Abstract
A few years ago, the brilliant view pointing of Joyner et al. [1] highlighted the physiological determinants of distance running performance, assuming that the barrier of the two-hour marathon would have been overcome in 2021-22. Eliud Kipchoge broke this time barrier, concluding the marathon in 1:59:40 on October 14 th , 2019. However, the record was not homologated because Eliud Kipchoge did not run under open marathon conditions and this time record was achieved with a rotation of 41 professional pacesetters. For these reasons, the current record is still 2:01:39, set in 2018, still by Kipchoge. We aimed at updating the key factors involved in the running performance.The relevant topics of this analysis are 1) briefly reporting the physiology of the endurance race (Marathon); 2) evaluating the impact on the performance of the environment and biomechanical factors; and 3) exploring the individual factors such as nationality, genetics, and sex.The main determinants of the performance are three [2][3]: maximal oxygen uptake (VO 2 max), running economy (RE), i.e. the energy demand of running and the anaerobic threshold (AT). VO 2 max values in elite marathon runners are between 70 and 85 ml kg -1 • min -1 [1,4] and running a marathon implies an average pace at 75-85% of VO 2 max [5]. The VO 2 max is inversely correlated with the marathon time and predicts 59% of its variance [6]. In fact, there is a lack of significant differences in VO 2 max between top class runners of different nationalities [7]; and both the high level of average pace and the maximal oxygen uptake can significantly differ among runners [8]. It shows that acting on this variable is not very useful for breaking the two-hours barrier.The marathon performance positively correlates with the ability to maintain a high percentage of stroke volume and maximal cardiac output and, inversely, with the cost of running, that is the cardiac output/meter [9]. Therefore, the improvement of the RE allows to run at a higher speed for the same oxygen uptake and for this reason is better predictor of performance than VO 2 max [7]. Congenital or acquired factors can modify the RE. East African runners are characterized by the high fatty acid oxidation and slimmer lower legs. The reduced body mass with less heat build-up (detrimental for the performance) can have a positive impact on RE [10,11]. Also, the earlier exposure in life to high altitude and exercise can produce positive consequences on exercise capacity. Reduced arterial desaturation during exercise, an increased ventricular and muscle mass, differences in myosin light chain composition and motor coordination [10,12].On the other hand, a 10-week strength training, in addition to significantly increasing strength (24% for upper body lifting, 34% for lower body lifting), reduces RE by 4%, without modifying the VO 2 max [13]. These data were confirmed in two meta-analyzes: even in highly trained runners, strength training improves maximum power and strength and, in addition, reduces the energy cost of running [14][15]. Moreover, a greater hip flexor muscle strength relative to extensor muscle seems to be associated with a better RE, especially in male runners [16].The RE is also influenced by diet. Three weeks of intense training combined with a lowcarb, high-fat ketogenic diet, in elite runners, despite an increase in peak aerobic capacity, impairs performance due to a reduction in RE [17]. Indeed, if such a diet increases the ability of muscle to use fat as a substrate, keto-adaptation reduces muscle oxidation of carbohydrates and the ability to use glycogen, a limitation in high intensity endurance exercise [17]. A chronic or periodized high carbohydrate availability, on the other hand, improves running performance, due to a reduced oxidative demand of the glycemic substrate [17].Nonetheless, the AT has a strong relationship with the level of performance in the marathon. The variable that has the highest correlation is the VO 2 max at least in elite male runners [19]. In races of 10 km or more (but not over shorter distances), a significant correlation between running speed and AT has been demonstrated, especially in the group of older athletes [20]. Therefore, training at the anaerobic threshold level induces a minimal increase in VO 2 max and in AT speed, but a significant increase in time to exhaustion at AT speed [21]. This is probably due to a better lactate clearance and to the improved performance. Female runners have a higher AT than males and for the same level of performance a lower AT speed and a lower VO 2 max; nevertheless, they have a better RE, per se highly correlated with AT speed [22].Finally, age seemed to have a different impact on the determinants of performance. Due to the relationship with age, the maximum heart rate is reduced, so the highest values of maximum oxygen consumption, in elite marathoners, are reached around 27 years for males and 29 for females [23]. However, the best performance is registered around the age of 35 due to the improvement in RE which offsets the drop in VO 2 max [24]. Furthermore, the psychological profile of the elite runners (emotional stability, high motivation, strong psychic vigor) matures over the years and collaborates in improving performance later [25].Topography influences the final time of the marathon. An analysis of the most famous marathon paths showed that the Berlin race (relatively flat with a final descent of about 15 km) has the fastest winning times [26]. Climatic factors have a strong impact too, for example tailwind and temperature. The first one reduces the RE, but, when excessive it does not allow the homologation of the race time. Hyperthermia and dehydration reduce running speed and increase the risk of withdrawal. The best records