Functional combination of tapering profiles and overlapping arrangements in nonspanning skeletal muscle fibers terminating intrafascicularly

Abstract

Using digital image analysis and several anatomical methods, morphometric analysis of nonspanning fibers which had tapering profiles at their intrafascicular termination sites and represented overlapping arrangements within the fiber fascicles was performed in the rat rectus abdominis. Special emphasis was focused on dimensional relationships occurring between overlapping portions and tapering segments and sarcomere lengths in non- and overlapping portions. Nonspanning fibers were found to overlap each other for more than 40% of their length. In length, their overlapping portions generally corresponded to their tapering segments, which were also greater than 40% of the fiber length. In addition, despite the presence of overlapping linkages, nonspanning fibers maintained a fairly uniform length irrespective of their overlapping and nonoverlapping portions. Overlapping linkages in fibers without tapering profiles have a larger cross-sectional area in the overlapping portion than in the non-overlapping one, resulting in a phenomenon which will cause different sarcomere lengths between the two portions during fiber stretching. The present results suggest that tapering profiles in the overlapping portion ensure uniform sarcomere lengths within nonspanning fibers, thereby providing mechanical stability in each fiber.

Myofascial Force Transmission Causes Interaction between Adjacent Muscles and Connective Tissue: Effects of Blunt Dissection and Compartmental Fasciotomy on Length Force Characteristics of Rat Extensor Digitorum Longus Muscle

“…Such muscle fibers end, in a variety of morphologies (e.g., Hijikata & Ishikawa, 1997;Hijikata et al, 1993;Huijing, 1999b), somewhere in the middle of the muscle belly. For non-spanning fibers, it has been argued (Trotter, 1990(Trotter, , 1991(Trotter, , 1993Trotter & Purslow, 1992;Hijikata et al, 1993;Trotter et al, 1995;Hijikata & Ishikawa, 1997), that shearing of intact endomysial -basal lamina -sarcolemma complexes of adjacent muscle fibers is determinant for intramuscular transmission of force from muscle fiber onto adjacent muscle fiber. In such a case, after transmission of force from a source fiber to target fiber, force could be transmitted further by serial transmission via sarcomeres onto the myotendinous junction of the target fiber.…”

Finite element modeling of aponeurotomy: altered intramuscular myofascial force transmission yields complex sarcomere length distributions determining acute effects

“…Trotter and Purslow 1992;Hijikata et al 1993;Trotter et al 1995;Huijing et al 1998;Huijing 1999a,b), and also using finite element modeling (Yucesoy et al 2002). Such force transmission is referred to as intramuscular myofascial force transmission (Huijing 1999a,b).…”

Extramuscular myofascial force transmission within the rat anterior tibial compartment: proximo‐distal differences in muscle force

“…This muscle, containing ®bres that do not necessarily span the distance between proximal and distal muscle ®bre attachment areas of a muscle on aponeuroses or bone, but end somewhere in a fascicle that itself is attached at both ends. It is evident that for such ®bres force must be transmitted to neighbouring tissues at least at one ®bre end (Loeb et al 1987, Trotter 1990, 1991, 1993, Scott et al 1992, Trotter & Purslow 1992, 1995, Eldred et al 1993a,b, Hijikata et al 1993, Hijikata & Ishikawa 1997, Monti et al 1999). With few exceptions (i.e.…”