Active muscles have higher energy needs, which are sustained by increased blood delivery of nutrients and oxygen. During exercise, circulating blood also helps remove metabolites and byproducts that can contribute to muscle fatigue. To meet changing demands, the body naturally adjusts breathing, heart rate, blood flow and blood pressure during exercise. However, many athletes and active consumers are looking for supplemental ways to enhance blood flow for greater benefits, including muscle performance and development.
“Compared to resting conditions, blood flow during maximal exercise can increase up to 20-fold on average,” explained researchers Ingrid Sarelius, Ph.D., University of Rochester, and Ulrich Pohl, Ph.D., alter-Brendel-Centre of Experimental Medicine, Munich, noting rising oxygen extraction during exercise alone cannot meet the increased need. (Acta Physiol (Oxf). 2010 Aug;199(4):349–365.) “Thus, the far more important way to meet the increased demands is an appropriate increase in muscle blood flow which also has the effect of increasing the microvascular hematocrit, and hence oxygen flux into the tissue from capillaries.”
Nitric oxide (NO) made in the body from the amino acid L-arginine, oxygen and cofactors such as NO synthase (NOS) enzymes cause vasorelaxation of smooth muscle. This can increase blood flow under the right conditions.
Arginine and other compounds feeding NO production, including dietary nitrates, citrulline and agmatine, have been popular targets for both blood flow research and sports supplement formulation. Beetroot and spinach are two nitrate-rich ingredients often used to boost blood flow. Phytochemicals from botanicals such as turmeric, grapes, strawberries, apples, black currants and pomegranates have also been studied and considered by formulators for impacting NO and blood flow.
For more information on blood flow mechanisms and the ingredients studied for delivering more nutrients and oxygen to muscles, check out the full article in the special digital issue on muscle building.