The new boat classes, introduced as part of the gender equality rulings that have been introduced at the behest of the International Olympic Committee, proved highly profitable for American rowers in this International Rowing Federation event.

Coxed by Isabel Weiss, the US women’s coxed four crew led from the start on Malta Lake, taking a boat-lead over Russia and Italy.

Italy upped the rate to 37 strokes per minute to move away from Russia, then again to 38 to try and take the lead, but the American boat, remaining at 36, crossed the line with a clear water lead to take the first gold of this regatta.

"We didn’t know what to expect," US rower Jennifer Mundelius said.

"We sort of embraced the crazy race mentality and went for it the whole way down."

The US crew of Sarah Maietta and Caroline O’Brien in the second new women’s category, the lightweight pair, did much the same and, despite running into what looked like some steering issues towards the end, maintained a lead throughout to finish well clear of Germany and Italy.

"We actually had a bit of a crooked start, which I think was due to our excitement, but we then managed to stay calm in the first 1000m as we knew we had good speed," said Maietta.

The US maintained the gold standard in the men’s coxed four after a monumental struggle with Italy and New Zealand.

Italy, the defending champions, went off very fast and took an early lead.

The US boat moved up in the third 500 metres, before coming past Italy in the final sprint, with New Zealand and Germany contesting bronze.

The Italians went to 41, but still made no impact on the leaders, and New Zealand, who had made the final through repechage, took silver at the last, also rating at 41.

"We really enjoyed the race, there was some great competition out there," said Woods Connell of the US.

"It’s our debut here so to win is awesome.

"Today we really trusted ourselves, especially in the middle portion."

The fourth US gold came from the women’s pair of Regina Salmons - an Under-23 gold medallist in the eight two years ago – and Alina Hagstrom in a hugely competitive final.

Australia’s Giorgia Patten and Bronwyn Cox, who reached the A final at a senior World Cup earlier ths season, took a slight early lead before the Americans pushed  through.

As the Australians slipped back to finish fifth,  Britain came up into silver position and held it under a late challenge from Chile’s defending champions Melita and Antonia Abraham.

Italy, reigning champions in the lightweight men’s pair, went for broke with a crew comprising of former gold medallist Guiseppe Di Mare and new partner Raffaele Serio after taking over the early lead from Greece.

But, coming into the final sprint, both Greece and Ireland  had enough in reserve to pass them, and  it was the Irish crew of Shane Mulvaney and David O’Malley who had most endurance as they took gold.

"That was a really long race as the conditions out there kept changing," said O’Malley.

"We kept swapping positions but we managed to come through like a train and we weren’t going to let anyone else through.

"We’ve got a load of friends over here from Dublin so it was great to win with them."

The lightweight quadruple sculls proved a happy hunting ground for Italy’s technically accomplished rowers as both men and women took gold.

The men took a lead going into the third 500m, with the United States, France and Denmark moving up to challenge.

In the end it was Ireland, who came flying through at the close, who presented the most danger, and after moving to 40, Italy just held on.

Ireland took silver ahead of the US.

In the women’s race, Italy held the status of defending champions and retained Paola Piazzolla from that winning crew.

Having set the fastest qualifying time they proved unstoppable, with The Netherlands taking silver ahead of France.

In the men’s pair, South Africa’s Charles Brittain and James Mitchell left their challenge late as they took gold ahead of long-time leaders Romania, with Italy claiming the bronze medal.

Romania had consolation in the women’s quadruple sculls, where they took gold ahead of The Netherlands and Great Britain.