It is assumed that the performance dominance of East African runners is primarily due to their high VO2max, high fractional utilization of VO2max, and high running economy. Their lifelong exposure to altitude has been intensively discussed as one important reason, since haemoglobin concentration and haematocrit are slightly elevated. To explain the underlying physiological reasons previous research focused on oxygen consumption while profound data concerning the oxygen transport are, however, still missing. We therefore investigated the essential structures of O2-transport, i.e. total haemoglobin mass (tHb-mass), blood volume (BV) and heart size, in elite Kenyan runners in a combined cross sectional and longitudinal study in order to detect de-adaptation processes of these parameters during a sojourn at near sea-level. Ten Kenyan runners (group K; competing between 1.500m and marathon) living and training at moderate altitude (~2100m) performed a 6 week training camp at 350m in Germany. Training (volume ~210km/week) was similar to that normally performed in Kenya. tHb-mass and BV were determined using the optimized CO-rebreathing method on the first day after arrival to Germany and weekly during their whole stay at low altitude. In addition BV and haemoglobin concentration ([Hb]) were also examined before departure at altitude. VO2max was determined in three field tests and running economy in a laboratory test on a treadmill. 11 German elite runners served as a control group (group G). The Kenyan runners had a significantly lower body mass (K 57.2 ±7.0kg; G 66.5 ±6.3kg) and BMI (K 18.5 ±0.9; G 20.4 ±0.9). Relative VO2max did not differ between the groups (K 71.5 ±5.0 ml/kg/min; G 70.7 ±3.7 ml/kg/min) and absolute VO2max did not change during the 6 weeks at low altitude. Relative tHb-mass (K 14.2 ±1.0g/kg; G 14.0 ±0.7g/kg) and BV (K 101.9 ±4.5ml/kg; G 99.6 ±5.8ml/kg) were similar in both groups but continuously decreased in K during the stay at near sea level (absolute tHb-mass from 813 ±90g to 767 ±90g, p<0.001; BV from 5828 ±703ml to 5513 ±708ml, p<0.01). [Hb] tended to decrease (-0.7 ±0.7g/dl) when commuting altitude but did not differ at near sea level between the groups (K 15.4 ±1.0g/dl, G 15.5 ±1.2g/dl). The relative heart volume was slightly lower in the Kenyan group (K 14.0 ±1.5ml/kg; G 15.2 ±2.0ml/kg) and did not change at low altitude. Running economy was higher (p<0.05) in K at speeds of 18km/h and above and can partly be attributed to the smaller calve circumference (p<0.001) and lower BMI (p<0.001). In conclusion, we state that the excellent performance of Kenyan runners is not simply due to an improved oxygen transport system when compared to European runners. Although Kenyans benefit from altitude effects a lower demand of oxygen at higher speeds seems to be the essential reason for their excellent performance.
© Copyright 2009 14th annual Congress of the European College of Sport Science, Oslo/Norway, June 24-27, 2009, Book of Abstracts. Veröffentlicht von The Norwegian School of Sport Sciences. Alle Rechte vorbehalten. / Übersetzt mit https://www.DeepL.com/Translator