Shushhh . . .tat tat. Shushh . . . tat, tat. Shushhh . . . tat, tat is the sound of Katie Taylor punching Paddy Barnes.

It disappears for a moment but comes back at a higher tempo. Shushhh-tat. Shushhh-tat. Shusssh-tat. Combinations chase up over his arms, under his elbows. In chains of three or four the punches glance around his body, his head his ribs, steam hissing from her boiler.

It is the fifth three-minute round and already past Taylor’s comfort zone. Her competitive boxing world is four two-minute sessions. She is now into her 15th minute.

The man she is fighting is 10 kilos lighter, a double Olympic bronze medallist, a 2010 European champion, the current Commonwealth title holder.

But here there is no deference to Taylor, no gender balanced response. Barnes comes back in great exhalations of air, his guard high, but his right and left hands flashing in blows low to the side of her arms. A flat square punch to her ribs draws no reaction. He follows with driving upper cuts that run a line from her navel up to the underside of her chin.

"See the intensity," says Pete Taylor oozing approval. "It's hard even for these guys. There's respect between them," he adds stepping through the ropes.

Katie attacks
Both boxers cast off their head guards and gloves. Taylor stares into nowhere in one corner, the ropes bearing the weight of her arms her mouth open. Barnes sits on the side of the ring awkwardly pouring liquid into his mouth, the plastic bottle squeezed between his heavily-taped hands.

“Okay,” says Pete throwing a small square mat into the middle of the ring. Barnes stands with one foot on the mat. He cannot take it off. Katie attacks him. Another three minutes.

“I say hold the centre,” says Pete. “When I put the mat in they have to. It shows you how easy it is when they have to do it.”

They switch. They move to both with one foot on the mat. Head to head their arms start driving again, sweat splashing across each other’s faces, noses pressed together.

Shushh. Shushh. Shushh goes Taylor ripping off five or six staccato combinations, her reddening face visible through the guard. Barnes is puffing, his mouth open sucking in air, scything and hooking in blows. Body. Body. Body. Head.

It’s an intensity verging on belligerent but there is no ill temper in the oddly intimate setting, the mood preoccupation and detached from the world, three people watching, the gym doors locked.

Temper flash
Momentarily her temper bolts and she's throwing the locker at him, Barnes in a ball, swaying from side to side in a controlled tailspin. He instantly snaps back and hits her very hard to the side of the head.

“That is more intense than competition,” says Pete, moving towards them with a length of tape. For the next three minutes they are tethered together in the hit zone, one metre apart, like a pair of ancient knife fighters.

“If you put two other guys in there they would be dead in two minutes,” warns Pete. “The reaction speed. If you look closely, they don’t hit each other that often. Their defence is brilliant. At that distance it’s brilliant. If they can avoid punches at that distance ...”

Katie’s hair is matted and stuck to her neck in clumps of sweat. The green tee-shirt she wears is wringing wet, glued in patches to her torso. Her left eye is black.

“Whoaaaah,” shouts Barnes carelessly flinging his gloves to a corner, the two of them then silenced by exhaustion.

Nine three-minute rounds of fighting come to an end.

“I think I got that yesterday,” says Katie of the yellow and black eye. “I don’t know. It could have been the weekend. I never know who it is.”

Few boxers work harder in the ring than Barnes. No woman in world boxing is as fast as Taylor.

Muscle mass

Depending on what scientific paper you read, men are almost twice as strong as women. In a 1993 study exploring gender differences in muscle make-up, female participants exhibited 52 per cent of men’s upper body strength. A later study published in 1999 similarly found women had 40 per cent less upper body skeletal muscle.

But this is where Katie lives her boxing life, making her own rules, setting her own benchmarks. She doesn’t just fight against men but fights against the best in the world.

Last year Barnes was in the final eight at the world Championships in Kazakhstan. He has twice medalled at Olympic Games and last summer was withdrawn from the European final in Minsk with a broken nose. He wanted to fight. Team Ireland said no.

Barnes’s fighting limit is 49kg, light flyweight, which is where he will compete at the end of this month in the Irish senior championships. Taylor is about 60kg, the limit for lightweight women.

But this is no charitable venture by Barnes. It is not a trek down from the Ardoyne for an 80 per cent sparring session with Katie to knock her into shape for the Irish championships at the National Stadium, where she hopes to fight for the first time.

