There are multiple muscles that could be considered to be the strongest muscle in the body. Since the definition of strongest can vary, it is hard to choose a single muscle that meets all possible criteria. The muscles that are most often considered to be the strongest are the tongue, soleus, masseter, gluteus maximus, heart, external muscles of the eye and muscles of the uterus.
Many consider the tongue to be the strongest muscle, even though it is actually a group of muscles, because it almost never stops working thanks to its incredible endurance. The tongue is used when a person eats and drinks, pushing food and liquid down the mouth into the throat. Even during sleep, the tongue is constantly working to keep saliva out of the mouth. Another contender for strongest muscle, the masseter, is also located in the mouth. It controls the force of the jaw during chewing and biting, and it has the greatest absolute strength of any muscle in the body, able to exert a bite force as great as 200 pounds (90.7 kg).
The gluteus maximus is the largest muscle in the body and it is often called the strongest because it is the primary muscle that keeps the body erect during walking. If a person's glueteus maximus is injured, he or she will often end up walking in a slouched or slumped posture.
On the other hand, there are the muscles of the eye, which are some of the smallest muscles of the body. Despite their size, they are often considered to be some of the strongest muscles in the body because of their endurance and elastic strength properties, which allows them to exert force quickly. The eye muscle's dynamic strength, basically the ability to complete repeated motions, is also very strong. The external muscles of the eye are constantly at work, moving the eyes at a nearly nonstop pace during the day.
Only women have the muscles of the uterus, another group of muscles that, when combined, are sometimes called the strongest in the body. These muscles are used during birth and are responsible for pushing the baby out through the birth canal. The amount of absolute strength and elastic strength generated by these muscles is incredible, but they are not used very often.
A muscle that is used often is the heart, which has greater strength endurance than any other muscle in the body. The heart is often considered to be the strongest muscle in the body because it is the hardest working. It never stops working, from birth until death, pumping approximately 2 billion times during a person's lifetime.