Increase in serum vascular endothelial growth factor levels during altitude training

The present study was performed to evaluate the effects of physical exercise at altitudes on serum vascular endothelial growth factor (VEGF) levels. Eight subjects underwent intensive swimming training for 21 days at 1886 m. After altitude training commenced, red blood cell (RBC) counts and erythropoietin levels increased, but both haemoglobin and haematocrit levels did not change significantly. The serum level of VEGF, measured by means of a highly sensitive chemiluminescence (ELISA), showed a transient decrease 10 days after start of the altitude training, thereafter increasing significantly to reach a peak level 19 days later, rising from 23.0 ± 5.3 to 46.0 ± 14.6 pg mL^-1 (P < 0.05 vs. before). On return to low altitude in Japan, the level of VEGF decreased, and 1 month later had returned to initial levels. Endurance training at altitudes increases serum VEGF levels; this could be an adaptive reaction to hypoxic conditions. This result suggests that VEGF may provide a new physiological parameter for hypoxic stress imposed by high altitude training.