Abstract: An exercising device for swinging a pair of synchronized jump ropes, comprises a first and second station, each having two rotatable shafts and a lever arm on each shaft extending radially from the shaft, each lever arm having radially spaced holes for attaching a jump rope. The first station is driven by a motor and the second station is freewheeling, being driven only by the first station, through the ropes, with both the driving and freewheeling stations being geared to internally synchronize the two ropes. The motor is electric and as a safety device a spring loaded movable element on a shaft at the driving station axially moves against the spring loading if a jumper interrupts the turning of the rope associated therewith, to interrupt the turning power, where the movable element in one version throws a cutoff switch to the motor and in another version is one plate of a two plate clutch. The clutch slips on interruption and resumes synchronous engagement thereafter.