One way travel to Isteria took about 20 hours, the time for the rest or break had been deducted, and if this was converted into distance then they had walked for about 80 km.
If it was the adults, their body might be used to farming works. But if she drank the elixir equivalent Lipo-D, then it wouldn’t be strange for the 6 year old Myra to exhibit such stamina.