Next time when you are out for Walking just observe yourself how you walk. Pay attention to how much you swing the hand forwards. Most of us swing our hands forward but we need to swing our hands backward too. Because Forward swinging movement is towards the Gravity thus it’s easier to do it. But the backward swinging is away from the Gravity thus it’s little tough to do it. But what happens over a period of time we only swing it forwards not at all backwards.This is not only with the hands even the Legs we do the same. Morely when we sit…as a child we have always been told to sit straight and upright. But how we all sit with Forward Bending. So as a whole we keep encouraging the Flexion movement than the Extension.Thus your Extension muscles are not being used and it becomes weaker which also an another reason for you to do more Flexion movement. So even as little as possible do Extension movements as well so that your Brain has the memory of it.