Went on a 7mile hike with around 2000ft elevation gain, on the way down Freya (4.5yrs old) started walking slower and needed more breaks. She has done longer hikes earlier this year with no problem. It has been a few months since our last hike but in the past she was always fine. The day after the hike she seemed extra tired and walked slowly when I took her out. Today she is still walking slower than usual when I take her out. Could her muscles be sore from the hike? She doesn't seem to have any injuries so I am thinking just muscle soreness, thoughts?

If her usual distance is between 1-3 miles and you do more than double that on a day it can cause soreness or stiffness. Weather can make a difference too. My girl (she's much older) feels those changes in weather come in and that makes a difference for her on those long walks.

have you checked her pads? are they torn up or blistered? jack was a rock start up till about 2 yrs ago, now he crashes after a hike as well as the next day, he is 8 now.
if she is just slow vs favoring a leg she may just be sore and not injured, unless its her feet/pads.
try giving her a good massage over her body

Bet you're right Jenn. Maybe not even torn up, just worn from walking on the rocks - which will cause them to be sore. My aunts Irish setter loved to run with us when we walked on the rocks at "home" in upstate New York. He never tore them but after a day out you could see where the pad was worn - kinda saw a hint of red through the black pad. The question and your comment reminded me of them ... don't have pictures, just some great memories.

Thanks for the responses! 2 days later and she is back to her normal self. Must have been sore muscles. I make sure her pads are in good shape and use mushers secret if any problems arise