This study compares the fatigability and isometric contractile characteristics in the biceps brachii muscle of old and young subjects, both male and female. The effects of age and gender on a surface electromyogram for various force levels of contraction during isometric contractions are investigated. Experiments are conducted with two age groups, namely young (ages 20-29) and old (ages 60-69), who performed sustained isometric contractions at various force levels (50%, 75%, 100% of maximal voluntary contraction). Traditional features such as root mean square (RMS) and median frequency (MDF) are computed from the recorded surface electromyogram. The results indicate that the MDF of the surface electromyogram is not significantly affected by age, but it is affected by gender in both age groups. There is a significant difference in the RMS of the surface electromyogram with age and gender at all force levels of contraction. The results also indicate a large inter-subject variation, which may be due to differences in the physiological cross sections, placements of electrodes, and muscle contractile properties such as muscle fiber size and number.