Effects of physical training and its cessation on the hemostatic system ofobese children

Background: Physical training can improve hemostatic function in adults, th ereby reducing heart disease risk, but no information is available in child ren on whether physical training can enhance hemostatic function. Objective: The purpose of this investigation was to examine the effects of a physical training program on hemostatic variables in a biethnic group of obese children. Design: Children were randomly assigned to 2 groups. Group 1 participated i n physical training for 4 mo and then ceased physical training for 4 mo, wh ereas group 2 did no physical training for the first 4 mo and then particip ated in physical training for 4 mo. Plasma hemostatic variables [fibrinogen , plasminogen activator inhibitor 1 (PAI-1), and D-dimer) were measured at months 0, 4, and 8. Results: Analyses of variance revealed no significant group-by-time interac tions for the hemostatic variables. When data from both groups were combine d there was a significant decrease in D-dimer after 4 mo of physical traini ng (P < 0.05). Factors explaining individual differences in responsiveness to the physical training revealed that individuals with greater percentage fat before physical training showed greater reductions in fibrinogen and D- dimer, and that blacks showed greater reductions in D-dimer than whites (P < 0.05). Stepwise multiple linear regression showed that only higher prephy sical training concentrations of fibrinogen, PAI-1, and D-dimer explained s ignificant proportions of the variation in changes in these variables. Conclusions: In obese children, 4-mo periods of physical training did not l ead to significant changes in hemostatic variables. Children with greater a diposity and concentrations of hemostatic factors before physical training showed greater reductions in hemostatic variables after physical training t han did children with lesser values.