I usually take a regular Meal Replacement shake about 30-45min before a long run. Before I started taking them, I was just running on an empty stomach. With the MRPs, I've noticed a significant increase in my energy levels throughout the entire run (which is typically the same length of time - 40min) Specifically, I use Champion Nutrition's Ultramet, although it probably doesn't make much of a difference what type is used. Following the run, I mix up some 100% ON vanilla whey with a high-glycemic carb drink such as Kern's All-Nectar