Sudden starts (echarse a / romper a)

Sudden starts with "echarse a"

To describe an action that begins abruptly or unexpectedly, use the reflexive verb echarse followed by a and an infinitive.

This structure is highly common for sudden bursts of movement (like running or shaking) and sudden changes in emotion.

The jockey arrives at the racetrack and suddenly starts crying.
El jinete llega al hipódromo y se echa a llorar.
The frantic horse sees the whip and suddenly starts running.
El caballo frenético ve el látigo y se echa a correr.
If you lose the bet, you will suddenly start shaking.
Como pierdas la apuesta, te echarás a temblar.

Breaking into action with "romper a"

Similarly, you can use the verb romper (literally "to break") followed by a and an infinitive.

Just like "breaking into a sweat" or "breaking into applause" in English, romper a is used for actions that start suddenly, intensely, or involuntarily.

It is two o'clock and the frantic horses break into a gallop.
Son las dos y los caballos frenéticos rompen a galopar.
The prize is for the jockey and the audience in the stands breaks into applause.
El premio es para el jinete y el público en la grada rompe a aplaudir.
He gallops in order to win and breaks into a sweat.
Él galopa para ganar y rompe a sudar.
He stops the stopwatch and breaks into laughter because of the bet.
Él para el cronómetro y rompe a reír por la apuesta.