Abstract des Autors

To investigate whether muscle fiber conduction velocity reflects muscle fiber type, we studied the extensor digitorum longus (EDL) and soleus (SOL) muscle in 7 male rats aged 12 weeks. Muscle fiber conduction velocity was measured with a surface electrode array during stimulated contraction and calculated from the delay between two action potentials along muscle fibers for a given inter-electrode distance. Conduction velocity in the EDL (2.71 +/- 0.50 m/s) was significantly higher (p < 0.05) than that in the SOL (2.14 +/- 0.34 m/s). Fiber type, fiber area and fiber diameter were determined by myosin ATPase staining and NADH-tetrazolium reductase staining. Muscle fiber composition of the EDL and SOL was 04.6 +/- 1.8% and 14.8 +/- 4.3% FT fibers, respectively, and mean muscle fiber diameter was 62.7 +/- 6.2 micro-m and 79.2 +/- 7.8 micro-m, respectively, that of the EDL being significantly smaller (p < 0.01) than that of the SOL. It was suggested that individual differences in conduction velocity wee caused by differences in muscle fiber composition rather than differences in muscle diameter. Verf.-Referat