[quote="xrodolfox"]If you are concerned with your goals, don't do swimming unless you get a coach. You will not get much out of it... unless you have fun and enjoy it.
Frankly, for intervals, any stroke works if you go hard enough. Most folks who go slower than a 1:50/100yds have a hard time really getting much out of intervals until they improve their stroke.
There are always exceptions, but those folks are easy to spot a mile away. They go apeshit hard and give their swimming 100% and really go like machines for the interval sets. Out of hundreds of swimmers I have coached, I have met exactly 3 folks like that over 10+ years. Only you really know if you can get your heart to 90% of your max and keep it there. Those folks who are that intense tell me they go so hard that it feels like their heart is going to pop out of their neck/head, and that their body screams "STOP STOP STOP". They then go a tiny notch below that intensity, where they feel uncomfortable and like they are going to vomit, and they stay there with the goal of staying in that uncomfortable place forever. And what happens, is that in spite of bad technique, they get better. And their body adapts. Next time around, they are doing faster interval. And they get better. Etc.
In swimming, we do these things called "Lung Busters". If you were here, and I got you to a decent freestyle, I would have you do those.
If running is your thing, sprinting *should* have you out of breath. If you aren't going out of breath, then you certainly aren't going to work on maximizing how efficient your lungs get. You need to get out of breath, catch it, get out of breath again, catch it, and repeat like 10X. Then you do that until you can do longer distances with less rest, and then you can do it 20X. Then faster and longer, until you can do it 30X... etc. That's interval training.
There are a million ways to make it more interesting, and thus, effective, but if your goal is to increase your lungs function, your recovery time, and your resting heart rate, then there is no substitute for doing lots of exercises where you work exactly that: your lungs.
You seem to have written up a simple set. Y x (.3 mile sprint+ .5 mile jog). That's a good start. Do it! See how it goes. Frankly, I find that it is much easier to do painful, repetitive stuff with friends and other athletes. Once you get started, seek out a team in that sport. I have quite a dozen times when I do stuff by myself, let alone the times I just half-ass it when I'm alone.... but I can't think of a time when I didn't give it at least 99% when I'm with others.
My friends at uni are all...well...lazier than me with this sort of thing. So it'll be and my MP3 player. I can usually put myself into a sort of semi trance when running for long distance, probably because when I walk I walk listening to music, and I just go into my own little world.
But I'll look out for people.
And I'm definitely not one of those people you spoke about at the top. If something doesn't feel right I stop.
If I can get a girl or boyfriend who loves swimming, then that might help me improve me technique etc.
I'm going to get so nervous when I start doing the 0.3's. This is going to be fun (and then hell).