Tracking of physical fitness components in boys and girls from the second to sixth grades.

The purpose of this study was to examine the tracking of field-assessed fitness components in boys and girls from the second to sixth grades. A total of 857 children (448 boys and 409 girls) from 11 urban schools were tested in grade 2; 565 children (297 boys and 268 girls) were tested again in grade 6. Only subjects who had completed all fitness tests on the two occasions were included in the analysis (n = 319: 203 boys and 116 girls). Fitness tests included a 600-m run, a flying-start sprint, the standing long jump, and a medicine ball throw. Additionally, subjects performed a skill task that involved slalom dribbling of a basketball. Baseline scores in grade 2 were correlated (Spearman Rank Order) with scores attained in grade 6. Boys had significantly (P < 0.05) better scores in all fitness tests compared with girls in both grades. Tracking of fitness components over the 4-year period in both sexes varied between 0.36 and 0.66. Tracking was consistently lower in girls than in boys, perhaps reflecting their earlier maturation.

Iron status of highly active adolescents: evidence of depleted iron stores in gymnasts.

Much attention has focused on the nutrition and hematological profile of female athletes, especially gymnasts. The few studies on iron status of male adolescent athletes found a low incidence of iron deficiency. The present studies investigated the iron status of male and female gymnasts (G) and compared it with athletes of other sports. Subjects were 68 elite athletes (43 M, 25F) ages 12-18, of four sports: gymnasts (11M,12F), swimmers (11M,6F), tennis players (10M,4F), and table tennis players (11M,3F). All lived in the national center for gifted athletes, trained over 25 hr a week, ate in the same dining room, and shared a similar life style. Mean levels of hemoglobin (Hb), red blood cell indexes, serum ferritin, serum iron, and transferrin were measured in venous blood. There was no difference in mean Rb among gymnasts (G) and nongymnasts (NG). However Hb was less than 14g/dL in 45% of MG vs. only 25% in NG, and less than 13g/dL in 25% of premenarcheal FG vs. 15% in NG. Low transferrin saturation (<20%) was detected in 18% of MG and 25% of FG vs. 6% and 8% in male and female NG, respectively (p<.05). The percentage of males suffering from low ferritin level (<20 ng/ml) was twice as high in G (36%) vs. NG(19%), and about 30% in all females. In summary, iron stores were consistently lower in MG vs. NG. Adolescent athletes of both genders, G in particular, are prone to nonanemic iron deficiency, which might compromise their health and athletic performance.

Use of the heart rate monitor to modulate physical activity in adolescents with congenital aortic stenosis: an innovative approach.

The task of setting exercise limitations on children with aortic stenosis is fraught with difficulties. In particular, teenagers are difficult to manage because of the increasingly professional demands of adolescents sports; the rapid changes in somatic growth, which are often accompanied by an increase in the severity of aortic valve disease; and the natural tendency of teenagers to disregard advice from authoritarian sources like a medical team. This article describes our innovative approach of using a heart-rate monitor as a means of modulating physical activity in adolescents with mild to moderate aortic stenosis. This approach enabled the setting of clear, precise, observable, measureable limits on physical activity, and self-controling of an acceptable level of physical activity. This created a different negotiation between the patient, his parents, and the medical team, and eased the concern and anxiety of the mothers.

Physiological and cognitive responses to cold exposure in 11-12-year-old boys.

This study investigated the effects of cold and exercise in the cold on the physiological and cognitive responses of 11-12-year-old boys. Children were dressed in sweat suits and exposed to cold (CD, 7°C), cool (CL, 13°C), and neutral (N, 22°C) environments for 110 minutes, with 10 minutes of light exercise (1 watt · kg body wt-1 ) midway through the exposure. A 30-minute "recovery" in neutral conditions followed each session. Session order was randomized. Rectal temperature (Tre) decreased significantly more in CD compared to CL and N, and continued to decrease during the recovery period. Chest skin temperature (Tch) was significantly different between conditions and remained stable even in CD, despite the decrease in Tre. Tch returned to prechamber values during the recovery period. Hand temperature (Th) decreased during CL and CL, and remained significantly lower than prechamber values following the recovery. Exercise heart rate was lower in the CD and CL(115 ± 13 and 119 ± 20 beats · min-1 ) compared to N (130 ± 17 beats · min-1 ). No differences were observed in oxygen consumption between sessions. No differences were also observed between sessions in cognitive performance on language and math tests. It was concluded that while the study conditions did not appear to affect cognitive capacity in boys, they proved sufficient to disturb core temperature. This disturbance was not corrected 30 minutes following cold exposure. Am. J. Hum. Biol. 9:39-49 © 1997 Wiley-Liss, Inc.