Negative weight training?

am I supposed to do positive weight training sets first to warm up and on my last set do negative training. And how long should I wait before training again? An example would be nice.

https://twitter.com/JayBilas/status/428272011660361728

There's no set rule on negative's. But they are extremely stressful and should be used sparingly. Most of the time, the positive-pause-negative reps will get the job done. Negatives can help you get beyond a plateau, should you have one.

You should wait at least 3 days to one week before training again.