Answer:
The sports in ancient Rome included things such as wrestling and boxing and that tells us a lot because they were some of the most warlike people and I think that wrestling and boxing helped make them competitive and want to win so that when they went into battle they would go with the confidence of a winner because in there mind they had already played out the fight and won it.
Not only that but it kept them in great physical strength and made them super athletic so that when they went into battle they could outlast their enemies.
Why do I think that was well I just listed the reasons above but here are the main points of it.
It made them athletic.
It made them stronger than their opponents.
They had the courage and mindset to win any battle.
And they had confidence which is in my opinion one the best to have because if you don't think your gonna win then you won't fight like you want to win.