Question for the swim gurus

Shorter repeats with short rest (comprising a set). For example, 10x100 or some such.

You want to be pushing yourself, but be able to make a consistent interval (say, even if your rest is :10 or :15, try to hang on and sustain the same pace for each repeat of a set). You don't want your form to fall apart. Sometimes it happens, and/or the wheels come off the last repeat or two, but you do learn to push AND pace yourself and this is the way to get faster most efficiently.

Assuming your technique is sufficient, I agree with everyone above.

If your technique still has a lot of room for improvement (the commonly quoted standard is being able to easily cruise at faster than 2:00 per 100 yd), then your top priority should be improving technique, not conditioning, because you're not limited by your "endurance", you're limited by your skill.  Doing hard efforts in long training sessions with deficient technique will only ingrain bad habits at best, and result in injury at worst.

Shorter intervals with short rest. Long straight sessions are for convincing yourself you can do the distance and for pacing. And pacing can also be done with 400-500's on short rest.

20 x 100 this morning plus another 5 with buoy and paddles.

Seems to be a consensus on the intervals :-P.  I was doing some 50's this am at :55, and I did a 700m at 14:30, so am pretty close to 2:00 per 100.  Not too long ago was 2:15-2:20 per 100, so that is good.  I just started a Masters Swim Tri Training, so expect that will help with any technique deficiencies.  Thanks so much for the replies!

All that is good, congrats on the improvement and continuing work. I'd say you're at the point where piling on the distance and intervals will definitely help, and to some extent, especially if you stay aware, your body really will do some self-correction in terms of style. Do (esp through Masters) get critique and continue to work on your form -- it's something all of us can use.

Depending on your starting point you should do short interval sprint training. IE 4x50 on 1:00. As you get more comfortable with those, you should up the distance, but keep the pace and have a slightly longer rest period, until you're used to that. Then again up the distance, keep the pace.

A good way to test your threshold pace, is to first swim an 400 and time yourself (FAST). Take that time and split it. You should swim 2x200 on your split time from the 400 you just swam and add 0:05 seconds for a little rest in between the200's . Then split the 200 time in half, swim 4x100 on that split time, again adding the 0:05 seconds for 8x50 time, still adding the 0:05 rest time. Make sure to keep your times and if you find that you are not making the time on 3rd 100 you will have to continue with no rest.The hardest part of this threshold test is the 8x50's surprisingly. Swim all lengths fast, yes even the 400, they call this 'race pace'.

At the end of this threshold test you will see if you can keep your race pace through those times, intervals, and for that many reps, if not, then you know what you need to work on and what time intervals you need to keep in order to maintain a faster pace over a longer period of time. Do this threshold test again somewhere down the line and see if you have improved.

Hope this helps! Message me if you have any questions.

I've done both ways.

Intervals score my vote.

Although I would qualify that I do a lot on form work. And by that I do not mean just drills...which I would guess at 5-10% of my load.

Thanks for this--will have to try it out next week.