An ergogenic aid can be defined as an equipment, technique, and substance used for enhancing sports performance. Ergogenic aids can be classified into different forms such as nutritional, pharmacological, and physiological aids. They range from use of accepted techniques such as high altitude training to consumption of illegal substances such as steroid. The efficacy of many of these is controversial, whereas the side effects are evident. An herb is a plant or plant part used for its scent, flavor, or therapeutic properties. In general, taking herb medication is considered as a safe practice. There are different forms of herbs such as tablets, capsules, powders, and fresh leaf. People use herbal medicines to maintain or improve their health. Herbs have been used to improve performance (both endurance and strength), facilitate recovery from work and exercise, maintain health, build muscle mass, and reduce body fat¹-³. Ginseng is one of the most widely used herbs for human physical and mental performance, which includes several species and is prepared by various methods⁴.

The term ‘ginseng’ usually refers to the species Panax ginseng, known as Korean ginseng or Chinese ginseng. Ginseng root extracts have long been used in traditional oriental medicine to restore energy and enhance well-being¹. Ginseng is a perennial herb which is indigenous to Korea, China (Panax ginseng C.A. Meyer), Himalaya (Panax pseudo-ginseng), Vietnam (e.g. Panax vietnamensis), Japan (e.g. Panax japonicus), and North America (Panax quinquefolium). Ginseng is available in many forms: whole root, root powder (white ginseng), steamed root powder (red ginseng), teas, tinctures, and standardized root extracts containing known and reproducible amounts of ginsenosides. The recognized primary active components of ginseng are a group of 30 different triterpene saponins, also referred to as ginsenosides, which vary in content and relative proportions among different species of ginseng^5,6.

In exercise and sports science, ginseng is believed to be a physical performance enhancer¹. Chen et al (2012)¹ reported that Panax ginseng supplements may enhance physical and mental performance if taken over a long enough period of time and in sufficient doses. Panax ginseng, when administered at an adequate dosage (between 200 and 400 g/day) for a period of longer than 8 weeks may improve physical performance¹. In general, ginseng supplements are safe, although individual variability exists and potentiation with stimulants may occur^7,8.

Cultivated ginseng can be classified into four types: 1) fresh ginseng, 2) white ginseng, 3) red ginseng (steamed and dried process), and 4) wild ginseng^9,10. RG contains bioactive compounds such as ginsenosides and phenolic compounds, and the compounds can vary according to the conditions of the heat process¹¹. Extracts of red and white ginseng contain different ginsenosides¹². Previous studies demonstrated that RG contain a large dose of ginsenosides and saponin through specific manufacturing processes such as steaming and drying ginseng¹³. Together with ginsenoside Rg3, a nitrogen-containing component and ginsenoside 20(R)-Rh1 were detected as characteristic components of RG, whereas malonyl ginsenoside Rb1/ isomer and malonyl ginsenoside Rg1/isomer were found to be characteristic components of WG¹⁴.

In particular, Korean Red Ginseng has ginsenoside such as Rg3, Rg 5, Rh1, and Rk1^15,16. For these reasons, the identification of bioactive components in RG has been regarded as an objective of scientific study^17,18. Recently, several studies have reported that RG has biological activities, such as vasodilation, antihypertension, antioxidant, anti-inflammatory, and improving cognitive function¹⁹-²².

RG study for exercise performance has been conducted predominantly with respect to aerobic capacity. RG supplementation demonstrated increase in the concentration of hemoglobin in the blood²³. It also showed stimulation of mitochondrial metabolism in the muscles²⁴. RG has been reported to improve the blood and organ lipid profile when combined with exercise¹³. It contains various biological and psychological activities and may also alleviate fatigue-related disorders. RG supplementation showed positive effect on fatigue resistance capacity, glycogen sparing, and oxidation of free fatty acid during prolonged sub maximal exercise²⁵.

In contrast, effect of RG supplementation on anaerobic capacity does not look promising as compared to aerobic capacity²⁶. A study by Engels, et al (2001)²⁷ reported no significant changes in anaerobic capacity after 8 weeks of RG supplementation. Similarly, Yoon, et al (2001)²⁸ also showed that there were no improvements in maximal and mean powers in Wingate power test. However, Hwang, et al (2004)²⁹ reported that RG supplementation can reduce generation of oxidative free radical resulting in possible positive effect on exercise performance.

However, the number of studies and quality of RG studies are very limited as compared to the studies investigating regular ginseng. Also, there are only a few studies written in the English language available to scientific community.

