Complexity of genetics in the athlete phenotype: A commentary on Adrenergic-β₂ receptor polymorphism and athletic performance

Human evolution is complex and involves steps that favor those who can succeed in the competition of life and pass favorable genes onto their offspring. These genes include significant and gross mutations such as those that cause cystic fibrosis (which is thought to have provided protective effects for Europeans against typhoid fever¹) and sickle cell anemia (which is thought to have provided protection against malaria in areas where malaria is common²). The genetics that have led to the superior athlete is likely much more complex and involves many proteins. As a people that have spent the majority of our history as hunters, gatherers, and nomads, human beings have had a need for mobility at various speeds and distances. For instance, to hunt game without modern technology, the hunter must have been able to outlast certain game and primarily used oxygen as a fuel source for prolonged exercise. In contrast, when in danger or another need for quick speed, the human had to use immediate fuel that was shorter acting, but allowed for more powerful muscles to contract. These conditions have led to various types of muscles (slow twitch muscles to fast twitch muscles) along with various pathways for fuel usage (fat for oxidative metabolism and sugars for glycolysis³). Most athletes, former athletes, and those who worked hard to be great athletes, but have failed, have found out the following: if you want to be a great athlete, choose the right parents. As a population, those individuals who have been able to hunt longer, gather more efficiently and escape from prey have likely been the ones to survive and pass on favorable genes to their offspring.

Several classic findings from the HERITAGE family study highlight the importance of genetics in the phenotypic response to exercise. Findings from the HERITAGE study determined that only a portion of maximal oxygen uptake (VO_2peak) can be improved through training, averaging around 20% improvement with a range of <5% to >50%, indicating that fitness is an inherited trait, and that the response to training is quite variable, suggesting a genetic component.⁴ Several more recent research studies and review papers have also made an attempt to classify the high performance phenotype based on genetics.^{5, 6} Modern studies have been performed in an attempt to classify the favorable athletic phenotype based on genetics in both laboratory and field-based settings. These studies have found several variants (including the β₂-adrenergic receptor, ADRB2) that have led to improved performance, whether measured through specific laboratory measures or through measures of performance.^{7, 8, 9, 10}

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