CSS Critical Swim Speed Training: The Scientific Foundation of Pool Workouts, From Testing to Progress Tracking with Your Coach

Coach’s Opening: Why Your Pool Workouts “Show Effort but No Progress”

Having coached triathletes for years, the sentence I hear most often by the poolside is: “Coach, I swim three times a week, 2,000 meters each session—how come my times haven’t budged in six months?”

I usually ask one follow-up question: “At what pace are you swimming those 2,000 meters?”

The answer is almost always the same—“Well… I just swim as hard as I can,” or “I rest when I feel tired.” That’s the problem. On the bike, we have power meters and know exactly how many watts we’re pushing; when running, we have GPS watches and know our per-kilometer split. But once we hit the pool, many people leave all the science on the deck and swim purely by feel. The result is that every lap is swum in a mediocre “comfortable gray zone”—not easy enough to build aerobic base, and not hard enough to push the threshold. Training without purpose, in other words.

Today I want to talk about CSS (Critical Swim Speed), which is exactly what will help you quantify this. It’s the swimming equivalent of FTP—the pace anchor for all your interval workouts. Once you learn it, every lap you swim will have a clear purpose, instead of being a vague “swim as hard as I can.”

I once coached an engineer named A-Kai who worked in the Hsinchu Science Park. After finishing his first triathlon, he was stuck at the swim leg for a full year. He was smart and trained consistently, but he had no concept of pacing. After I ran a CSS test for him and redesigned his workout plan, his CSS pace improved from 2:05 to 1:52 per 100 meters within eight weeks—that wasn’t talent, it was method. Now I’m going to hand this complete method over to you.

Concepts and Scientific Basis: What Exactly Is CSS

Starting from Physiology

The concept of CSS comes from the “Critical Speed” model in exercise physiology. Simply put, it represents the highest swimming speed you can sustain for a long period without rapidly accumulating fatigue. Physiologically, this speed roughly corresponds to your lactate threshold (sometimes called the anaerobic threshold)—the critical point where the rate of lactate production and the rate of lactate clearance are in balance.

Below this speed, you can swim for a long time (aerobic-dominant); once you exceed it, lactate begins to accumulate faster, and within a short time you’ll feel overwhelmed, your technique will break down, and eventually you’ll be forced to stop.

In research, CSS roughly corresponds to an intensity of about 4 mmol/L blood lactate—the pace you could theoretically sustain for about 30 minutes of all-out effort. Studies have compared “30-minute test swimming speed (V30)” with “CSS derived from 200m and 400m tests” and found them to be quite close, with CSS overestimating by only about 3%. That’s why the 200/400 test is widely adopted—it’s time-efficient, reliable, and doesn’t require blood draws to measure lactate.

CSS Is the Swimming Version of FTP

If you have a cycling training background, this analogy will make everything click:

Sport	Threshold Metric	Measurement Tool	Typical Test
Cycling	FTP (Functional Threshold Power, watts)	Power meter	20-minute test × 0.95
Running	Threshold pace / Critical speed	GPS watch	30-minute time trial
Swimming	CSS (Critical Swim Speed)	Stopwatch / Swim watch	400m + 200m test

FTP is the pace foundation for all your cycling intervals; CSS is the pace foundation for all your swimming intervals. With it, you can say precisely: “Today this set should be at CSS, and this set at CSS + 5 seconds,” instead of a vague “swim faster.”

Why CSS Is Trustworthy

Many people will question: without blood draws or a lab, can two timed efforts really estimate your threshold?

The answer is—for training purposes, yes, it’s accurate enough. Research shows a fairly strong correlation between critical speed and 200m performance (after controlling for stroke and sex, the correlation coefficient is about -0.78; the number is negative because “faster speed means shorter time”). More importantly, the value of CSS isn’t whether it’s a lab-grade precise number—it’s that it provides a stable, repeatable reference point. As long as you test the same way every time, you can honestly see whether you’re improving. For training, that matters more than precision to two decimal places.

I also want to be honest about CSS’s limitations, so you don’t treat it as a cure-all. First, CSS is slightly higher than “maximal lactate steady state (MLSS)”—studies comparing critical swim speed with MLSS show that critical swim speed is usually a bit higher. So strictly speaking, CSS is a “slightly aggressive” threshold estimate, which is why I set threshold workout pace zones at CSS ±2 seconds rather than forcing you to swim every lap under CSS. Second, the conditions on test day (sleep, fatigue, water temperature, psychological stress) all affect the results, so don’t put too much weight on the absolute value of a single test—look at the trend rather than a single data point. Keep these two limitations in mind, and you’ll use this tool more maturely, without doubting yourself over a “1-second regression” on some test.

