european college of sport science

08:30 - 10:00
Invited symposia
IS-PH04 The Physiology of East and North African Runners (EFSMA Exchange Symposium)
IS-PH04 The Physiology of East and North African Runners (EFSMA Exchange Symposium)
AFRICAN RUNNERS: NATURE OR NURTURE?
DICKHUTH, H.
UNIVERSITY HOSPITAL FREIBURG
In 1985, 50% of the best runners came from Europe, 21% from Africa and about 15% from North-America. 25 years later the situation had
changed completely.
We see a dramatic change in the countries of origin from which the best middle- and long-distance runners have come. Today 69% of
the best runners come from Africa and 47% of these from Kenya.
The East-African countries of Ethiopia and Eritrea, as well as Morocco, are also represented in middle distance running. It is noteworthy,
that in these countries we find no excellent sprinters.
On the other hand it is interesting that in 2008, the top sprinters essentially had their genetic roots in West-Africa, including those sprinters
from the Caribbean and the USA. It is interesting, that it is not possible to find excellent middle- and long-distance runners in those
countries.
Most of the sports medicine scientists believe that the differences in endurance and sprint performance have a genetic background. The
genetic type and the phenotype of East-Africans differ considerably from those of West-Africans. An explanation for this could be a selective
pressure caused by the dryness and high altitude conditions in North- and East-Africa. That would fit with the fact that the genetic
exchange between East- and West-Africa was prevented by the East-African rift and by the desert (Sahara).
In conclusion, a small genetic shift might be a small genetic shift (pressure) which is responsible for the different phenotype observed of
West-Africa and East-Africa.
But what are the physiological differences which allow East-African, especially Kenyan runners, to be top runners world-wide?
Literature:
Billat V, Lepretre PM, Heugas AM, Laurence MH, Salim D, Koralsztein JP: Training and bioenergetic characteristics in elite male and female
Kenyan runners. Med Sci Sports Exerc. 2003 Feb;35(2):297-304;
Larsen HB:Kenyan dominance in distance running. Comp Biochem Physiol A Mol Integr Physiol. 2003 Sep;136(1):161-70. Review.
Scott RA, Pitsiladis YP Genotypes and distance running : clues from Africa. Sports Med. 2007;37 (4-5):424-7.
Scott RA, Fuku N, Onywera VO, Boit M, Wilson RH, Tanaka M, H Goodwin W, Pitsiladis YP. Mitochondrial haplogroups associated with elite
Kenyan athlete status. Med Sci Sports Exerc. 2009 Jan; 41(1):123-8
PHYSIOLOGICAL APPROACH OF KENYAN TRAINING
BILLAT, V.
UNIVERSITE D`EVRY VAL D`ESSONNE
Introduction: The purpose of this study was to test the hypothesis that there was no significant difference between the aerobic and anaerobic
component of performance with the critical speed model and that training is responsible for two different physiological phenotypes
in two groups of Kenyan runners belonging to the same ethnic group and village (Kissi).
Methods: In order to compare the aerobic and anaerobic component of the Kenyan vs. non Kenyan best performers (from 800 to
10,000m) we compared their critical velocity and anaerobic distance capacity using the critical power model with 2 components (1). VO2
was measured breath by breath using a portable gas analyser (K4b2, Cosmed) during an incremental exhaustive running test performed
on a running track.
The subjects were 20 elite Kenyan runners: 13 men (10-km performance time: 10-km performance time of 28 min, 36 s ±18 s) and 7
women (32 min, 32 s ±65 s). The male runners were separated into high-speed training runners (HST: N = 6) and low-speed training
runners (LST: N =7) depending on whether they train at speeds equal or higher than those associated with the maximal oxygen uptake
(vVO2max). All but one woman were high-speed training runners (female HST: N =6). Subjects performed an incremental test on a 400-m
track to determine VO2max, vVO2max, and the velocity at the lactate threshold (vLT).
Results: There was no significant difference of critical speed or anaerobic distance capacity between Kenyan or non Kenyan runners
(21.3±0.6 vs. 22.1±0.6 km.h-1, p = 0.07) for CV and (213±68 vs. 185±69 m, p = 0.45) for ADC. Within each gender among the HST group,
10-km performance time was inversely correlated with vVO2max (rho =0.86, P =0.05, and rho =0.95, P =0.03, for men and women,
respectively). HST male runners had a higher VO2max, a lower (but not significantly) fraction of vVO2max (FvVO2max) at the lactate
threshold, and a higher energy cost of running (ECR). Among men, the weekly training distance at vVO2max explained 59% of the variance
of vVO2max, and vVO2max explained 52% of the variance of 10-km performance time. Kenyan women had a high VO2max and
FVO2max at vLT that was lower than their male HST counterparts. ECR was not significantly different between genders.
Conclusion
The critical speed, vVO2max and ADC of the Kenyan or non Kenyan top 20 best performer middle and long distance runners were not
significantly different. However, ADC is only an indirect marker of anaerobic capacity which must be explored with oxygen deficit. Caucasian
non Kenyan runners have a non significant higher vVO2max extrapolated from 3000m performance considering the time limit at
VO2max reported in literature (7 min). Kenyan have polarized training even inside one training session and practice skills that could
contribute positively to this ability for speed variation that allows for energetic optimisation (1).
References
1°) Billat LV, Koralsztein JP, Morton RH. Time in human endurance models. From empirical models to physiological models. Sports Med
27:359-379, 1999.
316 14 TH
ANNUAL CONGRESS OF THE EUROPEAN COLLEGE OF SPORT SCIENCE