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Experienced and accomplished swimmers (still practicing) tend to have well-developed swimming-specific fitness from their years of training, even after taking time off. When they begin retraining their stroke technique a challenge in that process is that they can get away with swimming fast or far with the old technique – they might switch from new pattern to old pattern when stress reaches a threshold because the new circuits are not yet strong. Outwardly they might be able to keep similar metrics and pace, but inwardly they notice the shift in loading and energy expense (hence, their motivation for changing technique!). In this case a special kind of discipline is required in training to resist sending signals through those old circuits long enough to build dominance in the new ones.

For less-developed swimmers, those without long and strong history in the sport, there may not be a deep base of swimming-specific fitness in place (like a big investment sitting in the bank account) as they begin learning better technique. When they start swimming intervals with some intensity or swim a continuous test distance they hit a wall in NNN number of meters, where their metrics and pace fall off dramatically, the moment they feel it is getting tough. An experienced swimmer can push past for a while and hold pace (while burning energy at a higher rate) but a less-developed swimmer typically cannot do this.

Low Fitness?

The question that often comes in some form from less-developed swimmers is, “I’ve been practicing technique for a while. But I am still getting exhausted at XX meters. It is because my fitness is too low?”

It could be.

We understand in TI that technique and fitness are always developed together. Let me refresh the definition of those two:

  • Fitness is your ability to generate and sustain power (metabolic systems).
  • Technique is your ability to deliver that power where it is needed, when it is needed, with consistent precision (neurologic systems).

Obviously, you want to have both well-developed together in order to swim with any sort of efficiency.

All repetitive movement is training the neuro-muscular system to prefer a certain pattern, and all movement requires muscle activation and metabolic support. In other words, every time you generate power you are also sending it somewhere, and through those movements your body is memorizing where and how to send it. But many adult-onset swimmers may not have evenly developed systems in both the neurologic and the metabolic side of the equation – and very few, even among swimmers with a long history, will be following programs designed to develop both sides proportionally. To address the weaker system we need to adjust variables of intensity both in terms its neurological load and its metabolic load on the swimmer in the practice planning.

In this essay when I use the term ‘metabolic’ I am referring to the systems that generate and sustain power, and when I use the term ‘neurologic’ I am referring to the systems that direct power with precision. They refer to a category of systems. Then one can view either category as having a degree of ‘fitness’ to it, according to how well-prepared the systems in that category are.


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Three Possible Weak Spots

To provide a simplified list for your self-examination, the weak spot in your performance equation could be one of these issues:

  1. Your ability to hold focus (awareness) is weak.
  2. Your ability to hold precise control (circuit strength) is weak.
  3. Your ability to sustain power (metabolic fitness) is weak.

First, understand that you have several systems that all have to be developed to an equal level of fitness and work together in order to hold a strong and efficient pace over a targeted distance. You will be limited by the weakest system in that team. Since the metabolic system is the easiest to measure and prescribe activity for it gets virtually all the attention in traditional training. However, for many adult-onset swimmers the metabolic is often not the weakest member of the team even though it be weak compared to your more accomplished peers. And training the metabolic more intensely will not magically remove the weaknesses of the other systems.

So we need a way to isolate the systems and run test for them to see which is more likely the limiting factor at this moment in your performance. Then you can train more deliberately in that weak area to bring it up to an even level with your other systems, then train all of them together, proportionally.

Giving adequate rest is an extremely important part of this test, because the objective depends on you giving enough rest to your metabolic system so it will not limit your performance unless it is absolutely the limiting factor. Usually, it appears that swimmers are pushing their metabolic limits so much so often, it is hard to recognize when neurologic failure is the primary cause of poor performance. That is what we are trying to expose with this test.

Who is this test suited for?

This test is suitable for those who are swimming slowly compared to your peers and not able to swim continuously farther than NNN meters (some disappointingly short distance) without crossing an uncomfortable threshold of effort. If you have not been practicing diligently to improve technique this test is not for you (yet), but if you have, and you are wondering if your weakest link is technique or fitness this test may help you identify which.

Test Instructions

0. Warm Up

Complete a gentle, varied warm-up for 10-15 minutes, covering up to 800m. Silent swimming, with mixed stroke styles is a great generic warm-up.

