The critical velocity test provides two measures: critical velocity (CV) and anaerobic running capacity (ARC). In theory, CV represents the maximum running velocity that can be maintained without fatigue, which is regarded as an aerobic measure. The ARC is an estimate of the anaerobic energy reserves in muscle, such as adenosine triphosphate and phosphocreatine. However, no previous studies have examined the effects of any nutritional supplements on CV and ARC. To examine the effects of a pre-exercise supplement on CV and ARC in college-aged men and women. Ten moderately-trained men and women (mean ± SD; age 25.7 ± 3.4 yrs; height: 172.2 ± 7.5 cm; weight: 70.9 ± 11.7 kg; o2max: 50.6 ± 6.6 ml·kg−1·min−1) volunteered to participate in this randomized, double-blinded, placebo-controlled, cross-over study. Thirty minutes prior to testing, participants consumed the active supplement (ACT; 17.6g; whey protein, cordyceps sinensis, arginine, creatine ethyl ester, citrulline, ginseng, and caffeine) or placebo (PLA; 17.6g; maltodextrin, natural and artificial flavors and colors). After 3 familiarization sessions, the testing was conducted over 3 non-consecutive days for the randomly-ordered ACT and PLA trials (6 days total). A maximal oxygen consumption test (o2MAX) on a treadmill was performed on day 1 to establish peak velocity output (PV) at o2MAX. Day 2 involved treadmill running at 110% and 90% of the PV, while day 3 involved running at 105% and 100% of the PV. CV was the slope, and ARC was the y-intercept of the linear relationship between running distances plotted over the times-to-exhaustion (s) at each velocity. The ACT supplement elicited a 10.8% higher (p = 0.02) ARC compared to the PLA. However, the 0.6% higher CV for the ACT trial was not different (p = 0.38) from the PLA trial. These findings suggest that the acute ingestion of this pre-exercise supplement may be an effective strategy for improving ARC (anaerobic energy), but appears to have no effect on CV (aerobic performance). Taking the ACT supplement 30 min prior to testing improved the anaerobic energy reserves associated with high-speed running, which may be useful for athletes who rely on these metabolic demands, such as football, basketball, baseball, softball, soccer, and rugby players.