This article is part of a series on why we do the things we do, the series explains set types and periodization through the lens of lactate metabolism. Fatigue is more nuanced than simply being about lactate accumulation and consumption and these articles are getting old. But I have left them in place because while lactate is not itself a cause of fatigue, it is closely related to the causes of fatigue in events from 1 minute to around 30 minutes. The previous article can be found here, the first article of the series is here. USA Swimming has adopted a set classification system that has seven levels. Recovery (REC), Endurance Level 1 (EN1), Endurance Level 2 (EN2), Endurance Level 3 (EN3), Sprint Level 1 (SP1), Sprint Level 2 (SP2) and Sprint Level 3 (SP3). Other sports and other countries use slightly different classifications but most systems break out along similar lines. Each category aims at a slightly different set of adaptations, as a result the set types have characteristic lengths, rests and intensities.
It is important to realize that different sets are doable in different amounts. As we will see in later articles, the stress induced by SP2 sets is much higher than that induced by EN2 sets. SP2 sets put a big hole in your schedule, recovering from them both during and between workouts is difficult. Conventional wisdom holds for this and other reasons to hold off on the more stressful work until relatively close to the main competition. But more on that later.
The bulk of any program in terms of yards, and to a lesser extent in terms of time spent, consists of endurance sets. These types of sets are meant to lead mostly to the aerobic adaptations pointed out earlier. In terms of the bathtub model, you are trying in increase the size of your bathtub drain.
Recovery swims are done at very easy paces and the rest intervals during the set are usually not critical. In an acute situation, a recovery set is used after a hard set or at a meet after a race. In this use the purpose is to help rid your muscles of lactate and other byproducts of effort. It has been shown that active recovery in the form of easy swimming is more effective than passive rest at lactate removal. In the long run recovery sets are used to loosen up or help get rid of stiffness in the days following a hard workout or competition. It is meant to help you recover for the next workout.
Many drill sets can also be thought of as recovery sets. In terms of your physiology this is true, even though the drill will have other useful adaptations outside of your aerobic metabolism. Recovery sets tend to increase fat metabolism at a given speed. Fat metabolism is not addressed in our bathtub model but becomes quite important in races over 40 minutes or so in length. Recovery sets address all the aerobic adaptations but on a minute per minute basis, induce adaptations at a lower rate.
EN1 type sets are also good at inducing the aerobic adaptations, but due to increased intensity they are more effective at creating these changes than the recovery sets. The intensity of these sets is from around 90 to 95% of critical pace for the stroke you are swimming. This can vary widely with the amount of rest and length of the swim however, longer repeat distances with short rest mean you can swim a little slower and get this adaptation. Longer rest for shorter repeats mean you need to swim a bit faster, closer to your critical pace. The duration of the sets needed to induce adaptations is over 16 minutes and rests are short, generally 20 seconds or less to keep your body from recovering. You want to keep your hr up for an extended time. These sets improve fat metabolism as the recovery sets do but not quite as well. These sets also increase the number of mitochondria in your muscles, as discussed before the mitochondria are the power plants of the cell and are where all the aerobic metabolism takes place. Having more mitochondria means a bigger bathtub drain and pays dividends in every distance of race.
EN2 type sets are done very near critical pace. A little faster than critical pace for shorter repeats and a little under critical pace for longer repeats. EN2 sets are the most effective way to develop your aerobic metabolism. Minute for minute, the best bang for your buck in aerobic developments, the stress is moderate and they can usually be performed multiple times in a week without causing problems for the athletes. The typical set length for EN2 sets is 16 to 40 minutes. Depending ont the set structure, rests can be from 5 to 40 seconds, or even up to one minute on a very long repeat. In terms of our model, EN2 pace work induces the greatest adaptations in mitochondria, it makes your bathtub drain bigger. It is also the best training pace for raising your MLSS, this is only natural since these sets are done close to MLSS pace. MLSS and critical pace are very close to each other.
EN3 sets are done at or very close to VO2max. As discussed before this is where your energy metabolism is at full tilt, the firehose is open, the drain is draining and overflow drain is draining as fast as possible. In fact it seems like this should be all we ever do. But like everything there is a downside, the EN3 sets are high stress and can be done in somewhat limited quantities. If we were to continue to do them they would bring on stagnation more quickly than other types of sets.
