It is well documented that the health and performance outcomes of an individual are the result of the interaction between genetics and the environment. Now with the advancement in medicine and research, it may be possible to isolate the specific genes responsible for both health problems as well as physical performance. In a recent study (using a mice model), performed by researchers at the Perelman School of Medicine at the University of Pennsylvania, a gene was identified that researchers suggest can explain endurance performance. They identified the gene codes for a protein known as Interleukin-15 receptor-alpha (IL-15R-alpha) which is implicated in muscle physiology. The senior author, Teivir S. Khumara, MD, PhD said, “we have shown that mice lacking the gene run six times longer than control mice and that the fatigable muscles of the mouse – the fast muscles in the front of the leg – have been reprogrammed and are now fatigue resistant.” Some of the molecular characteristics of the “knockout gene” mice muscle included: greater number of fibers with greater mitochondria density, better metabolic machinery to control muscle contraction through a better handling of Ca++, greater number of muscle fibers, smaller fiber areas, and greater number of nuclei per fiber.

The identification of this gene has implications on health as well as performance levels. With regard to performance, where everyone is looking for an advantage, knockout gene capability may be a viable (although unethical) solution. “If thinking about this discovery in that sense, this can be a “druggable target” since it may allow the reprogramming of the muscle function by increasing genes, proteins and pathways typically expressed in slow fibers,” said researchers in their press release. This type of fiber change can also be achieved through training, but it may take several years to observed significant adjustments. On the other hand, this gene identification may have positive impact with regard to health measures since one of the recommendations for obesity and diabetes is the increased participation in aerobic exercise. Due to the positive adaptations observed in the slow muscle fiber, gene adjustments may make exercise easier and attract more people to it. In that sense, the researchers said “the identification of these pathways should facilitate better understanding of these diseases and aid in the development of rational therapies and drugs for these disorders.” Researchers want to take a further step and investigate the role of the IL-15R-alpha gene on obesity, diabetes, aging and muscle diseases, as well as the development of a method that may allow it to be used with human patients.

Although this research was conducted on mice lacking the specific endurance gene, researchers do not know if the same gene is responsible for the endurance adaptation in humans, nor the frequency in which humans may have this gene deficiency. Although the results of this study show some promise for human health and add a bit of potential controversy for those involved in endurance sport performance, further research is required in this area before definitive answers will be clear. (Journal of Clinical Investigation, July 2011)