Practical Method One: How to Properly Perform a CSS Test

This is the foundation of the entire system—if you get this wrong, everything downstream is wrong. Please follow it exactly.

Pre-Test Preparation

• Choose the right venue: Find a standard 25-meter or 50-meter pool. Most sports centers in Taiwan have 25-meter pools, which work perfectly. Avoid testing during crowded times when you’d constantly have to dodge other swimmers.
• Warm up thoroughly: At least 800 to 1,000 meters of progressive warm-up, including a few short sprints (e.g., 4 x 50m, accelerating in the last 15 meters of each), to get your body ready. Jumping in cold and testing directly will definitely yield slower data.
• Be in good condition: Don’t test the day after heavy training, or when sleep-deprived. Ideally, schedule it on a relatively easy day.
• Prepare timing: A waterproof swim watch is most convenient; if you don’t have one, ask a friend or coach to time you with a phone stopwatch on the deck.

Test Protocol (Core)

1. First effort: 400m all-out timed swim. Push off from the wall (no diving start, for standardization), and swim 400 meters at the fastest pace you can sustain steadily. The goal is even splits or negative splits (second half equal to or faster than the first half). Record the total time, to the second.
2. Active recovery for 5 to 10 minutes. This step is extremely critical. Swim easy or rest completely, and wait until your heart rate drops below about 120 bpm and your breathing is fully settled before starting the next effort. If recovery is insufficient, the 200m will be too slow, and the entire CSS will be distorted.
3. Second effort: 200m all-out timed swim. Again push off from the wall, and swim 200 meters at the fastest pace you can sustain. Record the total time, to the second.

Calculating Your CSS

The formula is very simple:

CSS pace per 100 meters = (T400 − T200) ÷ 2

Where T400 and T200 are both converted to seconds.

Here’s a practical example. Suppose your results are:

• 400 meters: 6 minutes 20 seconds = 380 seconds
• 200 meters: 3 minutes 00 seconds = 180 seconds

Then CSS = (380 − 180) ÷ 2 = 200 ÷ 2 = 100 seconds / 100 meters = 1:40 / 100m.

This “1:40 / 100m” is your critical swim speed—the pace anchor for all your upcoming workouts. I recommend saving it in your phone’s notes or training log.

Common Test Number Comparisons

To give you a sense of the numbers, here are several common test results and their corresponding CSS:

400m Time	200m Time	CSS / 100m	Approximate Level
8:00 (480s)	3:50 (230s)	2:05	Beginner triathlete
6:40 (400s)	3:12 (192s)	1:44	Consistent finisher
6:20 (380s)	3:00 (180s)	1:40	Advanced age-grouper
5:40 (340s)	2:42 (162s)	1:29	Competitive level
5:00 (300s)	2:24 (144s)	1:18	Elite / former pro

Note: This table is a reference to help you figure out “which range you fall into,” not a target value. Everyone’s body type, technique, and training years differ, so comparing yourself to others is meaningless—comparing yourself to where you were three months ago is what matters.

Practical Method 2: Designing Interval Workouts Based on CSS

Now that you have your CSS, the key question is—what percentage of CSS should different workouts be swum at? I’ve organized the commonly used pace zones into a table, which is your core tool for planning workouts.

CSS Pace Zone Table

Zone	Relative to CSS	Purpose	Feel
Aerobic Base	CSS + 8 to 15 seconds	Build aerobic foundation, recovery days	Easy, can hold a conversation
Endurance	CSS + 4 to 8 seconds	Extend aerobic work, solidify technique	Comfortable but focused
Threshold	CSS − 2 to CSS + 2 seconds	Raise CSS itself	Hard, sustainable
VO2max	CSS − 3 to CSS − 6 seconds	Improve oxygen uptake capacity	Very breathless, short high-intensity efforts
Sprint	All-out	Neuromuscular, explosive power	Short distances, maximal effort

How to use it: Let’s say your CSS is 1:40 / 100m (100 seconds). Then “threshold sets” should be swum at approximately 98 to 102 seconds per 100 meters; “aerobic base” should be slowed down to approximately 108 to 115 seconds per 100 meters.

