A skateboard for use on pavement, ice or snow using a single narrow-footprint wheel, ice-blade or ski-runner attached to each foot, thus requiring the rider to dynamically balance the board. The skateboard is capable of self-propulsion at considerable speed on the flat or uphill by using an undulating motion. It can also lean up to 30 degrees and has a steering circle of only two feet. The board's construction comprises a front footboard, a rear footboard, and a strut which connects the two footboards and resists bending and extension. Each footboard includes a footpad, an attachment (i.e. a wheel, blade or ski), and a pivot joint connecting to the strut. The axis of this joint is aligned perpendicular to the footpad which allows the rider to steer each footboard independently by torsionally rotating the lower leg.