Vegeta hears the news of an interdimensional warp whole from H.E.L.L. (I think its that) He knows that all of the enemies him and the others worked so hard to defeat are coming right back. He even encountered Saibamen the other day in the fields.
Vegeta says to himself
Vegeta- They are stronger then before, i have to watch myself even more now. I need to train.

Vegeta goes to Bulmas father's house, and goes in the training machine nearby the house. There he trains nonstop at 10x the gravity he usually trains at. He finds it impossible but knows he needs that kind of training.