The different types of muscle are classified via their histological structure and actual mechanism for contraction. (aminoacidstudies.org)
While these studies are interesting, they don't posit any actual mechanism that would provide such benefits, nor are said benefits terribly pronounced. (religion.blogs.cnn.com)
While the actual mechanism for such protection is not fully understood, researchers are beginning to understand more about how it might work: (breastfeedingtoday-llli.org)