In glossary:randomized controlled trials (RCTs) where athletic populations are examined, PS did not consistently improve the outcomes examined.
In an RCT examining cycling, participants in a crossover RCT took 600 mg of PS for 10 days before performing a bout of cycling beginning at a moderate intensity (65% VO2max) and ending at a high intensity (85% VO2max). Cortisol Area Under The Curve was lower after PS supplementation, but lactate, testosterone, and growth hormone levels were not different after PS supplementation compared to placebo.[1]
PS supplementation improved cycling time to exhaustion at 85% VO2max by a surprising amount, from nearly 8 minutes to nearly 10 minutes in the PS group. The placebo group had no improvement in time to exhaustion. However, performance at lower intensities (45%–65% VO2max), serum cortisol levels, fatigue levels, tranquility levels, and fuel source utilization rates (carbohydrates versus fat) were not different between the two groups. The participants took a large dose of PS (750 mg) for 10 days before the cycling bout.[2]
However, PS did not improve biomarkers after downhill running; a later RCT by most of the same authors, also featuring 750 mg of PS daily, explored PS supplementation for 7 days before a bout of prolonged downhill running. The run was on average 51 minutes in duration, at a steep gradient (16.5% decline), and at 8.7 kilometers per hour (or 5.4 miles per hour). Exercise like this, featuring a lot of eccentric muscle activity, is excellent at inducing muscle soreness and inflammation. However PS did not reduce muscle soreness, or biomarkers of muscle damage, inflammation, or oxidative stress, compared to placebo.[3]
In a crossover RCT, physically active college males took 400 mg of PS for 14 days, and then performed a bout of lower body resistance training. They had no changes to mood, serum cortisol levels, or serum testosterone levels after PS supplementation, compared to placebo. In this RCT, participants were also tested on cognition, where the participants in the PS group performed better on 1 of 3 metrics related to performing simple math problems quickly, compared to placebo.[4]
Participants taking a combined PS (400 mg) and caffeine (100 mg) supplement for 2 weeks reduced their fatigue ratings immediately after resistance training, compared to placebo. However caffeine is known to reduce fatigue ratings,[5], so it is difficult to say how much PS contributed. Outcomes that PS might have improved, such as mood and cognition, were not improved with supplementation compared to placebo.[6]