Abstract
Unaccustomed eccentric exercise leads to impaired microvascular function but the underlying mechanism is unknown. In this study, we evaluated the role of oxidative stress and of nitric oxide (NO) bioavailability. Thirty young men and women performed eccentric contractions of the tibialis anterior (TA) muscle (ECC), with the contralateral leg serving as nonexercising control (CON). Participants were randomized into three groups ingesting an antioxidant cocktail (AO), beetroot juice (BR) or placebo 46 h postexercise. At baseline and 48 h postexercise, hyperemic responses to brief muscle contractions and 5 min of cuff occlusion were assessed bilaterally in the TA muscles using blood oxygen level dependent (BOLD) magnetic resonance imaging. Eccentric contractions resulted in delayed time‐to‐peak (~22%; P < 0.001), blunted peak (~21%; P < 0.001) and prolonged time‐to‐half relaxation (~12%, P < 0.001) in the BOLD response to brief contractions, with no effects of AO or BR, and no changes in CON. Postocclusive time‐to‐peak was also delayed (~54%; P < 0.001) in ECC, with no effects of AO or BR, and no changes in CON. Impaired microvascular reactivity after eccentric contractions is confined to the exercised tissue, and is not restored with acute ingestion of AO or BR. Impairments in microvascular reactivity after unaccustomed eccentric contractions may result from structural changes within the microvasculature that can diminish muscle blood flow regulation during intermittent activities requiring prompt adjustments in oxygen delivery.
Highlights
Muscle work involving unaccustomed eccentric contractions is known to result in pain, inflammation, and an overall decline in muscle function (Clarkson and Hubal, 2002)
There was an effect of time (P < 0.001) such that TTP was prolonged at 48 h, and an effect of sex (P < 0.001) such that TTP was faster in the women compared with the men (Fig. 5B)
A novel aspect of this study was the use of acute supplementation with antioxidant cocktail (AO) (Vitamin C, Vitamin E, alpha-lipoic acid) or nitrate-rich beetroot juice (BR) to test the hypotheses that oxidative stress and nitric oxide (NO) bioavailability are involved in impaired microvascular reactivity after eccentric exercise
Summary
Muscle work involving unaccustomed eccentric contractions is known to result in pain, inflammation, and an overall decline in muscle function (Clarkson and Hubal, 2002). Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. Results of impaired vascular function have been extended to the microvasculature with reports of attenuated vasodilation in response to adenosine (Heap et al, (2006)) and slowed hemodynamics at the onset of muscle contractions (Kano et al, 2005). The hyperemic response was preserved in the contralateral, nonexercising TA muscle, suggesting a localized effect of eccentric contractions on microvascular reactivity
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