I read with interest the recent publication by Joo et al. comparing posttetanic counts by accelerometry as compared with electromyography.1  They demonstrated that accelerometry counted more twitches than did an electromyography system. However, while their work was meticulously conducted and analyzed, there is a slight but fundamental misstatement in their conclusion. This stems from a nearly universal misunderstanding as to the meaning of the term “twitch” in an era of quantitative technology.

Since the introduction of peripheral nerve stimulators in the late 1950s,2  we have relied on visible and/or tactile assessment of the movement of the thumb in response to ulnar nerve stimulation (many other nerves can be stimulated and distal responses assessed; for the current discussion, I will restrict my comments to stimulation of the ulnar nerve). Since 1970, with the introduction of the “train of four” by Ali et al., this changed from estimating...

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