Fastest boxer
It's not a patronising acknowledgement to her unequalled achievements or Barnes's boxing philanthropy, a leg up for the European Championships in May or for the World Championships in autumn. It's not a dig-out. It's not a favour for an Olympic champion or a self promoting stunt from the Belfast champion. For Barnes too it's self-improvement.

“Sparring people in Belfast I only go through the motions,” he says. “Coming down here to Katie . . . she is, I suppose, the fastest boxer I’ve ever sparred. Ever.

“The competitiveness of it . . . I have to dig really, really deep in those nine rounds. We push ourselves. It’s my speed and her speed colliding. It’s great.

“I remember last year, I think it was four people I knocked out. See in there today, in there I was hitting her with my hardest and connecting. Smack, bang she peppered me. She peppered me so she did.

“It’s the speed,” he adds. “It’s the speed. I don’t get that anywhere else. That speed I try and deal with. If I’m boxing at a lower level obviously it will be that much slower, so I’m able to see shots coming. This helps because nobody is going to be as fast as her.”

Some months before the London Olympics, Katie flew to Los Angeles to make a commercial. A day before shooting she went to have a look at the famous Wild Card gym run by Freddie Roach on Sunset Boulevard.

A look wasn’t enough however. She jumped in and mixed it with some Mexicans, arriving back to the commercial shoot to send them into a flapping panic with a drop-dead shiner. It’s in her blood.

There are few if any women in mainstream sport, where physique and reaction speed are central, who have the skills to go head-to-head with men the way she does. Everything is against her, her genetics, her gender, her build, conventional wisdom, maybe even the impulse and yet. Today she is a woman fighting a man, making the once unacceptable acceptable. In less sure hands than hers or Barnes it could offend; just another voyeuristic Jerry Springer routine.

“I’m not going to get fights like that,” she says, emptied by the effort. The colour of her face beneath the light abrasions is bleached out and wan.

“Those spars are always all so intense,” she adds. “If you are making mistakes with the likes of Paddy it’s going to be painful. You have to be sharp. You don’t need many of those, not like that because of the intensity. I’m definitely tired and I’ve taken a few heavy punches. With the Senior Championships coming, that will make a difference.”

The Irish Senior title is like a ghost belt to her. She has won them all but has never fought. Last year there was one entry but the name was withdrawn. Part of her legacy is that few women will fight her, can fight her. By necessity she has been pushed towards men like Barnes and also Irish bantamweight Michael Conlan, another sparring partner.

Men's competition
A boundary, she crossed long ago, she is not permitted to do it in competition. The governing bodies won't allow it. She enquired last year about fighting in the WSB, a professional male competition in which Olympic boxers are permitted to compete. She said she would fight against men if they would sanction it. They wouldn't.

So here she is on a Tuesday morning with Barnes down by the harbour, the gleaming new Bray Boxing Club gym built entirely on her success, 21 major championship medals between them and a sparring session of greater passion and intent than any World Championship or Olympic bout and against a man who hits harder than any woman she has ever fought.

“Definitely not. There wouldn’t be anyone who hits as hard,” says Katie. “There are very few men that would punch as fast, punch in flurries like that and punch non-stop . . . yeah Paddy knocked someone out at the World Championships. I have to work myself up for these sessions, when I know Paddy is coming down from Belfast. I definitely have to.

To the limits
"These last couple of weeks I haven't been able to get many spars and at times I've been a little bit lethargic. You know when you don't have to feint, you don't have to think about it that much," she says.

“It’s always a huge challenge to work at that pace. Paddy out works every man so I’m pushing my body to the limit all the time. Especially when we’re wearing those bands. I can’t move. I’m in the pocket all the time. It’s great for me because I have to work, great endurance for my shoulders. He’s just perfect for that sort of thing.”

They are chatting by the ring as London Olympian Adam Nolan departs for duty to the local Garda station. Barnes is joking about the local mural of Conlan, which is painted on the side of a house near his home in Cavendish Street in West Belfast and bigger than anything Katie ever had in Bray. "Aye," says Barnes looking for mischief. "A few times I wanted to go over there and paint over it."

After the heightened aggression of the ring, there’s often lightness. But Barnes always rises to the wise crack. Out of ear shot Katie gathers her bags to leave. “Paddy comes all the way down from Belfast for this,” she says in a low voice. “It’s a compliment to me. That’s what it is. It’s a compliment.”

The gym doors burst open onto a bright day , the blind blue of sea water and a flock of 37 swans bobbing on the waves.