Some questions!

[Francois]

Yes, it means 'and even more than that'.
=> To win gold I would have to swim the race of my life. But I could swim the race of my life and still lose. I need to do even better than that: I need to give 200% !

FRC

[Jenny Lau]

Thank you two so much. About the above sentences I completely understand now. And there are other questions in the same article I feel complex, would you help me?
1.three one-hundredths of a second is 3/100 second?
35 hundredths of a second is 35/100 second?

2.Intense? That was an understatement.
Does the author want to say his training is more than intense because he swims for Olympics?
Here's the context: "Not only do you have allergic asthma, you have exercise-induced asthma too," he said. "The more intense your workouts, the worse your condition could get." Intense? That was an understatement. Heck, my eyes were on the Olympics!

3.I'd gutted through this sort of thing before.
What does "gut through" mean?
The context: I was in the water, racing the other guys. Midway through the race, my chest grew tight. It felt as if someone had wrapped a belt around me and was squeezing as hard as possible. I tried to take a breath. Hardly any air came in. Keep swimming. I¡¯d gutted through this sort of thing before. This time it was just too hard. I dragged myself out of the water.

[Casiopea]

1.three one-hundredths of a second is 3/100 second? 35 hundredths of a second is 35/100 second?

Sounds right. :D

2.Intense? That was an understatement.

understatement means, represent X as less than it actually is, express mildly. The opposite overstatement means, to over state, make X more than it actually is.

3.I'd gutted through this sort of thing before.

To endure, possibly through utter exhaustion.

[Francois]

I'd gutted through this sort of thing before.

To go through sth, using one's guts (courage) to make it.

FRC

[Jenny Lau]

Thank you two very much for your help!

[Casiopea]

Thank you two very much for your help!

You are welcome. :D