Despite their young age, limited training history, and lack of running tradition compared with other East African endurance athletes (e.g., Kenyans and Ethiopians), male endurance runners from Eritrea have recently attained important running successes. The purposes of our study were (i) to document the main physical and physiological characteristics of elite black Eritrean distance runners (n = 7; age: 22 +/- 3 years) and (ii) to compare them with those of their elite white Spanish counterparts. For this second purpose we selected a control group of elite Spanish runners (n = 9; 24 +/- 2 years), owing to the traditionally high success of Spanish athletes in long-distance running compared with other white runners, especially in cross-country competitions. The subjects' main anthropometric characteristics were determined, together with their maximum oxygen uptake (VO2 max) and VO2 (mL.kg(-1).min(-1)), blood lactate, and ammonia concentrations while running at 17, 19, or 21 km.h(-1). The body mass index (18.9 +/- 1.5 kg.m(-2)) and maximal calf circumference (30.9 +/- 1.5 cm) was lower in Eritreans than in Spaniards (20.5 +/- 1.7 kg.m(-2) and 33.9 +/- 2.0 cm, respectively) (p < 0.05 and p < 0.01, respectively) and their lower leg (shank) length was longer (44.1 +/- 3.0 cm vs. 40.6 +/- 2.7 cm, respectively) (p < 0.05). VO2 max did not differ significantly between Eritreans and Spaniards (73.8 +/- 5.6 mL.kg(-1).min(-1) vs. 77.8 +/- 5.7 mL.kg(-1).min(-1), respectively), whereas the VO2 cost of running was lower (p < 0.01) in the former (e.g., 65.9 +/- 6.8 mL.kg(-1).min(-1) vs. 74.8 +/- 5.0 mL.kg(-1).min(-1) when running at 21 km.h(-1)). Our data suggest that the excellent running economy of Eritreans is associated, at least partly, with anthropometric variables. Comparison of their submaximal running cost with other published data suggests that superior running economy, rather than enhanced aerobic capacity, may be the common denominator in the success of black endurance runners of East African origin.

We analysed seven genetic polymorphisms that are candidates to explain individual variations in human endurance phenotypic traits, at least in Caucasian people (ACE Ins/Del, ACTN3 Arg577Ter, AMPD1 Gln12Ter, CKMM 1170 bp/985 + 185 bp, HFE His63Asp, GDF-8 Lys153Arg and PPARGC1A Gly482Ser) in 46 world-class endurance athletes and 123 controls (all Spanish Caucasians). Using the model developed by Williams & Folland we determined (1) the 'total genotype score' (TGS, from the accumulated combination of the seven polymorphisms, with a maximum value of '100' for the theoretically optimal polygenic score) in the non-athlete (control) group, in the athlete group and in the total Spanish population, and (2) the probability for the occurrence of Spanish individuals with the 'perfect' polygenic endurance profile (i.e. TGS = 100). The probability of a Spanish individual possessing a theoretically optimal polygenic profile for up to the seven candidate genetic polymorphisms we studied was very small, i.e. ∼0.07% (or 1 in 1351 Spanish individuals). The mean TGS was higher in athletes (70.22 ± 15.58) than in controls (62.43 ± 11.45) and also higher than predicted for the total Spanish population (60.80 ± 12.1), suggesting an overall more 'favourable' polygenic profile in the athlete group. However, only three of the best Spanish endurance athletes (who are also amongst the best in the world) had the best possible score for up to six genes and none of them had the optimal profile. Other polymorphisms yet undiscovered as well as several factors independent of genetic endowment may explain why some individuals reach the upper end of the endurance performance continuum.

Using the model originally developed by Williams and Folland (J Physiol 586: 113-121, 2008), we determined 1) a "total genotype score" (TGS, from the accumulated combination of the 6 polymorphisms, with a maximum value of "100" for the theoretically optimal polygenic score) in a group of elite power athletes, endurance athletes, and nonathletic controls, and 2) the probability for the occurrence of Spanish individuals with the "perfect" power-oriented profile (i.e., TGS = 100). We analyzed six polymorphism that are candidates to explain individual variations in elite power athletic status or power phenotypes (ACE I/D, ACTN3 R577X, AGT Met235Thr, GDF-8 K153R, IL6 -174 G/C, and NOS3 -786T>C) in 53 elite track and field power athletes (jumpers, sprinters), 100 nonathletic controls, and 100 elite endurance athletes (distance runners and road cyclists) (all Spanish Caucasian males). The mean TGS was significantly higher in power athletes (70.8 +/- 17.3) compared with endurance athletes (60.4 +/- 15.9; P < 0.001) and controls (63.3 +/- 13.2; P = 0.012), whereas it did not differ between the latter two groups (P = 0.366). A total of five power athletes (9.4%, all sprinters) had a theoretically "optimal" TGS of 100 vs. 0 subjects in the other two groups. The probability of a Spanish individual possessing a theoretically optimal polygenic profile for up to the six candidate polymorphisms we studied was very small, i.e., approximately 0.2% (or 1 in 500 Spanish individuals). We have identified a polygenic profile that allows us, at least partly, to distinguish elite power athletes from both endurance athletes and nonathletic population.

Animal and human data indicate a role for the peroxisome proliferator-activated receptor-gamma coactivator 1alpha (PPARGC1A) gene product in the development of maximal oxygen uptake (V(O2 max)), a determinant of endurance capacity, diabetes, and early death. We tested the hypothesis that the frequency of the minor Ser482 allele at the PPARGC1A locus is lower in World-class Spanish male endurance athletes (cases) [n = 104; mean (SD) age: 26.8 (3.8) yr] than in unfit United Kingdom (UK) Caucasian male controls [n = 100; mean (SD) age: 49.3 (8.1) yr]. In cases and controls, the Gly482Ser genotype met Hardy-Weinberg expectations (P > 0.05 in both groups tested separately). Cases had significantly higher V(O2 max) [73.4 (5.7) vs. 29.4 ml x kg(-1) x min(-1) (3.8); P < 0.0001] and were leaner [body mass index: 20.6 (1.5) vs. 27.6 kg/m2 (3.9); P < 0.0001] than controls. In unadjusted chi2 analyses, the frequency of the minor Ser482 allele was significantly lower in cases than in controls (29.1 vs. 40.0%; P = 0.01). To assess the possibility that genetic stratification could confound these observations, we also compared Gly482Ser genotype frequencies in Spanish (n = 164) and UK Caucasian men (n = 381) who were unselected for their level of fitness. In these analyses, Ser482 allele frequencies were very similar (36.9% in Spanish vs. 37.5% in UK Caucasians, P = 0.83), suggesting that confounding by genetic stratification is unlikely to explain the association between Gly482Ser genotype and endurance capacity. In summary, our data indicate a role for the Gly482Ser genotype in determining aerobic fitness. This finding has relevance from the perspective of physical performance, but it may also be informative for the targeted prevention of diseases associated with low fitness such as Type 2 diabetes.