摘要：Considering the fact that mountainbike (MTB) marathon and ultraendurance events also as MTB stage races have become very popular during the last decade knowledge is sparse about the effects on hematological system due to prolonged strenuous exercise. Endurance trained athletes generally show an increased blood volume mainly due to plasma volume (PV) expansion, which already exerts after a few days of prolonged exercise, accompanied by lower hemoglobin (Hb) and hematocrit (Hct) levels. On a short term basis dehydration caused by prolonged exertive exercise leads to enhanced concentrations of Hb and Hct due to decreased PV. In contrast to acute exercise it has been well documented as a long term adaptation that regular endurance training over long term periods or repeated bouts of strenuous exercise, e. g. repetitive cycling races or cycling stage races over several consecutive days, lead to a fall in both Hb and Hct levels due to a progressive enlargement in particular in PV. Changes in hematological parameters are known to considerably influence physical performance, especially in aerobic endurance sports such as mountainbiking. An increase in PV normally results in enhanced aerobic performance due to reduced blood viscosity, thereby optimized microcirculation and improved oxygen delivery capacity to the working muscle (Schumacher et. al., 2000). Hematological parameters Hb and Hct are highly sensible to acute effects. The effects of prolonged exercise on hematological status are mainly dependent on total load (mode and duration) of exercise, as well as thermal stress (temperature and humidity) and fluid intake (FI) (Convertino, 1991; Fellmann et. al., 1999; Neumayr et. al., 2002; Sawka et. al., 2000; Schumacher et. al., 2000). The Transalp Challenge (TAC) is one of the hardest MTB marathon races in the world (besides Cape Epic/SA and Transrockies/USA), covering eight consecutive stages. The key data of TAC 2004 are: 22. 500 m (altitude difference), 662 km (distance), which reflects a daily average of 2.812,5 m along with 82.75 km. Therefore, the aim of this study was to determine development and changes in haematological variables Hb, Hct and PV during this MTB stage race.
