Test-Retest Cross-Reliability of Tests to Assess Neuromuscular Function as a Multidimensional Concept.

Bernecke, V, Pukenas, K, Imbrasiene, D, Mickeviciene, D, Baranauskiene, N, Eimantas, N, and Brazaitis, M. Test-retest cross-reliability of tests to assess neuromuscular function as a multidimensional concept. J Strength Cond Res 29(7): 1972-1984, 2015The purpose of this investigation was to estimate the test-retest cross-reliability of peripheral and central changes with respect to nonlinear and linear measures of a surface electromyography (EMG) signal measured during isometric maximal voluntary contraction (MVC) combined with superimposed electrical stimulation during a brief and fatiguing task involving the ankle plantar flexors over 2 follicular phases of menstrual cycle. Ten healthy female adults underwent 1 familiarization session and 5 identical test-retest sessions. The results showed that the decrease in plantar flexor EMG components (root mean square [RMS], mean frequency [MnF], wavelet packet entropy [WPE]) for soleus and gastrocnemius muscles, central activation ratio (CAR) and MVC, and contractile properties (P20, P100, PTT-100, and half-relaxation time) of the plantar flexor muscles at the end of 2-minute MVC were similar (time effect; p < 0.001, eta(2)(P) > 0.7, statistical power [SP] > 99%) and exhibited high stability over 5 trials (trial effect; p > 0.05; eta(2)(P) < 0.2, SP < 30%). High reliability between trials was found for 5-second MVC (intraclass correlation coefficient [ICC] > 0.82, p < 0.001) and meaningful reliability for 2-minute MVC (ICC > 0.66, p < 0.01). In conclusion, in young healthy women, measurements of neuromuscular function, such as RMS, MnF, and WPE of a surface EMG signal, MVC, and CAR from a brief and sustained MVC of the ankle plantar flexors, are reliable, and multidimensional stability was found with respect to both high and low correlation outcomes across the 5 identical test-retest trials of any 2 properties measured during brief and sustained MVC.