While sprinter Usain Bolt led a barrage of superstar performances at the Bird's Nest stadium, scepticism was also not hard to find following allegations of widespread drug abuse by elite athletes.
Britain's Coe won a narrow vote to succeed 82-year-old Lamine Diack as president of world body the IAAF, and improving the besmirched image of athletics will be his top priority.
"We are more than a discussion about test tubes, blood and urine," Coe told reporters yesterday. "It is ostensibly a clean sport, we have our challenges... And no one would deny that."
Kenya finished top of the medals table, but they were also the only team to fail doping tests after two of their athletes were caught out by pre-competition controls.
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Bolt's brilliant sprint treble after overcoming injury came at the expense of twice-banned American Justin Gatlin -- one of four former doping offenders in the 100m final.
When the Netherlands' Dafne Schippers ran the fourth fastest 200m in history, adding gold to her 100m silver, she immediately had to deny using chemical enhancement.
- Flying down to Rio -
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Bolt's reign as world sprint king was under serious threat from Gatlin, who was on an unbeaten streak of 28 races and had led the way in the 100m and 200m this year.