Olympic 500 metres champions Nao Kodaira of Japan and Norway's Håvard Lorentzen hold the overall advantage in the women's and men's events respectively after the opening day of action at the World Sprint Speed Skating Championships in Changchun.
Kodaira clocked a track record of 37.23sec to win the first 500m race of the event at the Jilin Provincial Speed Skating Rink.
The Japanese star was quicker than Angelina Golikova, who competed at Pyeongchang 2018 as part of the Olympic Athletes from Russia team, and recently-crowned Olympic 1,000m champion Jorien ter Mors of The Netherlands.
Kodaira then made a promising start to the 1,000m event but eventually finished fourth.
Ter Mors secured victory in a track record of 1min 14.62sec, breaking the mark set by American Brittany Bowe earlier on.
Bowe was second and third place was claimed by Ter Mors' compatriot Marrit Leenstra.
Kodaira has the lead going into the second day of the event in the Chinese city, where the second races in the 500m and 1,000m distances will be contested.
The 31-year-old is 0.21 seconds ahead of Ter Mors, while Bowe occupies third, 0.62 adrift of Kodaira.
Another track record fell in the men's 500m as Pyeongchang 2018 gold medallist Lorentzen clocked 34.89.
Japan’s Daichi Yamanaka came second and Tingyu Gao of China finished third.
Dutchman Kjeld Nuis showed the form which saw him clinch the 1,000m title at the Winter Olympics last month as he prevailed in a time of 1:08.97 to break the track record.
Lorentzen did enough for second, while defending world sprint champion Kai Verbij of The Netherlands was third.
Lorentzen, Norway's first Olympic speed skating gold medallist for two decades, has a 0.15 seconds advantage over Verbij heading into the final day, while Nuis remains in contention in third.