I have been a runner all my life and started eating a vegan diet 90 days ago. I researched lots of vegan energy sources for workouts and came up with the following morning formula: 1 cup of soy milk, 1 cup of water, 1 tbsp of the following ground seeds: chia, flax, hemp, and 1 tbsp of backstrap molasses. I shake it all together in a cup and slam it down. It is about a 400 calorie lean shot of energy and protein. I know we can't post links here, but the full nutritional breakdown is on my blog if you are interested.
I have run an average of 10 - 15 miles a week for 15 years. With this shake, I found myself being able to swim 30 minutes of laps and then run about 4 miles. The only thing stopping me from running further was having to go to work. I am actually going to train for one of those mini-iron mans next year. I had plenty of energy after the run also.
You should research those seeds I mentioned. They have been used for thousands of years for endurance.
Simple non-political vegan diet for the everyday person. http://www.bornagainvegan.org twitter: @bornagainvegan