The effect of acute intense intermittent exercise compared to moderate intensity exercise, on angiogenic factors and the effect of four weeks of intense intermittent training on capillary growth were examined in nine young healthy males, pre-conditioned by moderate intensity endurance training. The intense training consisted of 24 one-min cycling bouts at an initial work rate of 316 ± 19W (~117% of pre VO2 max), performed 3 times/week. Skeletal muscle biopsies and muscle microdialysates were otained from m.v. lateralis before, during, and after acute exercise performed at either moderate or high intensity. Comparison of the response in angiogenic factors to acute moderate versus high intensity exercise, performed prior to the intense training intervention, revealed that intense exercise resulted in a markedly lower (~60%; P <0.05) increase in interstitial VEGF than did moderate intensity exercise. Muscle interstitial fluid obtained during moderate intensity exercise increased endothelial cell proliferation in vitro more than interstitial fluid obtained during intense exercise (6-fold vs. 2.5-fold, respectively; P <0.05). The four weeks of high intensity training did not lead to an increased capillarization in the muscle but abolished the exercise induced increase in mRNA for several angiogenic factors, increased the eNOS protein levels, lowered TSP-1 protein levels in muscle but increased interstitial TSP-1 protein levels. We conclude that intense intermittent exercise provides a weak stimulus for VEGF secretion and endothelial cell proliferation and that intense intermittent training does not induce a sufficient angiogenic stimulus to induce capillary growth in muscle previously conditioned by moderate intensity exercise.
Experimental Physiology, 2013, Vol 98, Issue 2, p. 585-597