By Steve Cram BBC Sport

Sonia O'Sullivan will on Sunday try to repeat Paula Radcliffe's American marathon success and win her debut New York marathon.

Comparisons between Sonia and Paula, who has made such a stunning transition to marathon running this year, are inevitable.

But there is a big difference between the two. We always knew that Paula would end up doing marathons - it was a natural progression for her.

O'Sullivan won the Great South Run in a record time

Sonia has always been much more of a track athlete, who has great endurance but who has excelled from 1500m up to 10,000m.

The marathon was not a distance that you were ever sure Sonia would attempt.

Whatever she does at marathon is a bonus after the success she has had on track.

On the other hand, one of the reasons she's running in New York is because of what Paula has done.

She is such a competitor that she wants to see for herself what she can do - and it is Paula who has set all the benchmarks.

Can she run as quick? I do not think she is capable of two hours 17 minutes, but she will do well.

Motherhood makes a difference

Sonia is another athlete who has returned stronger after giving birth. She now has little Sophie to add to Ciara, and since the last one's birth she has been an athlete reborn.

In the Eighties we used to joke about athletes from eastern Europe being sent away to have a child, in order to flood their bodies with testosterone and make them better runners.

I am not sure there is any medical reason why it happens. There is no real evidence to support it.

Maybe you can put it down to the fact that it forces you to take a break from training, and so you come back refreshed with your enthusiasm back.

O'Sullivan with her daughter Ciara in 2000

When you have done years and years of training as a full-time athlete, you need something else to distract you.

I always trained best when I was busiest. Otherwise you fall into the trap of over-analysing everything.

Training becomes less important when you have kids. If you have nothing else to think of, you become introspective, analysing everything to death.

When you are young and coming through, you just do it and do not worry about it.

As you get older and get really good, you start obsessing about the little tiny things that you think you could improve.

When you have a family, your training is a distraction, a pleasant distraction.

Having children changes your perspective. Sonia takes her kids with her everywhere she goes, just as John Walker used to do, and it clearly works for her.