Usain Bolt eyes history against Gatlin after Michael Phelps heroics

Usain Bolt is chasing a place in Olympic history as the battle to be crowned world's fastest man takes centre stage following Michael Phelps' record-breaking exploits in the swimming pool.

A day after American swimmer Phelps brought the curtain down on his extraordinary career with a record 23rd gold medal, Bolt will attempt to complete the first leg of an unprecedented "triple-triple" in the 100m at the Olympic Stadium.

With semi-finals scheduled at 9pm local time (10am Monday AEST), Bolt is poised to line up for the final at around 10:25pm (11:25am AEST) where he will aim to clinch a third consecutive 100m crown after wins in 2008 and 2012.

The Jamaican superstar made his opening bow in Rio during Saturday's heats, coasting to victory in 10.07sec.

His biggest challenger is expected to be Justin Gatlin of the United States, the 2004 Olympic champion who has served two suspensions for doping offences during his career, and has served bans totalling five years.

Last week, US Olympic swimmer Lilly King said athletes with Gatlin's track record should not be allowed at the Games, following similar comments from Australian Mack Horton.

On the opening day of competition in Rio, he hit out at Chinese swimmer Sun Yang, who was found guilty in 2014 of taking a banned stimulant.

"I don't have time or respect for people who are drug cheats," Horton said.

With the swimming competition now over, Horton's Australian teammate Bronte Campbell has supported his stance.

"It was very interesting seeing some of the Russians competing here, it was very interesting seeing people with past doping violations competing and it's really rough competing against them knowing that they have these past strikes against their name," she said.

"It's not something you really want in your sport and I totally understand where Mack's coming from, it's a place of frustration."

Patrick Johnson, a two-time Olympian and the Australian record holder in the 100 metres, said athletes were now well aware of the shortcomings of anti-doping authorities and were voicing their frustration.

"There's a bigger understanding that athletes now need to take control and they want to voice their opinion because over the years they've been frustrated that we've got athletes coming back after their bans and then coming back competing and they get banned again," Johnson said.

"...It's a great opportunity where the athletes take a little bit more voice to say, look, we don't want drug cheats here, we want clean athletes."

Gold goes to Kenya's Jemima Sumgong

The 100m final is one of four track and field gold medals on offer on Monday, with the men's 400m and women's triple jump also up for grabs.

Kenya's Jemima Sumgong won the first athletics gold of the day, making light of searing heat to triumph in the women's marathon, which finished at Rio's Sambodromo, the home of the city's annual carnival parade.

Sumgong came home in a time of 2hr 24min 04sec to clinch Kenya's first-ever women's marathon gold.

"It was very hot but everybody had to get through the heat. I had to control my body and listen to my body very carefully," said Sumgong.