The bicycle (4) has two pedals (8-11) that are fixed to a rotary crank. The free ends of the pedals are directionally opposed to each other. A drive bar connects the drive unit to the rear wheel (2) of the bike. The drive unit includes a pivot, a high velocity compensating device (12) and a gear unit. The compensating device has two wheels that are connected by a rotary chain. The foot pedals are slidably position to change effective length during each rotation of the pedal assembly.
