Muscle quality evaluation using electrical impedance myography: inter-day repeatability

Introduction The assessment of Muscle Quality (MQ) is of considerable relevance when investigating changes in muscle, fat and connective tissue composition associated with use or disuse in training and recovery time. Recently, Electrical Impedance Myography (EIM) has been proposed as a non-invasive approach for the assessment of MQ in patients with neuromuscular disease (1) and in patients affected by disuse atrophy (2). The present study aimed at assessing MQ and Fat content (FM) in a population of healthy young football players and evaluate the inter-day repeatability of EIM measures with a novel and portable device. Methods Twenty-five participants, amateur football players, (17 M, 8 F; mean±SD: age = 26.6±5.2 yrs; height =1.74±0.08 m; body mass = 69.1±13.1 kg) underwent two EIM measurements within the same week at the same time of the day. MQ and FM were assessed using a portable, battery operated, EIM device (Skulpt, Chisel, San Francisco, USA), connected to a smartphone via Bluetooth. EIM involves high-frequency (50 KHz), low-intensity electrical alternating current applied to the muscle belly using 12 surface electrodes. Resulting voltages on the surface of the skin are detected and analyzed to produce EIM measurements by an internal algorithm. The device is applied on three body locations (triceps brachii, rectus abdominis and quadriceps femoris) for total MQ and FM estimations. Inter-day correlation coefficients with 95% confidence interval (ICC), and standard error of measurements as percentage (SEM%) were calculated. Paired Student’s t-test was used to assess differences between measures (p<0.05). Results MQ values were 59.3±18.0 Arbitrary Units (AU) and 59.7±18.6 AU, day 1 and 2, respectively (p=0.633). Inter-day ICC was 0.998 (0.997-0.999) with SEM = 3.38%. FM values were 21.2±5.4 % and 20.9±5.1 %, day 1 and 2, respectively (p=0.469). Inter-day ICC was 0.970 (0.900-0.998) with SEM%=4.31%. Conclusions Assessment of MQ and FM by EIM employing a light, novel and portable device seems to yield highly reproducible results with very high inter-day ICCs and narrow confidence limits, very useful to football players. Moreover, SEM values are low. Further studies are needed to compare Skulpt outputs with gold-standard techniques of body composition assessment (e.g. DEXA) to evaluate the validity of EIM in the assessment of MQ and FM, and for monitoring changes in MQ and FM induced by use and disuse. References 1. Rutkove SB. Electrical impedance myography: background, current state, and future directions. Muscle Nerve 2009; 40(6): 936-946 2. Tarulli AW, Duggal N, Esper GJ, Garmirian LP, Fogerson PM, Lin CH, Rutkove SB. Electrical impedance myography in the assessment of disuse atrophy. Arch Phys Med Rehabil 2009; 90(10): 1806-1810