Vietnam U23s defeated their Malaysian counterparts 1-0 in extra time in Thursday’s Southeast Asian Games semifinal thanks to the only goal scored by Tien Linh in the 111th minute.

The moment the striker took his jersey off to celebrate the goal in an exploding atmosphere, many football supporters across Vietnam, though overwhelmed with joy, noticed that the player was wearing an under-shirt vest that, to some, resembles a sports bra.

The vest, which is strange to many people, then started a widespread online discussion, where curious netizens questioned what the item exactly is.

For people who are football fans, they might already have the answer.

The vest that footballers wear under their jerseys, and sometimes over them during training, is a piece of equipment which holds a GPS tracking device.

Striker Nguyen Tien Linh takes his jersey off, revealing a GPS-tracking vest, after scoring the winner for Vietnam during the semifinal against Malaysia at the 31st Southeast Asian Games at Viet Tri Stadium in Phu Tho Province, Vietnam, May 19, 2022. Photo: Nam Tran / Tuoi Tre

Striker Nguyen Tien Linh takes his jersey off, revealing a GPS-tracking vest, after scoring the winner for Vietnam during the semifinal against Malaysia at the 31st Southeast Asian Games at Viet Tri Stadium in Phu Tho Province, Vietnam, May 19, 2022. Photo: Nam Tran / Tuoi Tre

Information and statistical data about the player’s movements are recorded by the device and then fed through to a software dashboard which can be accessed on a laptop, tablet or smart watch.

Most of the major football teams are using these statistics, with clubs and international sides sharing the data, according to international association football news website Goal.com.

Football teams use the GPS tracking data to optimize a player’s physical performance and to minimize the risk of injury by controlling the level of strain they are placed under.

Dedicated sports scientists and coaches use the statistics to analyze how the level of training affects each individual, so they can alter a training program to suit their particular needs.

Therefore, Tien Linh’s wearing the GPS-tracking vest during Thursday’s semifinal was actually no unusual occurrence, except that taking his jersey off to celebrate his goal earned him a yellow card.

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