Inter-rater reliability of muscle contractile property measurements using non-invasive tensiomyography

Tensiomyography (TMG) is a relatively novel technique to assess muscle mechanical response based on radial muscle belly displacement consecutive to a single electrical stimulus. Although intra-session reliability has been found to be good, inter-rater reliability and the influence of sensor repositioning and electrodes placement on TMG measurements is unknown. The purpose of this study was to analyze the inter-rater reliability of vastus medialis muscle contractile property measurements obtained with TMG as well as the effect of inter-electrode distance (IED). Five contractile parameters were analyzed from vastus medialis muscle belly displacement-time curves: maximal displacement (Dm), contraction time (Tc), sustain time (Ts), delay time (Td), and half-relaxation time (Tr). The inter-rater reliability and IED effect on these measurements were evaluated in 18 subjects. Intra-class correlation coefficients, standard errors of measurement, Bland and Altman systematic bias and random error as well as coefficient of variations were used as measures of reliability. Overall, a good to excellent inter-rater reliability was found for all contractile parameters, except Tr, which showed insufficient reliability. Alterations in IED significantly affected Dm with a trend for all the other parameters. The present results legitimate the use of TMG for the assessment of vastus medialis muscle contractile properties, particularly for Dm and Tc. It is recommended to avoid Tr quantification and IED modifications during multiple TMG measurements.