A monitoring system is for the regulation of the weight of a dumbbell, employable by a user for the execution of a gymnastic exercise, having a supporting frame, a dumbbell, placed on the supporting frame, equipped with a handle, having an axial development along an axis, capable of rotating around the axis, clockwise and counterclockwise, and equipped with a first end and a second end, a first plurality of weights, placed on the supporting frame, in which each weight is individually coupable to the first end by a first selection member, when the handle rotates one way, and detachable from the first end, when the handle rotates the opposite way, a second plurality of weights, placed on the supporting frame.