Three Practical Workout Examples

The following three workouts use a hypothetical athlete with a “CSS = 1:40 / 100m” as an example. You can scale them proportionally based on your own CSS.

Workout A: Threshold Intervals (the main workout for raising CSS)

• Warm-up: 300m easy freestyle + 4 × 50m build-up (15 seconds rest between each)
• Main set: 8 × 100m @ CSS (target 1:40), 15 to 20 seconds rest between each
• Advanced version: Change to 5 × 200m @ CSS, 20 seconds rest
• Cool-down: 200m easy swim
• Total volume: approximately 1900m

This is the most important workout. Short rest intervals while maintaining CSS pace directly stimulate your lactate threshold. You might only manage 6 reps at first—that’s fine, gradually build up to 8, then 10 reps.

Workout B: Aerobic Endurance (building the foundation)

• Warm-up: 300m + 200m kickboard
• Main set: 3 × 400m @ CSS + 6 seconds (target 1:46), 30 seconds rest between each
• Technique insertion: 4 × 50m unilateral breathing / catch-up drill
• Cool-down: 200m
• Total volume: approximately 1900m

This workout has a slower pace and longer distances, aiming to build a thick aerobic base. The swim leg of triathlons (especially 113 half-iron and 226 iron-distance) is essentially prolonged aerobic work, so this type of workout is essential.

Workout C: Mixed Pyramid (race pace feel)

• Warm-up: 400m progressive
• Main set (pyramid): 100 / 200 / 300 / 200 / 100m, all @ CSS, 20 seconds rest between each segment
• Bonus: 6 × 50m @ CSS − 4 seconds (fast set), 20 seconds rest
• Cool-down: 200m
• Total volume: approximately 1900m

The pyramid workout trains your ability to maintain pace over different distances and is also less monotonous, making it a good variation workout for the week.

Workout D: Short Interval VO2max (raising your oxygen ceiling)

• Warm-up: 400m progressive + 4 × 50m build-up
• Main set: 12 × 50m @ CSS − 5 seconds (target approximately 1:35 converted to 50m ≈ 47.5 seconds), 20 to 25 seconds rest between each
• Mid-set recovery: 100m easy swim
• Bonus: 4 × 25m sprint (all-out), 30 seconds rest
• Cool-down: 200m
• Total volume: approximately 1700m

This workout has the highest intensity. Schedule it at most once a week, and only for advanced athletes with a solid training foundation. VO2max short intervals push your oxygen uptake “ceiling” higher—once the ceiling is higher, the threshold naturally has more room to improve. Beginners should skip this one for now and wait until their aerobic base is solid.

Why These Percentages? The Science of Rest Intervals

Many people think the key to interval workouts is only “how fast you swim,” but the length of the rest interval is equally critical. The short rest in threshold workouts (15 to 20 seconds) is deliberately designed—it prevents full recovery, maintaining a certain physiological stress that forces the body to adapt to “continuously clearing lactate.” If you extended the rest to 60 seconds, the workout’s effect would shift from “threshold training” to “repeated sprints,” targeting something completely different.

Conversely, VO2max workouts (Workout D) actually need slightly longer rest (20 to 25 seconds) because the pace is faster and the stress per rep is higher; too little rest will cause you to fall apart mid-set and your pace to collapse. Remember one principle: the closer the pace is to CSS, the shorter the rest; the more the pace exceeds CSS, the relatively longer the rest should be.

How to Schedule Your Week

Using a triathlete who swims three times a week as an example:

Day	Workout Type	Focus
Tuesday	Workout A Threshold Intervals	Raise CSS
Thursday	Workout B Aerobic Endurance	Build foundation, work on technique
Saturday	Workout C Mixed Pyramid	Race pace, variety

If you can swim four times a week, you can add a pure technique / recovery swim (easy aerobic at CSS + 12 seconds throughout, combined with plenty of technique drills). Remember the principle: leave at least one day between high-intensity workouts—don’t schedule two threshold workouts on consecutive days.

Tracking Progress: How to Know You’re Actually Getting Faster

Retest Regularly

The most direct method is to redo the CSS test every 4 to 6 weeks. Use the exact same protocol, and as much as possible the same venue and time of day, for a fair comparison. Record the results each time, and you’ll see a clear progression curve.

