Figure 2 Traces demonstrating the increase in normalised threshold (NT) induced by a maximal voluntary contraction (MVC) for 60 s in a representative patient with amyotrophic lateral sclerosis for stimuli of (A) 0.1 ms and (B) 1 ms duration. The increase in threshold was accompanied by (C) an increase in superexcitability and (D) a reduction in the strength–duration time constant. These changes were consistent with the development of membrane hyperpolarisation. The filled bar represents the period of MVC.