Role of Exercise Training and Body Weight on Cardiovascular and Metabolic Responses to a Mixed Meal Tolerance Test

To begin to examine this question we recruited healthy endurance-trained (high fit, HF) and normally active (average fit, AF) subjects. It is well characterized that chronic endurance training results in enhanced peripheral insulin sensitivity. Therefore, our rationale was that inclusion of two healthy subject groups, with distinct differences in insulin sensitivity, would allow us to investigate how enhanced insulin sensitivity influences insulin-mediated changes in central sympathetic outflow. Direct measurements of central sympathetic outflow to skeletal muscle (i.e., MSNA) were recorded, and a mixed meal was used as a physiological method to evoke robust and sustained increases in MSNA, which have been primarily attributed to insulin. We hypothesized that HF subjects would have a greater MSNA response, for a given plasma insulin concentration, following consumption of a mixed meal (i.e., greater central insulin sensitivity).