Here is what I would do. start with a brisk 2 min jog as a warm up, then you will perform a sprint for as long as you can at maximal effort. If that is 15sec thats fine, if its 30 thats fine. take the rest of that minute and pace back down to your warm up pace. then repeat this up to 15 times max. I would suggest not going past 8 times before upping your sprint. meaning

5 thirty second intervals will be more effective then 10 fifteen sec intervals. Does that make sense? I want to make sure i'm clear.

once you've reach the point where you cant do another sprint, pace down to your warm up speed, and stay for 2min as a cool down.

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