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A muscle activation model of variable stimulation frequency response and stimulation history, based on positive
G H Otazu1, R Futami, N Hoshimiya
1Graduate School of Engineering, Tohoku University, Sendai, Japan. gonzalo@hoshimiya.ecei.tohoku.ac.jp
Abstract:
Muscle fiber response to a train of variable-frequency pulses includes the potentiation and catch-like effect. For better understanding of these phenomena, we built an activation model with emphasis on the calcium liberation from and re-sequestration into the sarcoplasmic reticulum, including calcium-induced calcium release. The model had two stable equilibrium points in the calcium concentration. Changes from the low to the high equilibrium point could be produced by high-frequency trains of pulses and would account for the potentiation. The model also showed a catch-like effect, as a long-lasting increment of muscle force after the application of a single extra pulse. The increase in force appeared in resting muscle, disappeared when the muscle was potentiated, and reappeared briefly if the stimulation was continued for long periods.