Why do a select few seem to pack on muscle just by looking at a barbell while most of us toil relentlessly for only meager gains? The answer is largely due to genetics. It
would certainly be fantastic if we could change our genetic makeup and become part of that lucky genetically gifted group that includes the likes of Arnold Schwarzenegger
and Cory Everson.
A fantasy, you say? What you don't know is that this fantastic fantasy may now be a bodybuilding reality. Exciting new research shows that we can transform the genetic composition of our muscles and reprogram our bodies to respond faster. In other words, we can actually alter our genetics.
Scientists are presently delving into the most revolutionary muscle-related discovery of the past decade- the alteration of genetic muscle fibers. This research is predominately coming out of the European community, spearheaded by Dr. Keijo Hakkinen of the University of Jyvaskyla in Finland. It has long been recognized that the body makes various adaptive responses when exposed to disease or injury. The concept of actually transforming the genetic makeup of muscle fiber, however, has heretofore been relegated to the athlete's wish list.
A person' s progress in resistance training is undoubtedly directly linked to his or her genetic makeup. It comes down to muscle fiber type. Bodybuilders are basically concerned with two types of muscle fibers: slow-twitch, also known as "red" because of the higher concentration of myoglobin, and fast-twitch, or "white." These two types of muscle fibers are differentiated on the basis of their rate of excitability; i.e., the speed of their mechanical responses.
Each skeletal muscle contains both types of fibers, with the proportional compositions being genetically determined. Slow-twitch fibers are adapted to sustained contractions and are therefore suited for endurance activities such as long-distance running and even maintaining posture. In fact, the leg muscles of world-class distance runners contain 75 to 90 percent slow-twitch fibers. Fast-twitch fibers, on the other hand, are better suited for shorter, more intense contractions. As you might expect, the leg muscles of world-class sprinters are composed of 80 to 90 percent fast-twitch fibers.
Obviously, the bodybuilder's primary interest is the fast-twitch fibers. Not only are these fibers stronger, but they also have a greater potential for growth. Current research proves that we can actually reprogram our genetically determined ratio of fast-twitch to slow-twitch muscle fibers, thereby drastically increasing the rate at which we build mass and strength.
Drs. Jansson, Esbjornsson, Holm and Jacobs from the Department of Clinical Physiology in Stockholm, Sweden, documented significant increases in fast-twitch muscle fibers in sprint-trained males. In fact, the subjects showed an increase in fast-twitch fibers as great as 6 percent in only four to six weeks. In contrast to previously held theories, the researchers stated, "This study indicates that it is possible to achieve a fiber-type transformation with high-intensity training" (Acta Physiol Stand '90). Similar results were achieved in experimental studies with rats in the mid-1980s, leading the researchers to believe that the change in fiber composition is induced by the synthesis of fast myosin. Such synthesis seems to be related to increased frequency of stimulation and possibly hormonal influences.
The importance of fast-twitch fibers for muscular development brings out two pragmatic training principles: 1) We need to concentrate primarily on training the fast-twitch fibers, since those are the fibers that give us the strength and size that we pursue; and 2) by selectively training our fast-twitch fibers, we can cause adaptive responses from the slow-twitch fibers and actually "reprogram" them into fast-twitch fibers.
How do we selectively train fast-twitch fibers for optimal growth? We must stimulate maximal neural activation of the muscle, as is most commonly seen in explosive-type movements. Dr. Hakkinen showed in both sprinters and weightlifters that an increase in fast-force production brings a dramatic increase in the ratio of fast-twitch to slow-twitch fibers.