Training alone or with a partner, which is best?

I would be interested to learn how many people train alone or train with a partner when looking to get fitter. I am going to restart my fitness campaign and after trying a few months ago alone I think I may benefit from having a friendly face. What do other people think of this issue?

 

To get the best out of fitness training there needs to be some kind of competitive edge which is best achieved with a training buddy.