What is the strongest human muscle?
Dear Straight Dope:
Please help settle a bet. I say the jaw muscles are the strongest in the human body, ounce-for-ounce. My friend says no way. Is it the tongue? The buttocks? Please let me know!
I just found the answer to this question in--where else--the dentist's office. The strongest muscle in the body is the masseter, the muscle you use to bite with. It's found on either side of the mouth. The dentist told me that many Eskimos have (or used to have, when they subsisted on tough whale meat, etc.) twice the biting strength as those of us who live on tamer fare. According to the 1992 Guinness Book of Records, in 1986 Richard Hofmann of Lake City, Florida achieved a bite strength of 975 lbs. for two seconds. That's more than six times the normal biting strength of a human. (Don't have a more recent Guinness book to see if that record has been broken.)
SDSTAFF Doug adds:
At the risk of getting Jill mad at me again for being a buttinski, I should point out that the question can be interpreted a few ways, and the answer Jill gives is true for only one of those interpretations. Specifically, the masseter is the muscle that can generate the largest externally measurable force attributable to the action of a single muscle. However, it has the good fortune of being very broadly attached to a short-armed lever--mechanical advantage counts for a lot. Human striated muscles don't differ in quality all that much, and other muscles typically have much smaller points of attachment (making them more likely to tear under stress), and/or less leverage. If you could somehow remove the muscles from their points of attachment and just measure how much they could lift, without the bones to help, the masseter would lose out against a lot of other muscles. The rule of thumb is that the power of a striated human muscle is highly correlated with the effective cross-sectional area (i.e., the number of fibers); the length of the muscle is meaningless. The two top contenders in this interpretation are the ol' gluteus maximus (which tends to be fatty, inflating its diameter) and the quadriceps.
People sometimes claim the heart is "strongest" is because it does more work over one's lifetime than any other muscle, and it's almost impossible to fatigue. Another muscle often mentioned is the tongue, although I don't know why--it works almost constantly (at least in some people), but generates little force and does fatigue. Just try sticking it out and wiggling it up and down for five minutes. You'll see.