Uniform and alternate electrically induced twitch responses. Description: left, uniform electrically induced twitch responses. Representative transmitted light movie of a skeletal muscle myofiber illustrating its uniform twitch behavior in response to bipolar electrical field stimulation of alternate polarity. Right, alternate electrically induced twitch responses. Representative transmitted light movie of a skeletal muscle myofiber showing its alternate twitch behavior in response to bipolar electrical field stimulation. Twitch responses to a pair of pulses (1 ms; 15 V/cm) interspaced by a 400-ms interval. High-speed time-lapse imaging was conducted for 2 s at 16.7 ms/frame using a Ă 10 objective magnification. (AVI 5445 kb)