I investigated the ground reaction forces (GRF), stride kinematics and metabolic cost of skateboarding on an instrumented treadmill. Superficially, skateboarding appears to be a hybrid of walking, running, and cross-country skiing. I hypothesized that the push-foot in skateboarding would exhibit a vertical GRF peak similar in shape to running but with a lower magnitude. Further I hypothesized that the push-foot would exhibit greater propulsive GRF than braking GRF. Regarding stride kinematics, I hypothesized that skateboarders would increase their stride length (sL) at faster speeds. Finally, I hypothesized that skateboarding would have a smaller metabolic cost compared to walking and running at comparable speeds. Subjects (9 males/2 females) skateboarded on a force-instrumented treadmill at 1.00, 1.25, 1.50, 2.00, 2.50, 3.00, 3.50, and 4.00 m*sec⁻¹, walked at 1.25m*sec⁻¹, and ran at 3.0m*sec⁻¹. Upon GRF analysis, I discovered two distinctly different groups of skateboarders: subjects who demonstrated a braking force (“brakers”) and subjects that did not (“nonbrakers”). The peak vertical and horizontal GRF for brakers resembled running with half of the magnitude. Both groups showed decreased SF at faster speeds, but brakers used slower SF than nonbrakers. Walking and skateboarding 1.25m*sec⁻¹ had the same metabolic cost at but at 3.0m*sec⁻¹, skateboarding required approximately half the metabolic cost of running. Skateboarding is a unique mode of locomotion, with two distinctly different forms, that allows a person to move at a running velocity with the GRF and metabolic cost of walking.