Chapter XVII HANDCYCLE  UCI CYCLING REGULATIONS  Definition  16.17.004  In the kneeling position, the athlete’s legs and feet must be supported and protected from  the ground surface.  16.17.003 For the individual road race, the recumbent handcycle must have a mirror fixed either to  the helmet of the athlete or at any point of the front of the bicycle in order to ensure rear  view vision.  16.17.002  In the recumbent position, the athlete must have a clear vision. As such, the horizontal  of his eye line must be above the crank housing/crank set, when he is sitting with his  hands on the handlebars facing forward at full extent, the tip of his shoulder blades in  contact with the backrest and his head in contact with the headrest, when applicable. A  quick release body harness is permitted.  16.17.001 A handcycle is either an arm powered (AP), arm-trunk powered (ATP) or kneeling  position (HK), three wheels vehicle with an open frame of tubular construction, which  conforms to the general principles of UCI construction for bicycles, except that the  chassis frame tubes need not be straight and that for the seat or backrest construction,  the maximum frame tube diameter may exceed the maximum defined by the general  principles of UCI.  The single wheel may be of a different diameter to the double wheels. The front wheel, shall be steerable; the single wheel, at the front, shall be driven through a system  comprising handgrips and a chain.  The handcycle shall be propelled solely, through a chainset and conventional cycle drive  train, of crank arms, chainwheels, chain and gears, with handgrips replacing foot pedals.  It shall be propelled from the hands, arms and upper body mainly.  (text modified on 01.02.09; 01.07.10; 01.02.17)  The measurement will be made as follows; from the position described above, the  distance will be measured from the ground to the centre of the eyes of the athlete seated  and compared to the distance between the ground and the middle of the crank housing  / crank set. The distance from the eyes to the ground needs to be at least equal or greater  than the distance of the middle of the crank housing to the ground.  (text modified on 01.01.04; 01.02.09)  (text modified on 01.02.09; 01.02.11)  (article introduced on 01.02.09)  E0121  PARA-CYCLING  73 