Rockstar Fit's Natalie Dau is preparing for perhaps her greatest challenge: completing a 100km race -- ultra-marathon -- in the heat and humidity of Singapore this October, having run no further than 30km previously. 

<p>Rockstar Fit's Natalie Dau is preparing for perhaps her greatest challenge: completing a 100km race -- ultra-marathon -- in the heat and humidity of Singapore this October, having run no further than 30km previously.&nbsp;</p>

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