There's no doubt that our genes play a major role in whether we excel at sprinting versus long-distance running or how rapidly we build muscle mass. The mystery is exactly which genes are responsible and how they're influenced by diet and other lifestyle factors. Even though we don't yet have all the specifics, it's clear that genes underlie our potential for physical performance as well as the exercise benefits associated with various chronic diseases such as heart disease, diabetes, and obesity. Predictably, a whole host of genes, ranging from those that are directly associated with body mechanics and muscle development and function to fueling and energy production, the exercise recovery process, motor nerve activity, and hormone levels all contribute to our fitness level and physical performance abilities.
What we do know is that what we eat is directly related to the availability of nutrients and to hormone levels, both of which are important to fitness and performance. Further, exercise influences the level of expression of genes critical to a variety of processes connected with physical activity. What's not yet understood is how these numerous effects are carried out. Scientists are actively pursuing the mechanism by which an initial exercise stimulus is converted into a cascade of events that leads to the final physiological response: physical performance. Different genes are involved in each of the steps along this complex process and it is virtually certain that which variations we have for each of these genes influences a number of outcomes with respect to fitness and performance.
Even for those of us who may not aspire to set sports performance records, knowing our genetic makeup will almost certainly be helpful in identifying the most appropriate exercise program for each of us. A major discouraging factor when exercising for health is the lack of results. This lack is likely due to the wrong match between our genetic potential and the exercises we choose. How much more effective our exercise programs are likely to be once these associations have been identified.
Some helpful clues are already emerging from the increased interest in personal genetics and physical performance. Two genes, ACE and ACTN3, have been associated with response to exercise. The ACE gene has a variant that's associated with our response to activities that require endurance, such as distance running and cycling and mountain climbing. ACE has also been linked to an increased tendency to build muscle mass in response to resistance training. A variant of the ACTN3 gene is associated with excelling in those activities that are more dependent on short bursts of power, such as sprinting and power lifting.
In addition to genes such as ACE and ACTN3 that have specific effects on muscle performance, there are genes related to energy production and recovery from exercise that are equally as important. One of the areas being investigated concerns the proteins that form the body's natural defense system against the formation of reactive oxygen species, more commonly called "free radicals". Free radicals are a normal byproduct of metabolism and are generated at a higher than normal level during exercise. Part of the process of recovering from exercise involves the elimination of free radicals. The genes MnSOD and SOD3 produce superoxide dismutases. These are enzymes that destroy free radicals and are part of the body's natural defense system against the buildup of these harmful molecules. Variations in these genes influence the effectiveness of these enzymes in eliminating free radicals and promoting recovery.
Additionally, researchers are focusing on just how regular physical activity works its magic in decreasing both the susceptibility to chronic diseases and the magnitude of the effects of these diseases. Clearly regular physical activity reduces bodyfat, which is essential for healthy weight maintenance and the harmful effects of obesity. It's also known to assist in moving blood sugar into the muscles where it can be used for fuel, a very effective lifestyle approach for protecting against diabetes. Plus, researchers have found that just a single exercise session makes a dramatic difference in reducing blood sugar levels and have defined the mechanism by which exercise blood sugar levels.
Exercise is also an effective and, presently, THE most effective known factor for increasing HDL-cholesterol ("good cholesterol"), a major factor in protecting against heart disease and stroke. Another gene, IL6, has been found to be associated with the response of HDL-cholesterol to exercise. IL6 is an important gene in the body's inflammatory response. A particular variation (-174 G>C) has been found to increase HDL-cholesterol levels over those typically seen with the more common variation.