Depending on the situation, a head start may be inherent, obtained by special privilege, earned through one's accomplishments, or granted mercifully by an opponent.
But in some cases, a head start is an advantage that may be earned by one more of the competitors.
[1] In multiple-event or multiple-day competitions, such as the modern pentathlon, the final event may use a head start where the leader of the competition starts first over his opponents based on the time or points advantage.
This may be risky, as the pitcher could throw the ball to the respective infielder, and if the runner cannot get back before the ball arrives in the hands of the infielder, the runner may be picked off.
In such cases, the head start is usually earned by working harder or by using more efficient means of reaching that point.