Therefore, we conducted systematic review to summarize the current evidence of RG supplementation on exercise performance and fatigue recovery both written in the English and Korean languages. We anticipate that this review will provide valuable information about current ongoing research on RG to our colleagues and help them to design and conduct future research projects.

This study reviewed 14 published articles investigating the effect of RG on exercise performance and fatigue recovery in human trials. This review has differentiated significance compared to previous review articles in terms of summarizing only RG supplementation related with exercise. Furthermore, the present review represents a systematic evaluation of clinical trials published in the Korean and English literatures. Finally, 14 studies that met the inclusion criteria were categorized based on aerobic, anaerobic, antioxidant function, and fatigue recovery. We observed that previous studies primarily focused on aerobic capacity and fatigue recovery as variables of ergogenic ability. To the best of our knowledge, only 10 outcomes have shown that RG supplementation can help in exercise performance. Specifically, only 2 of 22 outcomes were in aerobic category, 1 of 8 outcomes was in anaerobic category, 5 of 11 outcomes were in antioxidant category, and 2 of 7 outcomes were in fatigue recovery category. VO_2max and HR were commonly evaluated as an aerobic capacity outcome. There was some evidence that RG may have an effect on aerobic capacity, with 2 of 22 outcomes partially demonstrating improvement in Hb, and shuttle run test score in RG groups compared with control groups. However, most of the studies showed that RG supplementation had no effects on aerobic outcomes including VO_2max, HR, AT, VE, RBC, and time to exhaustion test. Most of the results clearly state that RG supplementation had no effects on anaerobic capacity and fatigue recovery. In terms of antioxidant function, 5 of 11 outcomes had positive significant effects. However, the outcomes observed heterogeneities between each variable, which means that the data in each category were inconsistent and statistically insufficient. Therefore, more studies are obliged to judge the effects clearly. Many studies conducted using animals have usually shown that RG may improve exercise performance; whereas, data from human subjects reveal contradictory results. We believe that the inference could be due to various methodological problems including small sample size, different dosage, and lack of placebo group. The actual composition of ginseng preparations has been a persistent issue, and differences in the effects of ginseng may be due to the dosage and type (powder, extract, etc) of RG consumed. There may be interactions with diet, lifestyle, exercise, and other drugs.

We wish to highlight some of the difficulties faced while conducting research on RG and offer some suggestions for future research. Most of the reported studies did not used standardized RG preparations. Moreover, the majority of studies did not describe a ginsenoside profile except for two articles^43,44. None of the studies reported independent testing of the preparation to confirm purity, consistency, and stability. In addition, dose ranges varied among the studies (900 mg to 5 g/day for capsules, 100 to 200 ml/day for liquid, and 1500 mg/day for powder). Non-randomization may lead to a substantial overestimation of the effect size. It is also suggested that post-harvest handling processing for RG should be standardized using the identified characteristic components as chemical markers to ensure the quality and efficacy of RG.

In the methodological aspect, the quality of most of the studies was poor, as they did not clearly describe adequate randomization, blinding, and/or description of withdrawals and dropouts. In addition, none of the studies conducted statistical calculation to determine reasonable subject numbers. Moreover, we observed that interpretation of the results was incorrect based on statistical analysis. For instance, a study concluded that RG had effects on exercise performance despite no significant interaction by repeated measures ANOVA. Therefore, the limitations in methodological quality could induce the different interpretation of RG supplementation on exercise performance. As such, it is necessary to conduct further studies that are of high quality and with larger sample sizes to contribute towards formation of a definitive conclusion. Specifically, it is required to describe the accurate information of ginsenoside dosage, and ratios to evaluate the efficacy of RG as an ergogenic aid. In addition, future studies need to fulfill accurate research procedures.

This review may serve as a foundation for future systematic reviews and further studies, but it also has some limitations. First of all, data synthesis for this study was limited by heterogeneity between outcomes. Pooling results were confounding, which was inappropriate. This phenomenon may be caused by the small sample size and varied supplementation dosage. Another limitation was that this review article included studies written in the Korean and English languages.

This review explores the scientific evidence for use of RG extracts as ergogenic aid for exercise performance. The results of this systematic review reveal that RG is not effective on aerobic and anaerobic capacity, antioxidant function, and fatigue recovery. However, we conclude that there is absence of strong scientific research evidence regarding the efficacy of RG on improving exercise performance in humans. In future studies, it is necessary to conduct further systematic review of high quality and involving large sample sizes with an aim to form a definitive conclusion.