Muscle fibre deformation: rigor extensibility of raw bovine muscle

Muscle which entered rigor restrained in a stretched condition shortened when freed, resulting in three types of wrinkling-(1) fibre wrinkling, (2) myofibril wrinkling and (3) myofilament wrinkling. The structural consequences of stretching muscle whilst it was in rigor were studied by light and electron microscopy. Rigor extension of contracted or stretched samples in excess of that required to straighten any wrinkles resulted in three types of damage to a high proportion of the sarcomeres. (1) Breaks occurred in the I bands, but not the clean breaks associated with post-rigor muscle. (2) Breaks occurred in the A bands on either side of the M line. (3) Z lines were pulled apart.