Explorer II - handbike from Polish company Sport-On, which allows invalids (but not only) to do mountain bike sports like XC, Down Hill or Dual. How ? Just look on the video.

Explorer II - presentation

Explorer is built with newest compounds based on normal MTB technologies. Frame from allminium, hydraulic  breaks and full suspension with lock make the bike light, agile and fast. Unlike normal bikes, Explorer is powered by hands. It makes this vehicle usable by people which don't have or have disabled legs.

Explorer II - another presentation with more details in English