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

Abstract

Muscles within the anterior tibial compartment (extensor digitorum longus: EDL, tibialis anterior: TA, and extensor hallucis longus muscles: EHL) and within the peroneal compartment were excited simultaneously and maximally. The ankle joint was fixed kept at 90°. For EDL length force characteristics were determined. This was performed first with the anterior tibial compartment intact (1), and subsequently after: (2) blunt dissection of the anterior and lateral interface of EDL and TA. (3) Full longitudinal lateral fasciotomy of the anterior tibial compartment. (4) Full removal of TA and EHL muscles.Length-force characteristics were changed significantly by these interventions. Blunt dissection caused a force decrease of approximately 10% at all lengths, i.e., without changing EDL optimum or active slack lengths. This indicates that intermuscular connective tissue mediates significant interactions between adjacent muscles. Indications of its relatively stiff mechanical properties were found both in the physiological part of the present study, as well as the anatomical survey of connective tissue. Full lateral compartmental fasciotomy increased optimum length and decreased active slack length, leading to an increase of length range (by ഠ47%), while decreasing optimal force. As a consequence an increase in force for the lower length range was found. Such changes of length force characteristics are compatible with an increased distribution of fiber mean sarcomere length. On the basis of these results, it is concluded that extramuscular connective tissue has a sufficiently stiff connection to intramuscular connective tissue to be able to play a role in force transmission. Therefore, in addition to intramuscular myofascial force transmission, extramuscular force transmission has to be considered within intact compartments of limbs. A survey of connective tissue structures within the compartment indicated sheet-like neuro-vascular tracts to be major components of extramuscular connective tissue with connections to intramuscular connective tissue stroma.Removal of TA and EHL yielded yet another decrease of force (mean for optimal force ഠ10%). No significant changes of optimum and active slack lengths could be shown in this case. It is concluded that myofascial force transmission should be taken into account when considering muscular function and its coordination, and in clinical decisions regarding fasciotomy and repetitive strain injury. In order to obtain whole body movement, forces need to be transmitted from the muscles to the skeleton to cause acceleration of the limbs. A major location for force transmission is the well-studied myotendinous junction (e.g., Tidball, 1983Tidball, , 1984Tidball, , 1991Tidball, , 1994Tidball & Daniel, 1986;Tidball & Quan, 1992). Such transmission involving transmission of force from one sarcomere to its serial neighbors and eventually onto the myotendinous junction. These junctions are located at the apical ends of muscle fibers, where sarcomeric forces are transmitted onto an...

Muscle Fiber and Motor Unit Behavior in the Longest Human Skeletal Muscle

“…The distortions created by these effects and the challenge to neural coordination must become more prominent in muscles with longer fascicles. Some force can be transmitted laterally between fibers (Street, 1983;Patel and Lieber, 1997;Huijing, 1999;Huijing and Baan, 2001;Monti et al, 2001). Lateral transmission of force occurs from z-lines to extracellular matrix via costameres and catenincadherin complexes (Young et al, 2000;Paul et al, 2002).…”

Evaluation and Imaging of an Untreated Grade III Hamstring Tear: A Case Report

“…Proximally, the semitendinosus and biceps are at the highest risk for injury owing to the pennation angle of their myofibers attaching to the common tendon of the hamstring complex [2]. The force generated by muscle is transmitted not only longitudinally along the axis of the muscle, but also radially to nearby muscles [17,34,38]. This altered pathway to transmit force to and along nearby muscles could minimize any functional deficits that would be detected if an injured muscle were tested in isolation instead of as part of a functional complex [4,17,32,41].…”

Functional and architectural complexity within and between muscles: regional variation and intermuscular force transmission

“…First, synergists can join at a common tendon, thus exerting force at a common insertion [8]. Second, synergists can be connected in parallel via common aponeuroses along the length of the muscles [23][24][25][26], resulting in the transmission of forces via connections of the intact inter-muscular connective tissue network. Third, muscles can be connected in series across adjacent limb segments by fleshy connections or via connective tissue networks.…”

“…synergists), substantial variation can occur depending on the role of the muscle [18][19][20][21]. The muscles within a limb, however, are often connected, resulting in the potential for intermuscular force transmission [22][23][24][25] (figure 1). For example, recent work has highlighted the connections between muscles, whether they are within a single limb segment [26] or between adjacent limb segments [27].…”