A mountain climbing machine, which does not require connecting with an external electrical power source, includes a running belt, front and rear rollers, and a generator operatively linked to one of the front and rear rollers for generating electrical power when the running belt is running, wherein a rotational speed of said generator is controlled by a consumption of the electrical power generated from the running belt so as to provide a resistance force at one of the front and rear rollers to maintain the running belt at a constant speed without connecting to the external electrical power source.

A bicycle simulator includes a base portion having a frame shape; a frame support portion supported by the base portion and supporting a bicycle frame connecting a front wheel of a mounted bicycle to a rear wheel of the mounted bicycle; a first treadmill extending in a running direction of the bicycle, supporting the front wheel of the bicycle, and rotating according to rotation of the front wheel; and a second treadmill extending in the running direction of the bicycle, supporting the rear wheel of the bicycle, and rotating according to rotation of the rear wheel, wherein the frame support portion is disposed between the first treadmill and the second treadmill.