THE SET IS THE INTERVAL
How to change your approach to swim training for maximum effect
by Chris Bagg
Millions of years ago, during the early Holocene period, swim coaches developed organized swim training, as melting glaciers caused water to cover North America as far inland as Michigan and Vermont. At that point in our species’ history, swim training largely consisted of long steady swims, with little pace variation beyond what was needed for survival. After tens of thousands of years of this, swimmers began to complain: “Swim training is so boring,” they said, having called a summit with the coaches of the era, who had something of a stone fist where their workouts were concerned. “Do you think you can make these swims, I dunno, a little more…dynamic? Some of us have played around with that model and we discovered we can actually swim *faster*, which would be really helpful since the saber-toothed tigers are pretty solid swimmers.”
Most of the coaches executed their swimmers on the spot by tossing them into a local volcano that resembled the garment that would eventually be called a “hood,” but a few of the coaches begrudgingly started breaking their workouts into chunks and Lo, Interval Training was Born.
OK, the history is probably less exciting than that, but many endurance sports can trace a parallel track: before, there was only doing the activity for long stretches of time. Eventually, most endurance sports developed intervals as a way to lessen boredom and increase effectiveness. Swimming is no different, but along the way something happened. By focusing on intervals swimmers and coaches lost sight of the big goal in the first place, which is to stress the body in ways that set you up for success on race day. Today we are going to explain how and why intervals work, and how you can start seeing the forest (the sets that make up your workout) instead of solely focusing on the trees (the intervals).
Every Workout Needs a Goal
If you are a coach or a self-coached athlete, you need to know what every single workout on your training plan intends to accomplish. Recovery workouts help restore function to your muscles and joints by facilitating blood flow and repair; endurance sessions improve things like mitochondrial density and mitochondrial enzymes, fat oxidation, capillary density, and blood volume; sweet spot and FTP sessions do more of the same things endurance sessions do, but with additional fatigue, too; VO2max and anaerobic capacity sessions help make you faster by increasing our ability to transport and absorb the primary endurance currency (oxygen) or through forcing our bodies to swim, bike, or run at speeds that are unsustainable beyond a minute; finally, technique sessions help us learn how to move our bodies in the most mechanically efficient means possible.
So what is the goal of that workout you have on your calendar, the one that features 10x100 with :10 rest? If you don’t know, you need to find out, so let’s do that together.
Why Swim Intervals Exist in the First Place
Fake history of training intervals, aside, we need to know why swim intervals exist in the first place. Most swim coaches and athletes design pool workouts intended to fend off boredom rather than encourage physiological development. Let’s call it the “spin class effect,” where dynamism, noise, and company make the session seem to go by faster, but that approach exposes a problem right off the bat: disassociating from your workouts puts the focus on *getting through* the session, rather than getting something out of the session. So we need to set aside the idea that intervals exist to “break up the boredom.” Sure, that might be a nice side-effect, but it can’t be the goal.
Interval training works because intervals allow us to stress our system in specific ways through manipulating their duration, intensity, and recovery periods. This is why we need to know what the goal of the session is. If it’s a recovery session we need to design intervals that facilitate blood flow and mobility and don’t add additional physical strain. Threshold intervals need to stress the threshold system for relatively longer periods of time, like eight minutes or longer. VO2max intervals need to, well, max out our aerobic systems, which is best achieved through short relatively all-out intervals with long periods of recovery.
But it is never one single interval that achieves our goal (unless you are very, very new to training). A group of intervals, along with their rest periods, achieve our goals in the pool, and what is “a group of intervals” other than a set?
Comparing Swim Intervals to Bike/Run Intervals
Let’s think about cycling or running training for a bit. At this point in those sports’ histories, we know that large volumes of easy work produce an aerobic base that makes higher intensity work more effective. As intensity goes up, interval length tends to go down. If you have an “endurance” ride or run, it is likely that you simply go out and ride your bike or run for some set amount of time, without deploying intervals. If you’re doing threshold or sub-threshold work, you might schedule intervals that are 10, 15, 20, or 30’ in length. Think about sessions such as 4x15’ at FTP with 5’ recovery on the bike, or 3x2 miles @ threshold pace with 2-3’ recoveries. These are relatively long intervals with short rest which will stress your aerobic system (remember that threshold is contained within your aerobic system!). VO2max intervals on the bike and run are also fairly similar: 5x3’ as hard as possible on the bike with 3-5’ recoveries, or 6x800m on the track as fast as possible with significant recovery. When you’re doing VO2max work you need intervals that are as had as possible, and then long recovery intervals that are easy as possible so you can endure the agony again.
But we don’t seem to do this in the pool. Many swimmers would see the 10x100 with :10 rest and think the goal is to swim those as quick as possible, but who knows what that session is trying to achieve. Is it a recovery set with not enough rest? An endurance set for a new swimmer? A threshold set for an advanced swimmer? A poorly written VO2max session that gives the athlete no chance of success (try swimming as hard as you can with only ten seconds of rest in between intervals—we guess you’ll start slowing down quickly)?
