I have been having some sort of pain or soreness on my left anterior deltoid muscle since last friday (three days ago). The soreness or pain started a few hours after I did my muscular endurance training session. I actually didn’t have enough time that day to do a full muscular endurance workout, so I only did the technogym lat row machine with 3 sets of 45 reps and the leg curl (stability ball) exercises with 2 sets of 65 reps. On thursday, which was the day before this workout session, I went to my Hapkido class which was a somewhat light to moderately intense workout, and I felt fine during the entire session and right after. However, I don’t know if would have anything do with the problem that I am having now, but as of last week for some reason I had muscle soreness on both my serratus anterior muscles for four days (from Wednesday to Saturday). This soreness started on wednesday, the day after I did my full muscular endurance training session. Also, on wednesday I did a 30 minute run. In addition, I always try to utilize proper form in all my muscular endurance exercises. So I don’t understand what I did wrong?