To what extent does genetic make-up contribute to athletic performance?


The question of how nature versus nurture in determining physical capacities, writes Dr Giles Warrington

PHYSICAL FITNESS is defined as the ability to perform everyday and sporting activities without undue fatigue.

An individual's level of physical conditioning is typically associated with diet and training status. As a consequence, a large body of the sports science and sports medicine research has focused predominantly on trying to increase our understanding of how the interaction of nutrition and training can, independently or in combination, influence and enhance athletic performance.

Although these "environmental" factors play a critical role in determining an athlete's physical capabilities, the extent that natural ability and an individual's genetic make-up influences sporting success has become an issue of extensive debate.

An internationally renowned scientist famously once said "If you want to be an Olympic champion, choose your parents carefully!" This implies you need to come from the right gene pool. This rather one-dimensional view point would suggest that elite performers are born to succeed and not made, and that an athlete's training environment plays only a nominal role in sporting success.

In 1953, James Watson and Francis Crick discovered the "double helix" structure of DNA, for which they were awarded the Nobel prize for medicine. The discovery of the structure of DNA is effectively the genetic code or "blueprint" of the human body. More recently, the Human Genome Project completed in 2003, after 13 years of painstaking research, genetically mapped the estimated 20,000-25,000 genes in the human body.

Arising from these landmark discoveries in molecular medicine, there has been an evolving debate within the scientific community on the influence of "nature" verses "nurture" in determining physical capacities and ultimately athletic performance.

Nature refers to the innate or genetic characteristics of an individual which contribute to athletic performance. In contrast, nurture relates to the experiential and environmental factors which influence both learning and performance and may include factors such as training, nutrition, lifestyle and socio-cultural determinants.

New research in genetics and genomics is making an increasingly important role in the diagnosis, monitoring and treatment of diseases but also may play a significant role in enhancing sports performance.

The human body is a complex biological system which responds to the influence of exercise and training in different ways.

To understand this concept, if you imagine putting a group of athletes of similar ability on the same training regimen over a period and implementing a programme of physiological testing to measure their level of physical fitness before and afterwards, they would all respond differently.

Trying to understand why some athletes benefit more from training and practice than others has become the focus of research and analysis within elements of the sports science and sports medicine community.

Furthermore, to what extent can "genetic profiling" provide information to specifically design training programmes to suit individual needs with a view to optimising training response and maximising athletic performance has become an area of much discussion and speculation.

Information revealed by the Human Genome Project has led to many researchers targeting specific genes to establish and assess the influence of physical training on gene expression.

For example, the ACE gene has been shown to respond to endurance training, whereas the NR3C1 gene has been associated with changes in muscle mass and strength.

This has led to some authorities to speculate on the potential occurrence of "gene doping", namely the non-therapeutic use of genes and gene therapies to artificially enhance human performance, much in the same way as drug doping has become the scourge of modern sport.

In emphasising the importance of nurture and the environment in influencing performance outcome, Nobel Laureate Herbert Simon stated, "it takes 10 years of extensive training to excel in anything".

In support of this notion, scientific evidence has suggested that it takes up to 10 years and 10,000 hours of "deliberate practice", which equates to about three hours of practice per day, for talented athletes to attain elite sports performance.

The principle of deliberate practice has also been extended to other fields of elite performance including virtuoso musicians and ballet dancers.

This implies that a long-term commitment to practice and training is necessary to produce elite athletes in all sports.

Accordingly, expert athletes accumulate more hours of deliberate practice through structured training programmes than their less accomplished counterparts. Of particular note is the observation that successful athletes devote more time in activities essential to high-level skill development associated with elite performance in many sports.

To date, the general consensus would suggest that for most sporting endeavours, genetic factors probably account for about 50 per cent of key physical capacities which influence athletic performance.

It could be argued that genetics play a greater role in activities at the wider ends of the sporting spectrum such as the 100m sprint or the marathon where specific physical capacities are a prerequisite for athletic success. Despite this, a broad range of athletes of a varied genetic disposition have performed at a world-class level in a variety of sports.

While the nature versus nurture debate continues, the focus of many sports scientists will be to increase our understanding of why individual differences in sports performance exist and how to best identify and develop sporting talent to its optimal performance potential.

Dr Giles Warrington is a sports and exercise physiologist and lecturer in the school of Health and Human Performance at Dublin City University