Using my earlier example of the athlete A-Kai, his tracking record looks like this:

Week	CSS / 100m	Notes
Week 0	2:05	Initial test
Week 4	2:00	Adaptation period, noticeable improvement
Week 8	1:52	Technical improvements starting to show
Week 12	1:49	Progress slowing, normal

Notice the slower progress from week 8 to 12—this is completely normal. Early in training, progress is fast (much of it driven by technique and neural adaptations), and the further you go, the more patience is required. Don’t panic when you hit a plateau; that’s your body consolidating.

Tracking Pace “Stability”

Beyond the CSS number itself, I care more about whether an athlete can maintain a stable pace during threshold workouts. Take 8 × 100 meters @ CSS as an example: someone who can hold every repeat within ±2 seconds is in a completely different physical condition than someone who goes 1:38 on the first repeat and drops to 1:50 on the last. Recording each split with a swim watch and observing whether the pace falls off noticeably in the latter half reflects true endurance far better than a single CSS number.

Heart Rate as a Secondary Reference

If you have a swim watch that supports heart rate in the water, watch for this: at the same CSS pace, does your heart rate gradually decrease? When your heart rate at 1:40 pace slowly drops from 155 bpm to 148 bpm, it means your cardiorespiratory system is becoming more comfortable at that intensity—this is a good sign of aerobic improvement, even if your CSS number hasn’t moved yet.

Using Stroke Rate and Distance Per Stroke to Fill Blind Spots

Advanced athletes can track two more technical metrics: stroke rate (strokes per minute) and distance per stroke (how far you travel per stroke, i.e., how many strokes you take per length). Real technical progress often shows up as “completing the same pace with fewer strokes.”

For example, in week 0, A-Kai took 22 strokes to swim one 25-meter pool length; by week 12, he only needed 18 strokes at the same pace—meaning he was catching more water with each stroke and being more efficient. When distance per stroke increases without a spike in stroke rate, that’s hard proof of genuine technical improvement. This metric can even reflect your progress earlier than the CSS number, because technical gains usually lead performance improvements. I recommend recording it alongside CSS in your training log.

A-Kai’s Complete Eight-Week Story

Let me flesh out A-Kai’s case a bit more so you can see how the method plays out in practice. His initial problem wasn’t a lack of effort—it was that every time he got in the water, he’d just grind out 2,000 meters at one pace, finishing exhausted and directionless.

The first thing I did wasn’t to add volume—it was actually to cut volume. I changed his training from “mindless 2,000” to a structured 1,900 meters, but with a clear pace target for every repeat. The second thing was spending two full weeks on technique only: his elbow dropped too low during the pull (commonly called “dropping the elbow”), so he couldn’t catch water—every stroke was wasted effort. I used lots of catch-up drills and unilateral breathing to rebuild his pull pattern.

Once the technique changed, something remarkable happened: when he retested in week 4, his CSS improved from 2:05 to 2:00, but he said it himself—“it feels easier than before.” That’s the sensation of improved efficiency. Then, from weeks 5 to 8, I finally introduced formal threshold intervals (Workout A). By then his body had enough technical foundation to handle the intensity, and his CSS pushed all the way down to 1:52. Eight weeks, 13 seconds of improvement, no secret formula—just three steps: “fix technique first, then add intensity, and pace everything by CSS throughout.”

Common Mistakes and Fixes

Having coached so many athletes, I see the same mistakes almost every month. Please read this section carefully.

Mistake 1: Swimming the 400 Too Fast During Testing

When many people hear “all-out,” they swim the first half of the 400 at sprint speed, then blow up badly in the second half, producing extremely uneven splits. This makes the 400 time slower than it should be, makes the 200 look relatively fast, and the resulting CSS comes out faster than reality (unrealistically optimistic).

Fix: Treat the 400 as a “controlled all-out” effort, aiming for even splits or a slightly faster second half. Better to be conservative early than to go out fast and fall apart.

Mistake 2: Not Resting Enough Between the Two Efforts

To save time, many people barely catch their breath after the 400 before charging into the 200, so the 200 comes out slower than their actual ability and CSS gets underestimated.

Fix: Honestly wait until heart rate drops below 120 bpm. Better to rest an extra minute than to let the data become distorted. Spending 20 minutes total on the test is perfectly reasonable.

