September 02, 2006
Some People Have Extra Muscles

Toshihiko Komatsu, a functional anatomist at Osaka University in Japan, found in a study of dissection results that where most humans have 2 muscles as upper arm biceps some people have 3 or even 4 bicep muscles. (triceps? quadraceps?)

However, in Komatsu's research, 14 to 20 percent of people were found to have three muscles and 1 to 4 percent were found to have four muscles in their biceps.

People with more than the usual two muscles also tended to have more muscles than normal in other parts of their body, such as their elbows or fingers.

Do some people have genetic variations that code for more muscles? Or does noise in the system cause some small fraction of developing embryos to grow extra muscles in assorted places?

If people who have extra muscles are symmetric in their muscle counts (e.g. 3 muscles on upper arms on both arms) then that tends to suggest genetic variations coding for this result.

Any time you read about people who deviate from the biological norm for some quality of their bodies keep in mind that anything that can happen naturally will some day become selectable using biotechnology. If the people who have extra muscles gain some performance advantage then expect some parents in the future to opt for genetic engineering to give their kids the extra muscles on purpose.

Adding extra muscles to adults will become possible when advances in stem cell research and tissue engineering provide the ability to grow replacement muscles either inside or outside the body. But making those muscles useful might be much harder because wiring up neurons to the muscles and then training the brain to control them appropriately could turn out to be quite difficult.

Share |      Randall Parker, 2006 September 02 10:14 PM  Trends, Human Evolution

Tom said at September 3, 2006 1:03 PM:

"(triceps? quadraceps?)"

triceps would be a problem, as that term is generally used to refer to the triceps brachii (which extend the arm), whereas biceps is generally used for the biceps brachii (the contract the arm). It wouldn't be entirely incorrect to refer to other two-muscle-combinations as biceps (such as the biceps femoris, on the thigh), but it isn't really general usage. My guess is that the new muscle won't lead to a change in the name "biceps brachii", and certainly not to "triceps brachii" (since that's taken), and thus the shortened name is likely not to change either. However, it would be kind of neat to be able to say "my biceps are triceps". :)

geo said at September 16, 2007 7:03 AM:

Where was this published? Can you please post the citation? Thanks!

jason said at October 21, 2007 3:15 PM:

This is all new to me but I thought I would share this. A few weeks back I had an elbow surgery and when the surgeon was done he explained that some of the problem with the ulnar nerve compression was that I had an extra muscle compressing the nerve in my triceps. I had not given it much thought until seeing this on the internet. In some it might be good to have extra muscles but seemingly in my case it was part of the problem. Guess that is what makes us all human and different.

Christy Monohan said at February 6, 2008 6:56 AM:

Like Jason's comment, I just had surgery to decompress the ulnar nerve two weeks ago. My surgeon said I have an extra muscle that was putting pressure on the nerve causing numbness in the fingers and pain in the elbow. Wow, I knew I was strong, diddn't know it was due to extra muscles! What a great improvement this surgery has done for me!

Michael said at April 5, 2008 12:43 AM:

This is funny, but same here. Had the surgery two weeks ago and doctor stated that I have an extra muscle putting pressure on the ulnar nerve. Maybe it is a next step. :)

Gemma Ryde said at May 3, 2008 11:51 AM:

I am a sprinter and I have an extra muscles in my calfs. My mum always says it will make me faster but I have had to give up running because of the problems I was having. I caused my feet to break my feet 3 times. I am considering surgery but need some advice. Just thought I would post a comment incase anyone had any suggestions.

LeeAnn Johnston said at July 22, 2010 2:05 PM:

MY son has extra muscle in his arm putting pressure on his nerve, he gets tingles in his arm and fingers and numbness, he is a softball pitcher and is very concerned at the outcome of this operation and hopes it is not a huge climb back to where he was. I see Christy Monohan comment great improvement the surgey has done for her, so I hope it will be the same for my son.

Paula said at July 30, 2010 11:45 AM:

I too had an extra muscle and would do the surgery over again if need it was so worth it. I had bad nerve pain and right after surgery the pain was gone, as the same with the carpal tunnels surgeries I had. Needless to say 4 months out from surgery I have no numbness at all and full usage of both arms again.....

D Scott said at December 14, 2010 11:10 AM:

My husband, who is a body builder, had carpal tunnel and ulnar nerve surgery 3 months ago on his right hand/elbow and this week for his left. The Dr. said that he had this extra muscle in both his arms and that was the cause of the pain, numbness and tingling for years. He has not yet recovered from the right side surgery and the pain continues, however not as severe. The Dr. indicated he won't know for upwards of a year if there is any permanent damage that has been caused by this extra muscle pushing down on the nerve. Thankful for the internet and all of the available information out there.

Gina said at October 26, 2016 8:42 PM:

I just had cubital and carpal tunnel release surgery today and I also have and extra muscle..encouraged to hear these positive stories..I did the left first and need the right done too. My surgeon thinks I have extra muscle bilaterally. So crazy!! But we have lots of rare stuff in our family so I wasn't too shocked

Anonymous said at March 3, 2017 2:05 AM:

I had ulnar nerve pressure release surgery due to an extra muscle in my right forearm ten years ago when I lost use of my right hand, and the left arm followed a year later for the same reason. Surgeons stopped the surgery to bring other doctors in to see, or so I was told when I woke up in recovery. It is rare, especially bilaterally, but unique and defining just like my rare mutation making the inside and outside rings around the pupils of my eyes different colors. The outer ring is blue. The inner ringer is yellow, which, when mixed with the blue makes green. Be proud of who and what you are. There are no accidents or coincidence.

Makaal said at May 29, 2017 8:39 PM:

I too had Ulnar Nerve Transposition surgery due to an extra muscle pushing on my nerve. I just had it done the end of April and already see the difference. I am wondering if this is genetic. No one else in my family has this as we know of.

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