Olympic champion Caster Semenya looked ominously comfortable in advancing to the women's 800 metres final at the World Athletics Championships on Friday but a host of challengers also looked impressive and should push the South African all the way.
Kenya's Margaret Wambui, bronze medallist at both the world indoors and Olympics previous year, won that heat, but Arzamasova's season's best of 2:01.92 was not fast enough to see her bag one of the faster loser places.
The South African, who had already taken a bronze medal in the 1500-meters, did not find things easy but proved far too strong down the back straight and became the eighth fastest woman in history with her new national record.
Semenya, however, maintained her languid stride a few metres back before closing the gap, easing past both on the final bend and running clear.
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Semenya, unbeaten over the two-lap distance for the last two years, added the global crown to the world title she won as a teenager in Berlin in 2009 and the Olympic victory she achieved in Rio last year, though her tally was expected to be lifted when Russian athlete Mariya Savinova's appeal against a doping ban was finalised later this year.
"I just want to keep winning", said the "That's all I'm concentrating on".
She came from behind and cruised to the finish line in the last 200m of the race.
"I pushed it 100 percent and I'm super-happy".