Yoo Hyun-jo overcomes 19-hour jet lag to fire 11 birdies and take lead

Yoo Hyun-jo surged to the top of the leaderboard at the KLPGA Tour HJ Shipbuilding & Construction·Dongbu Championship — purse 1 billion won ($747,000) — firing 11 birdies despite the fatigue of a long-haul flight and a 19-hour time difference.

Playing the second round Friday at A-One Country Club (par 72) in Yangsan, South Gyeongsang Province, under a modified Stableford format, Yoo carded 11 birdies with no bogeys to earn 22 points on the day. Her two-round total of 34 points put her one point ahead of Han A-reum (33 points) in second place.

The modified Stableford format differs from stroke play by awarding bonus points for aggressive scoring: an albatross earns 8 points, an eagle 5, a birdie 2, a par 0, a bogey minus-1 and a double bogey or worse minus-3.

What made Yoo's round all the more remarkable was that she had competed at the LPGA Tour's Lotte Championship in Hawaii last week before flying straight to South Korea. The time difference between Hawaii and Korea is 19 hours — Hawaii runs 19 hours behind Korea — meaning the return trip crosses the international date line and effectively flips day and night. That disorientation is compounded by the fatigue of an eight-to-nine-hour transoceanic flight.

From a sports-physiology standpoint, a 19-hour time shift completely disrupts the body's circadian rhythm. The reversal of melatonin secretion and core body temperature cycles maximizes sleep disturbance and daytime fatigue, slowing neural reaction times and delaying muscle recovery.

Yoo showed no sign of it. She reeled off five consecutive birdies on holes 1 through 5 and added three more in a row on holes 13 through 15, putting on a birdie parade throughout the round.

"I was still waking up at 4 a.m. today, so the jet lag hasn't fully worn off," Yoo said after her round. "But seeing the score I posted, I'm starting to think physical condition doesn't necessarily dictate performance. Strangely, I've actually played well before when I wasn't feeling my best — even my first win came when I had a slight crick in my neck."

Han A-reum, a second-year tour player still seeking her first victory on the regular tour, pulled off a surprise by claiming sole second place with a two-day total of 17 birdies against just one bogey.

"It was my first time playing in the final group, so I was very nervous," Han said. "I tried to stay calm and just focus on the moment without getting greedy. I'm happy that mindset helped me post a better score than the day before."

Kim Min-sun 7, who has two wins this season, carded eight birdies with no bogeys for 16 points on the day. Her two-round total of 31 points placed her in sole third, three points off the lead heading into the third round.

Defending champion Kim Min-sol made seven birdies but dropped shots with one bogey and one double bogey, adding only 10 points. She sits in sole eighth place at 25 points. Her rival Seo Gyo-rim managed just one point on the opening day and eight on Friday, missing the cut.