The impact of different types of physical activity on total and regional bone mineral density in young Brazilian athletes

Bone turnover is affected by exercise throughout the lifespan, especially during childhood and adolescence. The objective of this study was to investigate the impact of different sports on total and regional bone mineral density in male Brazilian adolescent athletes. Forty-six adolescents aged 10-18 years participated in the study: 12 swimmers, 10 tennis players, 10 soccer players, and 14 sedentary individuals. The athletes had engaged in physical activities for more than 10 h per week in the previous 6 months. Bone mineral density of the lumbar spine (L1-L4), left proximal femur region, and whole body was evaluated by dual-energy X-ray absorptiometry. Results showed higher mean values in the proximal femur region of tennis and soccer players (1.02 ± 0.18; 0.96 ± 0.16, respectively) than swimmers and controls (0.91 ± 0.14 and 0.87 ± 0.06, respectively) (P < 0.05). In relation to the impact of sporting activities based on bone age determination, we observed significant differences in bone mineral density at all evaluated sites at the end of puberty (16-18 years) compared with 10-12 years, with increases of 78% in the lumbar spine, 47% in the proximal femur, and 38% in the whole body.     

Effect of Students' After-School Activities on Teachers' Academic Expectancies

Teacher expectancies can have an impact on students' academic achievement. These expectancies can be based on diverse student characteristics, only one of which is past academic performance. The present study investigated three student individual differences that teachers may use when forming academic expectancies: the sex of the student, the family socioeconomic status (SES) of the student, and the student's after-school activities. Results indicated teachers held higher grade, graduation, and college attendance expectancies for females than for males and for middle-SES than low-SES students. Also, students who participated in extracurricular activities were expected to achieve more academically than either students who were employed after school or who did nothing after school. The latter two groups did not elicit different teacher expectancies. Interactions revealed that (a) lowest expectations were held for low-SES males who did nothing after school and (b) the difference in graduation expectancies between the SES groups was only half as great for students who took part in extracurricular activities than it was for students who had no involvements after school or who had jobs. Copyright 2000 Academic Press.