A method of operating a biomimetic mechanical joint having a plurality of fractional actuators configured for rotating a support member about a pivot device. The fractional actuators can be selectively recruited during operation, either individually or together, to efficiently rotate the support member about the mechanical joint throughout a range of movements and under a variety of load conditions. Each fractional actuator can be continuously throttled to reduce the speed or torque at which the actuator operates. The capability of selectively recruiting and throttling each fractional actuator results in an actuator system having two degrees of freedom, in which a single operating state of the mechanical joint may be reached with one or more of actuator arrangements and throttling settings. The method of the present invention allows for selection from the available actuator arrangements and throttle settings according to predetermined operating modes such as high-efficiency, high-acceleration or general-purpose, etc.