A human powered vehicle (HPV) is, broadly, any vehicle powered solely by humanmuscular effort. The most common HPV is the bicycle. Recumbent bicycles are a common variant, and have broken human powered speed records (but they cannot be used in UCI[?]cycling events). Human powered aeroplanes have been built and flown, there are examples in the IHPVA's Air section (see external web link below). Human powered boats and even submarines also exist.