Original article

Physiological performance factors in long-distance runners

0000-0002-4261-4516Daniela Alejandra Jiménez Torres^{1  *} 

¹Universidad Central del Ecuador, Facultad Cultura Física, Quito, Ecuador.

Abstract

Athletics, a universal sport that encompasses long-distance events, races from 5km to 42 km, which have gained in popularity during the last decade, which has generated a demand for information from coaches and athletes where the factors that affect Performance in these runners is one of the topics most studied by the scientific literature, particularly physiological factors: maximum oxygen consumption, running economy, types of muscle fibers, age, sex, fatigue and genetics. The objective of this review is to describe the physiological factors that affect athletic performance in long-distance runners.

Key words: Long-distance runners; physiological factors; sports performance.

Introduction

According to the International Association of the Athletics Federations (IAAF), long distance races are a type of athletics event that comprise races on foot between 5 000 meters to 42 km in the marathon.

Long distance races usually take place in urban settings through the main avenues of cities or towns where they are organized ^{(Salguero et al., 2011)}; (García & Llopis, 2010). A significant growth in the number of participants has been observed, so they have a commercial component, which include several different marathon programs that promote the participation of runners of different categories, sex, regions, and world.

Today, there is a high production of scientific papers related to sports performance, which deal with the factors that affect it, depending on psychological, physiological, biochemical, and anthropometric criteria ^{(Urdampilleta et al., 2012)}.

Sports performance has a multifactorial character, in individual sports the influence of physiological factors is significant. Hence, coaches and researchers have focused on the prediction of sports performance, cardiovascular factors, lactate, maximum consumption of oxygen (VO₂max), ^{(Saw et al., 2016)}, ventilatory threshold, running economy (RE), age, gender, muscular fiber, and the race of the long-distance runner (Orgueta-Alday & García-lopez, 2016), working speed in the VO₂max, time limit in VO₂max, race speed in the threshold of lactate (Grivas, 2020).

Research done in the genetics associated with sports performance of runners indicate that one of the aspects that determine the chances of becoming a champion is genetics, in which inheritance is fundamental for the potential of physical performance in interaction with other factors, such as environmental, the setting, training, and nutritional (Medellín, 2012).

The research of physiological indicators that affect performance in long distance runners is predominant; they are dealt with independently, like the process of biological maturation of young athletes ^{(Verdugo, 2015)}, the analysis of the influence of anthropometric, physiological, and biomechanical factors (Ogueta-Alday et al., 2013), assessment of gender differences that affect the participation in popular long distance events ^{(Salguero et al., 2011)}.

From a multidisciplinary perspective, there are various factors that affect sports performance, thus creating interest in the scientific community in relation to the study of these factors, especially the physiological aspects (Ortigosa, 2016). In sight of this situation, What are the physiological factors that affect sports performance in long distance runners most? Accordingly, the aim of this review is to describe the physiological factors that affect sports performance in long-distance runners.

Materials and methods

The review consisted in the narrative type. The databases of GOOGLE, PUBMED, REDALYC, LATINDEX, and Dialnet were consulted, using a search strategy designed to retrieve the results associated with the physiological aspects that affect performance in long distance runners.

A total of 50 documents related to the physiological factors that affect performance in long distance runners were selected. The search was completed with reading and tracking the referenced bibliography in the documents selected during the 2015-2021 period. The information search relied on the following descriptors: Long distance runners and maximum oxygen consumption, long distance runners and running economy, long distance runners and muscle fiber, long distance runners and fatigue, long distance runners and genetics.

Results and discussion

Among the physiological factors associated with sports performance of long distance runners, the VO₂max,, running economy/effectiveness, age, gender, muscle fiber, stand out.

Maximum oxygen consumption

Performance in endurance sports is closely related to VO₂max in such a way that this physiological indicator is associated with a drop in performance during the Dial net endurance events.

The VO₂max is an indicator of aerobic potential; however, there are factors that limit or can limit it, including the energy demand of respiratory muscles, respiratory muscular fatigue, limitation of pulmonary diffusion. The typical values range between 35-45ml/kg/min, whereas endurance athletes may reach 60-80ml/kg/min (Table 1)

Table 1 - Values of maximum oxygen consumption of long distance runners 

Author (year)	Study (title)	Values VO2max
Torres Navarro, V. (2017)	Consumo de oxígeno, velocidad y economía de carrera en jóvenes atletas y triatletas.triathletes.	62.7ml/kg/min
Ruiz Griman, D. J. (2014)	Consumo máximo de oxígeno, composición corporal y clasificación según el rendimiento en 10 km de corredores aficionados.	49ml/kg/min (men) 46ml/kg/min (women)
Niño Hernández, C. A (2012)	Estimación del consumo máximo de oxígeno mediante Pruebas de ejercicios maximales y submaximales	36.68 ml/kg/min (men), 29.07 ml/kg/min (women)
Rivera et al., (2012)	El modelo paralelo de procesamiento y la percepción de esfuerzo en corredores de fondo.	53.90ml/kg/min
Tucker et al., (2009)	The runners´s body. How the latest exercise science can help run stronger, longer, and faster.	65 and 85 ml/kg/min
Caldas Zárate, R., Marino Isaza, F., & Valbuena Ruiz, L. H. (1991)	Validación de un test de carrera sobre 3200 m. Para la determinación del consumo máximo de oxígeno y de las fracciones aeróbica-anaeróbicas a concentraciones definidas de lactato plasmático en corredores de fondo	66.3ml/kg/min
Padilla et al., (1991)	Capacidad aerobia y anaerobia en corredores de medio fondo.	66ml/kg/min

Running economy/effectiveness

The term running economy describes the stable state of oxygen consumption to a particular intensity. The changes of ER are directly reflected on changes in sport benefit; that is, the weight increase of sports shoes and alterations in the ER for sports performance. It means that and changes that cause or influence the running economy may appear in the final result of a competition (González-Mohíno Mayoralas et al., 2018).

ER is a critically important indicator of performance, being VO₂ necessary to maintain certain rhythm in the race, which will be a percentage of VO2max. The anaerobic threshold and the running economy are the factors to be improved in experienced runners. ER gains more importance the longer the distance to run is, so proper ER is essential for long distance runners.

Improvements in ER demands more efficiency; that is, consuming the least possible energy when running, along with a better biomechanics of the race. Well executed training of the race technique leads to higher biomechanical efficiency and favors the elimination of unnecessary movements that increase energy consumption. Besides, strength training delays the occurrence of fatigue, which contributes to maintaining a better ER.

Today, the true role of ER in performance is being discussed; possibly the two variables (VO₂max and ER) are inversely related, and athletes with a lower VO₂max can compensate it with better ER (Orgueta-Alday & García-lopez, 2016).

Age

It is a component to be considered to achieve optimum benefit in sports. Generally, the greatest achievements in long distance races are observed in the 30-40 year-old group. In this age group, there is an optimum balance of variables VO₂max, muscle strength, and ER.

It has been defined that VO₂max, gradually increases to approximately 20 years of age, and then decreases less than 1 % a year, unusually in the same way as muscle strength, which achieves optimum development between 20 and 30 years of age, diminishing inmost muscle groups due to a reduction in the muscle mass (McArdle et al., 2015). However, it has been observed that ER increases with age. Accordingly, one of the training objectives in the advanced age subjects is to influence on the capacities that will be affected in time.

Proper strength work and high intensity endurance slow down deterioration in such a way that it can be kept until 70 or older, very acceptable for long distance races.

Gender

It has a clear influence on the performance of long-distance races. For instance, in the Olympic Games, London 2012, the winner of the marathon (men) was Stephen Kiprotich, UGA, who recorded 2 h:08 min:01seg, whereas in the women’s event, the winner, Tiki Gelana made it in 2 h:23 min:07seg. In the 10 km, the winner was Mohamed Farah, GBR, with 27 min:30seg, and the winner among the women was Tirunesh Dibaba, in 30 min:20seg, setting a three-minute difference. (Olympic Games Committees, 2021). There is a 10 % difference, which also corresponds to the 12% difference observed among the best 10 qualified men and women for the New York marathon, between 2006-2010 (Hunter & Stevens, 2013). One possible explanation could be the lower values of strength and VO₂max shown by women in relation to men, with 20-25 % VO₂max greater than that of women at any age. It was attributed to greater muscle mass and other genetic and hormonal conditions, and to even less hemoglobin in women caused by the blood loss during menstruation.

The influence of gender in ER is still argued. Meanwhile, some authors claim that men are more economical than women, others have not found significant differences to similar relative intensities (Daniels & Daniels, 1992). On the contrary, some papers indicate that women are more economical (Helgerud et al., 2009) with a normally lower index of body mass and less need of energy to run at the same speed.

Muscle fiber

Physical training can change the distribution of the types of muscle fiber. The differences observed among short distance runners, mid distance runners and long distance runners in relation to the type of muscle fiber in the vastus lateralis muscle ^{(Svedenhag, & Sjödin, 1994)}, and has been found in long distance runners with 75% type I fiber (slow twitch fiber), and 25 % of type IIa fiber (intermediate twitch fiber), and a very low percentage, even null, of type IIb fiber (fast twitch fiber). The predominance of type I muscle fiber seems to relate to VO₂max and the ER. A greater percentage of slow fiber tend to produce a lower amount of lactate and lower energetic consumption, bringing about a better performance in long distance races (Orgueta-Alday & García-lopez, 2016).

Strength training plays an important role in the training of endurance sports. The benefits on performance are produced thanks to neuromuscular adjustments that consist in higher recruitment and synchronization of motor units as well as intra and inter muscular coordination.

The genetics of runners

Among the best runners of the world, the percentage of Europeans dropped (11 %), whereas the number of African runners have grown (85 %), with the Kenyans accounting for 55 %, ^{(Vancini et al., 2014)}. The domain of African runners in long distance races has motivated researchers to study their genetics in terms of physical endurance, resulting in 200 genetic variants.

The genotype and the environment determine the phenotype. The evidence points to the interaction between genetic and environmental factors as responsible in most individual differences to respond to training (Noakes et al., 1990); ^{(Tucker et al., 2013)}. In the variations of inter-individual muscular performance, the genetic factors represent between 50 and 80 % (Arden & Spector, 1997).

The mitochondrial deoxyribonucleic acid (mtDNA) and chromosome Y of athletes that started as long distance runners in Ethiopia and Kenya were studied. The polymorphisms of mtDNA are inherited from the mother and only change as a result on new mutations (Atkinson et al., 2009). This polymorph can influence the variation of aerobic performance of humans due to their participation in the codification of different subunits of the enzymatic complex of oxidative phosphorylation ^{(Scott et al., 2005)}. However, a cohort analysis made to elite runners in Ethiopia did not reveal the existence of mtDNA variants that influenced the performance of athletes in association with aerobic endurance during events (Scott et al., 2005); similar results were found in Kenyan runners ^{(Scott et al., 2009)}.

Regarding the effects of chromosome Y on aerobic endurance and performance, the findings were similar to the ones observed in the mtDNA studies, which suggested a significant number of athletes who inherited part of their male ascendency from outside Africa.

The most commonly studied genes associated with human performance are the angiotensin converting enzyme (ACE) and aplha-actinin-3 (ACTN3), ^{(Scott et al., 2005)}; ^{(Yang et al., 2007)}.

The ACE gene is a polymorphism of insertion (I) whose lowest levels are associated with deletion (D) ^{(Scott et al., 2005)}. The allele I of this gene has been associated with performance during tests of aerobic endurance ^{(Scott et al., 2005)}, and the capacity of training cardiorespiratory aptitude seen as the maximum absorption of oxygen, which seems to be determined by the ASSL1 and 21 SNP genes ^{(Tucker & Collins, 2012)}. Allele D is associated with performance during the tests of power ^{(Wilber & Pitsiladis, 2012)} , where the contribution of inheritance may vary from 46 % to 84 % (Tucker & Collins, 2012). However, there were no significant differences in the frequency of alleles I and D in the athletes from Ethiopia, Kenya, and the general population in their respective locations ^{(Vancini et al., 2014)} .

Gene ACTN3 has been associated with the highest level of physical endurance found in elite African runners ^{(Yang et al., 2003)}, at different frequencies in different populations (Mills et al., 2001). The R577X variant was found in elite athletes of white Australian populations, though they were deficient in the ACTN3 XX genotype, with a slightly higher frequency found in elite athletes who specialize in aerobic endurance events ^{(Yang et al., 2003)}. However, no evidence was found in relation to the possible relation of R577X polymorphism and performance in aerobic endurance events in east Africa ^{(Yang et al., 2007)}, which suggests that ACTN3 deficiency is not a determining factor of sports success observed in African runners ^{(Wilber & Pitsiladis, 2012)}.

Genetic studies in sports have gained interest as they may contribute to the identification of athletes with a higher response capacity or adaptation to physical training and the prevention of injuries (Maffulli et al., 2013). Practice has demonstrated that in a group of individuals who begin a sport, only a small percentage has a genetic background and the physical characteristics that confer success in sports, so they can become elite athletes ^{(Vancini et al., 2014)}.

A study to determine if the genetic characteristics of the domain of long distance races (Ben-Zaken et al., 2021), evaluated the polymorphisms of genes associated with endurance (PPARD T/C), the capacity of endurance training (ACSL A/G), speed (ACTN3 R/X), strength (AGT T/C), and recovery from endurance training (MTC1 A/T and IL6 G/C), in the best Israeli long distance runners with an Ethiopian origin (n = 37), Israeli runners with a Caucasian origin (n = 76), and controls made of non-athletic Israelis (n = 55).

The results suggest that the domain of Israeli long distance runners is associated with endurance polymorphisms, polymorphism linked to higher speed performance and better training recovery capacity.

Discussion

Maximum oxygen consumption

VO₂max has been used as an indicator of the aerobic power of subjects evaluated largely through aerobic tests. Recent studies, however, challenge this concept (Chamari & Padulo, 2015), considering the different values achieved after showing modifications in this test (Beltrami et al., 2012).

In the VO₂max plateau, a maximum value of lactate (6-9 mmol/L-1) is reached, according to research and the age of subjects), which demonstrates the anaerobic glycolytic participation, a predominant way observed before the cessation of the physical effort, because the intensities at the end of the VO₂max surpass the second ventilatory threshold, or the threshold of respiratory compensation (Beaver et al., 1986).

According to Chamari & Padulo (2015), to describe the result of an incremental test (VO₂max), no reference should be made to the maximum aerobic speed reached, but to the speed that permits that exercise remains longer, until reaching VO₂max.

The VO₂max test requires analysis, considering that it is an aerobic test; however, to reach the VO₂max, more intensity is given to physical effort, a moment in which the anaerobic glycolytic way predominates, which means no utilization of oxygen to obtain energy.

Running economy/effectiveness

The running economy is an important physiological measure for endurance athletes, the physiological and biomechanical factors determine and influence the running economy. The running economy is a useful predictor of performance in endurance race. If oxygen consumption remains stable at a given racing speed, the demand of energy is manifested when running (Barnes & Kilding, 2015).

Therefore, the runners with a good running economy use less oxygen with little running economy at a same speed in a constant state. As an indicator of performance in the endurance race, the running economy is the maximum expression of delayed fatigue (Latorre & Soto, 2000).

The running economy varies (Barnes & Kilding, 2015) up to 30 % among runners trained under a similar VO₂max. It is thought of as a multifactorial measure that shows the function of the metabolic, cardiopulmonary, biomechanical, and neuromuscular systems.

Age and Gender

Based on the review conducted, age and gender are factors that affect optimum performance in long distance races. Within the 30-40 age range, there is an optimum balance of variables VO₂max, muscle strength, and ER. There is a 10 % difference among the best 10 men and women of the New York marathon, between 2006-2010.

It has been observed that ER improves with age. Accordingly, one of the training objectives in the elderly is to influence on the capacities that will be affected with the passing of years.

The particularities and results of the similarities between genders (Garcia Avendaño et al., 2008) depend mostly on the somatotype, physiology, and body composition. The difference does not go beyond the normal limits of these biological aspects. In other words, there is no evidence that demonstrates that men are superior to women due to the features of their gender.

In relation to the similar physiology of men and women, it has been considered that the average fully matured women is characterized by lower body mass and size than men, which is translated into a smaller and slighter body structure. Consequently, women have a broader pelvis and shorter limbs, and muscles converging toward the knees, so the femur loses verticality and the lower leg bones show a smaller arch than that of men, causing a reduction in efficient mechanics when running.

The morphophysiological traits of women may cause limited performance in sports practice. Besides, they are more prone to suffer injuries due to knee instability.

The cardiopulmonary system also shows differences between the genders. The cardiac volume of a woman is below 25 %. It corresponds to the morphological conditioning factor that the thorax of women is smaller and with a 10 % lower pulmonary capacity than men. Likewise, the capacity of oxygen transport per litter of blood is 11% lower in women. Nevertheless, it is worth noting that for the same effort intensity, women with regular training have a similar cardiopulmonary volume to trained men or men with a similar activity level (Garcia Avendaño et al., 2008).

Muscle fiber

There are different types of muscle fiber, the fiber that predominates in long distance athletics are the slow twitch fiber, also known as red fiber or type I fiber.

The slow fiber has a high capacity to produce energy anaerobically at a low potency. These fibers have metabolic adjustments for slow and prolonged effort, tolerance to exhaustion, and the capacity of maintaining muscle contractions for a longer time.

Type I fiber or slow fiber contains a large number of mitochondria, high aerobic metabolism, and greater endurance to fatigue. One of the characteristics that stand out most is the high content of myoglobin, along with a large number of mitochondria and blood capillary that favor oxygen contribution and utilization (Billat, 2002).

The percentage of different types of fiber is conditioned by the genetics, though some parameters can be modified by strength and endurance training. Hence, a high prevalence of type I fibers at the muscular level seems to be a fundamental requisite for the success of endurance sports. According to ^{Sanchis (2015)}, the type I fibers in the muscles trained are linked to the previous years of endurance training.

The genetics of runners

Studies of mtDNA and chromosome Y provided no genetic evidence that support the biological background in relation to the racial differences in sports performance of African runners ^{(Scott et al., 2005)} (Onywera et al., 2006) ^{(Scott et al., 2009) (Wilber & Pitsiladis, 2012)}.

Considering the different levels of ligament unbalances between Caucasians and Africans in the analysis of the potentially causal ACE variant (genotype A22982G), no significant differences were found in the frequencies of the Ethiopian and Kenyan athletes and the general population ^{(Scott et al., 2005)}.

The ACE and ACTN3 genes are associated with performance in the aerobic endurance race; however, the data are insufficient to support this association. Based on the evidence provided, the phenotype possibly has a greater influence than the genotype on the success of long distance runners, ^{(Scott & Pitsiladis, 2007)}. Moreover, the results of athletic performance of certain populations are multifactorial. Therefore, the success of elite athletes due to SNP5 is unlikely (Pitsiladis & Scott, 2005); it must be the result of a broad combination of advantageous genotypes ^{(Scott & Pitsiladis, 2007)}.

Before considering that the genetic factors are directly responsible for the performance of African runners, it is necessary to conduct in-depth studies that determine the frequency of variants of other nuclear candidate genes in specific cohorts. According to the current trends in sports, a genomic research is recommended, so that multiple genes can be studied simultaneously, the study of the whole genome, instead of focusing on single candidate genes. That way, possible genes could be found, or the inconsistencies of this topic in relation to long distance runners could be elucidated ^{(Wilber & Pitsiladis, 2012)}; ^{(Skinner, 2001)}; ^{(Roth et al., 2012)}; (Onywera et al., 2006).

Despite current research, the findings have produced limited results with respect to the genetic variants associated with sports performance, the capacity of athlete training, and proneness to injuries ^{(Wang et al., 2016)}.

Conclusions

The influence of physiological factors on the performance of long distance runners can be affected by age, sex, and fatigue. Research has shown that the maximum oxygen consumption is an inappropriate predictor of endurance performance, contrary to running economy.

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Received: September 29, 2021; Accepted: October 13, 2021

^*Autor para la correspondencia: [e-mail]

La autora declara que no posee conflictos de intereses respecto a este texto.

Los autores han participado en la redacción del trabajo y análisis de los documentos.