Bryson DeChambeau has revealed that his quest for more speed led him to "see a tunnel" and that he came "very close" to blacking out, due to the intensity of his speed training during golf's off-season.
The reigning US Open champion has been working closely with World Long Drive champion Kyle Berkshire as he looks to increase his swing speed average on the PGA Tour this year.
DeChambeau's physical change has been one of the most talked about topics over the past year and after winning his first major title at Winged Foot, the 27-year-old vowed to work on hitting the ball even further.
Speaking to Sky Sports after shooting a 4-under par opening round at the Sentry Tournament of Champions on Thursday, DeChambeau admitted that pushing his body to the limit has taken its toll at times.
"There were times where I was seeing a tunnel and I had to stop," DeChambeau said. "I mean, you just have to stop. That's about when you stop. There's a lot to it. I did not blackout, but I came very close, just like he [Kyle Berkshire] did.
"He was a 117, 118 mile-per-hour golf swing in college and he has gone all the way up to 150 now. He's obviously done the right things and he's done it completely naturally and without anything and I wanted to learn from him.
"I took it upon myself to ask him some questions and we spent a few days together and we've been talking back and forth. He's been giving me tips on what to do and how to keep the speed out here on Tour.
"I spent my off-season swinging my butt off as hard as I can. There were times where everything hurt in my body and it was breaking down my whole nervous system and rebuilding it back up. I like doing that. It's fun testing the limits of my body and seeing what I can and can't do."
DeChambeau recently reached 211mph ball speed whilst warming up for this week's event and had to apologise to Hideki Matsuyama for the loud grunting noises coming from his practice area.
Averaging between 205 to 210mph is DeChambeau's goal and once he is hitting those numbers on the PGA Tour, he will be satisfied with where he is at.
"I'm going to keep getting speed until I try and get around 205 to 210, in that range," DeChambeau added. "Once I achieve those speeds and I'm comfortable with that, not trying to swing my butt off, it just happens naturally, that's when I'll probably stop and go down the chipping rabbit hole and try and understand my chipping and wedging a lot bit better.
"I still feel like I'm over a year, to year and a half out from it. That's what Kyle projected for me. He's like, I think you can get there within a year, year and a half if you keep pushing the boundaries.
"Now, the difference is I've got to keep playing golf, right? I've got to keep trying to play my best. I've got to putt, got to chip, and all that, whereas he had time to just go at it with the driver, and he made a gain of five miles an hour in a year.
"I think I can get a baseline average of probably four to five, so it's probably going to be a year and a half, hopefully, if I keep doing the right things and I'm healthy."