The ability to switch use fats as fuel over carbohydrates combined with the distribution of fast and slow-twitch muscle fibres are both important factors affecting endurance performance. The PPARA protein plays a role in these. Your FitnessGenes result tells you whether you have a version of PPARA that is predominant in endurance athletes, power/speed athletes or both.
We have a number of energy sources to draw upon when exercising, depending on how long and how intense the exercise. The three main ones are phosphocreatine (for short, intense bursts of activity), carbohydrates, and fat.
The PPARA gene produces a protein that is involved in the regulation of fuel choice. It plays a key role in increasing the use of the more efficient energy source of fat by activating genes involved in fatty acid transport and metabolism. There are two versions of the PPARA gene: the G allele and the C allele. Individuals who carry a G allele have been found to have inherently higher levels of the PPARA protein than those who carry the CC genotype.
A higher level of PPARA protein enables efficient switching between fuel types (fat versus carbohydrates), thus giving G carriers a much larger pool of energy to draw from during endurance exercise. Perhaps unsurprisingly, research has revealed a higher proportion of the G allele in groups of top endurance athletes, whilst the C allele showed up more often in elite athletes competing in power- or speed-orientated sports.
Source: 1000 Genome Project. Global averages for both sexes