It found 86.2% of respondents ‌suffered significant physical strain while playing in the heat, among 536 players from the K League and WK League surveyed during a summer when pitch temperatures exceeded 40 degrees Celsius (104 degrees ​F).

Nearly two-thirds (64.7%) complained of dizziness during matches or training, while 56.6% ​had severe dehydration, with 13% having lapses in consciousness.

"The fact that ⁠over 70 players experienced dizziness, dehydration, and even temporary loss of consciousness is ​a glaring red flag," KPFA President Lee Keun-ho, a former national team player, said ​in a statement.

The union called on the Korea Football Association (KFA), K League and WK League to introduce mandatory heat protocols, saying the current safeguards do not sufficiently protect players.

Reuters has contacted ​the KFA for comment.

Almost half the respondents said they were dissatisfied with the ​current cooling-break system that usually gives players a break of just over three minutes once ‌temperatures reach ⁠a specified threshold.

Nearly 90% supported changes to existing match operations during extreme heat. More than half favoured later kick-off times, while others backed postponing or cancelling matches when heat advisories are in effect.

The union said women players often face additional ​challenges, with some matches ​scheduled during the ⁠hottest part of the day on artificial surfaces and at venues without adequate air-conditioned changing facilities.

"Playing under the scorching sun ​on artificial turf that traps and radiates heat is essentially ​forcing athletes ⁠into a furnace," KPFA Women's President Ji So-yun said.

"Just as professional baseball proactively cancels games for the heat, football needs to stop mechanically following a rigid schedule and ⁠actually ​prioritise player health and safety."

The KPFA said the ​findings should also prompt a broader discussion on South Korea's football calendar, with some players supporting a ​switch to an autumn-spring schedule.