3. The next task will be a Dual Task (walking task and cognitive task) (Etemadi, 2016). Subjects will continuously walk for 60 seconds at a preferred speed along a 10 m walk way. The walking velocity will be calculated. During the walking task the participants will be required to make mathematical subtractions of 7 from random numbers between 200 to100. Responses will be recorded using a voice recorder. The score will be calculated as: correct response rate (CRR) = response rate per second × % of correct responses. The CRR had acceptable reliability (ICC = 0.61-0.75) in patients with multiple sclerosis (Ghanavati et al. 2014).