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    Why Work Makes Muscles Grow

    As any bodybuilder can attest, muscles grow when we make them do more work. Now, new research explains how muscle cells translate weight-lifting overload into bulk.

    The secret lies with a chemical factor produced by muscle cells during work (such as during weight lifting) that signals muscle stem cells to multiply and take on the load. The substance, serum response factor (Srf), apparently triggers muscle stem cells — dormant cells capable of differentiating into muscle cells — to proliferate and become muscle fibers. More muscle fibers means bigger overall muscles and more strength.

    The findings may lead to new ways to combat muscle atrophy associated with age and illness, according to study researcher Athanassia Sotiropoulos, of the medical research institute Inserm in France.

    "This signal from the muscle fiber controls stem cell behavior and participation in muscle growth," Sotiropoulos said in a statement. "It is unexpected and quite interesting."

    Using mice that were genetically engineered to lack Srf in their muscles, the researchers found that without the factor, overloading the muscles does nothing to boost growth.

    Srf sends its signals via a network of genes, including one called Cox2. Anti-inflammatory medicines such as ibuprofen blunt Cox2, raising the possibility that these drugs might inhibit muscle growth, Sotiropoulos said.

    Most likely, she said, therapies aimed at boosting muscle growth (for example, after a long period of bed rest) would be aimed at this complex web of chemicals working under Srf.

    The research appears today (Jan. 3) in the journal Cell Metabolism.

    You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

    What do you feel about this article?

     

    17 comments

    • SRH  •  4 months ago
      Naked women also helps a muscel grow. . .
    • pistolpete  •  Myrtle Beach, United States  •  4 months ago
      How long until we see a flood of supplements on the market claiming to mimic this muscle growth action?
    • ZackC  •  Columbus, United States  •  4 months ago
      The link only goes some #$%$ advertisement for social networks. bad link. stupid idea to force traffic to another site. third link today that was broken this way.
    • Peter Foster  •  Saratoga Springs, United States  •  4 months ago
      Signals?! What signals?! I must have missed the signals class!

      The most obvious Thing about this article is the necessity of signals being transmitted from one pat of the body to another.

      How is it these signals can be increased so that the messages being broadcast can be captured more effectively by other signals lying within the data range? Signals, even like eye to hand coordination... batting for instance. Signals being manifest in one area and branching into a designated area? Producing, as a side effect, the things that keep an organ full of itself?

      But since these 'seantests' know so much about these signals, perhaps they can quicken themselves, for they are at least attempting to promote their idea of stem cells, just like the idea of nanotechnology? And, where in either are these ideas are the signals and aren't the signals a manifestation of light? Like the electromagnetic activity of an electronic circuit. The male and the female of nature, one might say. SIGLOS DE LOS SIGLOS
    • Antonio  •  Centro, Mexico  •  4 months ago
      Srf, the prototype for "Super Soldier Serum"
    • Roger  •  4 months ago
      I stand on the treadmill and make the mice do the work.
    • Phil  •  San Luis Obispo, United States  •  4 months ago
      After reading this bodybuilders will cut out all ibuprofen use and start artificial Srf injections.
    • realist  •  4 months ago
      Great news for professional athletes maxed out on testosterone!
    • Mr. RD  •  Texarkana, United States  •  4 months ago
      So I have to actually work to make my muscles grow???? Who would of thought!! Thanks Yahoo....I've been trying to figure out how people have BIG muscles....I never of thought they have to actually work them to make them that big...WOW.... I can rest my mind now
      • N A 4 months ago
        Lol....The idea of the article is to explain why the work makes muscles bigger.

        But considering the average Yahoo article, I can see why you got it mixed up.
      • Mr. RD 4 months ago
        I thought it was common sense that if you move or work your muscles they grow or get bigger
      • A Yahoo! User 4 months ago
        well the explain HOW it works so that you understand HOW they manipulate it
    • day  •  4 months ago
      What is Why Works????
    • kozz  •  4 months ago
      If only it were that simple. Most of us also know the body generally increases muscle mass only as a last resort, as it is the least efficient way to generate more strength. The most efficient way is extra nerve tissue, then better form - all real-world movements are the result of something called kinetic chains which run through the entire body, never just one muscle group.

