Xtend® Energy is engineered to help you power through these very moments. Unlike other energy-infused aminos, Xtend® Energy provides a combination of quick-hitting fuel and time-released caffeine to keep you training at your peak for the long haul.* Since ZümXR® delivers caffeine for up to 6 hours after your first sip, you can count on Xtend® Energy to work when you do, as hard as you do, for the most enduring workouts.