Mistake 3: Swimming Every Workout at the Same Pace

This is the most common—and most damaging—mistake: whether it’s a threshold session or a recovery session, everything gets swum at the same “kind of tired” pace. This is exactly how the “comfortable gray zone” I mentioned earlier develops.

Fix: Strictly follow the CSS pace zone table. Recovery days should be slow enough that you can “easily hold a conversation”; threshold days should be hard enough that you can “maintain it but need real focus.” Intensity needs clear separation for training to provide stimulus.

Mistake 4: Training Only Fitness, Not Technique

Swimming is the endurance sport with the highest technical component. Given the same fitness level, someone with good technique can easily be much faster than someone with poor technique. Trying to push CSS purely through physical effort is extremely inefficient.

Fix: Keep a technical component in every workout (stroke drills, unilateral breathing, catch work, body rotation). CSS improvements from technical gains tend to come faster and last longer than from pure fitness training alone. More than half of A-Kai’s progress in the first eight weeks came from technique correction.

Mistake 5: Never Retesting, Adjusting Pace by Feel

Some people test their CSS once and use it forever, never retesting for six months. The problem is that once you improve, your old CSS pace is too slow for you—threshold workouts become aerobic sessions, and the stimulus is insufficient.

Fix: Retest every 4 to 6 weeks and update your pace anchors promptly.

Taiwan-Specific Context: Fitting Training into Real Life

Pool Selection

Most sports centers across Taiwan’s cities and counties have 25-meter pools with stable water temperature and quality—a good choice for CSS training. If you want a change of pace in summer, you can also practice “open-water transitions” at lifeguarded open-water venues (such as Sun Moon Lake or certain ocean swim spots)—but for CSS testing itself, I recommend staying at the same pool every time to minimize variables.

Race Alignment

If your goal is a popular Taiwan triathlon like Puyuma Ironman (Taitung), Challenge Taiwan, or the LAVA series, the swim leg is typically open water ranging from 1.5 km (standard distance) to 3.8 km (long distance). This kind of distance is essentially “the ability to sustain a pace below CSS for a long time,” so both aerobic endurance work (Workout B) and CSS threshold work (Workout A) are essential. Six to eight weeks before race day, I recommend lengthening the individual sets in Workout B (e.g., changing to 2 × 600 meters) to simulate race continuity.

Climate and Hydration

Taiwan’s summers are hot and humid—even in an indoor pool, you lose a significant amount of fluid during training. Be sure to replenish fluids and electrolytes after longer sessions. If a session exceeds one hour and is high-intensity, consuming roughly 300 to 500 kcal of a proper meal or snack afterward (for example, an onigiri plus a tea egg, or a bowl of braised pork rice with blanched vegetables) helps recovery—both are convenient options from Taiwan’s food scene. These are general ranges; actual needs depend on individual body weight, sweat rate, and training volume.

Actionable Advice for Athletes at Different Levels

First-Time Triathletes (Still Building Finish Capacity)

• Get your CSS tested first—don’t worry about whether the number looks good; it’s just a starting point.
• For the first three months, focus your training on technique and aerobic foundation (primarily Workout B), with threshold sessions at most once per week.
• The goal is “finishing the race distance comfortably,” not “swimming fast.” First build the ability to finish steadily, then talk about speed.
• Retest every 6 weeks and enjoy the sense of accomplishment from rapid early progress.

Advanced Athletes Who Finish Consistently (Looking to Break Personal Records)

• Arrange the three workouts (A/B/C) evenly, training three to four times per week.
• Pay special attention to pace stability in threshold workouts, tracking each split with a swim watch.
• Start adding VO2max short intervals (e.g., 10 × 50 meters @ CSS − 4 seconds) to stimulate your aerobic ceiling.
• Do race-specific pace simulations 6 to 8 weeks before race day.

Competitive / Elite Age-Group Athletes

• CSS is just a baseline anchor; you need finer zone divisions (further subdividing threshold into sub-threshold, threshold, and supra-threshold).
• Consider periodized training (base phase → build phase → pre-race taper), and think about working with a professional coach who has physiological testing capabilities for more precise lactate or power (swimming power meter) assessments.
• Progress is measured in seconds—even fractions of seconds—so tracking must be more rigorous, and refining technical details is where races are won or lost.

FAQ

Over years of coaching athletes, a few questions come up almost every time. Here they are, all organized for you in one place.

