the adjustable and detachable seat 20 the connecting member being arrestable by a pop pin 19 21 22 the hollow member may have a polygonal cross section preferably quadratic for example in the illustrated example the polygonal cross section is substantially square the seat is adjustable for height and connected to the seat socket 12 the seat post pop pin 19 permits height adjustment of the seat the fore and aft saddle pop pin 21 permits adjustment of the seat 20 by sliding fore and aft in the seat socket 12 because of the adjustability of the seat and the handlebar a rider theoretically may be as tall as 15 feet and weigh up to 900 pounds the handlebar and seat adjustability provides for a versatile bicycle which can be used by persons of many different physiques from small light and short to large tall and heavy referring now to fig3 the pedal mechanism 6 includes a cog 15 operative with an endless chain 16 having slots for engagement with the cog 15 additionally the pedal mechanism 6 includes a ring guard 17 protective of at least the interaction of the teeth of the cog 15 with the endless chain 16 the ring guard 17 is located internally of the perimeter defined by the endless chain 16 it would be desirable to provide attachments to the present invention for example a water bottle may be attached directly to the present invention or indirectly by means of a velcro device or any carrier means for attaching the water bottle to the stationary exercise bicycle additionally an ergometer may be attached to the present invention also a computer controlled energy measuring and indicating device may be attached to the present invention the stationary exercise bicycle may comprise a.