of the marathon runs were achieved in spring or autumn, early in the morning and with an external temperature between 10-15 C ° [26]. Recently it has been shown as airborne particulate matter (PM 10 ) can settle in the airways of runners [27]. The main marathons take place in large, generally highly polluted cities. The increased minute ventilation, induced by running, facilitates PM 10 deposition. Air pollution can reduce the marathon performance, at least in women (every 10 μg m -3 in PM 10 , performance decrease by 1.4%) [28], as well as having a negative impact on health. To ensure "clean air" for elite runners, the PM content should be less than 5.5 μg m -3 [27].Running in a sheltered position (drafting) is a way to improve performance especially as speed increases. The benefit is imputed to a reduced energy cost, but also to psychological reasons, especially not having to deal with the pace of the race [29]. Drafting is easier to achieve as the number of athletes increases, i.e. in the first half of the marathon when selection has not yet begun. Having several runners to set the pace during the marathon could reduce the race time, even if the phenomenon is forbidden by the rules of the IAAF. However, keep a pace as uniform as possible, with very little speed changes along the race, allows the runner to be faster [26].The availability since 2017 of the new advanced shoe technology (NAST) has led to an improvement in marathon performance. The athletes who ran with the NAST vs. no-NAST [30] significantly reduce the race time (-0.68%; p <001), primarily for the low weight of the shoes. It is also known that the involvement of the metatarsophalangeal joint increases with running speed, and that the foot dominates the stiffness of the foot-shoes and torque generation complex about the joint. By increasing stiffness, these shoes reduce the energy loss of the metatarsophalangeal joint [31]. This explains why top-level athletes benefit most from NAST, as the RE improves as speed increases. Furthermore, since a greater mass at a distal point (i.e. in shoes) impairs performance [30], the foot-shoe stiffness must be adapted to the mass of the runner.Elite African runners, at the same career level, have faster marathon times than non-Africans. They also reach better results at a younger age and show a higher level of performance improvement, during their career [32]. Among the different African ethnic groups, the East African marathoners, both male and female, particularly from Ethiopia and Kenya, are the fastest and the youngest [33]. There are several causes behind the better performance of East African runners. First, a better RE, with the same VO 2 max. This is due to the delayed depletion of glycogen and reduced thermal stress, but also to anthropometric factors (slender and long legs, resulting in lower internal work and high flexibility, short calcaneal tubers, long Achilles' tendons, low body fat, high percentage of type I fibers) [34].It is also difficult to define these characteristics as genetic. If the ACE I allele, associated with improved muscle and cardiovascular function during exercise, is overexpressed in Spanish runners [1], it has not been possible to define a single genetic profile in East African marathoners [35]. On the other hand, it is possible that exposure to altitude and high levels of physical activity, in the first years of life, can protect these athletes from desaturation during heavy endurance exercise [1,10].The economic stimulus must also be added to this motivation: the prize in money is certainly a psychological incentive for athletes who come from countries with low per capita income.At this point it is necessary to focus on the gender differences impacting on the performance. With the removal of the ban on participation in endurance races for women, there was a rapid improvement in marathon records, both for the increased number of runners in competitive races, and for the adoption of training techniques borrowed from the experience of males. However, the main difference is in the VO 2 max value, which is lower in women, due to greater muscle mass, heart size, higher hemoglobin concentration and lower body fat [36]; this is the physiological limit that explains the 10-12% slower times of women [37]. The superb performance of Paula Radcliffe (2:15:25), whose time is considered comparable to the men's marathon under 2 hours, is due to a value of VO 2 max comparable to that of males, to an excellent RE, increased by training and to a higher speed of running [36]. For 16 years, it was registered as World Record and, not surprisingly, it was recently beaten by Brigid Kosgei (2:14:04), another Kenyan runner.In conclusion, the two-hour barrier is close to being overcome. The main characteristics among elite marathoners (with an optimal VO2max) can be divided into physiological, environmental / biomechanical, and individual. Pathophysiology pathways suggest that a better RE and training modalities (particularly the strength training) at the AT level; and high carbohydrate diet availability are the main determinants of Marathon runners' efficiency. Moreover, the best period to achieve a record performance will be autumn or spring. The race path should grant the maintenance of a uniform pace, with the final stretch slightly downhill and a low airborne particulate content. The marathon runner should wear shoes with NAST, with other competitors supporting him (pacing and drafting), in accordance with the IAAF rules. Finally, it is likely that the athlete will be around 35 years old and from East Africa.No conflicts of interest, financial or otherwise, are declared by the authors.
Description
This article discusses factors affecting marathon performance, including physiological and environmental aspects.