If you mean that training is ongoing then both can be used, but "are" has more of a sense that the tournament is some way in the future (and training will continue up to that point), while "have been" has more of a sense that training is about to culminate in the event itself. "are" can also be used if they are training at this very moment, and "have been" if they have just finished a training sesssion.
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while "have been" has more of a sense that training is about to culminate in the event itself.
What do you mean by that? The training itself is going to take place during the event?