EN3 sets are also usually 16 minutes long but there is significant amounts of rest in them, up to 1 to 1 ratio of work to rest. Since your hr often gets very close to its max, this type of set affects your heart function. The amount of plasma in your blood goes up, maximum stroke volume is improved, and since you are working near VO2max, your VO2max level is improved.
If all you ever did were open water swims an hour or longer, you could pretty much end the discussion here in terms of metabolism and energy production. Go off and develop your aerobic metabolism and be happy and healthy live a good life out there with the sea critters and the jellyfish. Of course, there is more than one way to look at things and sprint sets have uses for marathon type swimmers, it's just that those benefits don't have to do with metabolism. However, the masters swimmers, most of their events are from one to four minutes and involve high lactate levels. A bathtub overflowing just at the last stroke. So to be sharp for raceday sprint work is included. Like sprint racing itself, sprint training also creates high lactate levels.
Work on critical paces has shown that doing a lot of sprint work, the SP1 and SP2 levels can be detrimental to your aerobic fitness. So at the extremes, if all you ever did was sprint work, your aerobic metabolism would get worse and you could actually end up slower in your chosen event for it. The mechanisms once again are not exactly clear, if nothing else, sprint work takes a lot of time in your workout. Thirty minutes spent on an SP1 set would not be unusual, but that is 30 minutes not spent developing your aerobic metabolism. There are other more in depth mechanisms used to explain why, but they are all offshoots of, if you do less aerobic work for one reason or another, your aerobic metabolism won't work as well. And included in that "One reason or another," is a 40 minute set of sprint work.
This is one of the major reasons why coaches tend to switch emphases a bit as the year goes on, too much sprint work early in the season could deteriorate your aerobic metabolism and leave you a step behind come the big race. How much istoo much sprinting? How early is too early to start to emphasize sprint work? That will be discussed in a follow-on article on periodization.
SP1 sets are also called lactate production sets, these sets are intense and faster than MLSS speed but due to the set structure with shorter intervals and longish rests, the lactate levels don't get too terribly high. On these you should have some lactate type fatigue setting in during the set but not so much that your arms start to burn and really struggle. You should be able to maintain a pretty consistent pace through the set. In terms of our bathtub model, you would say that these sets are meant to increase the size of the firehose and to an extent they also make your bathtub bigger. These ets also induce some aerobic changes, although in magnitude probably less than the recovery sets do. SP1 sets are high stress and can be taken in small doses for a good chunk of the season.
SP1 sets have intervals of 25 yards to possibly out to 200 yards. The speeds are at about 95% of max speed and the total time of an SP1 set would be 20 minutes or more. However rest durations on SP1 sets are equal to or twice the duration of the work interval. So of the 20 minutes half or more of the time would be taken up by rest between swims. These types of sets are usually done earlier in the season than the very hardest work that is the SP2 work.
SP2 sets or lactate tolerance sets are the hardest sets a swim group will do. They are similar to the distances and speeds of competition events. The idea behind a lactate tolerance set is to get accustomed to the type and amount of pain you might experience in a race. In this way you increase the size of your bathtub. It is thought that your muscles get better at buffering acid and that your brain resets the "STOP!" point on how much you will take and still swim.
SP2 set distances are usually directly relevant to your chosen event. An SP2 sets for a 200 person would consist of 150s to 300s, for a 100 person it would be 75s to 150s. These swims can be done straight through or perhaps broken up with 5 to 15 second rests in the repeat. The rest intervals usually involve active recovery and are 2 to 5 times as long as the swim interval. The effort is 100% for these sets and the lactate levels induced are quite high.
SP3 sets exist largely outside of the bathtub model. These types of swims are prominent but really don't do THAT much in terms of our bathtub model. The most applicable thing they do is to indirectly increase the size of the firehose. I say indirectly because these types of swims work on your neuromuscular system mostly. They enable you to turn over faster and recruit muscles faster. In a bit of an odd situation, while the SP3 sets are the fastest ones we do, they are not the most stressful. The intervals on SP3 work top out at 25 yards and the rest is complete, a work to rest ratio of 1 to 5 to 1 to 8. Since these sets are lower stress these are actually included both early and late in the season.
