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Abstract
Physical activity (PA) is inversely associated with C-reactive protein (CRP) levels in adults. However, exercise training interventions aimed at reducing CRP have yielded inconsistent results, with the cumulative body of evidence indicating exercise training in the absence of improvements in adiposity (%Fat) will not result a decrease in CRP. This study aimed to: 1) determine the independent and interactive associations of PA, %Fat, and oral contraceptive (OC) use on CRP in young women in a cross-sectional analysis (n=340), and 2) to determine the relative efficacy of 6-weeks of cycle exercise training, differing in intensity and matched on energy expenditure, on cardiometabolic risk factors, with a special emphasis on CRP in inactive, overweight/obese, young women (n=48). To assess primary aim 1, %Fat was measured via dual energy x-ray absorptiometry (DXA), PA was measured via accelerometer [stepsday-1], OC-use was measured via self-report, and CRP was determined from fasting blood samples obtained via venipuncture following a 12-hour fast using standard clinical procedures. Using Poisson regression, a significant 3-way interaction (%FatOC-usePA) was found, indicating that higher levels of PA reduced the %Fat and OC-induced elevation in CRP (Wald 2=6.6, P=.011). To assess primary aim 2, lipid, insulin, HOMA-IR, and CRP concentrations were measured using similar methods. Participants were randomly assigned to vigorous sprint-interval cycling (VIG-SIC) or continuous moderate-intensity cycling (MOD-C) for 6 weeks of exercise training. Participants in the VIG-SIC completed 5-7 repeated bouts of 30-second sprints, followed by 4 minutes of active recovery. MOD-C participants cycled at 60-70% of heart rate reserve for 20-30 minutes, with duration increasing biweekly, maintaining equal energy expenditure between groups. Total cholesterol, HDL-C, LDL-C, and triglyceride concentrations significantly improved after controlling for baseline values in both groups (all P<.05). A significant GROUPTIME interaction (P=.031) indicated exercise intensity modified the training response, with a reduction in CRP observed in the MOD-C group, but not in the VIG-SIC group after controlling for change in %Fat and baseline CRP. Young women, especially OC-users with higher %Fat, should engage in greater amounts of PA to reduce CRP. In addition, moderate intensity exercise may be more effective in reducing CRP in OW/OB young women.