Thomas B. Gilliam

Physical activity patterns determined by heart rate monitoring in 6-7 year-old children.

The purpose of this study was to examine 12-h heart rate patterns during the summer using a holter monitoring system (Oxford Instruments) in prepubescent children. Parental consent was obtained for the 40 volunteers (22 boys, 18 girls) ages 6 to 7 years. Heart rates exceeding 160 bts min-1 occurred 20.9 min and 9.4 min for the boys and girls, respectively, during the 12-h monitoring period (8:00 a.m.-8:00 p.m.). When comparing the heart rate profiles between the sexes, the boys had significantly (P less than 0.05) more heart beats at a level of 140 bts min-1 and above than the girls. Even though the children appear moderately active, they very seldom experience high intensity physical activity. Furthermore, the heart rate patterns show that the boys are more physically active than the girls.

Prevalence of coronary heart disease risk factors in active children, 7 to 12 years of age.

Forty-seven active boys and girls, 7 to 12 years of age, underwent a comprehensive medical and physical evaluation in order to assess their prevalence of single and multiple coronary heart disease risk factors. Each subject received a densiometric determination of body composition, blood lipid analysis, pulmonary function and a physical work capacity test to assess their peak oxygen consumption (Vo2max). Obesity (greater than 25% fat), elevated triglycerides (greater than 100 mg %) and the presence of Type IV hyperlipoproteinemia appear to be the more predominant risk factors. Twenty-nine (62%) of the children had at least one risk factor. Of these, seventeen had two or more risk factors with one subject having as many as five factors.

Echocardiographic measures in 6 to 7 year old children after an 8 month exercise program.

The influence of an exercise intervention program on cardiac dimensions was studied in 79 normal children (aged 6 to 7 years) in an experimental (n = 38) and control (n = 41) group. The experimental group participated in an aerobic exercise session that met four days/week for 8 months. Anthropometric measurements and M mode echocardiograms were obtained before and after the intervention program. Comparison of the data between groups revealed no significant (probability [p] greater than 0.05) differences in left ventricular end-diastolic dimension, shortening fraction or resting heart rate. Left ventricular posterior wall thickness exhibited a significant increase (p less than 0.0256) from 3.9 to 4.7 mm in the experimental group compared with an increase from 4.3 to 4.6 mm in the control group after correcting for preintervention differences with an analysis of covariance. Likewise, left ventricular mass increased significantly (p less than 0.0004) from 21.2 to 27.4 g in the experimental group compared with 23.4 to 25.8 g in the control group. These findings indicate that when compared with control subjects, young children involved in an aerobic exercise program showed progressive increases in left ventricular posterior wall thickness and left ventricular mass and no change in left ventricular end-diastolic dimension, shortening fraction or resting heart rate.

Isokinetic Torque in Boys and Girls Ages 7 to 13: Effect of Age, Height, and Weight

Abstract The purpose of this study was to investigate torque differences between 28 boys and 28 girls, ages 7 to 13 years, for the knee and elbow flexor and extensors at 30°/second and 120°/second using an isokinetic procedure (Cybex II). In addition, the relationships of these torque levels to size and age were determined. The results revealed significant (p < .05) sex differences for the knee flexor and extensor torque values at 120°/second independent of body weight. That is, the boys generated 29.2 and 39.5 foot pounds vs. the girls 26.2 and 35.4 foot pounds for knee flexion and extension, respectively. Similarly, torque differences (p < .05) between boys and girls were present for elbow extension at 120°/second when adjusting for differences in height. When examining the flexion/extension ratios, it is apparent that increases in body size (height, weight) and age had a significant effect on the ratio at 120°/second but not at 30°/second.

Exercise Programs for Children: A Way to Prevent Heart Disease?

In brief Physical activity patterns of 59 children were determined by recording heart rates before and during an exercise intervention program for coronary heart disease risk. Twenty-six children engaged in 25-minute aerobic activity sessions four days a week for eight months; the control group took regular physical education classes. Baseline data revealed that both groups had similar activity patterns, that the children seldom attained a heart rate greater than 160 beats min-1, and that the boys expended significantly more energy per day than the girls. The activity patterns of children in the experimental group improved significantly.

Transient VO2 Characteristics in Children at the Onset of Steady-Rate Exercise.

