Evaluation of Reliability of H-Reflex Recruitment Curve Parameters of Soleus and Lateral Gastrocnemius Muscles in Assessment of Motor Neuron Pools Excitability

Background and Objectives: In Recent years, recording of the H-reflex recruitment curve for assessment of the excitability of group Ia afferent monosynaptic reflex has been growing. The purpose of this study was to evaluate the reliability of H-reflex recruitment curve parameters of gasterosoleus muscle in the assessment of motor neuron pool excitability. Methods: In this descriptive study, 50 non-athlete healthy volunteers were assessed. Percutaneously, 40 electrical pulses of 1 millisecond duration and 3 stimulations per each stimulus intensity were induced on tibial nerves and H-reflex recruitment curve were recorded in 4 phases. Also, each person was assessed in two sessions with 1-week interval. Results: The intraclass correlation coefficients )ICCs( was obtained between 0.97-0.99 for inter-session reliability of intensity for recording the threshold, HMax and HLast reflexes, amplitude of HMax, and the total slope of the ascending and descending arms. The inter-session correlation coefficient (test-retest) of these variables were obtained between 0.91-0.95 for soleus muscle, and the inter-session ICCs for peak-to-peak amplitude of HMax and the total slope of the ascending arm of gastrocnemius were obtained 0.65 and 0.67. The slope of initial and final three points of the ascending arm revealed a different reliability in inter-session and intra-session reliability analysis (0.64-0.96). Conclusion: The reliability analysis showed a high inter-session and intra-session ICCs for the functional principal components of soleus recruitment curve. Also, recruitment curve parameters, such as intensity for record of threshold and HMax of soleus and lateral gastrocnemius muscles as well as total slope of ascending and descending arms, and peak to peak amplitude of HMax of soleus muscle had a very high Reliability