Abstract. The effect of age and gender on muscle fiber conduction velocity (MFCV) was examined. Subjects were 216 healthy persons (369 limbs), of which 102 were males (180 limbs) and 114 were females (189 limbs). The method of evoked potential was used for measuring MFCV. The muscles measured were the vastus medialis of the right and / or left limbs. The measurement was taken in a sitting position with the hip and knee joints flexed at 90°. On the effect of aging, a significant correlation between MFCV and age was observed in males (r=0.63, p<0.01) and in females (r=0.52, p<0.01). There was a tendency of delay in MFCV due to aging. On the gender difference, male MFCV showed a faster rate, compared with that of females in the age group from 20's to 40's. However, no gender difference was observed in the age group of more than 50 years. Based on these results, age and gender differences must therefore be considered when determining standard values of MFCV.

The relationship between muscle fiber conduction velocity (MFCV) of the vastus medialis and muscle strength of knee extensors was observed in patients with joint disorder of the lower limb, and the feasibility of MFCV as an index for evaluating the condition of muscular disuse was examined. MFCV was significantly slower in patients with joint disorder (2.91 ± 0.27 m•s-1) than in healthy subjects (3.22 ± 0.22 m•s-1 ; p<0.01). Muscle strength of knee extensors was significantly lower in patients (198.1 ± 72.2 N) than in healthy subjects (311.2 ± 79.6 N; p<0.01). Muscle strength displayed a significant positive correlation with MFCV in patients with joint disorder (r=0.63, p<0.01). In patients after joint surgery of the lower limb, MFCV increased with muscle strength recovery. Reduced MFCV in patients with joint disorder appears to primarily reflect muscle atrophy of type II fibers. MFCV of patients with joint disorder of the lower limb may thus reflect changes in muscle fiber type and diameter.