Clinical Research Directory

Dose-Response Effects of Short-Term Ashwagandha on Anaerobic Exercise and Cognitive Function in Resistance-Trained Athletes

Ashwagandha (ASH) is an herbal supplement derived from the Withania somnifera plant. It is commonly described as an adaptogen, a substance thought to help the body cope with physical and psychological stress. Previous research has examined ashwagandha supplementation using different doses and supplementation periods. This study examined the effects of seven days of supplementation on muscular strength, exercise performance, cognitive function, and selected physiological measures in healthy, resistance-trained men and women. It also examined whether these effects differed between low and high doses. The study used a crossover design in which each participant completed four conditions: no supplementation, a placebo containing maltodextrin, low-dose ashwagandha at 4 mg per kilogram of body weight per day for seven days, and high-dose ashwagandha at 14 mg per kilogram of body weight per day for seven days. The three supplementation conditions were separated by seven-day washout periods. During the blinded supplementation conditions, neither the participants nor the researchers conducting the assessments knew which supplement was being administered. At the end of each seven-day supplementation period, participants completed laboratory assessments. These included the maximum weight lifted for one repetition on the bench press and leg press, total lifting volume across multiple sets, and the speed and power of bar movement. Participants also completed a 30-second all-out cycling sprint to assess anaerobic power, total work, and fatigue, along with a color-word test to assess cognitive performance. Additional assessments included resting energy expenditure, heart rate, blood pressure, perceived exertion, self-reported readiness, focus, alertness, and selected blood markers related to cholesterol, liver function, and muscle damage.

Effects of New Zealand Blackcurrant Supplementation on Exercise and Cognitive Performance in Resistance-Trained Adults

New Zealand blackcurrant (NZBC) is a supplement made from a berry naturally rich in plant compounds called anthocyanins. Researchers have studied these compounds for years and found that they may help the body by improving blood flow, reducing post-exercise stress on the body, and supporting energy production. Most of that research, however, has focused on endurance athletes like runners and cyclists. Almost nothing was known about whether NZBC could benefit people who do strength training. That is what this study was designed to find out. Twenty healthy, resistance-trained men and women between the ages of 18 and 40 were recruited. Each participant completed four different conditions over the course of the study: taking no supplement at all, taking a placebo (a dummy capsule with no active ingredient), taking a low dose of NZBC (250 mg per day for seven days), and taking a higher dose of NZBC (600 mg per day for seven days). Neither the participants nor the researchers evaluating them knew which capsule was being taken at any given time, a design that helps ensure the results are as reliable as possible. At the end of each seven-day period, participants came into the lab and completed a full battery of tests. Measurements included how much weight could be lifted for one maximum effort on the bench press and leg press, how much total volume could be completed across multiple sets, and how fast and powerfully the bar could be moved. Participants also completed a 30-second all-out cycling sprint to test anaerobic fitness, and a paper-and-pencil color-word test to measure focus and mental sharpness. Strength increased noticeably. After taking either dose of NZBC, participants were able to lift more weight on both the bench press and leg press than when taking the placebo or no supplement. The lower dose had a particularly striking effect on leg training: participants pushed through roughly 38% more total volume in their leg press sets. For bar speed and explosive power on the bench press, the higher dose had the edge. Cognitive performance followed a similar pattern. The lower dose sharpened mental performance across several parts of the color-word test, while the higher dose made a more modest but still meaningful difference on one section. The sprint cycling test showed no differences between conditions. Importantly, both doses were safe and well-tolerated, with no meaningful side effects reported throughout the study. One week of supplementation was sufficient to produce real differences in strength, power, and mental sharpness, and neither dose raised any safety concerns.