title: Muscle force depends on the amount of transversal muscle loading.
abstract: Skeletal muscles are embedded in an environment of other muscles, connective tissue, and bones, which may transfer transversal forces to the muscle tissue, thereby compressing it. In a recent study we demonstrated that transversal loading of a muscle with 1.3Ncm(-2) reduces maximum isometric force (Fim) and rate of force development by approximately 5% and 25%, respectively. The aim of the present study was to examine the influence of increasing transversal muscle loading on contraction dynamics. Therefore, we performed isometric experiments on rat M. gastrocnemius medialis (n=9) without and with five different transversal loads corresponding to increasing pressures of 1.3Ncm(-2) to 5.3Ncm(-2) at the contact area between muscle and load. Muscle loading was induced by a custom-made plunger which was able to move in transversal direction. Increasing transversal muscle loading resulted in an almost linear decrease in muscle force from 4.8±1.8% to 12.8±2% Fim. Compared to an unloaded isometric contraction, rate of force development decreased from 20.2±4.0% at 1.3Ncm(-2) muscle loading to 34.6±5.7% at 5.3Ncm(-2). Experimental observation of the impact of transversal muscle loading on contraction dynamics may help to better understand muscle tissue properties. Moreover, applying transversal loads to muscles opens a window to analyze three-dimensional muscle force generation. Data presented in this study may be important to develop and validate muscle models which enable simulation of muscle contractions under compression and enlighten the mechanisms behind.
authors.affiliation: Institute of Sport and Motion Science, University of Stuttgart, Allmandring 28, D-70569 Stuttgart, Germany. Electronic address: tobias.siebert@inspo.uni-stuttgart.de.
authors.forename: Tobias
authors.initials: T
authors.lastname: Siebert
authors.affiliation: Institute of Motion Science, Friedrich-Schiller-University Jena, Jena, Germany.
authors.forename: Olaf
authors.initials: O
authors.lastname: Till
authors.affiliation: Institute of Sport and Motion Science, University of Stuttgart, Allmandring 28, D-70569 Stuttgart, Germany.
authors.forename: Norman
authors.initials: N
authors.lastname: Stutzig
authors.affiliation: Institute of Sport and Motion Science, University of Stuttgart, Allmandring 28, D-70569 Stuttgart, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Günther
authors.affiliation: Institute of Motion Science, Friedrich-Schiller-University Jena, Jena, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Blickhan
mesh_terms: D000818:Animals; D004548:Elasticity; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008422:Materials Testing; D008953:Models, Anatomic; D018482:Muscle, Skeletal / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013314:Stress, Mechanical; D013997:Time Factors; D014783:Viscosity
keywords: Force reduction; Impact load; Isometric contraction; Muscle compression; Viscoelastic material properties