Abstract: A crank for fitness equipment with a self-locking mechanism is provided. A crank body is provided with an installation hole, an internal thread is disposed in the installation hole, and an anti-loosening ring embedding portion is disposed at an outer end of the installation hole. An anti-loosening ring is tightly fitted to the anti-loosening ring embedding portion. A screw rod of a pedal is screwed into the installation hole of the crank body, and passes through the anti-loosening ring tightly fitted in the installation hole.

Abstract: A balance training device includes a base having a connection bar which includes a transverse bar and a tilt bar. A transmission unit connected to the tilt bar and includes a pedal frame, a crank, a link, a shaft, a driving wheel, a belt and a fly wheel. The link unit is connected to the transverse bar and includes a driving plate, a first link, a second link, a third link, a fourth link and a seat frame. The seat frame includes a seat with two handles on two ends thereof and the link unit moves the user back and forth, and up and down so that the user's upper body is exercised. The pedal frame includes two pedals so that the user's feet are rested on the pedals and the user's body is moved like riding a horse.