EXERCISE DOSE FOR CARDIOVASCULAR HEALTH OF OBESE YOUTHS

Abstract

The effect on cardiovascular (CV) health of lifestyle education (LSE) alone vs LSE+physical training (PT) at moderate and high intensities was investigated in obese youths. Subjects were 81 obese 13–16 y olds assigned to: (1) biweekly lifestyle education; (2) LSE+ moderate- intensity PT; or (3) LSE+high-intensity PT. The 8-mo PT intervention was offered 5 d/wk. The target energy expenditure for all PT subjects was 1047 kJ (250 kcal)/session. Pre- and post-PT measures included plasma fibrinogen (FIB), plasminogen activator inhibitor-1 (PAI-1), D-dimer and C-reactive protein (CRP); sub-maximal CV fitness (VO2-170; treadmill test), percent body fat (%BF;DXA), and visceral adipose tissue (VAT; MRI). Pre-PT, FIB and CRP were correlated with %BF (r = 0.51, p ≤ 0.01; r = 0.61, p ≤ 0.01), VAT (r = 0.27, p ≤ 0.05; r = 0.47, p ≤ 0.01) and VO2-170 (r = 0.39, p ≤ 0.001; r = 0.43, p ≤ 0.01); PAI-1 was correlated with %BF (r = 0.30, p ≤ 0.01) and VAT (r = 0.48, p ≤ 0.01); D-dimer was correlated with VO2-170 (r = −0.24, p ≤ 0.05). There were no within or between group differences in the pre- to post-PT changes for FIB, PAI-1, D-dimer and CRP (p > 0.05). Correlations with pre-PT levels, and changes in VO2-170, %BF, VAT, and PT process variables (attendance, average heart rate, energy expenditure) were performed to explore inter-individual variation in the response to the PT. The PT process variables were not correlated with any of the hemostatic or inflammatory markers. The change in PAI-1 was correlated with the change in %BF (r = 0.31, p ≤ 0.05) but not with the change in VAT or fitness (p > 0.05). The changes in FIB, D-dimer and CRP were not correlated with the changes in fitness or adiposity. The change in FIB was not correlated with its pre-PT level (p > 0.05). In conclusion, individuals with lower fitness and higher adiposity had higher levels of hemostatic and inflammatory markers, putting them at risk for future CV disease. No evidence was provided that PT had a direct influence on these markers, or that the PT intensities differed in effectiveness or efficacy. However, individuals who decreased most in %BF were those who had the greatest decrease in PAI-1, indicating that a beneficial effect of PT on adiposity may lead to a beneficial effect on some hemostatic factors. Supported by NIH HL55564.