In a recent, fairly brief, pool practice I did only one set of timed repeats – 3 rounds of 3 x 100 IM on 1:50. I’ll recap it here as a way of illuminating my thinking process, and particularly why I do most of my interval repeat sets in rounds like this.

If you ask, "What’s different about 3 x (3 x 100 IM) from 9 x 100 IM," the difference is in: (1) intensifying my focus; and (2) increasing the adaptation produced by the set.

This practice, on Nov 7, was only my second pool practice following five months of lake swimming (as  Swimming in Cold Water related, I continued swimming in open water until Oct 31) so one short repeat set seemed ambitious enough after such a long stretch without doing any.

I had two goals on this set: (1) To descend each round of 3 x 100 by swimming the successive 100s at approx 70%, 80% and 90%. (2) To swim a faster average for the second round and my fastest average on the third round. I can’t recall my times exactly but they were something like this:
1st round: 1:35, 1:31, 1:27 (avg 1:31)
2nd round: 1:34, 1:30, 1:25 (avg 1:29+)
3rd round: 1:33, 1:29, 1:23 (avg 1:28)

My most preferred way to swim this set would be to accomplish the faster averages by swimming more effectively, not by swimming harder. In other words, that my 9th 100 at 1:23 not feel appreciably harder than my 3rd 100 at 1:27. But, as often happens, I was happy to settle for swimming a bit more intensely, while feeling better.

I have a focal point for each stroke of the IM. My goal is to swim faster on succeeding rounds by feeling more "dialed-in" on that focal point with each round. After swimming the 3rd 100 at 1:27, I eased the physical effort on the 4th, but concentrated harder. Indeed my 1:34 felt easier than the 1:35 on the 1st 100. And my 1:33 starting the 3rd round felt easier yet.

Having my "easy" 100, feel easier - and yet be slightly faster than the previous "easy" 100 – is helpful, because it saves energy for the final 100 in the set, while also confirming that my efficiency is improving – which sets me up to finish the set well. On this set, as I mentioned above, I did swim harder on the 9th 100, than I did on the 3rd, but my stroke felt better, and that’s just as important as saving energy.

When you first begin training with this kind of set, it’s probably more realistic to use deeper focus to increase your ease on the slower repeats than on the faster ones, but what you learn by doing that will be valuable for replacing physical effort with mental focus at a higher speed/effort level later.

At the top, I mentioned that the second benefit of swimming 3 x (3 x 100) rather than 9 x 100 (i.e. descending only once from 1:35 to 1:23, but in smaller increments) was to increase adaptation. By progressing from slower to faster swims three times rather than once, your muscles learn the lessons (and your brain internalizes them) of adjusting stroke length, stroke rate, and power requirement three times, rather than once.

 Swimming in Cold Water