|Exercise performance data of 19 resistance trained men receiving placebo or supplement in a cross-over design. (best values marked by author, Bloomer. 2010. Table 3)|
You will notice, that Bloomer et.al. deliberately selected the Top-Sellers and most used nitric oxide products from the ever-growing range of preworkout supplements. The scientists did a particularly good job, so I will just leave the conclusion to them:
We conclude that when compared to a maltodextrin placebo, none of the products tested in the present study resulted in effects that are statistically different with regards to exercise performance, skeletal muscle blood flow, muscle pump, HLa, NOx, or MDA. The singleThese concluding statements should be considered within the context of the current study design, and may not be generalized to other designs inclusive of different exercise modes and intensities, and/or different outcome measures.
ingredient GlycoCarn® (combined with 16 grams of maltodextrin) resulted in the highest StO2 at the start of exercise and a reduction in exercise-induced lipid peroxidation, as measured by plasma MDA. Although not of statistical significance, SUPP1 resulted in a greatest power output during the bench press throws compared to the placebo and other conditions (range: 0.4%-5.8%), and GlycoCarn® resulted in a greater total volume load compared to the placebo and the supplements tested (range: 2.5%-4.6%). These data indicate that
- a single ingredient (GlycoCarn®) can provide similar practical benefit as compared to finished products containing multiple ingredients pertaining to many of the outcome measures included within the present design, and
- the tested finished products are clearly ineffective in terms of increasing blood flow and improving acute upper body exercise performance, and do not produce results that match the widely advertised marketing claims.