Force and membrane potential during and after fatiguing, intermittent tetanic stimulation of single XXXX muscle fibres.

@entity116 @entity308 @entity1238 @entity1295
Tension and membrane potential have been measured in isolated, short toe muscle fibres of @entity1238 during development of @entity1295 produced by intermittent, tetanic stimulation (0.5 s long 70 Hz trains repeated at 0.3-0.8 Hz) and during recovery. Fibres could be divided into three groups on the basis of their @entity1295 resistance. In the first group (type 1 fibres) tension fell to 40% of the original after about 70 @entity116 , in the second group (type 2 fibres) after about 300 @entity116 and in the third group (type 3 fibres) after about 600 @entity116 . Recovery was slow in type 1 and 2 fibres and faster in type 3. The former also displayed @entity308 ( @entity308 ), a 10-40 min period of severely reduced force production, eventually followed by complete recovery. As a result of fatiguing stimulation the membrane potential fell to -70 to -60 mV. It returned to the pre-stimulation value more rapidly than did tension. At the time of maximum @entity308 most fibres had repolarized to at least -75 mV and action potentials of normal configuration could be elicited. The results of the present experiments underline the importance of defining fibre types in studies of @entity1295 , also in amphibian muscle. Together with the results of a previous study (L  nnergren _ Westerblad 1986) they also demonstrate that both the decline phase and the recovery phase are markedly different when different modes of fatiguing stimulation are used.
