Effect of Exercise on Elevated C-reactive Protein Concentrations in Formerly Inactive Adults

BACKGROUND:

CRP, a marker of systemic inflammation, has been reported to be an independent predictor of cardiovascular disease in both women and men. Recently published data from cross-sectional analyses showed that CRP is inversely related to cardiorespiratory fitness, and that this association is independent of body mass index. Regular exercise may affect CRP levels, and can possibly be used as a means of reducing elevated CRP levels. Though there are a number of studies focusing on related topics, there are no published reports from randomized clinical trials on the effect of exercise training alone on CRP levels.

DESIGN NARRATIVE:

An estimated 200 individuals will be randomly assigned to either a no exercise control group or an exercise group. Exercising individuals will participate in 3 or 4 training sessions each week for 4 months, and will progress to a total energy expenditure of 16 kcal [kg(-1), week(-1)], which is an exercise dose at the upper end of current public health recommendations for physical activity. The target exercise intensity will be 50-70% of baseline volume of oxygen consumed (V02 max). VO2 max is the maximal rate of oxygen consumption during exercise, and is a measurement of fitness. The primary outcome measure will be plasma CRP concentration. Secondary outcomes will be changes in variables that are potential mechanisms through which regular exercise might reduce CRP. These variables include visceral adiposity, the cytokines interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), and heart rate variability as a measure of autonomic balance. Although the primary outcome is CRP level, this study will also contribute significantly to the limited body of literature examining the effect of exercise on the variables of visceral adiposity, cytokines, and heart rate variability.