This article is written by Tom Jenkinson, Coach at Envol, who are providing training support for UltraSwim 33.3 in 2024

*Image by Lloyd Images / UltraSwim 33.3 #2Montenegro*

If your squad pool-base training is similar to mine we rarely do intervals longer than 400m. Do this kind of training enough and you will get very good at swimming a fast 400 at the end of the series of 400s.

As a Marathon or Ultra distance swimmer your race performance will not correlate with a rapid 400 in the pool, so resist the urge to swim intervals as fast as you are capable of. It may look good on Strava, but the real focus should be on economy and speed below threshold - in other words, your sustainable swim speeds.

“Remember that the lower half of your performance curve is where you want to see real improvement - this is very different from the priorities of most competitive pool swimmers”

— Quote Source

Two important but simple metrics for you to track and improve over time are the number of swims per month and the accumulated swim distance per week. Remember, swim often, get your aerobic work done, and make sure your Easy/Steady is truly Easy/Steady.

For most swimmers following this advice is going to get you where you need to be, but for more advanced distance swimmers looking to maximize performance, I suggest that you incorporate additional test sets to fine-tune your swim training.

5x400 test set

We discussed at length Critical Swim Speed (CSS) testing and training HERE - If you haven’t read it please do, as it provides additional context. If you’ve got your CSS-based zones, you can test them by swimming this 5x400 test set.

Swim 5x400 with 15s rest between each 400.

Descending time (getting faster) - focus on swimming each 400 a little quicker than the one before. You can compare these resulting swim “gears” with your Zones 1-5 - how did they line up?

Even if you passed the test we should still be cautious about our conclusions, after all the CSS test itself and these 400s, are short-duration intervals. Just like sub-max benchmarking for the run and bike to get more precise input we need to test these paces with longer duration swims.

Testing Easy & Steady Paces

Swim 1000 continuous, Easy - Rest 10 seconds

Swim 1000 continuous, a little faster

Compare these average paces to the results from your 5x400 swim.

To test Steady Pace, use the same set and start with Steady Pace. This is VERY important - If you can not swim faster on the second 1000 then the first one was not Steady Pace!

Testing Holding 3rd Gear

Many trained swimmers will discover that “3rd Gear” is their distance race pace. Race pace in the sense that they are on borrowed time once they are working for any sustained period at a pace faster than 3rd Gear.

We can test that hypothesis by swimming 2000m (continuous) holding 3rd Gear Pace from your 5x400 test.

Alternatively you can try 4x500 with only 5s rest holding 3rd Gear Pace. The very short rest lets you assess with your rating of perceived exertion and get splits across the 2K. How did those splits compare to your 5x400 results?

Through this type of testing you may discover that you have been doing an inverted 80:20 training program with 80%+ of your swim volume being Z3 - Tempo/Moderately-Hard or even faster.

Given the culture of most swim programs, this is perhaps not surprising. The diagram below compares different intensity zoning systems. You can see a strong bias and focus on swim speeds over the Maximal Lactate Steady State (MLSS)/LT2 Threshold Pace. Again, not surprising when you consider that 1500m is considered “long-distance” and takes the elites around 15 minutes to complete! It would be the equivalent of most of the running world and its coaches being practically blind to training for events longer than 5000m.

This makes our training requirements rather unique in the swimming world as the focus and training principles of these leading systems are perhaps not the most optimal way to make real gains in true distance swimming performance.

The MyProCoach Swimming zoning model (triathlon training origin) that I use and that is linked in the CSS Training article, has much more in common with the zoning found in endurance run and bike training where Z4 is around LT2 (which is the same as MLSS in the diagram above).

It looks like this:

Zone 1 - 77 to 87% of Threshold Pace - Gear 1 Easy

Zone 2 - 87 to 94% - Gear 2 Steady - Close to LT1 (LT in the diagram)

Zone 3 - 95 to 98% - Gear 3 Moderately Hard - Above LT1 but below LT2

Zone 4 - 99 to 104% - Gear 4 Hard - Around LT2 (MLSS in the diagram)

Zone 5 - 105 to … - Gear 5 Very Hard - VO2 Max and above

More Tests?

If you want to take your testing further you can try these.

The 2K Best Effort

The 2000m best effort test which is performed as

100 Steady,

400 Fast, 100 Steady,

400 Fast, 100 Steady

300 Fast, 100 Steady

200 Fast, 100 Steady

200 Fast

This approach simulates the changes of pace you will experience in an open water race. It’s also easier mentally than holding a continuous pace. Finally, it teaches you to hold focus and form after a surge with 100 Steady. Racing well is about being able to recover without a major decrease in pace.

Other Options to Test Your Swim Gears

5x800 Descend 1-5

Rest 20 between the 800s, end with a 4th Gear effort, but don’t max out.

8x500 Double Descend

Rest 15 seconds between the 500s, descend in twos, end with a 4th Gear effort, but don’t max out.

5x1000 Descend 1-4 then swim Steady/2nd Gear

Rest 60s between the 1000s, this is a good set for Open Water as you may find that 2nd Gear “changes” after 4K of swimming.

Final Words

Incorporating these kinds of test sets into your swim training will keep you honest in your distance swim paces. They will also give you some variety and a few challenges along the way. This allows you to gain valuable feedback to address any true weaknesses in your swim training approach.

Happy Laps, Tom.