The 7 strongest muscles include 3 that I train and 4 that I don't.
The muscles I train are
2. Gluteus maximus
3. Soleus (calf)
The others are
4. Exterior muscles of the eye
5. Masseter (jaw)
7. Uterus (the gender-specific one in the hint)
Personal Trainer, Fitness Instructor since 1998.