It can be observed that some people respond better to training than others. The basis of this could be genetic. Studies from twins reveal much information. Twins who are genetically identical will respond to training in a similar way. This provides a evidence that athletic ability can be part genetic. The alpha actinin-3 gene may provide answers. There are two versions of this gene which are referred to as X or R. Two copies of the RR gene may mean an individual is best suited for strength sports, that require explosive power. The XX gene could mean that a person would be better at endurance sports. What is pivotal is the energy capacity in the cells of the muscles. This allows the body to take full advantage of a training regimen. As genomics advances so will training techniques.