Front leg when jabbing

[boxingbantz]

I have just come back from my first coaching session and have just been going through the basics/techniques etc which I have found all well and good.

One thing that has confused me somewhat is the coach has said when jabbing, your front leg (orthodox) DOESN'T bend as you throw the punch - this just doesn't feel comfortable to me. Maybe I am missing the point or doing it wrong but can someone explain to me what your front foot/leg should be doing during this punch?