I am aware of Delay Onset Muscle Soreness which usually sets in for me after about 14 hrs after strenuous exercise. I recently have experienced something strange though. I woke up this morning (Friday) with very sore thigh muscles. I did an upper body workout Thursday morning and started to feel the soreness from that before I when to bed that night. The only thing I did previously was a 8 mile MTB ride on Thursday a week before and a 10 mile ride on Saturday. I also walked on the beach for about 2 hours on Friday between riding Thursday and Saturday. I do not walk very much at all and I was feeling the shin splints a little the next few days but they quickly subsided. I just can't figure out where the thigh soreness came from. Has anyone ever experienced phantom soreness like this? Is it possible that it is from an activity that occurred a week prior? Maybe I have been "Sleep MTBing."?