cardio training for 1,6 miles

Question
Hello! I am actually a gymnast, but want to study sports here in Austria and we have to pass a test.

One of the categories is running/track&field.

We need to run 1.5 miles in or better under 12 minutes + sprint 65feet in or better under 2.80secs (runnung start).

I am in gymnastics 4 times a week. I can't add that much running training to my weekly workouts.
I used to run quite a lot 2 years ago, but quit because I had no time and started to get shin splints and knee problems.
I am able to get all the limits, but it's quite taxing for me and as I said; the faster, the better because in the end the overall score counts.

My plan is now:

Do track and field training once a week for one hour, mostly basic stuff like technique training. Go for a short run afterwards for about 1 mile as fast as posible.

Do one hour of interval training on weekends, either swimming or elliptical (can't run because of my shins+knee but I am in physcial therapy, I stretch, massage and have very good shoes!).
I will do about 30 minutes with some intervals, and then the last 20 minutes slow cardio.

The test will be in September. I want to go with this plan for the next 5 months or so. In the last 4 weeks before the test I will go for the "test run", so the 1.5 miles twice a week.

What do you think? Will this plan help me with endurance? What should I change? Is it better not to do intervals? Should I add another cardio workout per week? Is swimming or elliptical better?

Hope you can give some advice!

Answer
Lisa, It sounds like you've thought your plan out very well. Stick with what you have and add the following item.

When you are warm (so maybe after gymnastics training) run 2-4 65 feet sprints.  This will help you with your 65 feet sprint time. It will also help you with your 1.5 mile time if you don't let yourself have more than 20 seconds rest between each sprint. The nice thing about this addition is it should only take 1-2 minutes to complete. Plus, since it is so short it shouldn't affect your shin splints or knee pain too much.

Where do you feel your shin splint pain? Is it on the inside or outside or both sides of your shins?

Try performing this clamshell exercise (http://www.youtube.com/watch?v=CiqvDV8pzRk) once per day and perform it till it is reasonably difficult. Test a little running after a week of this and see if your knee pain is any better.