Why do sprinters lean forward during the start?

In sprinting, the start phase is critical for generating maximum acceleration. When a sprinter leans forward from the blocks, they shift their centre of gravity ahead of their base of support. This creates a controlled forward imbalance that the body can only correct by driving the legs powerfully forward and downward against the ground.

According to Newton's Third Law, the ground exerts an equal and opposite reaction force on the sprinter. Because the body is angled forward, this reaction force has a large horizontal component, propelling the sprinter forward rather than upward. The forward lean therefore maximises the horizontal force produced with each stride during the acceleration phase.

The other options do not accurately describe the purpose of the forward lean. Looking at the finish line is irrelevant at the start. The lean actually makes balancing harder, not easier, which is precisely the point: the instability forces the body to drive forward. While a forward lean can reduce frontal area and therefore air resistance to some extent, this effect is minimal at the low speeds of the starting phase and is not the primary reason for the technique.