A famous physician used to relate that in his entire career of treating thousands of patients, he had only one patient who followed his instructions exactly without deviation. The patient was the great sage, Rabbi Yisroel Salanter -- because he regarded doctor's orders as the fulfillment of the Torah obligation to guard one's health.

Someone once came to Rabbi Salanter's room and found him perusing a medical guide to exercise. He had the book open and did every exercise exactly as described -- since the doctor had advised him to do so.