Fig. 5.

Changes in excitability parameters following a maximal voluntary contraction in each group. Comparison of changes in excitability parameters recorded from the median nerve before, during, and after maximal voluntary contraction of the abductor pollicis brevis for 1 min. The black horizontal bar indicates the period of maximal voluntary contraction. Each trace represents the mean data for 12 normal controls (filled circles), 17 patients with CIDP (open triangles), and 14 patients with SBMA (open squares). Data were averaged over consecutive 30 s intervals. All data are normalized to precontraction. Threshold current using test stimuli of 1.0 ms duration (A). Threshold electrotonus (TE) showed greater threshold changes in both depolarizing (B) and hyperpolarizing (C). The error bars represent the standard error of the mean (SEM). These findings suggest hyperpolarizing changes after maximal voluntary contraction. The changes were more significant in NC and SBMA than in CIDP.