The first noninvasive measurements of muscle sarcomere length were made by laser diffraction during swimming in the glass catfish (Kryptopterus bicirri). Sarcomere length changes were recorded at a relatively constant swimming speed (approximately 3.2 body lengths s−1, tailbeat frequency 5–7 beats s−1) just dorsal to the vertebral column. 18 s of continuous diffraction data were obtained and yielded cyclic sarcomere length changes of only 65±10nm. Based on published fish morphology, architecture and behaviour, we suggest that these values represent white muscle cyclic sarcomere shortening and elongation during swimming powered by red muscle.
The interaction between actin and myosin represents the fundamental forceproducing mechanism in all skeletal muscles. Interaction between analogous proteins also occurs within cells, resulting in movement of subcellular organelles. Although considerable detail is known about the muscle sarcomere lengthtension relationship and how isometric force potential is a function of myofilament overlap (...
