This usually happens when we start brisk walk.our muscles take time.U must have seen sports persons doing warming up exercises before the main sport activity,similarly start with slow walk for short distance and then build up speed.For example on day 1 u walk 300 m in 30 min day2 200m in 20 min, to warm up ,another100 m in 5min and another 100m in 10 min to cool down . Keep increasing acc to your ability.After exercising if u feel stretched out go for a relaxing Ayurvedic massage .

Start Ashwagandha churna 5mg Twice a day after meals with lukeworm water or milk.Cap. Shilajit 2cap twice a day with water.Consult personally for proper advise.