Muscles hurt after hiking for a few reasons. The most common reason muscles hurt is because of overuse. When you hike, your muscles are constantly being put under tension and they can eventually wear down. Another reason muscles might hurt after hiking is if you’re not properly hydrated. Hiking can dehydrate you and when your muscles are dehydrated, they can become sore. Finally, if you’re not stretching before or after hiking, your muscles will also be more susceptible to injury.