Fiber reinforced elastomeric actuators are popular actuators for soft robots because of their inherent safety, energy density and a large repertoire of spatial motion patterns. However, a small subset of these actuators alone known as McKibben pneumatic muscles with antisymmetric fiber orientations have been extensively analyzed in literature. This paper analyzes the large deformation kinematics of generalized McKibben actuators with asymmetric and arbitrarily varying fiber orientations by formulating a simple and accurate isoperimetric problem that involves constrained volume maximization problem. This model maximally decouples kinematics and kinetostatics thereby significantly reducing the numerical complexity involved in analysis. The accuracy of the model is verified by benchmarking with existing models for the McKibben actuator case, and with experiments for novel designs with no associated prior literature. This model is deemed to be useful in the design synthesis of fiber reinforced elastomeric actuators for a desired kinematic and kinetostatic requirement.