Guayusa Extract on Exercise Training

Supplementation: Participants will supplement daily with organic guayusa extract, which is a caffeinated Amazonian 'super-leaf' belonging to the holly species that contains a very unique blend of polyphenol antioxidants and caffeine (\~20% caffeine, 30% chlorogenic acids, 5% catechins) during 6 weeks of high intensity exercise training. Investigators and participants will be blinded to condition.

Participants will supplement daily with placebo (maltodextrin). Investigators and participants will be blinded to condition.