DOMS is painful, and can really wreck havoc on your daily activities. But you should still be able to do things, albeit a little more slowly. However, if you literally can’t straighten your arm a few days after a round of bicep curls, it's probably time to call the doctor. Brickner says that this is a sign of rhabdomyolysis, a severe injury to the muscles from an excessive workout. Extreme exercise can actually cause cell death of the muscles themselves. When the cells die, they release toxins into the bloodstream, which can cause immobility of the muscles in question, stiffness, swelling, and a release of myoglobin into the kidneys, which can make your pee look bloody. Not so good.