Genetics & Abdominal Development

YassSpartan

You've seen it all over the news: Genetic engineering is the hottest and most controversial thing in science right now. Just mention cloning or the topic of genetic influences in athletic performance and see what kind of reaction you get.

Science is in fact demonstrating that genetics governs just about everything in our lives, including our success in the gym. Despite Thomas Jefferson's statement that "All men [and women] are created equal", every individual adapts differently to resistance training. These genetic factors seem to be quite evident when it comes to abs.

If you train and train and just can't seem to bring out your six-pack, several factors may be involved: body fat levels (this also has a strong genetic component, in addition to diet), proper exercise selection, and performing the right number of repetitions and sets to stimulate growth. The key to maximizing your genetic potential is to determine what rep, set and intensity ranges develop your abs best and how to manipulate your diet sufficiently to drop body fat.

Fast- vs Slow-Twitch Muscle Fibers
Human muscle fiber types can be devised into slow twitch (Type I) and fast-twitch (Type-II) muscle fibers. We're all born with a certain percentage of fast- and slow-twitch fibers, and most of us have about 50% of each. If you look at the rectus abdominis, it displays about a 50-50 distribution between fast- and slow-twitch muscle fibers. Some studies have suggested that the amount of fast- and slow-twitch fibers you posses could play an important role in regulating the amount of body fat you carry.

One study looked at the fiber-type distribution of the rectus abdominis in humans and their ability to store fat. A correlation was observed between abdominal fat deposition, fiber type distribution and insulin sensitivity in obese individuals, and a connection was demonstrated between the amount of Type I fibers and the level of body fat in these subjects. It would also appear to apply to non-obese individuals.

We're now learning that having a high degree of body fat has a certain genetic component. We also know that muscle fiber composition has a genetic link. With that in mind, plus the results of this study, we see that fiber composition along with your sensitivity to insulin may impact truncal fat deposition (the jiggle around the middle). So, if you have a large distribution of slow-twitch fibers and are insulin-resistant, you're probably going to have an easier time depositing fat in your abdominal region. Guess what? No six-pack.

But what does this really mean in terms of improving your physique? If you're one of those individuals with a higher percentage of Type I fibers, are you doomed to a life without great abs? Jim Stoppani, PhD, M&F's Science Editor, explains to what degree genetics may really hamper your success in developing your midsection. He says: "Ultimately, genetics do determine the degree of success you can have in sport - not everybody can build Bi's like Arnold. But everybody can build muscle."

"Now, if you're stuck with more Type I fibers than you'd like, don't view this as the end of the road", he continues, "In fact, in response to intense bodybuilding, your Type I fibers can take on the properties of Type II fibers. I'd therefore suggest that you pump iron, diet seriously and not worry too much about your genetics".

Love Handles & LPL
Ever wonder why you can't get rid of your gut? The answer, once again, lies in part in your genetic code and in a substance found in your body called lipoprotein lipase (LPL). LPL is an enzyme responsible for the uptake and storage of fatty acids in your body. The greater your LPL levels in a certain region, the more body fat you'll store in that area.

A few years ago, a study investigated the relationship between testosterone levels, LPL activity and fat accumulation in adults male. Researchers found that sex steroids suppress adipose-tissue LPL activity, which means that men with high levels of testosterone might store less body fat because the LPL would be sequestered. What's interesting about this study is that LPL activity decreased more in the thigh region than in the abdomen.

The role of genetics as a governing factor for success is perhaps most visible in bodybuilding. Understanding your genetics will enable you to customize your workouts and your eating program. Set goals realistic to your body type and, most of all, remember that bodybuilding is an individual sport. Self-improvement - not comparing yourself to others in the gym - is the key.

- Chris Street, MS, CSCS

References
-Hickey, M.S., et al. Skeletal muscle fiber composition is related to adiposity and in vitro glucose transport rate in humans. American Journal of Physiology 268:E453-E457, 1995
-Ramirez, M.E., et al. Evidence for sex steroid inhibition of lipoprotein lipase in men: comparison of abdominal and femoral adipose tissue. Metabolism: Clinical and Experimental 46(2):179-185, 1997.