Jang Ha-Na, who battled back problems in the first round which forced her to alter her swing, extended her lead after the second round of the LPGA Tour`s weather-hit Marathon Classic on Friday.
The South Korean Jang carded a four-under 67 to take a two-stroke clubhouse lead over Baek Kyu-Jung as play was suspended because of a lightning.
Jang, who is seeking her first win on the US LPGA Tour, was bothered by back pain in the opening round. Not only did she have to gingerly bend over and reach down to pick up her balls, but she also had to use one hand on her follow through instead of the usual two hands.
"It feels much better today than yesterday," said Jang, who had a one shot lead entering the second round and finished 36 holes at nine-under 133.
"Body is a little bit tight. But my swing is very good because it is just a one handed swing yesterday. No pressure on impact."
The start of the second round was delayed two and a half hours at the Highland Meadows Golf Club due to poor weather. With darkness drawing near, lightning flashed in the area and halted play briefly.
A total of 54 players still need to complete their second rounds Saturday morning.
Baek also shot a four-under 67 and is alone in second at seven-under 135.
China`s Feng Shanshan (67), Dewi Claire Schreefel (68) of the Netherlands and Australia`s Sarah Kemp (69) are one shot further back and tied for third at six-under.
"I`m happy that I actually finished the second round today so I have a lot more time to rest tomorrow and just get ready and be fresh for the weekend," Feng said.
Moriya Jutanugarn, of Thailand, Caroline Masson of Germany, and Americans Angela Stanford and Gerina Piller were at five under.
Jutanugarn tied for the low second-round score with a 66. Masson and Stanford have two holes left to play and Piller has three to go when the round is completed early Saturday.