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.
Gutin
B
B
Department of Pediatrics, Medical College of Georgia, Augusta 30912, USA.
Owens
S
S
Slavens
G
G
Riggs
S
S
Treiber
F
F
D000273:Adipose Tissue; D015992:Body Mass Index; D002648:Child; D004562:Electrocardiography; D015444:Exercise; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D009765:Obesity; D010275:Parasympathetic Nervous System / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology