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Abstract
The study comprises data on 12 Scandinavian runners who had either trained for two weeks in Kenya (n = 6; approximately 2000 meters above sea level (m.a.s.l.)) or in Portugal (n = 6; sea level (s.l.)) and on 13 Kenyan runners (9 junior and 4 senior) living and training at approximately 2000 m.a.s.l. Muscle biopsies were taken before and after the training camps in the Scandinavian runners and once on the Kenyan runners from the vastus lateralis (v.l.) and the gastrocnemius muscles. Muscle fiber size and composition were similar in the various groups (4.6-5.1 X 10(3) microns2; ST approximately 60-70%; FTa 30-40%; FTb < 6.0%) with a tendency for some more (approximately 5%) FTa fibers in the gastrocnemius muscle. Mean number of capillaries in v.l. varies between 405-493 cap.(mm2)-1, 2.0-2.7 cap.fiber-1, and 4.4-6.2 cap around the various fiber types, with the Kenyan seniors having the highest and the Kenyan juniors the lowest values. All runners had 10-20% more capillaries in their gastrocnemius muscle. Similar levels for citrate synthase (CS) activity were found in the v.l. of the Kenyan seniors and Scandinavian runners, whereas the Kenyan juniors were 10-15% lower. The 3- hydroxyacyl-CoA-dehydrogenase (HAD) activity was 20% higher in the Kenyan than in the Scandinavian runners. In the gastrocnemius muscle, both enzyme activities were 20-50% higher in Scandinavian and Kenyan runners. The ratio for lactate dehydrogenase (LDH) isoform1-2 and isoform4-5 was increased when training at altitude due to a lowering of LDH4-5 and became close to what was observed in the Kenyan runners.
... Firstly, Bengt Saltin's group revealed key physiological aspects of Kenyan runners that could contribute to their superior endurance running performance. 5,6 In their reports, while the elite Kenyan and Scandinavian runners were in the same range of maximal oxygen uptake, the Kenyans were metabolically more economical, especially at race-pace running velocities. 5 To date, these physiological advantages of Kenyan endurance runners have been confirmed by comparison to other ethnic groups of elite and non-elite runners, such as Japanese 7 and Caucasians. ...
... 8 Among other factors, clear evidence has been provided that elite Kenyan runners have long legs and thin/light calf muscles that may provide biomechanical and metabolic advantages. [9][10][11][12] In addition, as suggested by Saltin et al, 5,6 the architecture and function of the triceps surae muscletendon complex may also be of interest. Supporting this hypothesis, our own research group repeatedly found that elite Kenyan runners are characterized by a longer gastrocnemius Achilles tendon (AT), shorter fascicles in the medial gastrocnemius (MG) muscle and longer AT moment arm (MA AT ), as well as a lower foot lever ratio (forefoot length divided by MA AT ) than Japanese non-elite runners 13,14 and healthy Caucasian adults. ...
Aim:
The specificity of muscle-tendon and foot architecture of elite Kenyan middle- and long-distance runners has been found to contribute to their superior running performance. To investigate the respective influence of genetic endowment and training on these characteristics, we compared leg and foot segmental lengths as well as muscle-tendon architecture of Kenyans and Japanese males (i) from infancy to adulthood and (ii) non-athletes vs. elite runners.
Methods:
The 676 participants were divided according to their nationality (Kenyans and Japanese), age (nine different age groups for non-athletes) and performance level in middle- and long-distance races (non-athlete, non-elite and elite adult runners). Shank and Achilles tendon (AT) lengths, medial gastrocnemius (MG) fascicle length, pennation angle and muscle thickness, AT moment arm (MAAT ) and foot lever ratio were measured.
Results:
Above 8 years old, Kenyans had a longer shank and AT, shorter fascicle, greater pennation angle, thinner MG muscle as well as longer MAAT , with lower foot lever ratio than age-matched Japanese. Among adults of different performance levels and independently of the performance level, Kenyans had longer shank, AT and MAAT , thinner MG muscle thickness and lower foot lever ratio than Japanese. The decrease in MG fascicle length and increase pennation angle observed for the adult Japanese with the increase in performance level resulted in a lack of difference between elite Kenyans and Japanese.
Conclusion:
The specificity of muscle-tendon and foot architecture of elite Kenyan runners could result from genetic endowment and contribute to the dominance of Kenyans in middle- and long-distance races.
... Kenyan elite runners win many international track and road distance races, which has stimulated research into the causes of this success [1][2][3][4][5][6]. When examining the geographical distribution of the top 20 running performances for male and female athletes in both middle-and long-distance events (800 m, 1500 m, 3000 m, 5000 m, 10,000 m, 5 km, 10 km, half-marathon, and marathon) in the past 5 years (since the last Olympic cycle: 5 August, 2016 to 29 August, 2021), 41.6% have been achieved by Kenyan athletes [7]. ...
Background:
Advanced footwear technology improves average running economy compared with racing flats in sub-elite athletes. However, not all athletes benefit as performance changes vary from a 10% drawback to a 14% improvement. The main beneficiaries from such technologies, world-class athletes, have only been analyzed using race times.
Objective:
The aim of this study was to measure running economy on a laboratory treadmill in advanced footwear technology compared to a traditional racing flat in world-class Kenyan (mean half-marathon time: 59:30 min:s) versus European amateur runners.
Methods:
Seven world-class Kenyan and seven amateur European male runners completed a maximal oxygen uptake assessment and submaximal steady-state running economy trials in three different models of advanced footwear technology and a racing flat. To confirm our results and better understand the overall effect of new technology in running shoes, we conducted a systematic search and meta-analysis.
Results:
Laboratory results revealed large variability in both world-class Kenyan road runners, which ranged from a 11.3% drawback to a 11.4% benefit, and amateur Europeans, which ranged from a 9.7% benefit to a 1.1% drawback in running economy of advanced footwear technology compared to a flat. The post-hoc meta-analysis revealed an overall significant medium benefit of advanced footwear technology on running economy compared with traditional flats.
Conclusions:
Variability of advanced footwear technology performance appears in both world-class and amateur runners, suggesting further testing should examine such variability to ensure validity of results and explain the cause as a more personalized approach to shoe selection might be necessary for optimal benefit.
... Comparação da estratégia de corrida em atletas africanos e não africanos na prova de 5.000 metros do atletismo: estudo transversal Introdução Há algumas décadas, atletas africanos, vindos principalmente dos países do Leste, como: Quênia, Eritreia e Etiópia, dominam as corridas de média e longa distância do atletismo. Diferentes estudos têm sido realizados na tentativa de explicar tal domínio em relação a atletas do resto do mundo (1)(2)(3)(4)(5). ...
Introdução: Atletas africanos dominam as provas de longa distância no atletismo há algumas décadas. Vários fatores têm sido investigados para explicar esse fenômeno, porém, variáveis relacionadas a estratégia de corrida permanecem em aberto. Objetivo: Comparar a estratégia de corrida em atletas africanos e não africanos na prova dos 5.000 m. Métodos: Foram extraídos dados de 43 atletas das provas finais dos 5.000 m masculino dos três últimos campeonatos mundiais. Estes atletas foram divididos em dois grupos: atletas africanos (n=30) e não africanos (n=13). A velocidade atingida a cada quilômetro foi utilizada para determinar a estratégia de corrida. Resultados: Não houve diferença na velocidade de corrida ao longo das parciais (km) entre os grupos. As parciais um e dois foram menores que as demais parciais e as parciais três e quatro foram menores que a parcial cinco (p<0,05). Conclusão: Não houve diferença na estratégia de corrida entre atletas africanos e não africanos na prova dos 5.000 m e velocidade da corrida tende a aumentar ao longo da prova.
... Ένας άλλος παράγοντας που διαδραματίζει σημαντικό ρόλο στη βελτίωση των επιδόσεων στον μαραθώνιο είναι η RE. Έχουν πραγματοποιηθεί αρκετές έρευνες οι οποίες αναφέρουν ότι οι ελίτ Αφρικανοί δρομείς αντοχής έχουν καλύτερη RE σε σχέση με τους δρομείς των άλλων χωρών (Lucia et al., 2006;Saltin et al., 1995;Weston, Mbambo & Myburg, 2000;Wilber & Pitsiladis, 2012). Αυτό σημαίνει ότι οι Αφρικανοί δρομείς έχουν μικρότερο ενεργειακό κόστος κατά τη διάρκεια του τρεξίματος (Larsen, 2003). ...
Τα παγκόσμια ρεκόρ τόσο στους άνδρες όσο και στις γυναίκες από το αγώνισμα των 5 km μέχρι και τον μαραθώνιο δρόμο έχουν καταρριφθεί μετά την εισαγωγή στην παραγωγή του παπουτσιού με την πλάκα του άνθρακα (CFP) το 2016. Αυτή η σταδιακή βελτίωση της επίδοσης, συμπίπτει με τις πρόσφατες εξελίξεις στην τεχνολογία παπουτσιών που αυξάνουν τις ελαστικές ιδιότητες του παπουτσιού μειώνοντας έτσι το ενεργειακό κόστος τρεξίματος. Τα τελευταία CFP παπούτσια είναι γνωστό ότι αυξάνουν τη δρομική οικονομία περισσότερο από 4%, που αντιστοιχεί σε βελτίωση της επίδοσης μεγαλύτερη από 2%. Οι πρόσφατα τροποποιημένοι κανονισμοί σχετικά με τα αγωνιστικά παπούτσια για ελίτ αθλητές, που ανακοινώθηκαν από τη Διεθνή Ομοσπονδία Κλασικού Αθλητισμού (World Athletics) αναφέρουν ότι το πάχος της σόλας δεν πρέπει να υπερβαίνει τα 40 mm και δεν πρέπει να περιέχουν περισσότερες από μία άκαμπτες ενσωματωμένες πλάκες. Όλα αυτά είναι αντίθετα με την αληθινή ουσία και αξία του αθλητισμού, καθώς η τεχνολογία αυτή με σκοπό τη βελτίωση των επιδόσεων δεν θα είναι προσβάσιμη από όλους τους ελίτ αθλητές. Αυτό είναι ένα ιδιαίτερο πρόβλημα σε αθλήματα όπως ο
κλασικός αθλητισμός όπου ο κύριος χορηγός του αθλητή είναι πολύ συχνά μια εταιρεία κατασκευής παπουτσιών. Σκοπός της παρούσας ανασκόπησης ήταν να γίνει κατανοητό ότι οι πρόσφατες βελτιώσεις του χρόνου στον μαραθώνιο οφείλονται περισσότερο στην εξέλιξη της τεχνολογίας και λιγότερο σε φυσιολογικούς και προπονητικούς παράγοντες. Συμπερασματικά, μια απλή και πρακτική εφαρμογή για την επίλυση αυτού του προβλήματος είναι η πιθανή μείωση του πάχους της σόλας στα 20 mm. Αυτή η πρακτική λύση θα εμπόδιζε την τεχνολογία παπουτσιών να έχει πολύ μεγάλη επίδραση στο ενεργειακό κόστος τρεξίματος και επομένως, να διαδραματίζει πρωταρχικό ρόλο στις επιδόσεις των αθλητών.
... A former world champion and still the world record holder in the 60-m hurdles and former world record holder in 110-m hurdles had a high percentage of pure MHC IIx (24%) and a total fast-twitch fiber percentage of 71% (Trappe et al., 2015). Contrary, elite distance runners display an elevated percentage (70%) of slowtwitch muscle fibers (Saltin et al., 1995). However, the data is not so clear because high-level endurance performance in running events is also associated with high percentages of isoforms corresponding to Myosin Heavy Chain IIa (Kohn et al., 2011). ...
Usain Bolt's stunning sportive achievements sparked admiration from around the world and raised the question of the genesis of his sport excellence. In the light of the various theories of evolution, we try to understand whether there are evolutionary grounds for considering Usain Bolt a “hopeful monster”, i.e. a transgressive phenotype beyond the range of parental phenotypes. This hypothesis would call into question the gradualism defended by Darwin and would give room to saltationism by which profound changes can occur in one or a few generations. It seems that the saltational hypothesis is not scientifically adequate to justify Usain Bolt’s sport performance. Not knowing the genetic profile of Usain Bolt and his ancestors, we can hypothesize that his sporting excellence is the result of a given polymorphism or phenotypic changes induced by ecological determinants, among which training and nutrition stand out.We can admit that Usain Bolt is a rare case of developmental plasticity that enables his genome to generate a phenotype associated with a specific competence for sprinting.In the current state of scientific knowledge, there is no way to associate any polymorphism with performance in sporting events related to strength and speed but a challenging field is open for science. Aware of the difficulties in characterizing Usain Bolt, he is undoubtedly the result of an extraordinary combination of genetic and environmental factors. Resumen. Los impresionantes logros deportivos de Usain Bolt despertaron la admiración de todo el mundo y plantearon la cuestión de la génesis de su excelencia deportiva. A la luz de las diversas teorías de la evolución, tratamos de comprender si existen bases evolutivas para considerar a Usain Bolt como un "monstruo esperanzado", es decir, un fenotipo transgresor más allá del rango de fenotipos parentales. Esta hipótesis pondría en tela de juicio el gradualismo defendido por Darwin y daría lugar al saltacionismo mediante el cual pueden ocurrir cambios profundos en una o pocas generaciones. Parece que la hipótesis saltacional no es científicamente adecuada para justificar el rendimiento deportivo de Usain Bolt. Sin conocer el perfil genético de Usain Bolt y sus ancestros, podemos plantear la hipótesis de que su excelencia deportiva es el resultado de un determinado polimorfismo o cambios fenotípicos inducidos por determinantes ecológicos, entre los que destacan el entrenamiento y la nutrición. Podemos admitir que Usain Bolt es un caso raro de plasticidad del desarrollo que permite que su genoma genere un fenotipo asociado con una competencia específica para correr. En el estado actual del conocimiento científico, no hay forma de asociar ningún polimorfismo con el rendimiento en eventos deportivos relacionados con la fuerza y la velocidad, pero hay un campo desafiante para la ciencia. Consciente de las dificultades para caracterizar a Usain Bolt, es sin duda el resultado de una extraordinaria combinación de factores genéticos y ambientales.
... Immunohistochemical studies have shown that LDH is present both in the cytoplasm and in the mitochondria of skeletal muscle (Figure 2; Brooks et al., 1999). Moreover, endurance training upregulates the mitochondria-rich type I fibres and the heart-specific LDH isoform in skeletal muscle, suggesting a higher capacity for intracellular oxidation of lactate (Dubouchaud et al., 2000), whereas the activity of the skeletal muscle LDH isoform is upregulated in type II fibres (Saltin et al., 1995). This corresponds to the cell-to-cell lactate shuttle theory described above, whereby lactate is produced by type II fibres and consumed by type I fibres during exercise (Brooks, 2018). ...
New findings:
What is the topic of this review? Lactate is considered an important substrate for mitochondria in muscles, heart, and brain during exercise, and is the main gluconeogenetic precursor in the liver and kidneys. In this light, we review the (patho)physiology of lactate metabolism in sepsis and coronavirus disease 2019 (COVID-19). What advances does it highlight? Elevated blood lactate is strongly associated with mortality in septic patients. Lactate seems unrelated to tissue hypoxia, but likely reflects mitochondrial dysfunction and high adrenergic stimulation. Patients with severe COVID-19 exhibit near-normal blood lactate, indicating preserved mitochondrial function, despite a systemic hyperinflammatory similar to sepsis.
Abstract:
In critically ill patients, elevated plasma lactate is often interpreted as a sign of organ hypoperfusion and/or tissue hypoxia. This view on lactate is likely influenced by the pioneering exercise physiologists around 1920. August Krogh identified an oxygen deficit at the onset of exercise that was later related to an oxygen "debt" and lactate accumulation by AV Hill. Lactate is considered the main gluconeogenetic precursor in the liver and kidneys during submaximal exercise, but the hepatic elimination is attenuated by splanchnic vasoconstriction at high-intensity exercise causing an exponential increase in blood lactate. With the development of stable isotope tracers, lactate has become established as an important energy source for muscle, brain, and heart tissue where it is utilised for mitochondrial respiration. Plasma lactate > 4 mM is strongly associated with mortality in septic shock, with no direct link between lactate release and tissue hypoxia. Herein, we provide evidence for mitochondrial dysfunction and adrenergic stimulation as explanations for the sepsis-induced hyperlactatemia. Despite profound hypoxaemia and intense work of breathing, patients with severe coronavirus disease 2019 (COVID-19) rarely exhibit hyperlactatemia (> 2.5 mM), while presenting a systemic hyperinflammatory state much like sepsis. However, lactate dehydrogenase (LDH), which controls the formation of lactate, is markedly elevated in plasma, and strongly associated with mortality in severe COVID-19. We briefly review the potential mechanisms of the LDH elevation in COVID-19 and its relationship to lactate metabolism based on mechanisms established in contracting skeletal muscle and the acute respiratory distress syndrome. This article is protected by copyright. All rights reserved.
... A former world champion and still the world record holder in the 60-m hurdles and former world record holder in 110-m hurdles had a high percentage of pure MHC IIx (24%) and a total fast-twitch fiber percentage of 71% (Trappe et al., 2015). Contrary, elite distance runners display an elevated percentage (70%) of slowtwitch muscle fibers (Saltin et al., 1995). However, the data is not so clear because high-level endurance performance in running events is also associated with high percentages of isoforms corresponding to Myosin Heavy Chain IIa (Kohn et al., 2011). ...
Usain Bolt’s stunning sportive achievements sparked admiration from around the world and raised the question of the genesis of his sport
excellence. In the light of the various theories of evolution, we try to understand whether there are evolutionary grounds for considering Usain Bolt a
«hopeful monster», i.e. a transgressive phenotype beyond the range of parental phenotypes. This hypothesis would call into question the gradualism
defended by Darwin and would give room to saltationism by which profound changes can occur in one or a few generations. It seems that the saltational
hypothesis is not scientifically adequate to justify Usain Bolt’s sport performance. Not knowing the genetic profile of Usain Bolt and his ancestors, we can
hypothesize that his sporting excellence is the result of a given polymorphism or phenotypic changes induced by ecological determinants, among which
training and nutrition stand out.We can admit that Usain Bolt is a rare case of developmental plasticity that enables his genome to generate a phenotype
associated with a specific competence for sprinting.In the current state of scientific knowledge, there is no way to associate any polymorphism with
performance in sporting events related to strength and speed but a challenging field is open for science. Aware of the difficulties in characterizing Usain
Bolt, he is undoubtedly the result of an extraordinary combination of genetic and environmental factors.
Keywords: evolutionary biology; athletic performance; genetics; epigenetics.
Running economy (RE) at a given submaximal running velocity is defined as oxygen consumption per minute per kg body mass. We investigated RE in a group of 12 male elite runners of national class. In addition to RE at 14 and 18 km h−1 we measured the maximal oxygen consumption (VO2max) and anthropometric measures including the moment arm of the Achilles tendon (LAch), shank and foot volumes, and muscular fascicle lengths. A 3‐D biomechanical movement analysis of treadmill running was also conducted. RE was on average 47.8 and 62.3 ml O2 min−1 kg−1 at 14 and 18 km h−1. Maximal difference between the individual athletes was 21% at 18 km h−1. Mechanical work rate was significantly correlated with VO2 measured in L min−1 at both running velocities. However, RE and relative work rate were not significantly correlated. LAch was significantly correlated with RE at 18 km h−1 implying that a short moment arm is advantageous regarding RE. Neither foot volume nor shank volume were significantly correlated to RE. Relative muscle fascicle length of m. soleus was significantly correlated with RE at 18 km h−1. Whole body stiffness and leg stiffness were significantly correlated with LAch indicating that a short moment arm coincided with high stiffness. It is concluded that a short LAch is correlated with RE. Probably, a short LAch allows for storage of a larger amount of elastic energy in the tendon and influences the force–velocity relation toward a lower contraction velocity. Running economy was found to be significantly related to Achilles tendon moment arm, foot length ratio, whole body stiffness and leg stiffness, and muscular fascicle length.
The human skeletal muscle consists of two major cell types, slow-twitch fibers (also called type I fibers) and fast-twitch fibers (or type II fibers). These fibers have distinct characteristics, as fast-twitch fibers are able to generate a large amount of power at high shortening velocities, while slow-twitch fibers have a better energy efficiency, a higher resistance to fatigue and a more robust structural integrity. On average, most humans will dispose of a 50% slow-twitch and a 50% fast-twitch distribution. However a big heterogeneity exists, what results in people with predominantly slow or fast muscle fibers. The typology of a person is mostly genetically determined and is present across most muscles of the body. Taken together, the fact that muscle fibers have distinct characteristics and that muscle typologies range over the whole continuum from predominantly slow to fast in human, will have important implications for sports performance. Nevertheless, these typologies are currently not used in the daily coaching practice. This is probably due to the invasiveness of the current ‘gold’ standard to measure the muscle typology: a muscle biopsy, which is a labor intensive method and harbors a low generalizability. In 2011, our group introduced a non-invasive way to estimate the muscle fiber type composition through the measurement of carnosine – a metabolite which is abundantly available in fast-twitch fibers – using proton magnetic resonance spectroscopy (1H-MRS). The non-invasiveness of this technique enables the use in both the sports practice and science, and renews the interest of the muscle typology in sports. In the first study, the 1H-MRS method to determine the muscle typology was further optimized with the ultimate goal to make it applicable on various scanner systems of multiple vendors. 1H-MRS was found to be a reliable method to quantify carnosine in the muscle. Furthermore, best practices were proposed to prevent often encountered methodological problems and step by step guidelines were developed to allow broader utilization of this technique. Secondly, we investigated if pre-puberty carnosine measurements could give insights in the post-puberty carnosine concentrations, which would allow application of this technique in early specialization sports (study 2). Carnosine was shown to be a trackable metabolite through the disruptive puberty period (R2=0.249-0.670), which confirms the potential of the current technique to scan both future talents and elite athletes. Next to the methodological optimization, the relevance of the muscle typology for talent identification was examined. Before the start of the thesis, the construct validity of our method was already confirmed in athletics, in which clear differences were determined in the muscle typology of either sprint or endurance disciplines. Despite the fact that a comparable distribution of the muscle typologies could be expected in other cyclic sports such as cycling and swimming, this was not yet investigated in elite athletes. Therefore, study 3 established the muscle typologies of 80 world-class cyclists. Clear differences were found in the muscle typology between cycling events. Keirin, bicycle motocross racing (BMX), sprint and 500 m to 1 km time trial cyclists can be considered as fast typology athletes. Time trial, points race, scratch, and omnium consist of intermediate typology athletes, while most individual pursuit, single-stage, cyclo-cross, mountain bike, and multistage cyclists have a slow typology. Nevertheless, this distribution was not present in 73 elite swimmers (study 4), as no clear differences in the muscle typology were detected between short and long distance swimming events in the different strokes. However, there was some evidence to suggest that truly world-class sprint swimmers had a faster muscle fiber type composition when compared to elite swimmers competing at the international level. Moreover, breaststroke swimmers were identified to have a faster muscle typology in comparison to the either freestyle, backstroke or butterfly swimmers. Elite soccer players (n=118) were found to have an on average intermediate typology, which matches with the intermittent nature of this sport (study 6). In contrary to our hypothesis, no differences in the muscle typology were detected between different positions (keeper, defender, midfielder and striker). A big heterogeneity was established over all positions, indicating that the muscle typology is not of major importance for talent identification in soccer. To determine the influence of the muscle typology on individualized training and recovery cycles, we investigated if fatigue and recovery were different when both slow and fast typology subjects were exposed to the same high-intensity training (study 5). Fatigue during three Wingate tests, determined by the power drop, was 20% higher in fast typology athletes. Even though the same work was done during these Wingate tests, also the recovery from these Wingate tests was found to be 15 times slower in fast typology athletes (20 min in slow typology vs. longer than 5 h in fast typology). If a training plan would be composed with a minimum of recovery in between the training sessions, recovery might be insufficient for fast typology athletes, possibly rendering them with a higher risk for muscle strains. In study 6, we studied if the muscle typology is a risk factor for muscle strains in elite soccer players. We discovered that fast typology soccer players had a 5.3 times higher chance to get a hamstring injury, when compared to slow typology soccer players during a prospective longitudinal follow-up study over three seasons. Next to a higher accumulation of fatigue, a higher vulnerability in fast typology players could be expected due to the lower structural integrity in fast fibers. Bringing together, the muscle typology is an important characteristic, which could be non-invasively monitored using 1H-MRS. This technique could help athletes to make a scientific based decision on their ideal discipline during talent orientation. Moreover, it could help coaches tailoring training to enlarge the athletes’ muscle potential and to prevent fatigue accumulation. This endeavor might partly prevent fast typology athletes to be at a higher risk for strain injuries. Consequently, we believe that measuring the muscle fiber typology of athletes should be considered as a valuable procedure to help athletes to fully develop their potential based on the smart use of muscle profiling.
The effect of short-term altitude training on sea-level physiological characteristics in elite runners was investigated. Seven middle-distance runners (6 men, 1 woman) belonging to the Swedish national team (mean age 23 years) spent 2 weeks of training at 2000 m above sea level in Kenya. Treadmill tests were performed before and 6 and 12 d after the altitude sojourn. Six other runners (4 men, 2 women) had a corresponding training sojourn at sea level in Portugal (control group). Ro of the runners (1 man, 1 woman) in the Kenya group were omitted from the study because of gastroenteritis. The maximal oxygen uptake (VO2 max; pretravel: Kenya group 212 and control group 188 ml · kg−0.75 - min−1), maximal treadmill time and oxygen cost of running were unchanged in both groups. The maximal oxygen deficit increased in all subjects after the Kenya sojourn (mean 19±6%). Heart rates during running at specified submaximal running velocities were lower post-altitude (Kenya group), but tended to be higher after sea-level training (control group). Maximal heart rate was unchanged in both groups. Perceived exertion (Borg) during submaximal running was lower post-altitude. Submaximal and maximal blood lactate and plasma catecholamine concentrations were not altered in any of the groups. Post-exhaustive plasma ammonia levels were decreased 12 d after altitude descent in the Kenya group. The results suggest an unchanged aerobic capacity in elite middle-distance runners after short-term training at moderate altitude. However, a change in the circulatory regulation during submaximal exercise was observed. Furthermore, anaerobic capacity improved but this bore no clear relation to lactate or ammonia metabolism.
Studies of exercise performance during hypobaric hypoxia among subjects acclimatized to high altitudes have raised an intriguing metabolic paradox. On the one hand, the maximum aerobic metabolic rate declines as a function of high altitude, reaching values only slightly higher than the resting metabolic rate (RMR) at altitudes equivalent to that of the peak of Everest. On the other hand, when subjects perform incremental exercise tests to fatigue, the amounts of lactate formed also decline as a function of altitude. This effect is so dramatic that it is predicted that no lactate whatsoever can be produced at aerobic fatigue at altitudes equivalent to that of Everest. For practical purposes, the glytolytic pathway in muscle is blocked under these high-altitude conditions. The paradox is that anaerobic glycolysis works perfectly well when subjects acclimatized to high altitudes start from rest, and in fact it is well known that the anaerobic power output of muscle is unaffected by hypobaric hypoxia. Therefore, the problem arises as to why it seems to be impossible to activate the pathway in muscle brought to fatigue during aerobic work at high altitude, where the demands for glycolytic adenosine triphosphate (ATP) synthesis are normally exaggerated. To clarify this problem, it is necessary to focus closely on the nature of the coupling mechanisms between ATP demand and ATP supply during sustained work. I do this for two kinds of systems, both those that remain closely coupled as work rate increases and those that necessarily assume new steady states as work rates change.
The results indicate a gradual conversion of a part of the type IIB fiber population into type IIA fibers in response to an endurance training program. The pretraining percentage distribution of type IIA and IIB fibers was in the same range as that reported by Hedberg and Jansson (1976) for 68 sixteen year old boys (32% IIA and 13% IIB fibers). It is worth emphasizing that the classification of the type II fibers into the subgroups IIA and IIB in this study is based on differences in the pH sensitivity of the myosin ATPase. According to Brooke and Kaiser (1970) this difference is related to the reactivity of sulfhydryl groups of the myosin molecule. Thus it is conceivable that the observed changes indeed indicate a change in the structure of the myosin molecule.
