An actuator configured for tunable stiffness control and method is provided. The actuator includes a plurality of stiffness elements, one or more of the stiffness elements including a shape memory alloy (SMA). At least one of the elements has a stiffness characteristic different from another of the stiffness elements. The stiffness elements are actuable individually or in combination to provide an intermediate actuation output, which may be provided by partially transforming the smart material of one or more stiffness elements during actuation. Two or more of the stiffness elements may be actuable in combination to provide a combined output which may be non-linear, or may be functionally substitutional for an individual output of another stiffness element. The actuator may be actuable to provide a first and second output for the substantially same input, or may be selectively actuable to offset degradation of one or more of the stiffness elements.