PURPOSE: To freely and continuously vary gravity a load has and to apply it to a human muscular power training device.

CONSTITUTION: When a load element 3 is actuated, each physical quantity of torque and an angle is transmitted to a physical quantity detector 4. Its output signal is amplified by an amplifier 6, while a viscosity signal is introduced from a differentiating circuit 7 and an inertia signal is introduced from a differentiating circuit 5. Subsequently, the output signal is introduced from the amplifier as an elasticity signal and a gravity signal. This composite signal is electrically transmitted to a driver circuit 13 and then to a friction element 2. Thereby, gravity of the load element 3 is continuously varied, and it is possible for a man to carry out muscular training by the load element 3.