The effects of 15 days of detraining and 15 days of retraining were studied in 6 well-trained runners. Detraining resulted in significant decreases in the mean activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) of 24 % and 13 %, respectively, but no significant increases in these enzyme activities occurred with retraining. Maximal oxygen uptake (VO2 max) decreased by 4% with detraining (p < 0.05), and increased by a similar amount with retraining. Performance time in an intense submaximal run decreased by 25% (p < 0.05) with inactivity, but still averaged 9% below the initial level after retraining. Maximal heart rate and peak heart rate during the performance run were higher after detraining by 4 and 9 beats per min, respectively (p < 0.05). With retraining, these heart rate values were decreased by 7 and 9 beats per min (p < 0.05). Blood lactate concentrations after the VO2 max and performance run were approximately 20% lower after detraining and retraining (p < 0.05). Muscle fibre areas for three subjects tended to be larger in biopsy samples taken after detraining and retraining. These data suggest that even short periods of detraining result in significant changes in indices of physiological capacity and function in subjects near their upper limit of adaptation, and that a longer period of retraining is necessary for muscle to re-adapt to its original trained state.
To evaluate the effect of extreme endurance training on muscle fibre composition and activities of oxidative enzymes in different fibre types biopsies were taken from vastus lateralis, gastrocnemius and deltoideus of elite orienteers. Comparisons were made between the (trained) leg muscles and the (relatively untrained) arm muscles, and with leg muscles of 16--18 years old boys. The orienteers had the same percentage type I fibres and vastus lateralis and gastrocnemius as in deltoideus, but higher percentage type I fibres in vastus lateralis compared with the controls. The similarity between trained and untrained muscle in the orienteers suggests that training had not caused the high percentage type I fibres which rather might be the result of selection of individuals with the best prerequisites for high oxidative capacity. However, the distribution of type II subgroups in the leg muscles of the orienteers differed from both their own deltoideus and leg muscles of the controls, the relationship IIA/IIB being altered in favour of the more oxidative IIA. The leg muscles of the orienteers also showed an increased occurrence of the normally IIC fibre. These latter findings point at the possibility of a training induced alteration in the subgroup pattern. Unlike in the controls there was no significant difference in succinate dehydrogenase activity, measured in single fibres, between type I and II fibres in gastrocnemius of the orienteers. Thus, type II fibres have the ability metabolically to adapt to high oxidative demands. This might to some extent be mediated by a conversion from IIB to IIA form.
Succinate dehydrogenase (SDH) and cytochrome oxidase activities in the lateral vastus of the human quadriceps femoris muscle together with total body VO2 max were followed during an 8-10 week period of endurance training (n = 13) and a successive 6 week period without training (n = 8). During the training period there was a gradual increase in both VO2 max and muscle oxidative enzyme activities, all being significantly different from the pre-training levels after 3 weeks of training. After 8 weeks of training VO2 max was 19%, vastus lateralis SDH 32%, and cytochrome oxidase activity 35% above the pre-training levels respectively. 6 weeks post training VO2 max was still 16% above the pre-training level, and not significantly different from the level at the end of training (p greater than 0.2). In contrast vastus lateralis SDH activity had returned to the pre-training level. Cytochrome oxidase activity had returned to the pre-training level within two weeks post-training. The significantly faster post-training decline in skeletal muscle oxidative enzyme activities in contrast to that of the VO2 max indicates that an enhancement of the oxidative potential in skeletal muscle is not a necessity for a high VO2 max. Moreover, the fast return to the pre-training level of both SDH and cytochrome oxidase activities indicate a high turnover rate of enzymes in the TCA cycle as well as the respiratory chain.
1. Five subjects trained for 8 weeks on a bicycle ergometer for an average of 40 min/day, four times a week at a work load requiring 80% of the maximal oxygen uptake (V(O2 max.)). V(O2 max.) determinations were performed, and muscle biopsies from the quadriceps femoris muscle (vastus lateralis) were taken before, as well as repeatedly during, the training period. The muscle biopsies were histochemically stained for fibre-types (myofibrillar ATPase) and capillaries (amylase-PAS method), and analysed biochemically for succinate dehydrogenase and cytochrome oxidase activities.2. The training programme resulted in a 16% increase in V(O2 max.), a 20% increase in capillary density, a 20% increase in mean fibre area, and an approximately 40% increase in the activities of succinate dehydrogenase and cytochrome oxidase.3. The capillary supply to type I, IIA and IIB fibres, expressed as the mean number of capillaries in contact with each fibre-type, relative to fibre-type area, increased equally.4. The present study shows that endurance training constitutes a powerful stimulus for capillary proliferation in human skeletal muscle.