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Oxygen Transport In Kenyan Runners

2009; Lippincott Williams & Wilkins; Volume: 41; Issue: 5 Linguagem: Inglês

10.1249/01.mss.0000355292.70987.a0

1530-0315

Nicole Prommer, Stefanie Thoma, Lennart Quecke, Thomas Gutekunst, Christian Voelzke, Nadine Wachsmuth, Andreas M. Nieß, Walter Schmidt,

High Altitude and Hypoxia

It is assumed that the excellent performance of Kenyan runners is mainly due to a high running economy in connection with high VO2max. To explain underlying physiological reasons research mainly focused on muscular oxygen consumption. PURPOSE: To investigate basic factors of oxygen transport, i.e. total hemoglobin mass (tHb-mass), blood volume (BV) and heart size in elite Kenyan runners and adaptation processes of these parameters during a sojourn at lowland. METHODS: Ten Kenyan runners (group K; competing between 1.500m and marathon) living and training at moderate altitude (∼2100m) performed a 6-weeks lasting 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. 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). RESULTS: 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 lowland (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 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 Kenyans (K 14.0 ±1.5ml/kg; G 15.2 ±2.0ml/kg). 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). CONCLUSIONS: The excellent running performance of Kenyans is not due to an improved oxygen transport system but due to a lower demand of oxygen at higher speeds compared to German runners. Supported by BISp, No.VF070121/05-06.