1.Choose Suitable Interval Distance

Choose an interval distance that corresponds to the failure point distance you often experience. I am anticipating it should be something like 50, 100, 200, or 400 meters. And, you don’t know how many intervals you will do, because that is what this test will measure. You will allow this test to be open-ended – do as many as you can until you can’t swim within the parameters you’ve set for the test.

2. Rest Interval

Choose a generous rest interval – like 30 to 60 seconds, or more. But consider, you don’t want the rest interval to be too short (because your heart rate will not recover enough) nor too long (because your systems will ‘lose steam’ and it will be harder to build up metabolic momentum to start the next interval). So, there is an optimal rest window in there.

How to do this? Nasal breathing at the wall is a great way to find this window. When you get to the wall, do NOT talk or interact with anyone. Just sit down until you are buoyantly resting in the water, still. Think about what you just did on the last interval and what you are going to do better on the next one. Inhale/exhale only through the nose. Initially, when the heart rate is too high your body will want to emphasize the exhale, getting rid of carbon dioxide. But once it has reduced those levels, the breathing will shift to an inhale emphasis, and that means the chemical balance has shifted, and the heart rate is recovered.

3. Parameters To Hold

Aim to swim within these parameters:

Aim to swim at somewhere between 60-80% intensity level, (RPE 3 – see the chart on our Resources page) as if you were running a moderate pace, and aim to keep that intensity level consistent. You will want to note when that RPE changes (beyond your control) during the test because that is one feature we are looking for.

Level 1 – Choose one stroke-controlling focal point (one that you have been working with so it can be tested) and hold that focal point consistent on every length of the interval. You may alternate between two focal points, but be strict about switching after each length or interval only – according to your plan – your ability to hold attention as intended is what is being tested.

Level 2 – Aim to hold a consistent SPL on every single length.

Level 3 – Aim to hold a consistent Pace (a specific SPLxTempo combination) on every single length.

4. Self-Assessment Questions

As you go along, on one of those intervals you will feel like you are crossing a threshold to much more difficult effort. And that is when you ask the assessment questions (listed in the next section).

5. At Threshold, Keep Going or Stop?

When you feel you are approaching the threshold (of failure in one of your parameters) on an interval, take a good rest and try again. Use that rest time to refresh your attention, consider where there was an error in your control, and decide on a way you will improve your focus and control on the next interval.

The threshold may be experienced in:

  • Effort level
  • Attention
  • Control
  • Strength

If you can do the next interval and still maintain your parameters as intended, even as your strength seems to lower, that is ok. Keep going. But if you lose attention, or you lose control over a body part and you cannot regain it on the next interval even after resting extra – your test is done.

Assessment Questions

How many intervals did you successfully make within your parameters? More than you expected, with so much rest? Or still too few?

In that moment when you felt you were approaching or crossing the threshold into failure, what appeared to be the weakest system? What started failing first?

  • My ability to hold attention on a focal point?
  • My ability to hold precise control a certain part of my body?
  • The strength in my muscles? (so I could not keep up the speed)

You may ask, what is the difference between the last two? There is a neurologic difference. A swimmer with well-trained attention and control can swim for hours without refueling  and maintain nearly perfect precision in stroke form, but just can’t muster any more strength to go faster – speed drops in gradual steps according to drops in energy level – but control over movement precision remains.

In this test you are searching for the strength difference between the neurologic and the metabolic systems.

You might be able to swim farther but your stroke control falls apart. This indicates weakness on the neurologic side and suggests this is currently your limiting factor in swimming farther and faster.

Or, you might be able to swim farther with acceptable stroke control, but your strength falls way off (speed goes way down). This indicates a weakness on the metabolic side and suggests this is currently your limiting factor in swimming farther and faster.

If they both seem to fall away together, then you might have a fairly even balance of neurologic and metabolic development, and you can continue to distribute challenges in your practice time between those two.


I run these tests with my athletes from time to time to help us see where the weak spots are and relieve the uncertainty about what should be emphasized in practice.

If this intrigues you and you try the test I would appreciate hearing how you experienced it, and what it revealed to you.


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