In vivo Evaluations of Fiber Tension and Sarcomere Imaging

INTRODUCTION: Spasticity and contracture commonly occur in neurological disorders. Biomechanical changes of spastic muscle fibers are still not clear and mainly sarcomere length was investigated in spastic fibers in vivo. On the one hand, it was reported that single fibers from spastic muscle of children with cerebral palsy had shorter in vitro length of about 1.84 μm. On the other hand, in vivo sarcomere length of spastic muscles was found significantly longer, averaging 3.48 μm. Furthermore, it is not clear whether spastic fibers are under higher tension and stiffer under in vivo conditions and how sarcomeres adapt to the potentially increased tension. The purpose of this study was to simultaneously evaluate the fiber tension and sarcomere length in vivo, which may help us better understand biomechanical changes and sarcomeric adaptations associated with spasticity/contracture.