Vitamin C improves arterial distensibility following maximal exercise in healthy subjects

Maximal exercise is known to induce oxidative stress. We hypothesised that, by reducing NO availability, this may reduce large artery distensibility and thereby cardiovascular efficiency (cardiac work relative to tissue perfusion) and that these undesirable effects could be prevented by the free radical scavenger Vitamin C (Vit C). We tested the hypothesis in a double-blind, placebo-controlled, cross-over study in 8 healthy male volunteers who undertook exhaustive bicycle ergometer exercise on 2 occasions following either intravenous Vit C (2 g) or normal saline (placebo). For 15 minutes pre and 30 minutes post exercise we measured 1) pulse wave velocity (PWV, inversely related to arterial distensibility) non-invasively in the upper limb using oscillometry (QVL™, SciMed, Bristol) from transit times of pressure waveforms between 2 cuffs for 15 seconds every minute and 2) blood pressure (BP - Finapres, Ohmeda) continuously. PWV was increased immediately after exercise but fell below baseline levels by 10 minutes following placebo, describing a curve as shown. Vit C shifted the curve downwards (mean difference±SEM, 10±3.5%, 95% CI: 1.9-18.2, p=0.02) without changing BP pre, during or post exercise compared to placebo. This study demonstrates that arterial distensibility is transiently reduced following maximal exercise and increases later in the recovery period. Pretreatment with Vitamin C, by reducing oxidative stress and therefore increasing NO availability, improves arterial distensibility and potentially cardiovascular efficiency. In cardiovascular diseases where oxidative stress is increased, the adverse effects seen in health would be exaggerated suggesting a potentially important role for antioxidant therapy. (Graph Presented).