Muscle fiber permeabilization pipelines. (a) Skeletal or cardiac muscles are initially excised along with connective tissues into samples of up to 1 cm thickness and can be stored at −20°C/−80°C for extended periods or immediately permeabilized for experimentation. (b) The permeabilization process reduces the sarcolemma’s ability to isolate sarcomeres from the extracellular space. This, in turn, provides the experimenter access to the sarcoplasm via the diffusion of chemicals across the (remaining) sarcolemma. (c) These samples are then either further stored or loaded onto an experimental rig for mechanical testing.