The Lymphatic system is where you dump all the toxic products you burn during a work out. It runs alongside the cardiovascular system, except unlike that system it does not have a pump, heart. So when you work out the heart rate increases and that in turn will allow you to drain all the lymphatic fluids. However after the work out, when you heart returns to normal, the lymph system does not keep draining and so the toxins remain in your system, so you feel sore. Massage keeps the lymphatic system draining. I do not work out as I have RA, but I always have a weekly back massage, after which I have to go to the toilet, as my bladder is full, even if I emptied my bladder before the massage. Best of Luck