Boost blood volume by 100%, even with short-term supplementation
The amino acid L-arginine is one most bodybuilders are familiar with. After all, it’s been part of preworkout supplement formulas for years. Arginine is considered a conditionally essential amino acid, meaning the body can product it adequately under normal conditions. However, studies have shown in cases of injury or severe stress arginine stores become depleted.
The theory behind ingesting arginine before you train is based on the fact that exercise is a stress and arginine is the major rate-limiting precursor to nitric oxide (NO, a potent vasodilator) production in blood vessels. As such, supplemental arginine may serve to top up arginine reserves and promote greater blood flow to muscles when you train, thus aiding nutrient delivery and metabolite removal.
The science behind arginine as a preworkout erogenic is positive. It can increase growth hormone, unsulin release and mTOR (a molecular marker for anabolism), all of which, in the long term, equate to increased strength and muscle building. Science has been inconclusive in terms of acute (i.e., short-term) arginine supplementation leading to increased blood flow during exercise. The current consensus is that the body produces adequate amounts of arginine under healthy conditions to support NO production during exercise.
In a new study published in the Journal of Applied Physiology, Nutrition, and Metabolism, scientists from Brazil tested the specific acute effects of preworkout arginine supplementation of NO production, as well as muscle blood volume and oxygenation during recovery from three sets of heavy resistance exercise. In this randomized, double-blind and placebo-controlled study 15 healthy college-age male participants were given either 6 grams of L-arginine or a placebo, which they took 30 minutes before performing biceps curls (they completed three sets of 10 reps) at maximum voluntary contraction. Blood samples were taken before supplementation and periodically for two hours post-supplementation. Further, muscle blood volume and oxygenation levels were measured at certain stages throughout the experiment period.
The researchers reported that, compared to the placebo group, acute arginine supplementation increased muscle blood volume by greater than 100% during recovery from each set of biceps curls. They noted no measurable differences in muscle oxygenation or strength performance between groups.
The Doc’s Take
Most anecdotal evidence indicates arginine supplements aid recovery and help build muscle. Still, “bro-science” isn’t convincing enough for some people to spend their hard-earned cash on scientifically unproven supplements. The study presented herein clearly illustrates the blood flow-promoting effects of L-arginine during exercise recovery, which (over the long term) may aid muscle growth. The lack of support from other arginine studies is likely a result of differences in research design. Regardless, most research supports the use of arginine supplements to optimize strength and growth over the long term.