Do I need to have an undergraduate degree in biomechanical engineering to study biomechanics in graduate school?
No! Most of the students who come to Stanford to study biomechanics do not have undergraduate degrees in BME; instead, they have degrees in mechanical engineering, and are interested in biomechanics but have not had much formal study in the area. There are many opportunties to learn about biomechanics during the masters degree, and all of the graduate students can take undergraduate classes to make up deficiencies in specific areas. Additionally, if you find that you are not interested in biomechanics, you can always choose to focus in another discipline of mechanical engineering instead.