The middle of my back as well as my upper abs cramped up while doing kettlebell swings with 25lbs. I haven t had problems with that weight before, nor have I ever experienced cramping during that exercise. Prior to doing the swings, I had biked for 5 miles, did 6 pull-ups , and 20 air squats. I discontinued doing the swings and came home. My upper abs and and back remains tight. I don t have any pain just discomfort from the tight muscles. Any suggestions to loosen the muscles?