What signal may indicate that a referee considers a player's jumping action as reckless?

The indication that a referee considers a player's jumping action as reckless can often be represented by showing a yellow card. A yellow card serves as a caution and signals to the player that their action was deemed inappropriate or unsportsmanlike but did not warrant immediate dismissal from the game. In situations where a player's jumping is perceived as careless or endangering the safety of themselves or others, the referee may opt to issue a yellow card to convey this message effectively.

While a whistle blow can signal a foul, it doesn't specifically indicate the severity of the action. A red card signifies a more serious infraction that results in expulsion from the match, while hand signals provide visual communication but do not alone convey the specific nature of the infraction. Hence, the yellow card is the most appropriate form of signaling that a player's jumping action is being considered reckless.