I don't think there's a separate program for biomechanical engineering grad work but in the department of mechanical engineering there are two profs who do research in biomechanics who you could work for.
http://mech.mcmaster.ca/research.html (go to the bottom)
However, in undergrad there aren't that many biomechanical engineering courses available, only two (1-biomechanics, 2-experimental and computational biomechanics). But I know that the people in electrical and biomedical engineering have the option to take these courses as technical electives.
If you're looking to do research in biomedical engineering though there are many different ways you could do that. There is the school of Biomedical engineering which has research in many different areas including medical robotics if you're interested in that. (This program accepts people in engineering as well as people from sciences and will give you a M.A.Sc)
http://msbe.mcmaster.ca/research/research.html
You could also do biomedical research with the faculty of electrical and computer engineering. I think they only accept engineers and you get an M.Eng out of it.
http://www.ece.mcmaster.ca/research/bme.htm
If you're really interested in the science of biomechanics and don't care so much for engineering then you could do research with the department of kinesiology (you get a M.Sc).
http://www.science.mcmaster. ca/kin...mechanics.html