One of the youngest Major League Soccer referees trains in North Texas

A Dallas-based MLS referee shows how he trains like the players to keep matches on track.

Throughout the World Cup, all eyes have been on the players. But it's the referees who keep the matches on track.

NBC 5 spent the day with Dallas-based Major League Soccer referee Lorenzo Hernandez to see what it takes to officiate at the highest levels of the sport. From sprint workouts at a Cedar Hill middle school track to strength training inside MENT Fitness, Hernandez's full-time job is preparing to keep up with some of the world's best athletes.

"We gotta make sure we stay top tier in the physical realm so that we don't lose our mental state whenever we're in the game," Hernandez said.

Hernandez started playing soccer when he was just four years old and continued through college. He started officiating as a teenager to make extra money and later decided to pursue officiating full-time.

"I grew up playing since I was four," Hernandez said. "I stopped playing around college just to take officiating more seriously. If you're injured, you can't referee."

Hernandez and his brothers grew up watching their father referee, eventually following in his footsteps. After eight years of working his way through youth, amateur and professional matches, Hernandez is now one of only 30 senior match officials in Major League Soccer and the only one based in Dallas.

"You're really having to go all over the field, and your job is to make the decision as the head referee," he said.

When he's not traveling across the country to officiate MLS matches, Hernandez can usually be found training in Cedar Hill.

Some days he's running laps, sprinting, and working on conditioning at the track. Other days, he is attending group classes at MENT Fitness, focusing on strength, agility, and recovery.

"You have to sprint. You have to move laterally," Hernandez said.

His training closely mirrors that of the players he officiates. His workouts, meals, sleep, and recovery are all tracked through wearable technology to make sure he's physically and mentally prepared for every assignment.

The physical demands are only part of the job. Referees also carry a heavy mental load.

"In a game, I would say we're making hundreds and thousands of decisions," Hernandez said. "A lot of it is very dynamic, but when it comes to making the decision, it's trying to arrive so that you can be focused, composed."

His commitment to his role is forever etched in ink. Hernandez has a tattoo of a field and the words "Law 5" a nod to his responsibilities as a match official.

"Law 5 in the law book is where it describes what the referee does in the game," he said. "You're there to manage the game so that the game can flow, so it can be an enjoyable thing to watch. We want a safe game. We want to keep them injury-free if possible."

Professional referees are also expected to remain completely impartial.

"We're compared to judges, police officers. We have to be very impartial," Hernandez said.

That mindset even changes how he watches soccer. Hernandez says he doesn't watch matches as a fan. But with the World Cup taking place in North Texas, he found himself enjoying the tournament from a different perspective, soaking up the energy, and cultural exchange and celebrations.

He isn't calling any World Cup games, which means he's had about a month off to train. If he does in the future, he wouldn't be allowed to officiate games for teams from countries where he has personal ties, including the U.S. and Mexico. Which means this time, he had the rare opportunity to support a team without worrying about it impacting his credibility as a match official.

"As someone born in the U.S. with a family of Mexican descent, I can say, 'I'm supporting the United States, I'm supporting Mexico,' " Hernandez said.

Watching several of his colleagues officiate World Cup matches has only strengthened his own ambitions.

He's only in his second year as a tier one referee. But says he intends to keep training so he can continue living his dream for the next 20 years. His next goal is to become a FIFA referee and one day earn an assignment at the world's biggest tournament.

Hernandez says one of the biggest impacts of the World Cup has been seeing more people become interested in the sport and ask questions about the rules, officiating, and how the game is managed. He hopes that curiosity continues long after the tournament ends.

He also shared a few fun facts about what it takes to keep up.

Referees run an average of 6to 8 miles during a match and have every decision reviewed. Their performances are also graded to help determine future assignments.

He says they also wear fitness trackers and their bosses collect data to monitor workouts, recovery, sleep, and training load to help prevent injuries and prepare them for competition.