Ginseng (Panax ginseng) is one of the most-studied herb for human physical performance. Panax ginseng, is also known as Chinese ginseng, Korean ginseng or Asian ginseng. Do not confuse Panax ginseng with American ginseng, Siberian ginseng, or Panax pseudoginseng. Possible Panax ginseng benefits include improved concentration, memory, thinking, physical stamina, and athletic endurance. Many of these claims are often based on uncontrolled and non-randomized trials.
Panax Ginseng and Physical Performance
Ginseng is categorized an adaptogen. People often use adaptogens in combination with exercise because exercise is considered a form of stress. A systematic review of controlled clinical trials by B. K. Vogler et al.  evaluated double-blind, randomized, placebo-controlled trials of ginseng root extract for any indication. When evaluating the effects of Panax ginseng on physical performance in young, active and healthy volunteers during maximal and submaximal exercise, researchers found no improvement of physical performance after ingestion.
Another more recent evaluation of the ergogenic properties of ginseng by Dr Michael S. Bahrke and William P. Morgan  revealed that published literature does not resolved the equivocal nature of research evidence involving animals or humans. Because the use of ginseng continues to grow, there is clearly a need for systematic research dealing with the efficacy of ginseng.
Many animal studies show improvements in exercise performance , but the use of large doses or administration via infusion limits extrapolation of these data to humans.
There are also some animal as well as clinical trials that report positive effects of ginseng on sexual impotence (aphrodisiac effect) .
Ginseng for Improved Cognition
Animal studies  are showing that orally administered ginseng, at a dose of 20 mg/kg for 3 days, improved learning and memory in rats performing a maze task. A favourable effect on various tests of psychomotor performance such as attention, auditory reaction time, processing was reported by L. D’angelo and others . Action on serotoninergic transmission could be the mechanism behind positive effect of ginseng on learning and memory .
Are There Any Side Effects From Panax Ginseng Ingestion?
When used appropriately, ginseng appears to be safe. The most common side effects include hypertension, diarrhea, restlessness, mastalgia and vaginal bleeding.  A few cases of estrogen-like effects were reported in postmenopausal women using topical creams or taking pills containing ginseng .
Vogler, B. K., M. H. Pittler, and E. Ernst. “The efficacy of ginseng. A systematic review of randomised clinical trials.” European journal of clinical pharmacology 55.8 (1999): 567-575.
Bahrke, Michael S., and William P. Morgan. “Evaluation of the ergogenic properties of ginseng.” Sports Medicine 29.2 (2000): 113-133.
Bucci, Luke R. “Selected herbals and human exercise performance.” The American journal of clinical nutrition 72.2 (2000): 624s-636s.
Nocerino, Emilia, Marianna Amato, and Angelo A. Izzo. “The aphrodisiac and adaptogenic properties of ginseng.” Fitoterapia 71 (2000): S1-S5.
D’angelo, L., et al. “A double-blind, placebo-controlled clinical study on the effect of a standardized ginseng extract on psychomotor performance in healthy volunteers.” Journal of ethnopharmacology 16.1 (1986): 15-22.