Rory McIlroy shrugged off concerns about his fitness regime Wednesday as he prepared to tee off on American soil for the first time this year at the Northern Trust Open.

The 26-year-old Northern Irishman arrived in California to be greeted by headlines concerning his use of heavy weights following remarks by veteran US golfer Brandel Chamblee earlier this week.

Chamblee had cautiously questioned whether McIlroy risked facing the sort of back problems that have plagued former world number one Tiger Woods by using weights to strengthen his back.

McIlroy responded to Chamblee's remarks by posting a video of himself on Twitter performing a set of squats.

The world number three said his game had improved by using weights.

"I definitely feel like the more I got into exercise and fitness and everything, the better my game became," McIlroy said.

Asked if he had performed squats before his practice round at the Riviera Country Club on Wednesday, McIlroy quipped: "Not yet, I'm planning to though - maybe with Brandel on my back."

McIlroy said he had begun using weights regularly in 2010 as he sought to recover from an injury - and had soon felt the benefits.

"I think from the start of 2011, the direct correlation between leading a healthier lifestyle and my performance on the course was the same," McIlroy said.

- 'Trying to be strong' -

"Obviously I'm trying to be strong, but the whole reason I started this is because I was injured.

"The golf swing is way worse for your back than anything I do in the gym. So I'm trying to make my back as strong as I possibly can so that when I come out here and swing a golf club I'm robust enough to take that."

McIlroy is playing the Los Angeles event for the first time as he attempts to reclaim his world number one ranking from Jordan Spieth ahead of the year's first Major at Augusta.

McIlroy would complete a career Grand Slam with victory at the Masters, where he had a four-shot lead heading into the final round in 2011 before a spectacular collapse.

McIlroy said his appearance at the Riviera Country Club in Pacific Palisades was linked to his preparations for Augusta.

"I think the Masters at this point of the year is on pretty much everyone's mind," McIlroy said.

"This is the start of the road to the Masters and I think everyone's, if not thinking about it directly, it's definitely in the back of their minds.

"You're building up to it. You've got some great events in between now and then, but obviously I'd love my game to be in peak shape for Augusta in April."

McIlroy will face a strong field with the main threat coming from Spieth, who arrives from a dominant 2015 already with a win under his belt this season following victory at the Hyundai Tournament of Champions last month.

"These tournaments that we've got coming up, we've got some of the strongest fields of the year, and you know, it's great," McIlroy said.

"I feel like when I come back to the States, the golf tournaments that I do play over here are the strongest fields. I like that. I like the challenge. I like to go up against all those guys."
Source: AFP