What is the absolute limit for human athletes? Here’s the science …

The Olympics have drawn to a close and this year saw the shattering of 19 different world records, some by staggering margins. US swimmer Kate Ledecky broke the 800 metre freestyle record,

which she herself had previously set, by almost two seconds – a mammoth margin compared to the tenths and hundredths of seconds which often decide Olympic success. As we continue to swim

faster, jump higher and throw further than ever before, these performances have left us wondering just how much further athletic performance can be pushed. Many have tried to establish what

the absolute limits for human performance are and science can provide us with some clues as to what they could be and when we will likely reach them. It is clear, that there has been a

dramatic improvement in athletic ability over the past century. This is reflected by the continuous improvement of world records in track and field athletics from the early 1900s, which tend

to follow a linear rather than an exponential trend. However, this progress is not distributed evenly across the various disciplines of track and field athletics. Over the last 100 years,

large improvements have been made in the javelin and shot put, for example, while much smaller gains have been made in short-distance races, such as the 100, 200 and 400 metres. In 1909, for

example, the men’s shot put record was 15.54 metres; the current record, set in 1990, is 23.12 metres. This means that we had an increase of almost 50% in throwing distance in just over 80

years. By contrast, the improvement we have seen in the men’s 100 metres over the last century is a relatively small 8%. The rate of improvement for women, however, has been extraordinary,

and overall greater than that observed for men over an identical period of time. Looking at the 100 metres, for example, women improved their performance by a huge 30% in just 80 years. As

we have seen previously, men had just an 8% improvement in more than 100 years. This difference is even bigger in many other disciplines. It has also previously been demonstrated that the

sequence of records in the history of athletics is not distributed in a random fashion, but that a distinct regularity exists. WHY ARE WE GETTING BETTER? Could such regular improvements over

time be due to cyclical training techniques, whereby a novel training technique is applied to a generation of athletes until something more effective is found and then applied to the next

generation? Or could it be down to the more effective discovery of elite athletes in consecutive human generations? The honest answer is that evidence is currently lacking as to which

potential mechanisms might be dominant. Some factors do seem to play a part, however. First, economic advances and broader coverage of sports by the media have contributed to a growth in the

base number of athletes, including those competing at higher levels. Statistically speaking, this increases the chance that “extreme outliers” (or peak performers) will occur in a normal

distribution of athletes, and may partly account for the improvement in records. Second, genetics might be involved. Several genes influence athletic performance, which can thus be

considered a polygenic trait – one in which a large number of genes, each one having a relatively small effect, contributes to an outcome. A high degree of natural selection will have

occurred over time, and the best athletes might be increasingly characterised by a prevalence of these genes. This may also account for the lower improvement of athletic performance in

sprints (for example, 100, 200 and 400 metres) when compared with middle and long-distance events (1,500 and 10,000 metres and the marathon). The performance of sprint athletes mostly

depends on two variables: reaction time and fast muscle fibres. In endurance athletes, meanwhile, peak performance is regulated by slow muscle fibres, and by aerobic capacity. The latter can

substantially be increased by either regular training or manipulation (blood doping, for example). Conversely, reaction time, which is strongly dependent on the nervous system, has a

limited margin of improvement when compared with muscular power and aerobic capacity. Indeed, the nervous system cannot increase the speed of transmission of an eletric impulse, therefore

there is little potential to improve reaction time through training. Here, genetics is key. Equally, jumping events are limited by tendon stress limits, which cannot be overcome past a

certain natural limit and this might explain why the curve of improvement for these specialities is now almost flat. Whether and by how much genetic selection has helped the progression of

world records may soon be known, however, as high throughput microarray-based epigenetic technology, which allows DNA profiling, will soon be widely available. The introduction of

professional coaching, improvements in training techniques and the introduction of ergogenic aids – substances used for the purpose of enhancing performance, in the form of nutritional

supplements for example – have also profoundly changed sports performance. Investigating the science of running economy has greatly improved long distance running, while the Fosbury flop

technique (see video below) improved high jump performance. REACHING A PEAK If these considerations are true, then limits will be approached, and a point will be reached, perhaps soon, when

performance levels become essentially static, with only the occasional, once-every-generation “super-athlete” able to set new records. Indeed, this situation may have already been reached in

some events, such as the long jump and short distance runs, as progression of world records in these events has nearly stopped or has substantially slowed. Doping practices might also have

played a role in the progression of some world records. Also, the greater the role that equipment and technology plays a part in a sport, the greater the likely ongoing improvement. Thus,

ergonomics/wind resistant clothes and better running shoes have enabled runners to optimise energy consumption. The performances of athletes are the product of genetic endowment, hard work

and, increasingly, the contribution of science. The latter began many years ago, when scientists, physiologists, nutritionists, biomechanists and physicists began applying their knowledge to

the benefit of athletic performance. As a result, merely practising a sport for hours is no longer enough to enable an athlete to win. Future limits to athletic performance will be

determined less and less by the innate physiology of the athlete, and more and more by scientific and technological advances and by the still evolving judgement on where to draw the line

between what is “natural” and what is artificially enhanced. A previous study determined that by the year 2007, world records would have reached 99% of their asymptotic value, which

represents the limit for human performance. Although world records initially progressed according to a linear model in the Olympic disciplines of track and field athletics, in most instances

the progression curve has flattened out over the past 20 years (for example, in running and jumping), while in some sports (for example, shot put) no improvement has been recorded since the

mid-1990s. Hence, if the present conditions prevail for the next 20 years, this will support the hypothesis that most of the male world records will probably no longer be substantially

improved, although some female world records can still be expected to be broken, given increased access and participation. Nevertheless, if gene doping happens, we may never be able to

predict what the limits of human performance are. The probability is that further improvements will be mostly due to chance (occurrence of “extreme outliers” in the normal distribution of

top-class athletes), the use of mechanical aids, the introduction of genetic or other forms of doping and, finally, environmental and ecosystem revolutions (pollution, for example). These

would probably make any current mathematical model unreliable for forecasting progression of world records in athletics.