RESUMO
OBJECTIVE: The beat-to-beat variability in electrocardiogram intervals (RR, i.e., heart-period variability) provides information on cardiac autonomic activity that predicts arrhythmias and mortality rate in animals and adults. We determined the effect of physical training on heart-period variability in obese children. METHODS: Thirty-five subjects were randomly assigned to physical training and control groups. The training involved 4 months of exercise, 5 days per week, 40 minutes per day. Cardiovascular fitness was measured with submaximal heart rate during supine cycling; percentage of body fat was measured with dual-energy absorptiometry; and resting heart-period variability parameters were measured in a supine position. A pretraining to posttraining change score was computed for each variable. The effect of the training was determined by comparing the changes of the training and control groups. RESULTS: Compared with the control group, the trained group (1) reduced submaximal heart rate and percentage of body fat (p < 0.01); (2) increased in the root mean square of successive differences, a time-domain parameter reflective of vagal tone (p < 0.05); (3) decreased in low-frequency power expressed as a percentage of total power, a frequency-domain index of combined sympathetic and vagal activity (p < 0.03); and (4) decreased in the ratio of low- to high-frequency power, an index of sympathetic-parasympathetic balance (p < 0.01). CONCLUSIONS: In obese children, physical training alters cardiac autonomic function favorably by reducing the ratio of sympathetic to parasympathetic activity.
Assuntos
Exercício Físico , Frequência Cardíaca , Obesidade , Tecido Adiposo , Índice de Massa Corporal , Criança , Eletrocardiografia , Feminino , Humanos , Masculino , Sistema Nervoso Parassimpático/fisiologia , Sistema Nervoso Simpático/fisiologiaRESUMO
We hypothesized that high school students who experienced prior maltreatment would be more likely than their peers to report health risk behaviors and suicide attempts. Before the establishment of a high school-based clinic, an anonymous needs assessment survey was completed by 600 adolescents (grades 9 to 12). Sociodemographic information was obtained and questions were asked about physical and sexual abuse, health-related behaviors and habits, and suicide attempts. Thirteen percent of the adolescents had been maltreated: 5.2% reported prior physical abuse, 5.4% sexual abuse, and 2.7% both physical and sexual abuse. Multivariate statistical techniques were used to clarify how previous abuse was related to adolescent risk-taking behaviors and suicide. Students with a history of physical abuse were three times more likely than non-abused peers to drink alcohol and smoke cigarettes, almost twice as likely to use illicit drugs, six times more likely to self-induce vomiting, and five times more likely to attempt suicide. A student with a history of prior sexual abuse had a three and one-half times greater chance of being sexually active and was more than three times more likely to attempt suicide. These data on a nonclinical, nondeviant population of adolescents indicate that physical or sexual abuse in childhood may have a significant impact on adolescent health risk behaviors and suicide attempts.