The aim of this series of studies is to elucidate the role of mechanical stresses in the processes of cell activation. The experiments were done with a huge unicellular organism, the Physarum polycephalum plasmodium, which is a classical object in studies of the nonmuscle motility. The contractile properties of this amoeboid cell were investigated with the help of an inexpensive electronic-mechanical measuring system. A short description of this device is presented, which allows one to maintain a given kinetics of either the length or the load of the object and to measure either its tension force or deformation, respectively, as a response. Some examples of the longitudinal dynamics of the plasmodial strand and its activation under periodic switching of regimes of measurement in certain phases of the contraction-relaxation cycle are shown.