Intermittent electrical stimulation with occluded circulation results in a twofold greater rate of glycogenolysis in type II compared to type I muscle fibres, likely due to accelerated ATP turnover.
Glycogenolysis in type I and II muscle fibres was investigated in five healthy volunteers during electrical stimulation of the quadriceps muscle group with blood flow occluded. 2. The quadriceps femoris muscles were stimulated intermittently (1.6 s stimulation, 1.6 s rest) at a frequency of 50 Hz for 64 s and isometric contraction force was recorded. Muscle biopsies were obtained at rest prior to and immediately after stimulation. Single muscle fibres were dissected free and were identified as type I and II fibres. ATP, phosphocreatine (PCr) and glycogen contents were measured luminometrically and enzymatically in single fibres and mixed fibre muscle. 3. Electrical stimulation resulted in a marked decline in contraction force and near total depletion of PCr in both fibre types. The ATP turnover rate (P 0.05), is in agreement with the suggestion that glycogenolysis in this fibre type is already occurring at a near-maximal rate with circulation intact.
Greenhaff et al. (1993) studied this question.