Sen. Bernie Sanders (I-VT) released letters from three doctors on Monday, which claim that the 78-year-old presidential hopeful is fit to undertake the “vigorous activities” that the office entails. According to the campaign, Sanders’ primary care physician, Dr. Brian Monahan, said the Democratic presidential candidate is in “good health currently” and has been engaging in campaign events “without limitation.” Sanders underwent a heart procedure in early October after a heart attack, and has since had “continuous EKG monitoring” along with a “treadmill stress test” in December, which Monahan said he completed successfully. University of Vermont cardiologist Dr. Philip Ades said Sanders is able to exercise at a level that is about 50 percent higher than those his age and had a diagnosis similar to his. “[S]hould he be elected, I am confident he has the mental and physical stamina to fully undertake the rigors of the Presidency,” Dr. Martin LeWinter, Sanders’ personal cardiologist, wrote.