Danijel Tosovic1, Laura Seidl2, Estifanos Ghebremedhin2, Mark J Brown2. 1. The University of Queensland, School of Biomedical Sciences, Department of Anatomy & Developmental Biology, St. Lucia 4072, Australia. Electronic address: danijel.tosovic@uqconnect.edu.au. 2. The University of Queensland, School of Biomedical Sciences, Department of Anatomy & Developmental Biology, St. Lucia 4072, Australia.
Abstract
INTRODUCTION: Mechanomyography (MMG) has recently shown promise in monitoring recovery of injured muscles. However, delivering a maximal percutaneous neuromuscular stimulus (PNS) could potentially be painful on severely damaged muscles. The aim of this paper was to determine whether delivering a sub-maximal PNS could still obtain accurate MMG recordings of muscle contraction time (Tc). The effect of muscle architecture on determining the minimal level of current was also investigated. METHODS: Six muscles were investigated; 5 lower limb and the 1st dorsal interosseous. A 'current ramp' procedure was performed to determine minimal stimulus intensity required for accurate Tc recordings. A current ramp entails beginning at a low current (30mA) and increasing in increments of 10mA until a maximal muscle contraction is observed. RESULTS: For lower limb muscles, 130mA was the largest current required to obtain accurate Tc recordings in at least 95% of the population. This was up to a 50% reduction in the amount of current delivered for some muscles. Fibre type distribution showed the greatest relationship with mean minimum current. DISCUSSION: Future studies investigating injured or uninjured muscles via MMG, could use these submaximal currents to obtain accurate MMG recordings, whilst improving patient comfort and reducing experiment duration.
INTRODUCTION: Mechanomyography (MMG) has recently shown promise in monitoring recovery of injured muscles. However, delivering a maximal percutaneous neuromuscular stimulus (PNS) could potentially be painful on severely damaged muscles. The aim of this paper was to determine whether delivering a sub-maximal PNS could still obtain accurate MMG recordings of muscle contraction time (Tc). The effect of muscle architecture on determining the minimal level of current was also investigated. METHODS: Six muscles were investigated; 5 lower limb and the 1st dorsal interosseous. A 'current ramp' procedure was performed to determine minimal stimulus intensity required for accurate Tc recordings. A current ramp entails beginning at a low current (30mA) and increasing in increments of 10mA until a maximal muscle contraction is observed. RESULTS: For lower limb muscles, 130mA was the largest current required to obtain accurate Tc recordings in at least 95% of the population. This was up to a 50% reduction in the amount of current delivered for some muscles. Fibre type distribution showed the greatest relationship with mean minimum current. DISCUSSION: Future studies investigating injured or uninjured muscles via MMG, could use these submaximal currents to obtain accurate MMG recordings, whilst improving patient comfort and reducing experiment duration.