A biophysical way to train faster without guessing
Training zones are intensity bands that group your swims by how your body and stroke respond. They help you choose pace, rest, and focus so each set builds fitness and skill on purpose. In competitive swimming, this paper argues zones should blend physiology and biomechanics, not one metric alone.1
The reason this matters is simple. Swimming performance is not only “how fit you are.” It is also “how well you move.” The authors frame it clearly. Swimming speed is shaped by both physical conditioning and technical proficiency, so training zones should be built from physiology and biomechanics together.1 That single sentence explains why some athletes work hard all season yet plateau. They train intensity, but they do not train the right intensity, and they do not protect technique while doing it.
The Stopwatch Wake Up
When performance forces better questions
The inspiration behind awareness of this article usually shows up in a very normal place. It is the practice where you feel strong, your lungs are fine, and your splits still drift. You leave the pool thinking you trained hard, but you cannot explain what the hard work actually targeted.
Fernandes, Carvalho, and Figueiredo push back on the “one number solves everything” habit. They note that coaches often use a single value from oxygen uptake, blood lactate, or heart rate to define a zone or describe an event, even though those variables change across the full duration of exercise.1 Their proposal is a zone system built on oxygen uptake kinetics across low, moderate, heavy, severe, and extreme intensity domains, alongside lactate and heart rate. Then they add stroke frequency, stroke length, and an inter-arm timing metric called the index of coordination, because technique is not optional in the water.1
If you have never heard “oxygen uptake kinetics,” here is the simple meaning. It is how quickly your body ramps up oxygen use when you start swimming and how that response behaves as intensity rises. At lower intensities, oxygen use rises and then settles into a steady state. Above key boundaries, that steady state breaks, fatigue builds faster, and technique tends to degrade more visibly.1
The paper’s core performance message is that each training day should have a job, and you should be able to prove it. Below or around the anaerobic threshold, the swimmer can stay closer to homeostasis with stable internal and external indicators. Above that line, stability fades and anaerobic contribution grows, with technical degradation more evident near the pace associated with maximal oxygen uptake.1 That is not a scare tactic. It is a coaching map. It tells you where you can build volume with control and where you must train intensity with precision.
- The zones are tied to intensity domains and anchored by key boundaries such as the anaerobic threshold and maximal oxygen uptake intensity.1
- The zones include both internal load signals like oxygen response, lactate, heart rate, and perceived effort, and external load signals like stroke frequency, stroke length, and coordination timing.1
- The zones connect to practical training methods and set styles, so you are not left guessing how to apply the science in a real pool session.1
That is the performance hook. This is not a paper that exists only for labs. It is trying to build swim training zones you can actually run on deck, with a lane line, a stopwatch, and a plan.
The Curiosity Current
What you gain by exploring the full framework
The intention to explore this work often comes from a practical frustration. You may already track heart rate, splits, and maybe lactate. Yet the story still feels incomplete. This paper’s biophysical approach is an attempt to close that gap by layering multiple signals, then pairing them with training methods that match the domain you are targeting.1 Below are four science-backed benefits, supported and sometimes challenged by other peer reviewed research.
Zones become less fragile when they use more than one signal
A major benefit is resilience. Instead of betting everything on a single metric, the model blends oxygen response patterns, lactate, heart rate, perceived effort, and technique markers to describe intensity domains and training areas.1 This direction matches broader endurance literature. A major review on training intensity distribution notes that intensity is typically divided into zones using parameters such as heart rate, blood lactate, gas exchange, power or velocity, and perceived exertion.2
The payoff in the pool is that you can cross-check. If pace says one thing but heart rate and perceived effort say another, you do not just shrug. You ask whether fatigue, technique drift, or recovery status is changing the session. That is how training stops being emotional and starts being repeatable.
Technique stops being a side note and becomes part of the zone definition
The paper explicitly pulls biomechanics into the zone conversation by tracking stroke frequency, stroke length, and the index of coordination across intensity domains.1 That focus is not random. A peer reviewed study in elite swimmers argues the anaerobic threshold is not only a physiological boundary but also a transition after which technique changes, and it showed strong relationships between threshold velocity and inflection points in lactate, stroke rate, and stroke length.3
This is where semantic keyword variations start to matter in real life. “Lactate threshold pace” is not just a lab label. It is a place where your stroke rate and distance per stroke often start to shift. “Aerobic threshold speed” is not just easier work. It is where you can rehearse clean mechanics for a long time. Your coach can now treat technique as an intensity-dependent skill, not a constant.
