Carlin has become famous on the IRB Sevens World Series circuit for his lightning quick feet. A glimpse of this YouTube video and it is easy to see why he is rated as arguably the fastest rugby player around!
The former American football and athletics prospect clearly loves to sprint and he got an invitation via Twitter he could not turn down on the eve of the men's tournament in Moscow.
Nikki, who plays for Belfast Harlequins and Ulster, led the way with the Twitter banter - tweeting Carlin, 'Looks like I win by default. Better luck next time, knew you were scared haha!' - before the man himself showed up.
Amy, who was part of Ireland's Grand Slam success earlier this year, showed her background in athletics and weight-lifting as she went stride for stride with Isles before he managed to pull away in the second half of their 100 metres race.
Click here to see how Amy got on against the 23-year-old flyer from Ohio.
Nikki enjoyed testing herself against the American Sevens star, tweeting him afterwards: "Great sport! Thanks for the races! Pity the ref said I cheated in the first one...best of luck for tomorrow!' Carlin replied: 'Thank you and God bless!'
Asked on her Twitter page how she fared against Isles, she said: "I improvised in the first lift race and won. He smoked me in the second straight race. Amy nearly had him though!"
Speaking about the Ireland squad's stay in Moscow so far, Davis said: "It's great, it's very hot. The last time we were here we didn't get a chance to see this part of Russia. It's really nice, it makes you appreciate being away from home at times.
"We can't wait to play now. We've seen the stadium and it's amazing. We can't wait to play China and get a chance to play inside the stadium. We've South Africa first up on the second pitch on Saturday morning."
Ireland Women's Rugby World Cup Sevens Fixtures -
Saturday, June 29 - Pool B
South Africa v Ireland, Gorodok Stadium, 10.06am local time/7.06am Irish time
Australia v Ireland, Gorodok Stadium, 12.40pm local time/9.40am Irish time
China v Ireland, Luzhniki Stadium, 3.58pm local time/12.58pm Irish time
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