Englewood-based Greg Roskopf has spent decades treating some of professional sports’ most celebrated athletes, including Peyton Manning, using his Muscle Activation Techniques (MAT), a training methodology designed to reduce injury and pain. It’s been his partnership with golfer Bryson DeChambeau, however, that has garnered the most attention—and for good reason. DeChambeau’s massive physique has him smashing golf balls farther than even Tiger Woods ever imagined, and the revolutionary strategy helped him capture the 2020 U.S. Open.

Before DeChambeau attempts to defend that title this week at Torrey Pines Golf Course in San Diego, we spoke with Roskopf about how he helped the golfer reach his swing goals, the MAT method, and DeChambeau’s growing feud with Brooks Koepka.

5280: When the PGA Tour came back from its suspension of play due to COVID-19 in 2020, the joke was that Bryson DeChambeau looked like he had spent his off time eating a linebacker. That said, he’s not the first golfer to bulk up—look at Tiger Woods and Brooks Koepka. What’s different about how you train DeChambeau?
Greg Roskopf: What I’ve done with him from a weight-training standpoint—he’ll come out here for two days at a time for two hours a day—I overload his system through weight training so the muscle communication breaks down and shows up as weak. Then, in a controlled setting, I fix what I break. It’s like a vaccination.

Can you give us an example?
When we started, he could do 90 pounds of trunk rotation for five reps. Five reps was an overload on his system. I then put him back together so he can do 90 pounds again and it doesn’t overload his system. It’s basically getting to the tissue growth and repair phase immediately. That day we did 90 pounds, then we went up to 110 pounds, then we shut him down and taught his body how to tolerate 110 pounds.

By the time we were done, in one day, he was doing 150 pounds for five repetitions. Now he’s doing like 220 pounds on that movement.

So you’re basically maxing him out and fixing him so he can come back and max it out again? You’re hyper charging muscle development?
I’ve worked with pro athletes forever. Most of the time people get to me because they are injured. Well, with Bryson, once we had everything fixed where he was no longer broken from a neuromuscular standpoint, then we said, Well, let’s challenge his body, break him down, and fix him in a controlled environment and then he can continue to get stronger and produce more force.

Can you explain what MAT is?
I see guys on the tour, you probably know who (Editor’s note: Brooks Koepka does this), lying on the ground getting stretched out by his trainer. That’s the last thing you want to do when somebody is in pain, because the body’s tightening up as a protective mechanism. Instead, I learned how to evaluate range of motion. Because of all the specialists I learned from, I find wherever there is a limitation in range of motion that correlates with muscle weaknesses. So, a range of motion assessment is the first step in MAT, then we manually identify which muscles related to that movement are weak, and through hands-on stimulation—I wouldn’t call it a massage; it is a very specific stimulatory effect—we stimulate the muscle.

Over the past year, what has been the coolest thing you’ve seen DeChambeau do?
When he hit it over the water on that par-5 (Editor’s note: in March 2021, DeChambeau hit a 377-yard drive that nearly reached the green of a par-5 at the Arnold Palmer Invitational). I mean, that’s not normal golf.

The traditional thinking was that to win a U.S. Open, a golfer had to hit fairways because the rough was too penal. DeChambeau proved that wrong last year by using his strength to muscle balls out of the long grass. How does he feel about his chances at this year’s U.S. Open at Torrey Pines?
I did talk to him last week and asked him how the course was going to play for him, and he goes, It’s like last year. If I’m in the rough, I’m just going to force it out of there.

Beyond bulking up, DeChambeau’s focus on science has earned him the nickname “the Mad Scientist.” What’s he like to work with?
I’ve trained 2,000 people across the country in this technique, and Bryson has come in with questions, really inquisitive questions, that forced me to look at things in a way that I may not have looked at otherwise. In the same way that he’s experimenting with putting and hitting the ball with different drivers, he works through everything to determine, Is this a better answer?

What do you think about DeChambeau’s rivalry with Koepka?
I don’t know a lot about the underlying relationship. But Brooks was the guy that was known for working out and Bryson all of a sudden snuck into that same deal—they’re both being looked at as the workout guy or whatever and that brings competitiveness. I don’t know. I mean, I don’t get caught in that type of drama. But it’s fun to watch.

The interview has been edited for clarity.