Buckling knee

Question
Hey, I'm Andrea, and I'm a junior high cross country and track runner.
At the moment, I've been having a little trouble with the stability of my knees.  After running multiple sprints, my knees lose all feeling in them and just flat out give way under me.
This happened once last year when I was standing, trying to catch my breath after running a 400 and I just fell backwards.
My coach told me to just walk it off and continue to run the workout which I did, rather reluctantly, I admit. ;)
This incident was kind of scary to me.  What if I was running alone and no one was behind me to catch me?
I was hoping that you could tell me the cause of this strange occurrence and give me some advice as to what I should do to prevent this and/or treat it.
Thanks,
Andrea

Answer
Hi Andrea
This situation can occur but not always and varies depending on the individuals fitness level.When you push real hard right to the end of an interval workout or race,most all the blood is pooled in the lower extremities and when you stop quickly at the end of your interval or race it takes a little time for the blood which is where oxygen is transported to recirculate back up to the HEART which will make you a little unstable if you are up right.What you can do is when you finish is just keep moving easy for a little bit and then just bend over at the waist with your hands on your knees for a minute and this will help the blood recirculate back more rapidly.I hope that i made this clear and you understand.If you have other questions Andrea just get in touch,and please let me know how that works for you.

All the very best to you

John