Multiple sclerosis (MS) is a common, chronic, autoimmune, and often disabling disease of the central nervous system with no cure. Therefore, the aim of this study was to investigate and compare the strength and activity of the lower body muscles of active and inactive multiple sclerosis patients during walking activity. In this study, 35 people with MS from Mazandaran province participated voluntarily and were divided into two groups based on the level of physical activity: active MS (20 people) and inactive MS (15 people). Maximum quadriceps muscle strength was assessed using the Brzeski formula, and muscle activity and co-contraction of the lower limb muscles were assessed by recording electromyographic signals. Data were analyzed using t-test and SPSS software version 22 at a significance level of 0.05. This research showed that there was a significant difference between the strength and electrical activity of the muscles of the active and inactive groups of MS (P>0.001). So that the mean electrical activity of the muscles (P=0.001), the maximum electrical activity of the muscles (P=0.001) was lower in the active MS group, but the muscle strength (P=0.001) in the active MS group was higher than it was more in the inactive MS group. On the other hand, co-contraction in the active MS group was not different from the inactive MS group (P<0.05). Long-term exercise has a positive effect on muscle strength and reduces the need to send electrical signals in active patients. Also, changes in activity intensity can affect the need for electrical activity, and future studies can further investigate this hypothesis.