Q1: I’m a complete beginner and can’t even finish 400 meters. Can I still test CSS?

Don’t rush into it. The CSS test requires you to swim 400 meters “continuously and with rhythm.” If you can’t finish 400 meters, the priority is building foundational continuous swimming ability and technique, not rushing to get a number. Spend a few weeks building your continuous swimming distance to over 400 meters first; only then does testing CSS make sense. At this stage, the focus is on technique and relaxation, not speed.

Q2: After getting my CSS, how often will I need to adjust my pace?

If you train consistently, you’ll typically improve to the point where “the old pace feels too easy” within 4 to 6 weeks. That’s when you should retest and update your pace. If you notice threshold sets getting easier and your heart rate getting lower, that’s your body telling you “it’s time to retest.”

Q3: Will CSS measured in a 50-meter pool and a 25-meter pool be the same?

Strictly speaking, there will be slight differences—a 25-meter pool has more turns, and each push-off the wall can “steal” a bit of speed, so times in a 25-meter pool are usually slightly faster. This isn’t a problem; the key is always testing in the same type of pool. As long as you consistently test at the same venue, you can fairly compare your progress without worrying about absolute differences between pools.

Q4: Can I test CSS using breaststroke or other strokes?

Yes, but note that comparisons are only meaningful within the same stroke. Triathlon races are primarily freestyle (front crawl), so it’s usually recommended to test with freestyle. In research, the concept of critical speed applies to all four strokes (freestyle, backstroke, breaststroke, butterfly), but CSS values from different strokes cannot be compared with each other. If you race freestyle, test with freestyle.

Q5: Do I need a swim watch? What if I don’t have a waterproof watch?

Not necessarily. A swim watch is convenient, but not essential. You can have a teammate or coach time your 400 and 200 with a phone stopwatch from the pool deck, and you can still calculate CSS. During training, many pools have large clocks on the wall that you can use to monitor your pace. Tools are aids; the method is what matters.

Q6: I’ve hit a plateau and my CSS hasn’t budged for weeks. What should I do?

Plateaus are normal—don’t panic. First, check three things: First, is your training varied enough? If you’ve been doing the same workout plan for a long time, your body adapts. Try switching to Workout C or D to add new stimuli. Second, is your recovery sufficient? Progress happens during rest, not during training; overtraining can actually stall you. Third, is there still room for technical improvement? When fitness hits a ceiling, technique is often the next breakthrough. If necessary, find a coach to video-analyze your stroke.

Conclusion: Make Every Lap Count

Back to the opening phrase, “training without progress.” The real reason is often not that you aren’t working hard enough, but that your effort lacks direction. What CSS gives you is that direction—it lets you know how fast to swim each interval, what each workout is training, and whether you’ve actually improved after six weeks.

I often tell my athletes: swimming isn’t about who swims the most, but who swims with purpose. Get your CSS measured, structure your workouts around that pace, and honestly retest every six weeks. Do these three things, and you’ll find that progress is no longer a matter of luck, but something that can be designed and anticipated.

Before you hit the pool next week, spend 20 minutes getting your CSS measured. Those 20 minutes will change all your training from that point on. In swimming, it’s never about who is naturally more comfortable in the water, but who is willing to use the right methods and accumulate patiently. I wish you a downward progress curve the next time you retest. See you at the poolside.

---

This article is for educational purposes and does not replace individual assessment by a physician, physical therapist, or nutritionist.

References

• Critical Swim Speed (CSS) Calculator — Topend Sports: https://www.topendsports.com/testing/tests/critical-swim-speed.htm
• Validity and reliability of critical speed, critical stroke rate, and anaerobic capacity in relation to front crawl swimming performances — PubMed: https://pubmed.ncbi.nlm.nih.gov/11842355/
• Does critical swimming velocity represent exercise intensity at maximal lactate steady state? — Springer: https://link.springer.com/article/10.1007/BF00863406
• Stroke-Specific Swimming Critical Speed Testing: Balancing Feasibility and Scientific Rigour — PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC10875687/

Related Reading

• CSS Critical Speed Explained: The Science of Designing Swimming Interval Workouts
• 8-Week Swimming CSS Pace Training: Core Workouts for Mastering Critical Speed
• Swimming CSS Critical Speed Testing and Training Applications: Finding Your Aerobic Threshold Pace
• Building Your Swimming Aerobic Base: CSS Critical Speed Training Methods