[Dynamics of muscle relaxation following unfused tetanus of different durations]

The isometric force of human m. flexor digitorum sublimis and its first time derivative were recorded during muscle relaxation. It was shown that after the prolonged unfused tetanus (phase iii) and in contractions in response to the repeated double pulses so called delayed relaxation with increase of TR/2 and typical "shoulder" on the relaxation curve can be observed. Delayed relaxation never can be seen in twitch. It was supposed that such type of relaxation is characteristic of the states of high activation of contractile machinery.