The most neglected, receive more abuse than any other part and some people don't even like them!
Yet the feet don't even have to be in pain or feel like they have a problem for them to cause issues in almost any other region of the body.
The structure of the feet essentially enables us to float as we walk...... the entire weight of your body is actually suspended by the soft tissue and the ligaments attached to the 26 bones we have in each foot. The arches allow for the force to be distributed as they bend and twist allowing for the mammoth amount of movement each foot has.
Within the feet there are nerve endings called proprioceptors, these nerve endings sense the position and movement of the foot, they then inform the rest of the body for co-ordination of body movement and position. When you walk, that trailing foot each swing bends and stimulates the nerve sensors in the ankle, foot and toes, this sends information all the way up to the shoulder on that same side causing the shoulder muscles in the back to relax but the shoulder muscles at the front to contract, making the arm naturally swing forward, perfectly synchronised. Therefore you can understand how if your foot isn't functioning properly (maybe there's been an injury, you have flat feet etc.) the nerves are stimulated in a more confusing manner so that shoulder won't be synchronised, causing joint and muscle aches. No wonder you feel fatigued when your feet are aching, your body is fighting itself, just to walk!
It doesn't end there though, there are thousands of nerve impulses being fired when we walk, if those feet aren't doing their job then the whole body becomes involved and things can spiral..... The shoulder that was fighting itself causes neck strain, this irritates the small nerves that go through the muscular areas at the base of the skull, headaches happen, upper back strain may cause a spine misalignment irritating the nerves coming out of the vertebrae, causing digestive disturbances perhaps or other health problems as the autonomic nervous system (which controls organ/gland function) is imbalanced. This suggests anything organ, muscular, ligamentous etc. could be affected just from walking poorly, or from an old sprain injury that occasionally niggles or from those flat feet.
The moral here is take care of your feet, listen to them if they begin to ache, give them a rub when they ask for it, rotate your toes and your ankles and rest them if required.