I'm 19, only run teh 400ih like 6 times and i have a pr of 56.5. I run the open 400 in about a 50 flat right now and i feel like i can go at least under 55.00 in the 400ih. My left leg is lead, i feel most comfortable with that on the turns anyway. I feel like it alows me to lean into the turn. I actually have a lot of trouble when i try to lead with my right leg and i need to work on alternating more.