Abstract: A running exerciser assembly includes two side frames mounted in parallel with each other. Two plates each are horizontally formed on a top portion of a corresponding one of the two side frames, two L-shaped flange portions each are laterally formed on an upperside of a corresponding one of the two plates, and two cavities each are longitudinally defined between a corresponding one of the L-shaped flange portions and the associated plate and each face toward each other. Two recesses each are longitudinally defined in a bottom portion of a corresponding one of the two side plates and each include an opening facing toward each other. A supporting plate is mounted between the two side frees and includes two distal ends each securely fitted in a corresponding one of the two cavities. Two sliding posts each are slidably mounted in a corresponding one of the two recesses near a first end portion of the associated side free.