Caffeine is a stimulant drug used for mental alertness and to accelerate energy and power. It is also used to delay muscle fatigue as it goes deep into the muscle tissues.

Yohimbine HCL, sometimes called yohimbine hydrochloride, yohimbe, or yohimbe bark, is an herbal supplement which serves as a stimulant and possible aphrodisiac for users. Yohimbine has also been shown to be successful in treating erectile dysfunction and impotence in men. It may serve to boost the sex drive of those who take it for aphrodisiac purposes. Some people are recommended to take yohimbine to combat their lower sex drives caused by antidepressants. Yohimbine has also been shown to help blood pressure levels and assist in weight loss. For these reasons, yohimbine is a popular supplement amongst athletes as well as many others wishing to improve their health.