Compartmental fasciotomy and isolating a muscle from neighboring muscles interfere with myofascial force transmission within the rat anterior crural compartment

Abstract

Muscles within the anterior crural compartment (extensor digitorum longus, EDL; tibialis anterior, TA; and extensor hallucis longus, EHL) and within the peroneal compartment were excited simultaneously and maximally. All muscles were kept at constant length with the exception of EDL, for which muscle length was changed by moving its proximal tendon. Active and passive force was measured at proximal as well as distal EDL tendons and at the combined distal tendons of TA and EHL (TA+EHL). In the initial experimental condition, a difference (F(proximal) > F(distal)) in EDL force, amounting to 0-14% of proximal force, was confirmed for most EDL lengths. This is interpreted as a clear proof of extramuscular myofascial force transmission, as no significant EDL length effects could be shown on TA+EHL force. Repeated measurements were confirmed to cause marked changes of both proximal and distal length-force characteristics, such as a shift of the whole ascending limb of the active curve, including optimum length, to higher lengths without decreasing optimum force, and decreasing active force at low lengths (by approximately 57%). Repeated measurements also lowered proximal and distal EDL passive force (by up to 35%). The proximo-distal difference in passive as well as active EDL force was decreased, but persisted. At most lengths, this difference for active force amounted to a constant fraction (14%) of proximal force. TA+EHL force was not affected significantly. Subsequently, acute effects of experimental surgical alterations were studied: The first manipulation was full lateral fasciotomy of the anterior crural compartment that caused a further decrease in active force at the proximal EDL but not at the distal EDL tendon. Passive forces showed no further significant changes. The proximo-distal EDL active force difference decreased to 0-5% of proximal force. After fasciotomy, TA+EHL force increased by 30%. This was interpreted as evidence of increased intramuscular and decreased extramuscular myofascial force transmission. The second manipulation was full isolation of EDL from TA+EHL, but not from extramuscular connective tissues, which caused a further decrease of the EDL proximo-distal force differences, indicating a stiffening effect of the presence of TA+EHL on the extramuscular matrix. For EDL active force the difference was no longer significantly different from zero. In contrast, for EDL passive force the proximo-distal force difference persisted. It is concluded that extramuscular myofascial force transmission is an important feature of the anterior crural compartment. The magnitude of this force transmission requires that it be considered in analysis of muscular function.

No functionally relevant mechanical effects of epimuscular myofascial connections between rat ankle plantar flexors

“…Previous studies using rats have clearly shown that connective tissue linkages between synergistic muscles are capable of transmitting substantial forces Huijing et al, 2003;Maas et al, 2001Maas et al, , 2004Maas et al, , 2005. However, these studies involved several aspects that were non-physiological.…”

The Architectural Design of the Gluteal Muscle Group: Implications for Movement and Rehabilitation

“…In vivo, the relationships change slightly because of submaximal muscle activations, 14,27 the interactions between muscles and connective tissues, 15 and tendon elasticity. 18 However, they should be considered as an accurate general framework for muscle physiology.…”

Directional Differences in the Biaxial Material Properties of Fascia Lata and the Implications for Fascia Function

“…Because fascia attaches to and envelops many limb muscles, it is often hypothesized that it broadens the insertion of muscles, distributing or redirecting muscle force transmission [1][2][3][4] . Several studies have shown that disrupting the fascia 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 3 between or around muscles decreases the muscle's force output [1][2][3] . Fascial continuity among limb segments and between the limbs and the trunk have led others to posit that fascia plays a role in transferring load and coordinating movement among limb segments and body regions [5][6][7] .…”