The online version of this article (doi:10.1186/1476-7120-10-34) contains supplementary material, which is available to authorized users.
The authors declare that they have no competing interests.
BDJ was responsible for conception and study design, data collection, data analysis, statistical analysis and interpretation, and drafting the article. KJM assisted with study design, statistical interpretation, and revised the article for intellectual content. SCN contributed to study design, statistical interpretation, and revised the article for intellectual content. TDM participated in study design, statistical interpretation, and revised the article for intellectual content. JPW contributed to the development of the scientific question, study design, statistical interpretation, and revised the article for intellectual content. All authors read and approved the final manuscript.
Acute doses of elevated retrograde shear rate (SR) appear to be detrimental to endothelial function in resting humans. However, retrograde shear increases during moderate intensity exercise which also enhances post-exercise endothelial function. Since SR patterns differ with the modality of exercise, it is important to determine if augmented retrograde SR during exercise influences post-exercise endothelial function. This study tested the hypothesis that (1) increased doses of retrograde SR in the brachial artery during lower body supine cycle ergometer exercise would attenuate post-exercise flow-mediated dilation (FMD) in a dose-dependent manner, and (2) antioxidant vitamin C supplementation would prevent the attenuated post-exercise FMD response.
Twelve men participated in four randomized exercise sessions (90 W for 20 minutes) on separate days. During three of the sessions, one arm was subjected to increased oscillatory and retrograde SR using three different forearm cuff pressures (20, 40, 60 mmHg) (contralateral arm served as the control) and subjects ingested placebo capsules prior to exercise. A fourth session with 60 mmHg cuff pressure was performed with 1 g of vitamin C ingested prior to the session.
Post-exercise FMD following the placebo conditions were lower in the cuffed arm versus the control arm (arm main effect: P < 0.05) and without differences between cuff pressures (20 mmHg: 5.7 ± 2.2%; 40 mmHg: 4.7 ± 1.3%; 60 mmHg: 5.4 ± 2.4%) (P > 0.05). Following vitamin C treatment, post-exercise FMD in the cuffed and control arm increased from baseline (P < 0.05) but were not different (control: 7.1 ± 3.5% vs. cuffed: 6.6 ± 3.3%) (P > 0.05).
These results indicate that augmented oscillatory and retrograde SR in non-working limbs during lower body exercise attenuates post-exercise FMD without an evident dose–response in the range of cuff pressures evaluated. Vitamin C supplementation prevented the attenuation of FMD following exercise with augmented oscillatory and retrograde SR suggesting that oxidative stress contributes to the adverse effects of oscillatory and retrograde shear during exercise on FMD.
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- Brachial Artery Flow-mediated Dilation Following Exercise with Augmented Oscillatory and Retrograde Shear Rate
Blair D Johnson
Kieren J Mather
Sean C Newcomer
Timothy D Mickleborough
Janet P Wallace
- BioMed Central
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