Olympic Track and Field 2016: Live Results and Highlights from August 12

Michelle Carter's gold medal in the shot put highlighted the United States' opening day of the track and field competition at the 2016 Rio Olympics.

Several American runners—most notably LaShawn Merritt, English Gardner and Tianna Bartoletta—moved on to the semifinals in their respective sprints. Jeff Henderson advanced in the long jump, too.

The women's heptathlon is shaping up to be one of the most intriguing events at the Rio Games. Reigning gold medalist Jessica Ennis-Hill (Great Britain) started the day off with a bang, winning the 100-meter hurdles stylishly. Ennis-Hill leads the competition after four events.

Elsewhere, the men completed heats in the 800-meter event, and there were few surprises. Defending gold medalist David Rudisha (Kenya) handily qualified for Saturday's semifinals.

The star of the track and field events on Friday was Ethiopia's Almaz Ayana. She turned in a spectacular performance to win the women's 10k, crushing the longstanding world record and stopping the clock in 29:17.45.