NEW YORK (AFP) - A bulked-up Bryson DeChambeau says he plans to pack on even more muscle as he prepares to follow up his US Open triumph with an assault on the Masters.

The 27-year-old American, who used protein shakes and exercise to build muscle mass over the three-month coronavirus pandemic layoff, captured his first Major title at Winged Foot, winning the US Open by six strokes on Sunday (Sept 20).

He shrugged off potential punishment of deep rough and focused on driving distance, his 325 yards off the tee a record for US Open winners. He found only 23 fairways over four days but skilled wedges and strong putting powered him to victory.

"I was hitting it (like) a normal average tour player a year ago," said DeChambeau. "And then I all of a sudden got a lot stronger, worked out every day, been working out every day, and all of a sudden - not because of clubs, but because of me - I was able to gain 20, 25 yards."

FITNESS THE DIFFERENCE

Technology for clubs and balls has produced greater distances but DeChambeau says his fitness, being a disciple of the example Tiger Woods set in winning the 1997 Masters, has been the difference maker.

"We're constantly trying to just hit it as hard as we possibly can," he said. "I don't think that science is that big of a role in the market. I would say it's more of athleticism playing probably a bigger role for that for sure."

R&A chief executive Martin Slumbers mentioned DeChambeau in July when talking about how keeping golf's balance of skill and technology might require changes.

"It's tough to rein in athleticism," DeChambeau said. "We're always going to be trying to get fitter, stronger, more athletic. Tiger inspired this whole generation to do this and we're going to keep going after it. I don't think it's going to stop.

"Will they rein it back? I'm sure something might happen. But I don't know what it will be. I just know that length is always going to be an advantage."

DeChambeau weighs 235 pounds (106.5kg) but hopes to be heavier before the rescheduled Masters, which tees off in seven weeks time in early November.

"I think I can get to 245. It's going to be a lot of working out," he said. "It's just I've gained so much so quickly in a year... eventually there comes a point where you can't gain much more but I still feel like I can get up there if I work hard enough."

But he is watching his health as he maximises his mass.

"I am talking to a doctor," he said. "I got all my blood sample tests, everything back a couple weeks ago. Everything is fine so far.

"We're going to keep monitoring it and making sure I'm as healthy as possible because I do want to live for a long time." TAKING ADVANTAGE OF COVID LAYOFF

Two-time Major winner Zach Johnson says DeChambeau had size to build on.

"He was really big to begin with," Johnson said. "I could see it with his neck, shoulders and back. It's not like I'm overly checking him out, but he looked heavier.

"He always hit it far. Given how he works and how he approaches his body, it's a way to play and it's not wrong at all. It's very different but also very effective."

DeChambeau saw the virus shutdown as a chance to work on his body.

"I felt like it was an opportunity to do something great - change my lifestyle, make it healthier, make it better," he said. "That's what I think I did this year and I'm going to keep trying to do that."