title: In-vivo measurement of muscle tension: dynamic properties of the MC sensor during isometric muscle contraction.
abstract: Skeletal muscle is the largest tissue structure in our body and plays an essential role for producing motion through integrated action with bones, tendons, ligaments and joints, for stabilizing body position, for generation of heat through cell respiration and for blood glucose disposal. A key function of skeletal muscle is force generation. Non-invasive and selective measurement of muscle contraction force in the field and in clinical settings has always been challenging. The aim of our work has been to develop a sensor that can overcome these difficulties and therefore enable measurement of muscle force during different contraction conditions. In this study, we tested the mechanical properties of a "Muscle Contraction" (MC) sensor during isometric muscle contraction in different length/tension conditions. The MC sensor is attached so that it indents the skin overlying a muscle group and detects varying degrees of tension during muscular contraction. We compared MC sensor readings over the biceps brachii (BB) muscle to dynamometric measurements of force of elbow flexion, together with recordings of surface EMG signal of BB during isometric contractions at 15° and 90° of elbow flexion. Statistical correlation between MC signal and force was very high at 15° (r = 0.976) and 90° (r = 0.966) across the complete time domain. Normalized SD or σN = σ/max(FMC) was used as a measure of linearity of MC signal and elbow flexion force in dynamic conditions. The average was 8.24% for an elbow angle of 90° and 10.01% for an elbow of angle 15°, which indicates high linearity and good dynamic properties of MC sensor signal when compared to elbow flexion force. The next step of testing MC sensor potential will be to measure tension of muscle-tendon complex in conditions when length and tension change simultaneously during human motion.
authors.affiliation: TMG-BMC Ltd., Splitska 5, Ljubljana 1000, Slovenia. andrej.meglic.info@gmail.com.
authors.forename: Srđan
authors.initials: S
authors.lastname: Đorđević
authors.affiliation: Faculty of Electrical Engineering, University of Ljubljana, Tržaška 25, Ljubljana 1000, Slovenia. saso.tomazic@fe.uni-lj.si.
authors.forename: Sašo
authors.initials: S
authors.lastname: Tomažič
authors.affiliation: University of Nottingham, School of Graduate Entry Medicine and Health, Derby Royal Hospital, Uttoxeter Road, Derby DE22 3DT, UK. marco.narici@nottingham.ac.uk.
authors.forename: Marco
authors.initials: M
authors.lastname: Narici
authors.affiliation: Institute for Kinesiology Research, Science and Research Centre of the University of Primorska, Garibaldijeva 1, Koper 6000, Slovenia. rado.pisot@zrs.upr.si.
authors.forename: Rado
authors.initials: R
authors.lastname: Pišot
authors.affiliation: TMG-BMC Ltd., Splitska 5, Ljubljana 1000, Slovenia. andrej.meglic.info@gmail.com.
authors.forename: Andrej
authors.initials: A
authors.lastname: Meglič
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D009129:Muscle Tonus / Q000502:physiology