Sitting with a first day total of 4350, Mayer is comfortably in the lead at the halfway mark, sitting nearly 300 points ahead of second-placed compatriot, Makenson Gletty.

Very little separates second from eighth, with Gletty on 4064 and eighth-placed team-mate Axel Hubert on 4010.

In between, also in the mix for the podium, are Simone Cairoli of Italy, Estonia's Taavi Tsernjavski, France's Ruben Gado, Estonia's Risto Lillemets and Belgium's Benjamin Hougardy.

Despite being dominant in the overall standings, Mayer only won two events today - the 100 metres in a time of 10.68sec; and the shot put with a mark of 16.20 metres.

On his other events, Mayer was second in the 400m and long jump, as well as fifth in the high jump.

Gado clocked the best time in the 400m, finishing in 48.34; while Cairoli, Lillemets, Gletty and France's Basile Rolnin all cleared 2.00m - the best height in the high jump.

Hubert pipped Mayer by a centimetre in the long jump with a best of 7.41m.

All decathletes are chasing the mark of 8350, with Mayer needing just 4000 points on day two to qualify for the Tokyo 2020 Olympics.

In the women's heptathlon, that qualifying mark is 6420 points; and the closest to that so far is France's Cassandre Aguessy Thomas, currently in the lead with a total of 3641.

Similarly to the men's competition, only 56 points separates second from sixth. 

Ukraine's Ganna Kasyanova sits on a total of 3563 ahead of Colombia's Evelis Aguilar and Annaelle Nyabeu Djaba of France; with all three covered by less than 20 points.

Close behind are Estonia's Mari Klaup and Austria's Sarah Lagger in fifth and sixth.

Aguessy Thomas won none of her four events today, but consistency paid off.

Tomorrow, she has only three events to reach the qualification threshold for Tokyo 2020.

Aguilar was a dominant winner in the 200m to open the day in 24.02sec, while Nyabeu Djapa got the better of Aguessy Thomas to win the 100m hurdles.

Aguessy Thomas finished second again, this time in the high jump behind Lagger, who posted a best mark of 1.77m.

Aguilar won her second event of the day - while struggling in the hurdles and the high jump - throwing a best mark of 14.14m in the shot put to move her into third.