This study continues our exploration into the mechanisms underlying the control of blood flow. During the experiments, we noninvasively measure skin blood flow (SkBF) and forearm blood flow (FBF) with a FLPI and venous occlusion plethysmography (VOP), respectively. The FLPI uses a low energy laser to measure SkBF. VOP uses blood pressure cuffs on the upper arm and wrist, and an elastic strain gauge encircling the forearm between the cuffs to measure the change in forearm-circumference over time from which we calculate FBF. For each experiment, we collect SkBF and FBF data for a 20-minute baseline, expose the skin of the forearms to negative pressure and then collect SkBF and FBF data for an additional 30-90 minutes. Each subject participates in 2 experiments that differ only in the protocol for the application of negative pressure (i.e. continuous, pulse).