The 30-year-old from London, Ont., raced to a personal best 12.65 seconds in the 100-metre hurdles, good enough for second overall at behind British star Jessica Ennis.
But Zelinka quickly tumbled to 19th place after finishing tied for 10th in her high jump group B — and one of the lowest scores of the two groups. The result is disastrous for Zelinka, who now has a long way to battle back into medal contention.
Brianne Thiesen of Humboldt, Sask., meanwhile is eighth overall after finishing 11th in her high jump group A and sixth in the hurdles.
Next up for Zelinka and Thiesen is the shot put and 200 metres.
The heptathlon concludes Saturday with the long jump, javelin throw and 800-metre race.
Introduced at the starting line, Ennis got a massive round of applause from the fans, who carried thousands of British flags, some with the words “Go Jess” stamped down the middle.
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