It has been demonstrated that daily stretching leads to an increase in blood flow to the skeletal muscle during exercise in rats; however, little is known about the effects of daily muscle stretching on adaptions of muscle blood flow in humans. PURPOSE: Therefore, the purpose of this study was to investigate the effect of passive stretch on vascular control (VC) during exercise. We tested the hypothesis that acute static stretch would not elicit changes in deoxygenated or total heme (deoxy-[heme], total-[heme] respectively) during exercise. Furthermore, we hypothesized that chronic stretch would elicit a decrease in oxygen extraction (deoxy-[heme]) through an increase in blood volume (total-[heme]). METHODS: 4 healthy males (24.8 ± 3.6 yr, 179 ± 2.2 cm, 92.1 ± 7.8 kg) completed a controlled passive stretch of the plantar flexors. 2 subjects completed 2 days of a 30 min stretching protocol, while the other 2 subjects completed 2 days of a 10 min stretching protocol. Following the first two days of stretching, all subjects completed a moderate intensity (40% PPeak) plantar flexion constant load test to determine acute effects of stretching on VC. All subjects then continued with the 10 min stretching protocol for the remainding 5 days, resulting in 7 consecutive days of stretch. Following the 7th day of stretch, subjects completed another moderate intensity (40% PPeak) constant load test to determine the chronic effects of stretching on VC. Near-infrared spectroscopy was used to continuously measure deoxy-[heme] and total-[heme] during exercise. RESULTS: Although no statistical differences were found, the 2 subjects who had completed the 30 min acute stretching protocol showed a marked decrease in deoxy-[heme] following acute stretching (5.13 ± 2.98μM to 1.40 ± 1.83μM), however no differences were observed in the 2 subjects who completed the 10 min acute stretching protocol. Following exercise in both the acute and chronic stretch protocols, no differences were observed in total-[heme]. CONCLUSIONS: The observed decrease in deoxy-[heme] lead us to believe that an acute static stretch of 30 minutes improves VC through better matching in the oxygen perfusion to extraction ratio during exercise. This VC enhancement was lost with chronic stretch, which could have been due to an insufficient stimulus on the microvasculature.