Temporal stability of ambulatory blood pressure and heart rate in youths.

BACKGROUND: The use of ambulatory blood pressure monitoring for pediatric populations is increasing. OBJECTIVE: ; To determine the 2-year stability of ambulatory blood pressure in youths. METHODS: We evaluated 2-year stabilities of resting and ambulatory blood pressures in 197 youths (aged 13.9+/-2.3 years at initial evaluation). Readings were taken every 20 min during the daytime (0800-2200 h) and every 30 min at night (0000-0600 h). RESULTS: Daytime and night-time systolic blood pressure increased (P < 0.01 for both) as did resting systolic blood pressure (P < 0.05). Measures of diastolic blood pressure did not change. Changes in systolic blood pressure were related to changes in body size. Estimates of stability for resting and ambulatory measurements were similar, ranging from 0.65 to 0.75. In addition, correlation coefficients for relationships between first and second readings for resting and ambulatory measurements were similar ranging from 0.43 and for resting heart rate to 0.72 for 24h systolic blood pressure (P < 0. 001 for each). The only significant correlation between change scores for resting and ambulatory values was that between resting and night-time diastolic blood pressures (r = 0.33, P < 0.001). CONCLUSION: Measures of blood pressure derived from ambulatory blood pressure monitoring reflect changes in blood pressure in youths at least as well as do changes in resting blood pressure despite the high degree of variability in levels of physical activity and affective states of the children during the ambulatory recordings.

Effects of Theraband and lightweight dumbbell training on shoulder rotation torque and serve performance in college tennis players.

The purpose of this study was to determine whether a 4-week isotonic resistance training program using Theraband elastic tubing and lightweight dumbbells would significantly increase concentric shoulder rotator strength or velocity of serve or both in a group of elite-level tennis players. Twenty-two male and female varsity college tennis players were randomly assigned to control or 4-week training groups. Subjects were pre- and posttested in concentric internal and external rotation torque using an isokinetic dynamometer. Functional performance was assessed before and after training by recording the peak and average velocities of eight maximal serves. The experimental group exhibited significant gains in internal rotation torque at both slow (120 deg/sec) and fast speeds (300 deg/sec) for total work and in peak torque to body weight ratio and torque acceleration energy at the fast speed. This group also exhibited significant gains in external rotation torque for the same parameters at fast speed. Regarding speed to serve, the experimental group exhibited significantly greater increase in peak speed (+6.0% compared with -1.8%) and average speed (+7.9% compared with -2.3%) compared with the control group. Men exhibited greater internal and external rotation torque on all parameters and in peak and mean speed of serve on both evaluations. Men also exhibited greater imbalance in external to internal rotation torque ratios. In conclusion, resistance training using Theraband tubing and lightweight dumbbells may have beneficial effects on strength and functional performance in college-level tennis players.

Effect of physical training on heart-period variability in obese children.

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.

Weight-independent cardiovascular fitness and coronary risk factors.

BACKGROUND: It is unclear whether cardiovascular fitness influences risk factors for coronary artery disease and non-insulin-dependent diabetes mellitus independently of level of body fat because fitness is often measured in tasks that involve moving body weight (eg, running) and because body weight and level of body fat are correlated. OBJECTIVE: To measure fitness during a task in which body weight was controlled experimentally (ie, supine cycling). DESIGN: Cross-sectional. PARTICIPANTS: Seventy-four children, 7 to 13 years of age, recruited through school flyers and newspaper advertisements, varying in level of body fat from 7% to 61%. There were 31 boys and 43 girls; 35 were white and 39 were black. MAIN INDEPENDENT VARIABLES: Cardiovascular fitness was expressed as submaximal heart rate while cycling at a power output of 49 W, and level of body fat was measured with dual x-ray absorptiometry. MAIN OUTCOME MEASURES: Blood pressure and levels of triglycerides, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, insulin, glucose, and glycohemoglobin. RESULTS: Controlling for age and sex, level of body fat was significantly (P < .01) related to unfavorable levels of systolic blood pressure (r = 0.32), triglycerides (r = 0.42), high-density lipoprotein cholesterol (r = -0.31), insulin (r = 0.50), and total cholesterol to high-density lipoprotein cholesterol ratio (r = 0.37); submaximal heart rate was not significantly correlated with any of the other variables. CONCLUSIONS: When cardiovascular fitness was measured in a weight-independent task, it was not significantly related to level of body fat or the major coronary artery disease and non-insulin-dependent diabetes mellitus risk factors. In addition, we confirmed previous findings that higher levels of body fat are associated with a very unfavorable risk profile.

Factors associated with the use of violence among urban black adolescents.

OBJECTIVES: The purpose of this study was to examine social and psychological factors associated with the use and nonuse of violence among Black adolescents living in a community with a high level of violent crime. METHODS: Adolescents (n = 225, 44% male) 11 to 19 years of age living in or around nine housing projects in an urban area were administered an anonymous questionnaire. RESULTS: Self-reported use of violence was associated with exposure to violence and personal victimization, hopelessness, depression, family conflict, previous corporal punishment, purpose in life, self-assessment of the probability of being alive at age 25, and age and was higher among males. CONCLUSIONS: These data support the hypothesis that exposure to violence is associated with adolescents' self-reported use of violence. However, adolescents with a higher sense of purpose in life and less depression were better able to withstand the influence of exposure to violence in the home and in the community.

Use of multiple drugs among adolescents who use anabolic steroids.

BACKGROUND: Because adolescent users of anabolic steroids are concerned with increasing muscle size and strength, they may be unique among substance users and unlikely to use other drugs. Alternatively, if the factors that cause the use of anabolic steroids are similar to those associated with the use of other substances, adolescents who use anabolic steroids would be expected to report use of other drugs as well. METHODS: We administered a questionnaire based on the 1989 Secondary School Health Risk Survey and the 1990 Youth Risk Behavior Survey of the Centers for Disease Control and Prevention to 1881 students enrolled in compulsory health-science classes (mean [+/- SD] age, 14.9 +/- 1.0 years) in the Richmond County, Georgia, school system. RESULTS: A higher percentage of boys (6.5 percent) than girls (1.9 percent, P < or = 0.001) reported using anabolic steroids without a doctor's prescription. Among ninth-grade students only, 5.4 percent of boys and 1.5 percent of girls reported using anabolic steroids (P < or = 0.001). Among users of anabolic steroids, 25 percent reported sharing needles to inject drugs. The frequency of anabolic-steroid use was significantly (P < 0.001) associated with the frequency of use in the previous 30 days of cocaine (r = 0.44), injectable drugs, alcohol (r = 0.23), marijuana (r = 0.42), cigarettes (r = 0.25), and smokeless tobacco (r = 0.40). On the basis of multiple regression analysis, the use of marijuana, shared needles, smokeless tobacco, and cocaine accounted for 33 percent of the variation in anabolic-steroid use among the ninth-grade students. CONCLUSIONS: In our study, adolescent users of anabolic steroids were likely to use other drugs as well, and many were sharing needles.