There are sports players working in a sweat for their fellow players to win gold medals. They are sparring partners of the players who will compete in the Olympics. The players of individual sports such as judo, taekwondo, and boxing, absolutely need a partner for their training.
The sparring partners should have some level of competency enough to spar with the national team members and also have a spirit of sacrifice to support the players and follow them like a shadow. On top of that, they need to identify the characteristics of the opponents their players will fight against in the games to offer them the experience like the actual battles, and should be careful not to have them injured while sparring. Also, they encourage the players when they are exhausted and tired.
Sparring partners help their fellow players improve their skills, putting aside their own lives. But it is not just for the fellow players. They themselves also grow up together. In fact, many sparring partners have become skilled while taking on the role of training the players and won the medals at the next Olympics. Sacrificing yourself for the other person is not a loss but a plan for your growth.