The popular notion of how muscles function has been turned on its head with the publication of new and revealing ultrasound images. Scientists long believed that muscle fibres lie in straight lines. These new images, however, reveal that muscle fibres in fact buckle when they are shortened and at rest.
http://www.neura.edu.au/news-events/news/researchers-gain-new-insight-how-muscles-work
Prof Simon Gandevia, Neuroscience Research Australia