Let's say you volunteer for a research study at the University of Minnesota. If you are seriously injured or disabled, who pays for your medical care? Not the U. Have a look at this consent form for the CATIE study, which spells it out for you. The University of Minnesota does "not provide financial assistance for medical or other costs."
What if you're permanently disabled and can no longer work? Will you be compensated? Nope, afraid not. "In the event of personal injury resulting from the research procedures, financial compensation cannot be provided."
Of course, you can always sue them. (What the consent form doesn't mention, of course, is that the local courts have ruled that the U is immune from such litigation.)