Bryson on a high at Mexico's altitude

MEXICO CITY • Physics major Bryson DeChambeau was smiling after solving the high-altitude puzzle, and he was giddy with joy after charging into a one-stroke lead at the halfway stage of the WGC-Mexico Championship on Friday.

The American put on a putting clinic as he made seven birdies in an eight-hole stretch en route to an eight-under 63 at Mexico City's Club de Golf Chapultepec, which sits more than 2,300m above sea level.

The 26-year-old rolled in 143 feet of putts and, at 11-under 131, he is one stroke ahead of South African Erik van Rooyen, who matched the course record of 62 on his 30th birthday, and American Patrick Reed (63).

Japan's Hideki Matsuyama (64) and American Justin Thomas (66) trailed by two strokes, while Northern Irishman Rory McIlroy (69) fell three behind after a frustrating afternoon.

"When you have days like that you can't help but smile out there," said a beefed-up DeChambeau, who has added about 14kg of rippling muscle over the past year in an effort to increase his power.

"Making those putts the way I did, striking the ball like I did, it was surely a joy out there."

It was his silky putting touch that was most responsible for his sizzling score, not least the 45-footer that he sank at his 16th hole, the par-three seventh.

"I just threw my hands up in the air. I mean, c'mon," said the five-time PGA Tour winner, who has also won on the European Tour. "The confidence has got to be high and it is high. Everything's going pretty well, firing on all cylinders."

The same could be said for van Rooyen, who has chipped in three times already, twice on Thursday and once on Friday.

"When you shoot nine under everything's going well," he said.

"What a way to kick off the 30s."

Reed matched van Rooyen's nine birdies, though the former Masters champion also added a bogey.

"The putter was working," said Reed, as happy with his green-reading as his stroke. "What you see is not always what you get here."

Matsuyama might have enjoyed a share of the halfway lead but for two late bogeys, while Thomas could not build on a six-under stretch over five holes from his sixth.

Overnight leader McIlroy endured a miserable day on the greens, at least until he sank a couple of birdies at the 16th and 17th holes. He also was poor on the par-fives, parring all three.

"I made a couple of nice putts coming in. I guess my patience was rewarded a little bit," he said.

The world No. 1 is seeking a Grand Slam of the elite World Golf Championships.

He won the WGC-HSBC Champions in Shanghai in November to go with the 2015 WGC Match Play and the 2014 WGC Invitational at Firestone titles.

AGENCE FRANCE-PRESSE, REUTERS