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

J Pediatr. 1997 Jun;130(6):938-43. doi: 10.1016/s0022-3476(97)70280-4.


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.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adipose Tissue
  • Body Mass Index
  • Child
  • Electrocardiography
  • Exercise*
  • Female
  • Heart Rate*
  • Humans
  • Male
  • Obesity*
  • Parasympathetic Nervous System / physiology
  • Sympathetic Nervous System / physiology