Before revision:  Here, we develop a geometric framework for characterizing tunable materials by combining classical oscillatory rheology that uses Lissajous force-length loops to characterize non-tunable materials, with the technique of work loops that is used to study muscle's work output under varying stimulation. We derive the force-length loop under varying stimulation by splicing Lissajous loops obtained under constant stimulation .
After revision:  Here, we develop a geometric framework for characterizing tunable materials by combining classical oscillatory rheology that uses Lissajous force-length response is well-studied under fixed and time-varying stimulation. Under fixed stimulation, oscillatory force measurements characterize muscle rheology using dynamic material moduli. Under time-varying stimulation, work loops characterize work production and absorption using force-length loop under varying stimulation by splicing Lissajous loops obtained under constant stimulation .