Natural barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach acid.
You can always sit on the ground and stretch your legs in a pike position, lean in a crescent shape to stretch your back and sides of your torso, roll ankles, and even pull your arms across your body to create a simple stretch.
Im not quite sure but i would go with
1. changing to a completely new type of activity - overcoming a plateau
2. making your goals easier - restarting after a break
