I just started training for an upcoming sprint tri a couple weeks ago. I've been commuting on a bike for about a year and been swimming for about a year and half. My weak point is the running, so I've been trying to work on that. I just got fitted and bought a proper pair of running shoes and generally run 2-3 miles every other day and swim about a mile on the days that I don't run, along with commuting on my bike everyday 18 miles per day. On days that I run I've noticed that a couple hours afterwards I'll be sitting down and when I get up I get light headed and see stars. I eat a pretty well balanced nutritious diet, low fat, lots of fruits, veggies, carbs, and protein so I'm confused why I feel like this. Could this all be solved by switching from water to some sort of electrolyte replenishing drink and if so, what brand does everyone recommend?