When rats were subject to prolonged swimming, a water extract of the stem (500mg/kg for 25 days) appears to have anti-fatigue effects which was thought to be due to the (+)-syringaresinol-di-O-beta-D-glucoside component (similarly effective at 50mg/kg).[9] This has been noted elsewhere, where five different extracts of eleuthero were tested with the one lowest in eleutherosides B and E failing to have any effect and the one with the highest Eleutheroside E content (3.32% of the 1g/kg dose) outperfoming red panax ginseng; a time-dependent effect was noted, with days 5 and 7 outperforming day 1[61] and elsewhere in mice swimming performance has been enhanced with extracts containing high levels of Eleutheroside E and E2 but to a slightly lesser potency than red ginseng.[62]
Anti-fatigue effects seem to be related to Eleutheroside E and (+)-syringaresinol-di-O-beta-D-glucoside components. When comparing eleuthero to panax ginseng they seem somewhat comparable in efficacy
When tested in humans (n=9) subject to a 75% VO2 max cycle to exhaustion, 800mg of eleuthero root (0.11% eleutheroside B and 0.12% eleutheroside E) in two divided doses with meals for 8 weeks was associated with improvements in time to exhaustion (placebo improved 6%, eleuthero improved 25.5%) paired with an increase in VO2, heart rate (4.3%), free fatty acids (19.5%) and respiratory exchange ratio (2.7%) with a decrease in glucose during exercise (6.7%) with no influence on the rate of perceived exertion.[63] This increase in lipid oxidation has been noted elsewhere with the herb, although with a reduced heart rate.[64]
Performance enhancement has been noted elsewhere with a 35% ethanolic extract of eleuthero in liquid form (Taiga Wurzel at 25 drops daily) for 30 days prior to a VO2 max test where max VO2 in relation to body weight increased by 8.6% (without comparison to body weight, the benefit was not statistically significant) and max VE increased by 7.4%; this study failed to note changes in the respiratory quotient or heart rate, and eleuthero outperformed echinacea (purpurea)[65] and elsewhere a VO2 max test on a weighted cycle ergometer noted a 23.3% increase in workload (cycle time and resistance worked against) relative to control, which outperformed the 7.3% increase in placebo (relative to control) after 8 days of ingesting 4mL of eleuthero tincture (300mg plant extract equivalent) in two divided doses of 2mL in the morning and PM.[66] Time to exhaustion was 5.4% greater in placebo and 16.3% greater with eleuthero.[66]
Despite the above three trials, one review[67] conluded no significant effects associated with eleuthero due to the aforementioned studies being low in methodological quality and other trials of higher quality showing no effects. Two trials using ENDUROX (brand name)[68][69] failed to find any influence on heart rate or fat oxidation during submaximal exercise (800mg eleuthero leaf) and no influence on fat oxidation or oxygen consumption with 1200mg eleuthero leaf extract, respectively. One study (not located online; McNaughton et al.) failed to find an effect with 1000mg of the root extract failed to find an effect on VO2 max or grip strength (instead noting an increase in pectoral and leg strength by 15% and 13%) while the other studies noted that 3.4mL of eleuthero root extract tincture failed to find a significant influence on fat oxidation and oxygen consumption[70] and 1,200mg of the leaf extract has also failed again during submaximal exercise.[71]
Evidence is mixed currently, and conclusions are hard to draw as although the studies suggesting promise with eleuthero supplementation are less statistically robust (poor metholody and sample sizes) other more well controlled studies seem to evaluate submaximal exercise more, whereas the promising studies were in regards to anti-fatigue effects during maximal exercise
At this moment in time, a clear performance enhancing effect of eleuthero is not present but performance enhancement cannot be ruled out yet