A pre-workout is a type of supplement designed to be taken around 15-30mins before your exercise bout. The most common ingredients in such supplements include nitric oxide pre-cursors such as L-arginine and L-citrulline, as well as some stimulants including caffeine and taurine. However supplement companies are using the findings of many research projects that support the use of vasodilators (nutritional components that widen blood vessels) such as nitrates from beetroot, and agmatine, a putative neurotransmitter and potential antidepressant.
The use of L-arginine and the likes of is still very much a contemporary ingredient of pre-workouts, but the use of beetroot based products are becoming ever more popular among professional and recreational athletes alike.
Halaris, A & Plietz, J. (2007). Agmatine : metabolic pathway and spectrum of activity in brain. CNS Drugs. Retrieved 29th January, 2014, from