Genetics & Performance: Genotype + Environment = Phenotype

Genetics and Athletic Performance

While genetics do play a role you always have multiple pathways to athletic success

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To understand an individual's performance, we must understand what is going on with that person's known biological energy systems. These include the cardiovascular, respiratory, nervous and muscular systems. Generally, the determinants of performance can be summarized as follows:


For a simple definition of these components (a more detailed examination of each term will follow later), "genotype" is your genetic performance potential, the "environment" is what you're exposed to throughout your life, and "phenotype" is your performance capacity. While a person must have the right parents in order to be a world-class athlete, we can't overlook the importance of the will to win. Determination to persist with a grueling training schedule, the ability to deal with the many psychological pressures of competition and the competitive athletic lifestyle and a capacity to ignore pain during training and/or the competitive event are all ingredients of success. This article, however, focuses on the role of heredity in determining your ability to train and perform.

Getting back to the components of the above performance formula, or your performance potential, this refers to your entire genetic makeup. It is given to you at the moment of conception, and it ultimately limits what your performance capability will be and what interaction you will have with the environment. There may be some truth to the statement that we are all "prisoners of our genes."

All individuals are not the same, even at birth. They have different cardio respiratory capacities, skeletal muscle fiber makeup, etc.-all of which affect their trainability. You have undoubtedly noticed how some people are more trainable than others. This has to do with their genotype, or their inherited genetic potential. Individuals who are more trainable are genetically more reactive with the environment than others. Even if you don't have the genotype to become a Mr. or Ms. Olympia, however, there is no need to despair. Proper training and diet can positively change your mental outlook and physical appearance and enhance your overall life.

The environmental factors include, but are not limited to. training, nutrition, psychosocial behaviors and aging. The majority of articles written and the bulk of exercise research is performed in the area of environmental factors, which, unlike your genotype, can be controlled to elicit changes in phenotype-that is, performance. Once you determine and accept your genetic potential, you can design your environment to reach your genetically predetermined potential.

Depending on the sport, the environmental factors can play a varying role. The level of skill involved in the sport is largely affected by training-an environmental factor. In other words, training can have much more of an effect on low-skill sports (running, cycling, weight-training) than it can on high-skill sports (tennis, golf, gymnastics). While genetics plays a role in all sports, trainability and skill acquisition are more limited in high-skill activities.

Although the fiber-type composition of skeletal muscle is determined almost exclusively by your genetics, it is possible to design a training program that is best suited for your given genetic makeup. Human muscle fiber types are generally classified in two main types-slow-twitch and fast-twitch-that occur in a mosaic pattern and vary in proportions, cross-sectional areas and metabolic profiles between trained and sedentary individuals. An individual who has a predominance of slow-twitch muscle fibers would need to incorporate a high number of sets and reps to elicit an optimal response to training. On the other hand, someone with a high amount of fast-twitch muscle fibers would respond better to lower reps and heavier weight.

Muscle biopsy samples taken from athletes following various training programs have shown that fast-twitch muscle fibers respond best to workouts that involve two to six repetition-maximum sets in the four-to-six-rep range. A repetition-maximum set is a set performed with the maximal weight that can be handled for the given number of repetitions desired. Slow-twitch muscle fibers respond to more repetition-maximum sets-six to 10 sets of 12 to 20 repetitions. Training programs that contain workouts with both schemes of sets and reps appear to be best in eliciting maximal hypertrophy in both fiber types. Obviously, once you deter-mine your fiber composition, you can better design the optimal training program for you.

While most muscles on average individuals are mixed-50 percent fast-twitch fibers and 50 percent slow-twitch-the muscles of most elite athletes contain a larger percentage of one type or the other. An athlete's fiber-composition makeup may be one factor that allows him or her to excel at a particular event. Distance, endurance athletes have a high percentage of slow-twitch muscle fibers. Some marathon runners have had muscles with as high as 90 percent slow-twitch fibers. Strength athletes, on the other hand, have muscles composed almost entirely of fast-twitch fibers.

Many professional bodybuilders have determined through trial and error the repetition schemes that work best for them. Much of what they choose has to do to their genetically determined fiber composition. Athletes like Mike Quinn, Troy Zuccolotto and Sandy Riddell train extremely heavy with lower-rep ranges. Others, such as Robby Robinson and Lee Labrada, choose weights they can handle for higher repetitions. Their training selection is due to a large extent to the response they obtained from training. Ultimately, the primary determinant for the response to a given workout scheme is muscle-fiber composition.

