Introduction: This study aimed to investigate the onset time and the electromyographic activity level of the selected lower limb muscles in the active and inactive old women.Materials and Methods: In this case-control study, 28 old women with a Mean±SD age of 61.07±0.88 years were selected in the inactive (15 people) and active (13 people) groups. The electrical activity of the selected muscles of the lower limbs was collected by the EMG device in a stair down movement. Results: The onset time of tibialis anterior, vastus lateralis, and biceps femoris muscles are faster in the active group (p <0.05). Besides, the activity level of the rectus femoris muscle in the interval of 100 ms before the initial contact and the ratio of the vastus medialis muscle to the biceps femoris muscle was significantly lower (p <0.05) in the active group.Conclusion: It seems that the muscles of the lower limbs in the group of women with regular physical activity are activated faster than the inactive group and the decrease in the activity of the rectus femoris muscle and the ratio of the vastus medialis to the biceps femoris muscle in the active women may be accompanied by fatigue and reduced intra-articular forces. Therefore, it is recommended that old women participate in regular and active exercise programs to improve their onset times of muscle activity.