Early in the season, before your fitness has really come around you can still work on SP3 without inducing a lot of stress, the work on your turnover and coordination is quite effective and this type of work continues to a degree all through the year. SP3 sets also become a mainstay in the taper, in a taper the general idea is to reduce the training loads so your body gets into the supercompensated state, but you also want to do some fast swimming as well to keep your feel for the water, the SP3 sets can fit the bill late in the taper.
Please see below a summary chart of all the different set types.
Total Set Time
400 IM pull / 400 IM kick / 400 IM order
5 - 30 secs
90 - 95% critical Pace
20 - 120 mins
800 / 8 x 100 / 600 / 6 x 100 / 400 /
4 x 100 (:20 rest on all)
25 - 3000 yds
10 - 45 secs
95 - 103% critical pace
15 x 100 on Critical Pace + 0:15 holding Critical Pace
50 - 2000 yds
30 - 240 secs
>103% critical pace
3 x 100 max (:05)
4 mins rest between sets
25 - 200 yds
30 secs - 3 mins
95% max pace
15 - 45 mins
5 x 50 at goal pace (:30)
1 minute between sets
~ Race Distance
2 - 5 mins
15 - 45 mins
3 x 100 at goal 200 race pace (2:00)
4:00 active rest between sets
10 - 25 yds
1 - 5 mins
15 - 45 mins
12 x 25 on 2:00 from a dive
So now that you have an idea of the general structure of workouts we can look at some ways in which modifying a workout on the part of a swimmer can change what the workout does and may change it significantly from what the coach had intended.
Resting too Little
A common thing that might happen is if the coach puts up an SP1 set. It might be:
12 x 50 (:40) FAST!
Without more input from the coach is is entirely foreseeable that the swimmers may decide it is too much rest and shorten the interval. What is probably happening is that the swimmers don't understand how fast "FAST" is supposed to be in this case. The swimmers swam it "moderately fast" and don't think they are working hard enough. So they swim slower than the coach intended and rest less than the coach intended.
What happens is that the high quality SP1 set turns into an EN1 or EN2 set. The problem with that is that there are not enough yards in this set to get aerobic adaptations from it. So you get a set that is neither here nor there, not fast enough to increase the size of your tub and not long enough to make a bigger drain.
Swimming too Slowly
Swimming too slowly might happen if the coach puts this EN2 set up on the board.
15 x 100 on critical pace + :20
Without further instruction and if the swimmer does not recognize it as an EN2 set, then the set may end up being swum too slowly. Instead of swimming them near his critical pace and getting 15 seconds rest he may find it easier to swim them at 10 seconds slower than critical pace and get 10 seconds rest. In doing so he turns the set from a an EN2 set with very profound effects on his mitochondria, into an EN1 set with much less of an effect and a lower quality.
Swimming too Fast
So the coach puts this on the board:
2 x 800 swim easy (:30)
The swimmer doesn't recognize or doesn't understand set design and so does this at a pace very near to his critical pace. Or how about the swimmer goes out and does the first 400 faster than his critical pace, the 2nd 400 is slower than that and the 2nd 800 repeat is a very difficult slog but he manages to get within 2 seconds of critical pace. He swam that fast because because he "Can't go that slow". Did he do the right thing? Faster is always better, right?
Well what we didn't know about the swimmer is that he is a 51 year old sprinter with excellent times in the 50 and 100 and has struggled his whole life with big yards workouts. So while this set was of decent quality, the BIG main set for the week is in two days on Thursday morning when the coach planned on a 40 minute SP2 set. Come thursday, our swimmer in question is still not quite recovered and just doesn't feel right during the big set for the week.
So those are three problems that can arise when the swimmers don't understand what the underlying purpose of a set is. A problem by the way that YOU my dear reader won't have any longer because you are now versed in a nearly universal language of set construction.
How we change the mix of set types through the year to peak for the big race.