Another Country VS the U.S.

One thing noticeably different after returning from another country: all my body parts were fine when I was away. I felt healthy, I could see clearly because I was not looking at technology all day, I didn't have many pains. The moment we arrived back to the airport in the US, I felt my shoulders stiffing up as if I were siting at an office desk all day. It's strange. And all of a sudden, my knees start hurting probably due to the changing weather. Definitely a very uncomfortable feeling.