"Especially around links golf you have to be super patient. When it stays like this, bogey is sometimes not the worst thing that can happen to you.
"You've just got to focus. If you don't have a 100 per cent focus there, you're probably not going to hit a good shot. I just tried to stay pretty patient and positive."
After two consecutive strong tournaments, despite her last-round collapse at the Marathon Classic, Ko says she's playing with more confidence and looks forward to the rest of the week.
"I feel every tournament I play I'm getting more and more confident. To me confidence is such a big key … That's what I'm trying to continue to do."
Olson was the only player to shoot below 70 in what some said was a four-club wind on the famous links in eastern Scotland, her four-under 67 earning her a three-stroke lead.
"It was the best ball-striking day of my life," said Olson, who grew up hitting a low ball in strong winds in North Dakota, standing her in good stead for links play. "But I can't even describe how difficult it was out there."
Only two others in the 144-player field — Sophia Popov of Germany and Marina Alex of the United States — shot under par, both with rounds of 70.
"It was brutal," said Popov.
Danielle Kang would agree. The in-form player — and, at No 2, the highest-ranked competitor at Troon this week — finished eagle-birdie-birdie just to shoot 76 along with defending champion Hinako Shibuno of Japan.
Meanwhile, Danny Lee has started strongly at the PGA Tour's Northern Trust event in Massachusetts – the first tournament of the FedEx Cup playoffs. Lee shot a five-under 66 to sit in a tie for 12th, two shots off the lead. The top 70 players in the season-long FedEx Cup rankings move into the next tournament, with Lee's impressive start vaulting him from 53rd to 41st in the projected standings.
On the European Tour, Ryan Fox shot one-under to sit four back from the lead at the Wales Open. Fox was at three-under with five holes to play but a double bogey on the 14th hole dropped him back to a share of 13th.
Michael Campbell also struggled late in his round with three bogies in his last five holes dropping him to a tie for 56th at two-over.
- with AP