Muscle contraction is a largely mechanical process taking place at the sub-cellular level. While being an intrinsically active system the contractile apparatus also displays some intriguing passive mechanical properties including negative stiffness and a fundamental nonequivalence of isometric and isotonic loading protocols. We reveal the origin of this unusual behavior by analyzing a conceptual model which represents a delicate generalization of the Huxley-Simmons model. Our analytically explicit study sheds light on the crucial role of long-range interactions in this system. The model can be easily adapted to a wide class of biological phenomena involving cooperative switching mediated by effective backbones, from muscle power-stroke to gating, binding and folding.