Not at all. While the admissions committee at Trinity has found, in their own experience as physicians, that people with an internal drive to contribute their time and energy to others do often make great doctors, it is not mandatory at all. The school has some official relationships with international healthcare organizations that do volunteer work, but participation is not required. Most of the service opportunities mentioned on the blog are entirely student driven. The faculty and staff understand, appreciate, and even expect that your top priority at Trinity is your education.