Temperatures peaked at 44.4 degrees celsius earlier in the day, but had eased to 34.3 that evening when training began.

During the session, Torran began to struggle and eventually lay down.

Trainers at first thought Torran was fatigued, but after he collapsed a second time they realised something was wrong and called an ambulance.

Coroner Barry King found the trainers had acted responsibly in determining to go ahead with the training, but did not have the first-aid knowledge to readily recognise or treat Torran's heat stroke symptoms.

"It is possible that the deceased would have survived had they been so equipped," he said.

"The evidence established that the training provided to sports trainers and other first responder should be altered to incorporate recent approaches to treating heat-related illness.

"Heat stroke is a rare condition, but the fact that it is potentially fatal means that first responders need to be alert to it and to be able to deal with it appropriately."

As a result of Torran's death, changes have been made to the training provided to first responders treating people affected by heatstroke, which Mr King said may help the teenager's family "gain some solace for their terrible loss".

During the coronial inquest, held in October last year, it was revealed Torran and his teammates were advised via Facebook before training to drink plenty of water beforehand.

Edward Easter, who was then an NRL game development officer, but quit sports training after Torran's death, arrived early to check conditions and ensure all that was needed was there, including water and ice.

He went through the NRL heat guidelines checklist, which assesses 10 factors, and landed on a score of 57.

Training can go ahead for scores of between 56 and 65, but precautions are recommended including more drink breaks.

Mr Easter also started off the shorter session with a longer than usual talk to the teenagers to give more time for conditions to cool.

He told the inquest Torran, a determined boy, was pushing himself hard and performing well at first.

But he began to struggle, slowed in pace then stopped completely and lay down.

He was out of breath but could communicate, saying he was exhausted, and was encouraged to get up to stop lactic acid building up in his bloodstream, coach Luke Young said.

"I just assumed he was conceding to the fatigue and tried to get him to push through," Mr Young said.

Mr Easter said he also thought Torran was just tired at that point.

After he lay down a second time, the teen began to mumble, then closed his eyes and stopped talking.

His breathing and pulse rates, which had settled, came back up again, alarming Mr Easter as these were signs of heatstroke, not just heat exhaustion.

"I hadn't seen that before," he said. "I was a bit surprised by the way it went."

Torran was placed in the recovery position and attempts were made to cool him with ice. But his condition deteriorated and an ambulance was called, with paramedics recording his temperature as 39.2C.

Mr Young said he was confident all that could have been done to help the boy had been done.

"I acknowledge it was hot ... but I don't believe it was the hottest day ... to the point where it felt unsafe," he said. "It just didn't strike me as an extremely hot day, given Perth summer."

-with AAP