Of all the environmental factors, nutrition plays such a crucial role in performance that you cannot over-look the importance of a proper diet. By combining the proper nutrient environment with adequate rest and recuperation, you can enhance your progress and achieve your potential. Even the extremely gifted athletes have come to realize the role diet plays in determining athletic performance. No longer can their meals be put together haphazardly; we have now developed an extreme science in order to maximize the training response.

While we still don't know the optimal diet for performance, we have learned a great deal over the past decade about the role of various nutrients in growth and performance. Many dietary manipulations are still untested in the laboratory; however, each day new discoveries are being made that help the athlete and the general public alike.

The importance of a high-carbohydrate diet for both strength and endurance athletes has only recently been studied and determined to be of primary importance. Although the optimal intake of protein continues to be controversial, recent evidence suggests a higher requirement for athletes than for the general population. A level as high as 2.2 grams per kg of bodyweight is now being recommended for most athletes in training. The more educated you become in terms of nutrition, training and recuperation, the more efficiently you will be able to obtain your optimal development and performance.

Some factors previously thought to be genetically determined are proving to be environmentally controlled. Until recently we thought that the aging process was a genetically predetermined event. As we got older, we expected our performance to deteriorate. Recent studies on subjects whose ages ranged from mid-60s to mid-90s showed significant improvements in muscle strength, size and cardiovascular endurance with training. Every year masters athletes set numerous records that far exceed those that were achieved by younger competitors only a few years before. While some deterioration with aging appears to remain genotype-dependent (that is, genetically determined), many of the effects of aging are preventable and are controlled by environmental factors, two of which are diet and exercise.

So now we come to phenotype, your entire physical, biochemical and physiological makeup as determined by genetics and environment. In other words, it's the combined effect of your genetic predisposition and such factors as training, diet, psychological makeup, rest and age. Although performance capacity varies over time and appears to be ultimately limited by genetic makeup, knowledge of your own genotype will enable you to develop a training pro-gram to best enhance your performance.

Most sports require a number of different qualities for optimal performance. Few athletes have all these qualities; the ones who do are the Mike Tysons, Michael Jordons, Cory Eversons and Lee Haneys of the sports world, the athletes who excel above all others for extended periods of time. A few others can become proficient in a given sport without having all the "right" genetics. A prime example is basketball's Spud Webb. The genotype for a basketball player includes being tall. Although he is short (5'6"), Spud makes up for it with speed and superior jumping ability.

Many of the qualities that make up a potential athlete are modifiable to some extent. The list includes strength, weight, endurance, body composition and skill. In determining whether to make the effort, you need to answer three important questions: How much do these qualities contribute to a given performance, how modifiable are they, and is it worth trying? Scientists can partially answer the first two questions; the third can only be answered by you.

While there are many different physiological parameters involved in determining a person's exercise performance, each parameter can be measured and adapted following a training program. Genetics may make up the initial values of each parameter, but it is still unknown whether the response to exercise training is heterogeneous within a group and whether this heterogeneity in trainability is related to genotype. Baseline values of elite athletes may actually be above those found in sedentary people who have been trained. In fact, the values of many parameters for an elite athlete are far above those found in the general population of people who have exercised regularly after they stopped training due to injury or by choice.

Studies performed on identical twins suggest a large genetic component involved with the training response to exercise. The genotype dependency of the training response became more stringent as the subjects were getting closer to maximal train-ability. Apparently, we can all adapt to an exercise program, but the ultimate level appears to be determined genetically.

Scientists classify individuals with differences in trainability as responders and nonresponders. The performance capabilities between both groups overlap to some extent, with the overall response falling on a continuum. Many good athletes fall within the responder's range of responses, yet the truly elite athletes fall at the top of the measured parameters. While some Eastern bloc countries weed out youngsters at an early age and only train the responders to a specific sport, ethically this approach is very hard to accept. Knowing whether you are a responder for a given sport might help in choosing the activity you are best suited for; however, the sole reason for participating in sports should not be because you are good at a given event.

It's important for responsible leaders and educators in sports to stress the role genetics plays in performance and communicate the idea that not all people can be champions. In the future it may be possible to use genetic engineering to "make" people into responders. In the meantime, for the majority of us sports participation should be solely for the purposes of health and enjoyment.

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