Cordyceps sinensis is an herb that has been used for centuries in China as a health stimulant. It is considered a bioactive compound with the purported ability to alter metabolism and has been used to treat multiple conditions including lung, kidney, and cardiovascular problems as well as for body strengthening after illness or strenuous training. Cordyceps belong to the group known as “adaptogenic” herbs, which are considered to have antistress properties and enhance endurance and strength. Although there are many claims regarding the effect of cordyceps on exercise performance, these reports are not supported by research. In a well-designed study that examined the effect of cordyceps on endurance exercise, no improvement in endurance was detected.