Elite runners need a specific combination of physiological abilities to have any chance of running a sub-two-hour marathon, new research shows.
The study is based on detailed testing of athletes who took part in Nike’s Breaking2 project – an ambitious bid to break the two-hour barrier.
Professor Andrew Jones, of the University of Exeter, said the findings reveal that elite marathon runners must have a “perfect balance” of VO2 max (rate of oxygen uptake), efficiency of movement and a high “lactate turn point” (above which the body experiences more fatigue).
The VO2 measured among elite runners shows they can take in oxygen twice as fast at marathon pace as a “normal” person of the same age could while sprinting flat-out.
“Some of the results – particularly the VO2 max – were not actually as high as we expected,” Professor Jones said.
“Instead, what we see in the physiology of these runners is a perfect balance of characteristics for marathon performance.
“The requirements of a two-hour marathon have been extensively debated, but the actual physiological demands have never been reported before.”
The runners in the study included Eliud Kipchoge, who took part in Breaking2 – falling just short of the two-hour target – but later achieving the goal in 1:59:40.2 in the Ineos 1:59 challenge.
Based on outdoor running tests on 16 athletes in the selection stage of Breaking2, the study found that a 59kg runner would need to take in about four litres of oxygen per minute (or 67ml per kg of weight per minute) to maintain two-hour marathon pace (21.1 km/h).
“To run for two hours at this speed, athletes must maintain what we call ‘steady-state’ VO2,” Professor Jones said.
“This means they meet their entire energy needs aerobically (from oxygen) – rather than relying on anaerobic respiration, which depletes carbohydrate stores in the muscles and leads to more rapid fatigue.”
In addition to VO2 max, the second key characteristic is running “economy”, meaning the body must use oxygen efficiently – both internally and through an effective running action.
The third trait, lactate turn point, is the percentage of VO2 max a runner can sustain before anaerobic respiration begins.
“If and when this happens, carbohydrates in the muscles are used at a high rate, depleting glycogen stores,” Professor Jones explained.
“At this point – which many marathon runners may know as ‘the wall’ – the body has to switch to burning fat, which is less efficient and ultimately means the runner slows down.
“The runners we studied – 15 of the 16 from East Africa – seem to know intuitively how to run just below their ‘critical speed’, close to the ‘lactate turn point’ but never exceeding it.
“This is especially challenging because – even for elite runners – the turn point drops slightly over the course of a marathon.
“Having said that, we suspect that the very best runners in this group, especially Eliud Kipchoge, show remarkable fatigue resistance.”
The testing, conducted in Exeter and at Nike’s performance centre in Oregon, USA, provided a surprising experience for a group of amateur runners in the UK.
“We tested 11 of the 16 runners at Exeter Arena a few years ago,” Professor Jones said.
“Some local runners were there at the time, and it was a real eye-opener for them when a group of the world’s best athletes turned up.
“The elite runners were great—they even joined in with the local runners and helped to pace their training.”
Athletic performance is a complex trait that is influenced by both genetic and environmental factors. Many physical traits help determine an individual’s athletic ability, primarily the strength of muscles used for movement (skeletal muscles) and the predominant type of fibers that compose them.
Skeletal muscles are made up of two types of muscle fibers: slow-twitch fibers and fast-twitch fibers. Slow-twitch muscle fibers contract slowly but can work for a long time without tiring; these fibers enable endurance activities like long-distance running.
Fast-twitch muscle fibers contract quickly but tire rapidly; these fibers are good for sprinting and other activities that require power or strength. Other traits related to athleticism include the maximum amount of oxygen the body can deliver to its tissues (aerobic capacity), muscle mass, height, flexibility, coordination, intellectual ability, and personality.
Studies focused on similarities and differences in athletic performance within families, including between twins, suggest that genetic factors underlie 30 to 80 percent of the differences among individuals in traits related to athletic performance. Many studies have investigated variations in specific genes thought to be involved in these traits, comparing athletes with nonathletes.
The best-studied genes associated with athletic performance are ACTN3 and ACE. These genes influence the fiber type that makes up muscles, and they have been linked to strength and endurance. The ACTN3 gene provides instructions for making a protein called alpha (α)-actinin-3, which is predominantly found in fast-twitch muscle fibers.
