The present study used passive limb movement as experimental model to study the effect of increased blood flow and passive stretch, without enhanced metabolic demand, in young healthy male subjects. The model used was 90 min of passive movement of the leg leading to a 2.8-fold increase (P<0.05) in blood flow without an enhancement in oxygen uptake. Muscle interstitial fluid was sampled with microdialysis technique and analyzed for vascular endothelial growth factor (VEGF) protein and for effect on endothelial cell proliferation. Biopsies obtained from the m.v. lateralis were analyzed for mRNA content of VEGF, endothelial nitric oxide synthase (eNOS) and matrix metalloproteinase-2 (MMP-2). The passive leg movement caused an increase (P<0.05) in interstitial VEGF protein concentration above rest (73±21 versus 344±83 pg/ml). Addition of muscle dialysate to cultured endothelial cells revealed that dialysate obtained during leg movement induced a 3.2-fold higher proliferation rate (p<0.05) than dialysate obtained at rest. Passive movement also enhanced (P<0.05) the eNOS mRNA level 4-fold above resting levels. VEGF mRNA and MMP-2 mRNA levels were unaffected. The results show that a session of passive leg movement, elevating blood flow and passive stretch, augments the interstitial concentrations of VEGF, the proliferative effect of interstitial fluid, and eNOS mRNA content in muscle tissue. We propose that enhanced blood flow and passive stretch are positive physiological stimulators of factors associated with capillary growth in human muscle.