The scientists investigated the effect of 42-54 days of supplementation with 1 g/d of quercetin with vitamins and other substances in a soft chew or placebo chew on 58 healthy, moderately trained men and women. During a maximal effort uphill treadmill run and four physical performance measures (Army Physical Fitness Test, [APFT], Baumgartner Modified Pull-Up Test [BMPU], Wingate Anaerobic Test [WanT], and a 36.6-m sprint) peak oxygen uptake (VO(2peak)) was evaluated before and after the supplementation period. The results are unambiguous:
Pretreatment-to-posttreatment changes in VO(2peak) and physical performance were not significantly different (p > 0.05) in Q and P.So, if you planned on taking quercitin as an ergogenic, you better forget about that. If you intent to take it for its positive effect on healthy aging, be aware that it also prolongs the metabolism of caffeine and other things in your liver.