Abstract: Supporting leg for mobile construction equipment such as mobile cranes, having a supporting foot (1) which can be elevated and lowered in relation to the foundation by means of a moving mechanism (3) inserted between the equipment (2) and the supporting leg. Wherein the moving mechanism (3) has a clearance (4) between the foot elevated position and the foot lowered position, and a spring (8) urges the mechanism (3) against the elevated position, whereby an alarm switch (9) is activated to give an automatic indication in case the stability of the construction is reduced. The allowable reduction of load on the supporting leg before the activation, can be adjusted by the spring force applied.