RIO DE JANEIRO: Veteran cyclists Fabian Cancellara and Kristin Armstrong hammered home their Olympic superiority Wednesday as Michael Phelps headed back to the pool in his bid to add to his remarkable 21 golds.

With rain and strong winds lashing Rio, 35-year-old Cancellara marked his impending retirement by reclaiming the men’s cycling time trial title he first captured in Beijing in 2008.

The four-time world champion Swiss was totally dominant as he beat Tom Dumoulin into second and Tour de France champion Chris Froome into third.

Cancellara finished the route in 1hr 12min 15.42sec, beating Dumoulin of the Netherlands by 47sec, with British star Froome, who also won bronze at the London Olympics in 2012, more than a minute behind.

Armstrong, who turns 43 on Thursday, produced a courageous display in similarly treacherous conditions to claim her third consecutive women’s time trial gold.

The grim weather — which forced the cancelation of the day’s rowing regatta and delayed the start of the tennis — proved no obstacle for Armstrong as she completed the challenging road course in 44min 26.42sec.

Her victory spared the blushes of organizers, relegating drug-tainted Russian cyclist Olga Zabelinskaya — who only returned from a doping ban last year — into silver.

“I don’t have words to describe it. When you’ve already been two times at the pinnacle of the sport, why risk coming back for the gold medal? The best answer I can give is that I can,” said Armstrong, who retired after each of her two previous Olympic successes, only to come back in search of more glory.

“Today the stars aligned,” she said.

Armstrong’s win launched a busy fifth full day of action where 20 gold medals were to be decided.

Phelps will head back into the pool a day after a spellbinding display which took his astonishing gold medal tally to 21 with wins in the 200m freestyle relay and 200m butterfly.

Phelps returns for the heats and semifinals of the 200m individual medley. If he comes through, he will compete in Thursday’s final.

Another US swim phenomenon Katie Ledecky is back in action the day after she secured her second gold of the Games in the women’s 200m freestyle.

Ledecky is part of the USA’s 4x200m freestyle squad, which also features Allison Schmitte and Missy Franklin who won gold in London.

Brazil’s struggling football stars will capture the hosts’ attention as Barcelona’s Neymar attempts to finally kickstart their campaign for a first football gold after being booed off in back-to-back goalless draws with South Africa and Iraq.

Defeat against Denmark in Salvador would represent a disaster for Brazil, still nursing the scars from their humiliating 7-1 drubbing by Germany in the semifinals of the 2014 World Cup on home soil.

Gymnastics continues with the star turn undoubtedly Japan’s Kohei Uchimura. The 27-year-old is seeking to follow up his individual all-round gold won in London.

Meanwhile, games organizers said an attack on a bus carrying journalists on Tuesday, which left three people injured on an “act of vandalism.”

Rio 2016 security chief Luiz Fernando Correa said the attackers used stones, contradicting accounts by witnesses who said shots had been fired at the vehicle.

“We think it’s an act of vandalism rather than a criminal act with the intention of injuring someone,” Correa said.

Correa defended security along the bus route and said it would be “impossible” to provide complete protection.

“It would be humanly impossible to exclude a person within range of throwing,” Correa said.

Brilliant Cuban light flyweight Joahnys Argilagos underlined his rich potential as he became the first boxer at the Rio Olympics into the semifinals to guarantee at least a bronze medal on Wednesday.

The 19-year-old prodigy and world champion had Kenya’s Peter Warui running around in circles on his way to a unanimous points decision, as Cuba extended their ominous perfect start.

Cuba, with its rich boxing heritage, is among the most successful countries in Olympic boxing history and strongly fancied to do well again in Rio.

Julio Cesar La Cruz, a three-time world amateur light heavyweight champion with spectacularly graceful movement across the ring, was equally emphatic in a unanimous points victory over the hopelessly outclassed Mehmet Unal of Turkey.

Argilagos displayed the full array of his electric footwork, at one point ducking a haymaker from Warui, whose momentum took him tumbling into the ropes.

The Cuban merely grinned back at his opponent and later delivered a sucker-punch while appearing to look in the opposite direction.

Argilagos faces Colombian Yurberjen Martinez — who he has trained with in the past — in the semis on Friday, after he defeated Samuel Carmona Heredia of Spain on a split points decision.

“I felt more confident than in my first fight,” said Argilagos, after delivering one of the most impressive displays in Rio to date.

“I knew I was going to bring joy to Cuba and I stuck to my tactical masterplan.”

“The Colombian is going to be a very tough rival,” added Argilagos, also a former youth world champion and one of the hottest prospects around.

“We have never fought but we have trained together and I know that he has some good weapons.”

Martinez made his own small piece of history, with his bronze meaning Colombia has its first medal in Olympic boxing in 44 years.