Abstract The transient oxygen uptake (VO2) response during the initial phase of exercise was investigated in 28 children (mean age ± SD = 10.2 ± 2.28 years) during constant load submaximum bicycle ergometer exercise (mean power output ± SD = 56 ± 4.0 watts; mean VO2 ± SD = .92 ± .141 [mdot] min-1). The VO2 half-time (VO2 - t½) averaged (± SD) 34.8 (± 12.70) sec which is similar to that observed in adults. Examination of the VO2-t ½ response as it related to age (7 to 14 years) showed that younger children attained steady-rate VO2 more quickly than older children (r = .77 between age and VO2-t½, P < .05). Body size, maturational level, exercise intensity, cardiorespiratory factors, and anaerobic potential are suggested as possible factors accounting for the positive age vs VO2-t ½ relationship.

Ventral motor neuron alterations in rat spinal cord after chronic exercise.

The observed differences in the soma and nuclear diameters reflect chronic changes specific to each exercise regimen used.

Children-Adult Comparisons of VO2 and HR Kinetics during Submaximum Exercise

Abstract Oxygen uptake (VO2) and heart rate (HR) kinetics for submaximum exercise were compared in prepubescent boys (mean age ± SD = 10.2 ± 1.28 years, N = 21) and adult men (30.0 ± 5.64 years, N = 21). Standard open circuit spirometric techniques were used to determine VO2 and a bipolar ECG was used to measure HR. The kinetics of VO2 and HR were determined for each subject using graphic procedures. Subjects performed submaximum exercise on the bicycle ergometer at an intensity of 42 ± 1.3% (mean ± SE) of VO2 max for the children and 39 ± 0.7% of VO2 max for the adults (p = .07). There were no group differences in VO2 t1/2 (children t1/2 = 18.5 ± 0.75 secs and adults t1/2 = 17.4 ± 0.39 secs, p = .18) and HR t1/2 (children t1/2 = 11.4 ± 1.86 secs and adults t1/2 = 13.6 ± 1.66 secs, p = .38). These data suggest that children and adults do not differ in cardiorespiratory adjustments during low intensity exercise. This is in contrast to suggestions of other investigators that children have a faster cardiovas...

Comparison of blood lipids, lipoproteins, anthropometric measures, and resting and exercise cardiovascular responses in children, 6--7 years old.

The purpose of this investigation was to determine sex differences and interrelationships in anthropometric, blood lipids and lipoproteins, steady rate and maximal bicycle ergometric measures in boys (IV = 38) and girls (N = 28) ages 6 to 7 years. After adjusting for a significantly (P i 0.05) higher sum of skinfold measure for the girls, significant (P 0.05) existed in preexercise and maximal heart rates. Multiple regression analyses resulted in weak but significant (P C 0.05) prediction equations for cholesterol and cumulative work performed on the bicycle. A significant (P < 0.05) negative correlation between HDL-C vs triglycerides (r = 0.46) was obtained for the girls. These data indicate that sex differences exist for selected ergometric, anthropometric, and blood lipid and lipoprotein measures as early as 6 years. Also, the association among blood lipid and lipoprotein measures may differ between boys and girls.

Heart rate response to bicycle ergometer exercise in children ages 6-7 years.

The purpose of the present investigation was to compare the heart rate response of pre-pubertal males and females during rest, steady-rate power output, peak power output, and recovery. Sixty-six children (38 males and 28 females) ages 6-7 years performed a continuous bicycle ergometer exercise test, including 4 min of steady-rate work (males = 15.3 +/- 0.17 W.min-1, females = 15.0 +/- 0.16 W.min-1) followed by a progressive increase in resistance until volitional fatigue, and a 5-min recovery period immediately following termination of exercise. Mean steady-rate heart rate response of 119.0 +/- 1.75 beats.min-1 for males was significantly (P less than 0.05) lower than the females (132.1 +/- 2.92 beats.min-1). Peak heart rate response was similar between the sexes (190.1 +/- 1.21 and 192.1 +/- 1.73 beats.min-1 for males and females, respectively; P greater than 0.05). Sex differences in heart rate recovery from peak values were significant (P less than 0.05) during the first 3 min of the 5-min recovery period, but not thereafter (P greater than 0.05). It was concluded that sex differences in heart rate response were present in these prepubertal children at rest, during steady-rate power output, and during the first 3 min of recovery.