kicking techniques

Question
What am I doing wrong if I experience some muscle soreness in the groin area after practicing the kicking motion of this stroke?

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Followup To
Question -
Having problems with moving through water while kicking using a kickboard.  (A lot of effort to get forward momentum going.)

Also having a hard time trying to think about the correct motion of the legs during the kick and glide actions while trying to breast stroke. (Most of the propulsion is from the arms; not much distance covered during the glide.)

What can be done to improve in these areas?
Answer -
William--
Here are a couple of suggestions that may help with your kicking problems.  First of all, remember that the kick should be done completely underwater, if you are making a big splash, you are just kicking air and not enough water.  Try to keep your legs relatively straight(little knee bend).  The whip-type action from your hips through your knees and ankles to your toes is what propels you forward, too much knee bend and you start pulling water towards your head instead of pressing it backwards.
If you are having trouble keeping the technique together on the breast stroke kick while you are swimming with your arms, back up and work just the kick(without a board), than when you get comfortable with that, try to do the following drill:  one(1) pull, three(3)kicks for one length; one pull two kicks for one length; one pull one kick for one length; repeat the whole drill.  This will help with the kick and the glide.
Another drill to help get the feeling of the glide is to swim the whole stroke, but hold the glide position(make sure you are in a good streamlined position during the glide)for 2 to 3 seconds.  
Sorry for the delay in responding and I hope these drills help.
Let me know if I can be of any other help
George  

Answer
William--
There are 2 possibilities.
First of all, you may be doing the kick properly and just experiencing stiffness from a previous lack of use of the muscles in your groin area.
Second, and more probable, is that when you are doing the breast kick, you are letting your knees go wider than your feet which does cause stress on your groin.  When doing the kick correctly your knees don't get more than 12 to 18 inches apart and your feet whip together in a small half circle.
I hope this helps,
Let me know how it goes.
George