Dalilah Muhammad, the 2013 World Championships silver medalist, won the 100th medal for the US Olympic team at the Rio Olympics after finishing first in the women's 400-metre hurdles final in 53.13 seconds.Denmark's Sara Petterson took silver with a new national record of 53.55 seconds ahead of American Ashley Spencer (53.72) while Czech Republic's Zuzanna Hejnova, two-time world champion and the 2012 London silver medalist, finished off the podium with 53.92 seconds on Thursday, Efe news reported.Muhammad's world-leading time of 52.88 was the fastest running time in the discipline since 2013.Muhammad started in the final as a favourite to clinch gold with fellow American Ashley Spencer who began competing hurdles full-time in this year.