Hi welcome to HCm
I have gone thru your query regarding your body aches due to long walks .I can understand your concern .
In fact ,cause of your aches is not long walks but it happens when all of a sudden ,you start walking abruptly for long walk ,Your calf muscle to your heel, can be irritated by walking too much, It should be started modrately after warming up and increased gradualy.
Any exercise overdone , increases the stretch on the tendon, irritating it and making it weaker,as a result cause inflammation and pain .Otherwise long walks should not cause you body aches if they are carried on on even grounds .
In severe cases, limit or stop walking and place hot or cold packs on the injured area for 15 to 20 minutes, When you return to walking, stick to flat surfaces to keep your foot in a neutral position, and gradually increase your distance and intensity.
Keep your posture erect .
Keep your spine elongated and lean your whole body slightly forward
Make sure that your walking shoes have a spacious toe box which make your walk comfortable .
Some yoga , streching - side ways ,in front ,to back and towards sky will unwind your muscles and relieve pains .

Hot oil massage also strengthen your muscles and relieve pains . |

Eat Fiberous & calcium-rich foods like yogurt , cheese and greens -a balanced diet and ginger ,lemon juice and turmeric powder help alley inflammation & pains .

Avoid fried , fast foods , tea , cofee , alcohol , smoking , constipation ,dehyderation

Hope this helps solves your query .Take care , All the best .
Don't hesitate to get back if have any further query