We need to build SETS of intervals that clearly accomplish our goals. Since we don’t have many ways of measuring physiology in real time in the pool, we need to sensible about what we are designing, and what those sets will “mean” to the body. Maybe you need endurance work, which could be accomplished in the pool in two ways: long continuous swimming (good, but perhaps slightly boring), or moderately-paced intervals with short rest. So that 10x100 set needs more information, like an intensity or goal pace. Maybe we know this swimmer’s threshold pace, so we could re-write the sentence as “10x100 @ CSS pace + 6”/100 with :10 rest in between intervals” (or pick a sendoff that will accomplish the same goal). The rest is quite short, which doesn’t allow the body to exit the stimulus we’re looking for, and this swimmer has just accomplished 1000 meters of endurance stimulus without facing the mental hurdle of swimming a kilometer straight.
Building Sets to Accomplish Your Goals
So let’s talk about how different sets can accomplish the goal of the workout.
Endurance
As we just saw, endurance sets should be moderate effort and short rest. The key here is not swimming the intervals too hard, which will shift the stimulus to something else. For a new swimmer, an endurance set might only be something like 5x100 at 5/10 effort with :15 rest. For a deeply experienced athlete, an endurance set may be 10x400 at 5/10 effort with :20 rest. You should never feel like you are straining to accomplish the interval or, if you are using sendoffs, to make the sendoff with sufficient time to rest for 15-20 seconds.
Threshold
Swimming at or just below threshold is probably your best bang for your training buck, but it can also incur quite a bit of fatigue, which is why we can’t do threshold training every day of the week. Threshold sets *usually* total up to the distance of your next race, unless you’re mostly racing Ironman (3800m of threshold work is…probably way too much for a single session). Rest is slightly longer than endurance sets, but not much longer, since we’re still at a kind of controlled but hard pace. Here are some sample sets:
5x400 @ 7-8/10 effort with :20 rest
6x300 @ 7-8/10 effort with :15 rest
10x200 @ 7-8/10 effort with :10-15 rest
15x100 @ 7-8/10 effort with :10 rest
Not incredibly exciting, but threshold sets are rarely “exciting” across all three intervals. If you are working fairly hard and are starting to struggle in the final interval of the set, you have achieved this goal perfectly.
VO2max
VO2max work requires intervals that are long enough to actually get your body into maximal oxygen uptake, but short enough that you can carry the same effort throughout the whole interval. Very often this is something like 90” to five minutes in a cycling or running context, followed by 1:1 or 1:2 recovery periods (the ratio is between work and rest, so a 1:1 interval is something like 3’ work, 3’ rest, while a 1:2 interval would be 3’ work, 6’ rest). You can also simply prescribe “as much rest as you need to be fully recovered,” but in our experience Type A triathletes overestimate their ability to be fully recovered. It takes about 90” to get into VO2max, so pick an interval that will take you at least 90” to swim at maximal effort. Here are some sample sets:
6x100m AS FAST AS POSSIBLE, :60 rest on wall, 50-100m backstroke, float, or very easy pull
6x150m AS FAST AS POSSIBLE, :60 rest on wall, 100-150m backstroke, float, or very easy pull
5x200m AS FAST AS POSSIBLE, :60 rest on wall, 100-150m backstroke, float, or very easy pull
2x(10x(25m SPRINT, 25m FLOAT) with 5’ easy swimming between sets of 10x50
Get the idea? During an VO2max set you should be *resting* more than you are swimming. Make sure you’re taking the easy swimming very easy. If you do this you’ll actually be able to hit the higher paces required to stimulate VO2max. Shorten your recoveries and…well, we don’t know what you’re doing any more in that case.
Recovery and Technique Sets
Swim recovery sets as easy as is possible while maintaining proper technique. For technique take as much recovery as you need in order to approach the drills with focus and intent. Say it with us:
“Recovery and technique sets sit outside of normal endurance athlete time, where the goal is usually to get as much work per unit time as is possible. Recovery and technique sets reward ignoring time and listening to what your body needs right then.”
Conclusion
Swim development is challenging for all of us. Swimming is an alien movement (quadripedal and prone vs. bipedal and upright) in a medium that can kill us, so it’s understandable we all have some obstacles. But the biggest confusion about swim intervals is that they look like track intervals, where the goal is very often to run as fast as possible. Swimmers tend to look at intervals in the pool and think “10x100 with :10 rest…that must be intended to be hard, since the only thing I ever do is swim as hard as is possible because isn’t that what intervals mean?” If you’re seeing intervals and inferring you should be swimming as hard as possible, it is likely you have burnout in front of you, rather than sensible aerobic development.