TOKYO — The hottest athletes at the entire Tokyo Olympics may be the goalies in field hockey.

Consider the conditions during Tuesday’s semifinal between Belgium and India: a heat index of 100 degrees, an artificial turf field, little to no cloud cover or wind, and a 10:30 a.m. start. Woof.

Now listen to what Belgium’s goalkeeper Vincent Vanasch was wearing during the 5-2 win at Oi Hockey Stadium: a helmet, a black long-sleeved jersey, shorts, and pads over his hands, shoulders, chest, knees, shins and feet — helpful with a rocketing ball but not for Tokyo summers.

“Inside it feels like 50 degrees,” said Vanasch, 33. From Celsius, that translates to roughly a million degrees Fahrenheit. (Actually 122.) He continued, “But you just cope with that.”

The many things done by the second-ranked Belgian team to cope with the Tokyo heat have it one win away from its first Olympic gold. And it all began in what is essentially a heat chamber at a university back home.

Mick Beunen, a former Belgian national player who has overseen the team’s training since 2010, studied physical education and training science at Katholieke Universiteit Leuven. There he met Peter Hespel, a professor of exercise physiology and sports nutrition.

Beunen, 49, had previously sent players to the university’s Athletic Performance Center, led by Hespel, for evaluations. But in planning for Tokyo’s oppressive humidity and heat, he sent all potential national team players last year.

In an “environmental facility,” Hespel said in an email, they can simulate conditions between 12 and 40 degrees Celsius (roughly 54 to 104 degrees Fahrenheit) and altitudes from sea level to about 7,000 meters. They set the conditions to 35 degrees Celsius (95 degrees Fahrenheit) and 70 percent relative humidity, a typical summer day in Tokyo, and had players exercise to mimic the strain of a game.

Experts measured sweat rate, sweat composition, body core and skin temperatures, and players’ perceptions of fatigue and overheating, Hespel said. From that, he said, they created a ranking of all players based on their risk of heat-related fatigue, illness or injury, and trainers created “heat acclimation plans” specific to each player.

The data, Beunen said, was not used to weed out players but rather to identify which ones were most affected by the heat and to help them improve.

“We just want to be the fittest team, so there’s been a lot of work done over the years to make everybody better,” he said in a phone interview.

Belgium’s team trainers have also amassed useful data in other ways. They check players’ temperatures before, during and after practice. And since the start of Beunen’s tenure, he said, the team has used wearable technology to measure players’ heart rates, sprint speeds, distances covered and other metrics that help coaches and trainers identify who is at a higher risk of injury or who is getting fatigued.

Beunen said the data, accessible in real time on a smartphone or tablet, allows him to help head coach Shane McLeod fine-tune his substitution plan during games.

“If you see the figures during hot conditions, then you can adapt to that and you can help the players to overcome it,” Beunen said.

The Belgian team, used to much cooler summers back home, also came to Japan early and trained in Hiroshima for a week to get acclimated.

At the Olympics, Beunen said, players drink what he called slurries — essentially electrolyte-rich drinks mixed with crushed ice — during games and before they start running around, to lower body temperatures even slightly. Beyond that, Vanasch said, he has been drinking nothing but water nonstop from morning to evening.

Luckily he doesn’t have to race around the field like his teammates, but Vanasch, the goalkeeper, has to carry a lot of gear, so he wears a cooling vest under it all and also applies a cooling spray. During Tuesday’s game, he changed into clean gear at halftime.

Belgium’s training really shined late in that game. Tied at 2 with fifth-ranked India through three quarters, Belgium convincingly pulled ahead in the final frame despite playing in its seventh game in 11 days.

“We knew the conditions would be difficult,” said forward Cedric Charlier, 33, while coated in sweat after the victory. “We trained harder, did lots of double training sessions, and are ready to go really deep into what we have inside.”

Thursday brings the stiffest test: Belgium, which won silver at the 2016 Olympics, faces top-ranked Australia. Beunen said the team’s success so far was proof that its preparations for the Olympics and heat were working. But even though Belgian players have competed in warm places like Australia and India, he said, the Tokyo Games were the “hardest tournament that they ever played.”

Thankfully, Vanasch said, the final game is at night in Tokyo, away from the punishing daytime sun. “We are ready to push another gear,” he said.