I do 6kms brisk walk in 66mints but after the walk i have pain around the calf muscles , & ankles and some times also at the back what should i do.

Pes Planus/flat feet: These symptoms are very similar to complaints i see with patients with hypermobile, or flat feet. While walking, the lack of rigidity fails to absorb shock, and as the foot pronates, or "flattens" and moves outward "abducts", the calf muscle (gastrocneumius) is overstretched. Orthotics with a heel lift, for support, and stretching exercises can be very helpful.