Resistance training and bone mineral density in adolescent females.

OBJECTIVE: To examine the effects of 15 months of resistance training on bone mineral density (BMD) in female adolescents (aged 14 to 17 years). STUDY DESIGN: Participants were randomly assigned to either a training (n = 46) or control group (n = 21). BMD and body composition were measured by using dual-energy x-ray absorptiometry. Strength was assessed by means of one-repetition maximums for the leg press and bench press. The exercise group trained 30 to 45 minutes a day, 3 days per week, using 15 different resistance exercises. Control participants remained sedentary (<2 hours of exercise per week). RESULTS: Leg strength increased significantly (40%) in the exercise group, but there were no changes in the control group. Femoral neck BMD increased significantly in the training group (1.035 to 1.073 g/cm(2), P <.01) but not in the control group (1.034 to 1.048 g/cm(2)). No significant changes were seen in either group in lumbar spine BMD (1.113 to 1.142 g/cm(2) and 1.158 to 1.190 g/cm(2), respectively) or total body BMD (1.103 to 1.134 g/cm(2) and 1.111 to 1.129 g/cm(2), respectively). CONCLUSION: Resistance training is a potential method for increasing bone density in adolescents, although such a program would be best done as part of the school curriculum.

Frequent occurrence of IgE and IgG4 antibodies against saliva of Aedes communis and Aedes aegypti mosquitoes in children.

We examined the prevalence of IgE and IgG4 class antibodies to the saliva of Aedes communis and Aedes aegypti mosquitoes in the sera of three groups of exposed children using a sensitive immunoblot method. The frequencies of IgE antibodies to the major 36-kD A. communis and A. aegypti saliva antigens ranged from 82 to 90% in the 20 Finnish, 17 Kenyan, and 20 Mexican children. The corresponding IgG4 antibody frequencies were 85, 41, and 20%, respectively. The nonexposed 20 Icelandic children did not show IgE or IgG4 antisaliva antibodies. Several of the Finnish children showed also IgE and IgG4 antibodies to a 22-kD A. communis saliva antigen. The Finnish children abnormally sensitive to mosquito bites had frequently IgE and IgG4 antibodies to the 22-kD A. communis saliva antigen, suggesting that these antibodies play a role in the pathogenesis of immediate cutaneous mosquito bite reactions. In contrast to this, no increase was found in the A. aegypti antibody frequencies in the Kenyan and Mexican children with papular urticaria, suggesting that humoral immune response to A. aegypti saliva is not involved in the development of this disorder. The present results show that humoral IgE and IgG4 immune responses to Aedes mosquito saliva antigens is common in children living both in temperature and tropical zones. The IgE antibodies seem to be involved in the immediate mosquito bite whealing, and the occurrence of the IgG4 subclass antisaliva antibodies might be an indicator of intense mosquito bite exposure.