computer workshop. The intervention was assessed by (1) comparison of total energy expenditure between groups with the doubly labeled water technique, (2) determination of changes in thigh muscle volume by magnetic resonance imaging, and (3) determination of changes in maximal oxygen uptake by use of respiratory gas exchange responses. RESULTS: Total energy expenditure was significantly greater (15.3%) in the training group compared with the control subjects (p < 0.003). Five weeks of training led to a 4.3% +/- 1% increase in thigh muscle volume (p < 0.0002) and a 12.1% +/- 3.7% increase in maximal oxygen uptake (p < 0.004); there were no changes in the control group. The training effect was most pronounced in the least fit subjects. CONCLUSIONS: Exercise training programs for female adolescents can be successfully integrated into a high school summer curriculum. Quantifiable, substantial structural and functional responses occur with relatively short periods of training. Approximately 60% of the training response was related to factors independent of muscle size per se. These data may serve to better design physical activity programs for female adolescents.

Are obese children truly unfit? Minimizing the confounding effect of body size on the exercise response.

To test the hypothesis that obese children are unfit (i.e., have abnormal responses to exercise testing consistent with reduced levels of habitual physical activity), we used new analytic strategies in studies of 18 obese children performing cycle ergometry. The subject's weight (mean +/- SD) was 168 +/- 24% that predicted by height, and the age range was 9 to 17 years. Size-independent measures of exercise (e.g., the ratio of oxygen uptake (VO2) to work rate during progressive exercise and the temporal response of VO2, carbon dioxide output (VCO2), and minute ventilation (VE) at the onset of exercise) were used. The ability to perform external mechanical work was corrected for VO2 at unloaded pedaling (change in maximum oxygen uptake (delta VO2max) and in anaerobic threshold (delta AT). On average, obese children's responses were in the normal range: delta VO2max, 104 +/- 41% (+/- SD) predicted (by age); delta AT, 85 +/- 51%; ratio of change in VE to change in VCO2, 111 +/- 21% and ratio of change in VO2 to change in work rate, 100 +/- 24%, but six of the obese children had values of delta VO2max or delta AT that were more than 2 SD below normal. In addition, obese children did not have increased delta VO2max or delta AT with age as observed in nonobese children. Although the response time of VO2 was normal (99 +/- 32% of predicted), those for both VCO2 and VE were prolonged. We conclude that the finding of obesity in a child is not a reliable indicator of poor fitness but that testing cardiorespiratory responses to exercise can be used to identify subjects with serious impairment and to individualize therapy.

Avaliacao da obstrucao aorto-iliaca pelo Doppler ultra-som. / Evaluation of the aorto-iliac obstruction by Doppler ultrasound

Apos breves comentarios sobre a patologia oclusiva aorto-iliaca, os autores descrevem a utilizacao do Doppler ultra-som como metodo mais adequado ao estudo nao invasivo da obstrucao aorto-iliaca, ressaltando ainda seu valor na interpretacao das alteracoes hemodinamicas das lesoes anatomicas encontradas no estudo angiografico. Valorizam a associacao de varios parametros obtidos com o uso do Doppler ultra-som no estudo deste segmento arterial, descrevendo e comentando aqueles que consideram de maior importancia, apresentando casos clinicos ilustrativos