A study has been made of the isometric twitches of hypothenar and calf muscles in man. The twitch contraction time for hypothenar muscles ranged between 55 and 78 ms, while for the calf muscles it ranged between 90 and 125 ms. According to their speed of contractions the hypothenar muscles were considered belonging to the so called intermedious group while the calf muscles integrate the slow group. It has been also demonstrated that these techniques can successfully be applied to the investigation of several neuromuscular disorders.