      It's also not as if they didn't know muscle fibers came from muscle stem cells. All they discovered is a trigger, which no doubt they'll misuse to generate new muscle tissue that has no purpose, nor nerves to control it, nor CVS to feed it blood, in the body where it's generated.
      • A Yahoo! User 4 months ago
        wow, thank you for elaborating. these are all very valid point to consider when dabbling with the human body
      • tomgreen99200 4 months ago
        Finding the trigger completes the bigger picture or at least helps complete it. Why don't you get that?
      • Sunny 4 months ago
        It is good to be inefficient. You don't become fat that way.
    • Harry Arnold  •  New Orleans, United States  •  4 months ago
      All that I can tell everyone is this.... I've been taking steroids for the past 3 weeks now and I have gained 7 l#$%$ of muscle which is hardly any growth at all for such supplements. I've come to the conclusion that steroids help protein synthesis and in turn speed up muscle building, but only if you eat. So in other words, your better off just focusing on diet for mass rather than steroids. But if you want raw strength, steroids are the way too go. I'm 147 l#$%$ benching 250 l#$%$ on the free weight and 295 l#$%$ on the assist. Stuff works wonders, but really not worth it if dea agents were to bust down the door and stick me with a class 3 controlled su#$%$tance charge. Btw.... Roid rage is #$%$ and my testes are the same size as always. I don't see why it should be illegal???
    • Robert F  •  Bossier City, United States  •  4 months ago
      therapies for promoting muscle growth? why not just quit being so friggin lazy thinking that there is some magic pill that will fix everything and get into the gym and lift some weights? lifting moderately heavy weights promotes muscle growth...end of story and anything else is a lie
      • FHDendy 4 months ago
        @Robert you should work the brain muscle more often, they are mainly talking about people coming from bed-rest or medical conditions. I just don't see a coma patient taking your advice, or what about the pregnant woman who is put on bed rest, or an infirm 90 year old, you see them in the gym pumping a lot of weight do you.
      • Anonymous 4 months ago
        Idiot. That is not the only thing that causes muscles to grow. So does a better diet. So too does EXTREMELY heavy weight, much more than moderately heavy. THINK!
    • A Yahoo! User  •  Berkeley, United States  •  4 months ago
      Anti-inflammatory medicines such as ibuprofen blunt Cox2, raising the possibility that these drugs might inhibit muscle growth ... which is why you should vaporize THC ... a much better and safer anti-inflammatory.
      • A Yahoo! User 4 months ago
        hey- health and safety first!
      • JeffC 4 months ago
        ANY anti-inflammatory will keep muscles from growing.
      • Sunny 4 months ago
        JeffC, only COX2 inhibitors. There are other actions by which other antiinflamatory medicines act.
    • katspaw  •  4 months ago
      Why Work Makes Muscles Grow...is anyone out there so stupid that this is news to them!!
    • Redwing  •  4 months ago
      That means Democrats have no muscles.
      • katspaw 4 months ago
        Hush or they will demand you share yours!
      • tomgreen99200 4 months ago
        Everyone has muscles you silly person.
      • Djon 4 months ago
        And republicans are muscle heads
    • S  •  Irvine, United States  •  4 months ago
      When i was an LAX baggage handler i had big muscles. When i was a Kinko's copies employee the muscles went and the brain turned to mush. Can you imagine hovering over a copy machine all day long pressing the green copy buuton and removing staples and restapling all day long. What on earth was i thinking? I should of gone the Kinko's Loss Prevention Agent route.When they would walk in the door you knew heads were going to be lopped off o plenty ! All captured on survelliance video too. If you knew you were doing something wrong. That was the time to empty your locker and get out of that front door in a MAX hurry before all the embarassment begins.
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