They are among the world’s toughest athletes – men for whom some of the most grueling training imaginable is all part of the routine. For the “beasts” of the Oracle Team USA America’s Cup crew and those who work with them, the pursuit of peak condition is as relentless as the races in which they push themselves to the limits. Punishing gym regimes – they push weights around as well as merely lifting them – swimming and boxing are key to making these extreme sailors as ready to defend their America’s Cup title next year in Bermuda as they can be. And for the man overseeing it all, physical performance manager Craig McFarlane, there is the pride of helping his charges to be “absolutely the best at what they are doing.” The New Zealander’s first sporting love and profession was rugby, and he had never coached sailors before joining Team USA in 2011. But he says he finds the same intense competitive spirit amongst the America’s Cup crew that he encountered in the rugby world. “Here, you have guys who have been coming in from individual sports and have to change into a team environment,” he tells CNN’s Sailing Success show. “And they have gelled really well. Read: Japan to make America’s Cup history “They are very competitive – there’s no shortage of that. We do a lot of competitive stuff and break down some barriers. We embarrass them now and again. “Once you humiliate yourself a couple of times, make fun of yourself, you’ve broken down a few barriers.” The nature of McFarlane’s training is governed by the nature of the boats raced in the America’s Cup – “the new boats are very physical, so we are improving physically until the Americas Cup comes in 2017” – and he says it brings huge rewards. “They are all professional athletes, they are motivated to train – and so as long as they are hitting their numbers and improving, then I’m probably doing my job,” McFarlane explains. “When you see them out on the boat, it is even more impressive. It is just phenomenal seeing them in their environment. They are absolutely the best at what they are doing. “You do your job in here, but you don’t know how it’s going to translate out on the water. But you like to think the physical side is prevalent.” Read: Sailing’s money men Boxing, overseen by coach Brent Humphreys, is a big part of that physical side. But why does it help you become a better sailor? Skipper Jimmy Spithill – who led Team USA to an astonishing 2013 America’s Cup comeback when it roared back from 8-1 down to defeat New Zealand 9-8 – says fight training helps the crew think more sharply when exhausted and under pressure. The Australian, who swaps the water for the air as a pilot in his spare time and had the idea of introducing boxing to the training regime, is more than happy to ride with the punches. Routines include taking hits to the stomach and kidneys to build stamina as well as boxing with the “wrong” arm in order to balance left-right reflexes. “It’s great for hand-eye coordination and hand speed,” the 37-year-old Spithill tells CNN. “I think we’ve really seen the benefits. We’ve seen with the guys that they think a little better. Read: The ‘ditch-digger’ who landed a dream job on Oracle Team USA “They work well on their feet, and you need to be able to make a decision when you’re exhausted.” After all, as he says: “If you make a mistake in boxing, it’s pretty obvious what’s going to happen.” Not that Spithill – whose team is second equal in the America’s Cup Match Racing Series ahead of this weekend’s leg in Portsmouth – makes too many of those. McFarlane recalls: “He had to do 12 rounds recently with the shore crew. “He is one of the fittest guys in the team. He can handle the beating, so to speak, but it’s very hard to beat him. It’s very hard.” Read: How tea baron became sailing’s ‘lovable loser’ But physical and mental toughness is not only conditioned by what happens in the gym – these athletes are what they eat, too. “They’ve got a fairly big appetite,” Scott Tindal, the team’s physical therapist and nutritionist, says with a wry grin. “I think they went through about 3,500 eggs in a couple of months.” Tindal’s contribution lies in “ensuring that the guys are healthy, that their bodies are working and trying to maximize their performance with the right food and beverage.” “Food’s been a big part of this campaign, and if you look from the start of the campaign to where we are now, it’s just unbelievable where they’ve got to,” he adds. “And they’re only going to get better. They’re not cover models or anything like that, but you look at the guys now and physically, they’re just beasts.” Who will win the 2017 America’s Cup? Have your say on our Facebook page But even “beasts” have to stop somewhere. McFarlane says the danger of “overloading” is ever-present and explains: “In rugby, there are a lot of contact injuries. “Here, it’s mainly use and overuse-type injuries, so you are looking at managing the load that they put on their bodies. Read more: Sailing Success goes behind the scenes of the America’s Cup “It’s all about discussing and talking to the guys – and if they are sore, you say back off a bit and rest.” But they don’t back off that much – and the rest of the America’s Cup field had better beware.