AS Commonwealth Games competitors reach the final phase of their preparation for Glasgow 2014, they will be wondering whether their dedication, hours of training and perseverance will bring home Gold for them.
But what if these elements are not enough? What if it's really down to something over which they have no control - their genes?
The renowned Swedish exercise physiologist Per-Olof Astrand once said: "The most important thing an aspiring athlete can do is to choose the right parents."
So, are some people born to run? And others destined always to lag behind? If we all raced against each other, someone would win, someone would finish last and we'd have people spread out in between. But would that be due to diet, training, gender, or genetics?
In Claude Bouchard's Heritage Family study between 1992 and 1997, about 500 relatively sedentary individuals trained for 20 weeks. Participants' ability to improve their fitness varied greatly, despite the fact all adhered rigorously to the same exercise regime.
The study showed some people could increase their aerobic capacity up to 40 per cent, while others saw no change. Since the study involved about 100 families, Bouchard's team was able to check to see if genetics was at play. Indeed, it was. Genes could account for about half of the difference they were seeing in people's ability to increase their aerobic capacity. It showed a good portion, but not all, of a person's capacity to get more fit was set by their heredity.
We have established, therefore, that genetics is really important in understanding the differences between us as individuals, but what, if anything, can it tell us about the differences in success between nations?
In fact, genes are not different in different nations: we all have the same genes. But some versions of genes differ between populations. By definition, the Out of Africa hypothesis - the argument that every living human being is descended from a small group in Africa, who then dispersed into the wider world displacing earlier forms such as Neanderthal - means all non-Africans carry only a subset of the variation that is in Africa.
Yet when we looked at the Ethiopian and Kenyan Olympic athletes to see if some of these African specific variants could be responsible for their endurance running abilities, we found no evidence to support that case.
However, the frequencies of variants can vary significantly between different populations. Think, for example, of dark-haired southern Italians with brown eyes and blue-eyed, blonde Norwegians. It is not that there are no brown-haired Norwegians but they are less common - these differences are due to different rates of genetic variants.
So could these frequency differences explain the differences in success between nations? In my opinion, probably not. We do not find stark divides between populations, but instead gradual changes of genetic variant frequencies. Secondly, there are hundreds of genes involved in sporting performance each explaining only a small amount (1-2 per cent) of the differences between us. It is unlikely everyone in West Africa - where most of the world's great sprinters originate - has the quick version of all of these, or even most of these variants; and we tend to forget many West Africans are not world-class sprinters - it is only certain individuals within that population.
That leads me to the conclusion that the differences in success rates between nations comes down to something else - and that something is whether or not the individuals with the best genetic profile for sport are actually doing sport and training hard.
But the significance of good genetic variants in producing successful athletes cannot now be ignored. Increasingly, gene therapy is used to combat certain health conditions and diseases. Currently, gene doping to boost athletic ability is strictly forbidden at Olympic and Commonwealth level - but for how long will that remain the case?