There is no one answer for this question since there are different ways to measure strength. There is absolute strength (maximum force),dynamic strength (repeated motions), elastic strength (exert force quickly), and strength endurance (withstand fatigue).
& There are three types of muscles in the human body: cardiac, smooth and skeletal.
& Cardiac muscle makes up the wall of the heart and is responsible for the forceful contraction of the heart. Smooth muscles make up the walls of the intestine, the uterus, blood vessels, and internal muscles of the eye. Skeletal muscles are attached to the bones and in some areas the skin (muscles in our face). Contraction of the skeletal muscles helps limbs and other body parts move.
& Most sources state that there are over 650 named skeletal muscles in the human body, although some figures go up to as many as 840. The dissension comes from those that count the muscles within a complex muscle. For example the biceps brachii is a complex muscle that has two heads and two different origins however, they insert on the radial tuberosity. Do you count this as one muscle or two?
& Although most individuals have the same general set of muscles, there is some variability from one person to another. Generally, smooth muscles are not included with this total since most of these muscles are at cellular level and number in the billions. In terms of a cardiac muscle, we only have one of those- the heart.
Muscles are given Latin names according to location, relative size, shape, action, origin/insertion, and/or number of origins. For example the flexor hallicis longus muscle is the long muscle that bends the big toe:
Flexor = A muscle that flexes a joint
Hallicis = great toe
Longus = Long
& The following are muscles that have been deemed the strongest based on various definitions of strength (listed in alphabetical order):
External Muscles of the Eye
The muscles of the eye are constantly moving to readjust the positions of the eye. When the head is in motion, the external muscles are constantly adjusting the position of the eye to maintain a steady fixation point. However, the external muscles of the eye are subject to fatigue. In an hour of reading a book the eyes make nearly 10,000 coordinated movements.
The gluteus maximus is the largest muscle in the human body. It is large and powerful because it has the job of keeping the trunk of the body in an erect posture. It is the chief antigravity muscle that aids in walking up stairs.
The hardest working muscle is the heart. It pumps out 2 ounces (71 grams) of blood at every heartbeat. Daily the heart pumps at least 2,500 gallons (9,450 liters) of blood. The heart has the ability to beat over 3 billion times in a person’s life.
The strongest muscle based on its weight is the masseter. With all muscles of the jaw working together it can close the teeth with a force as great as 55 pounds (25 kilograms) on the incisors or 200 pounds (90.7 kilograms) on the molars.
Muscles of the Uterus
The uterus sits in the lower pelvic region. Its muscles are deemed strong because they contract to push a baby through the birth canal. The pituitary gland secretes the hormone oxytocin, which stimulates the contractions.
The muscle that can pull with the greatest force is the soleus. It is found below the gastrocnemius (calf muscle). The soleus is very important for walking, running, and dancing. It is considered a very powerful muscle along with calf muscles because it pulls against the force of gravity to keep the body upright.
The tongue is a tough worker. It is made up of groups of muscles and like the heart it is always working. It helps in the mixing process of foods. It binds and contorts itself to form letters. The tongue contains linguinal tonsils that filter out germs. Even when a person sleeps, the tongue is constantly pushing saliva down the throat.