The purpose is to determine whether regular endurance exercise and/or body weight influence the way our nervous and vascular systems respond during the metabolism of meals.

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).

Inclusion Criteria:

• healthy, not currently taking any medications

Exclusion Criteria:

• unhealthy, taking medications

young, lean, healthy men