A variant in this gene, called R577X, leads to production of an abnormally short α-actinin-3 protein that is quickly broken down. Some people have this variant in both copies of the gene; this genetic pattern (genotype) is referred to as 577XX.
These individuals have a complete absence of α-actinin-3, which appears to reduce the proportion of fast-twitch muscle fibers and increase the proportion of slow-twitch fibers in the body.
Some studies have found that the 577XX genotype is more common among high-performing endurance athletes (for example, cyclists and long-distance runners) than in the general population, while other studies have not supported these findings. The 577RR genotype is associated with a high proportion of fast-twitch fibers and is seen more commonly in athletes who rely on strength or speed, such as short-distance runners.
The ACE gene provides instructions for making a protein called angiotensin-converting enzyme, which converts a hormone called angiotensin I to another form called angiotensin II. Angiotensin II helps control blood pressure and may also influence skeletal muscle function, although this role is not completely understood.
A variation in the ACE gene, called the ACE I/D polymorphism, alters activity of the gene. Individuals can have two copies of a version called the D allele, which is known as the DD pattern, two copies of a version called the I allele, known as the II pattern, or one copy of each version, called the ID pattern.
Of the three patterns, DD is associated with the highest levels of angiotensin-converting enzyme. The DD pattern is thought to be related to a higher proportion of fast-twitch muscle fibers and greater speed.
Many other genes with diverse functions have been associated with athletic performance. Some are involved in the function of skeletal muscles, while others play roles in the production of energy for cells, communication between nerve cells, or other cellular processes.
Other studies have examined variations across the entire genomes (an approach called genome-wide association studies or GWAS) of elite athletes to determine whether specific areas of the genome are associated with athleticism.
More than 150 different variations linked to athletic performance have been identified in these studies; however, most have been found in only one or a few studies, and the significance of most of these genetic changes have not been identified. It is likely that a large number of genes are involved, each of which makes only a small contribution to athletic performance.
Athletic performance is also strongly influenced by the environment. Factors such as the amount of support a person receives from family and coaches, economic and other circumstances that allow one to pursue the activity, availability of resources, and a person’s relative age compared to their peers all seem to play a role in athletic excellence.
A person’s environment and genes influence each other, so it can be challenging to tease apart the effects of the environment from those of genetics. For example, if a child and his or her parent excel at a sport, is that similarity due to genetic factors passed down from parent to child, to similar environmental factors, or (most likely) to a combination of the two? It is clear that both environmental and genetic factors play a part in determining athletic ability.
Scientific journal articles for further reading
Ahmetov II, Egorova ES, Gabdrakhmanova LJ, Fedotovskaya ON. Genes and Athletic Performance: An Update. Med Sport Sci. 2016;61:41-54. doi: 10.1159/000445240. Epub 2016 Jun 10. Review. PubMed: 27287076.
Ahmetov II, Fedotovskaya ON. Current Progress in Sports Genomics. Adv Clin Chem. 2015;70:247-314. doi: 10.1016/bs.acc.2015.03.003. Epub 2015 Apr 11. Review. PubMed: 26231489.
Webborn N, Williams A, McNamee M, Bouchard C, Pitsiladis Y, Ahmetov I, Ashley E, Byrne N, Camporesi S, Collins M, Dijkstra P, Eynon N, Fuku N, Garton FC, Hoppe N, Holm S, Kaye J, Klissouras V, Lucia A, Maase K, Moran C, North KN, Pigozzi F, Wang G. Direct-to-consumer genetic testing for predicting sports performance and talent identification: Consensus statement. Br J Sports Med. 2015 Dec;49(23):1486-91. doi: 10.1136/bjsports-2015-095343. PubMed: 26582191. Free full-text available from PubMed Central: PMC4680136.
Yan X, Papadimitriou I, Lidor R, Eynon N. Nature versus Nurture in Determining Athletic Ability. Med Sport Sci. 2016;61:15-28. doi: 10.1159/000445238. Epub 2016 Jun 10. Review. PubMed: 27287074.
More information: Andrew M. Jones et al, Physiological demands of running at 2-hour marathon race pace, Journal of Applied Physiology (2020). DOI: 10.1152/japplphysiol.00647.2020