The grey zone gets a warning label and a strategy
In the discussion, the authors describe heavy intensity as a “grey training zone,” where fatigue will appear sooner or later, and they place events like the eight hundred and fifteen hundred within that neighborhood.1 This is not saying “never train there.” It is saying “treat it as a tool, not a default.”
That warning lines up with endurance research on training intensity distribution, where polarized and pyramidal patterns are often contrasted with threshold-heavy approaches, and where overemphasis on middle intensity can be a concern depending on the athlete and phase.2 In elite junior swimmers, a crossover intervention found a short period of polarized training produced small improvements in one hundred meter time-trial performance with less perceived fatigue compared with threshold-oriented training, even though physiological adaptations did not clearly differ between approaches.4
The practical takeaway is simple. You can manage training intensity distribution with intent. If you choose more work in the grey zone, you should have a reason, a recovery plan, and a technique guardrail. Otherwise, you end up training tired, swimming flat, and calling it “grind.”
Oxygen response patterns help explain why small pace changes feel huge
The paper uses oxygen uptake kinetics to describe how exercise behaves across intensity domains, including the shift from steady state at lower intensities to non-stabilizing behavior as intensity rises and fatigue accelerates.1 This connects well with research around maximal lactate steady state in swimming. In elite female swimmers, a study examining oxygen kinetics and energy contributions around maximal lactate steady state reported that small increases above that intensity were associated with progressive fatigue and many swimmers reaching exhaustion before sustaining the full duration, even when aerobic contribution remained very high.5
It also matters that oxygen kinetics in swimming is not identical to cycling or running. A Frontiers study comparing heavy-intensity responses found oxygen uptake kinetics were slower in swimming than in arm cranking and cycling, suggesting exercise mode and posture matter for how the body meets oxygen demand.6 That supports the paper’s push for swimming-specific zone building rather than copying land-sport templates.
If you want one phrase to remember, make it this. Swim intensity domains are not just about how hard you try. They are about how your body responds over time, and how your stroke holds up while that response unfolds.
The Lane Made Personal
Turning a framework into your daily cues
The motivation for personalization is built into the paper’s logic. Two swimmers can hit the same pace and still have different internal stress, different stroke rate changes, and different coordination patterns. That is why the authors propose multiple markers and suggest practical options when you do not have every lab tool available.1
For example, they note that stroke frequency might help delineate the boundary between moderate and heavy intensity domains when lactate is inaccessible. They also suggest heart rate combined with rating of perceived exertion can help establish a boundary between heavy and severe intensity domains, and they mention using an eight millimoles per liter lactate value as a practical limit for severe intensity when ventilatory data are not available.1 The point is not that one number fits everyone. The point is that you can build a workable field system that respects both physiology and technique.
This is where a simple toolchain helps. Use one place to track your swim intensity zones and your subjective signals, and one place to shape your season. You can log your zone work in Training and build your season inside Blocks so the framework is not a one-time read. It becomes a living plan.
Here are conversational AI prompts designed to increase engagement while staying faithful to what the research can support. They help you turn oxygen uptake kinetics, lactate guidance, and technique markers into a clear weekly practice.
Act as my swim coach and sport scientist. Ask me about my main events, my current weekly volume, and which sets make my stroke fall apart. Then help me choose a simple set of swim training zones using pace, heart rate when available, and perceived effort. Make it practical for a normal pool session and keep the cues easy to remember.1
I want to protect technique as intensity rises. Based on the idea that technique and coordination change across intensity domains, help me pick one technical metric to track during easy work and one to track during race pace intervals. Then write a short post practice checklist so I can review stroke rate and distance per stroke without overthinking it.13
Help me manage the grey zone wisely. Ask me how many hard days I can truly recover from, what my sleep has been like, and which sets leave me feeling flat. Then propose a training intensity distribution for the next few weeks that keeps most work easy, includes a small amount of very hard work, and uses middle intensity only when it serves a clear goal.241
Turn this into a weekly plan I can follow. I will paste my available training days and my upcoming meet date. Build a simple week that includes easy aerobic work at aerobic threshold speed, a focused set near lactate threshold pace, and a short race pace interval session. For each day, give one sentence on the purpose and one sentence on the technique priority.15
If you use prompts like these, the paper’s “biophysical approach” becomes less abstract. It becomes a way to decide what to do today, how hard to do it, and how to know whether the set delivered what it promised.
The Practice You Can Live In
Where art, science, technology, and design meet your week
The customizable purpose of this framework is not to turn you into a robot. It is to help you build an objective training program and keep systematic control and evaluation, while respecting that technique and physiology are always linked in swimming.1 Think of it like good design. You choose inputs that matter, you reduce noise, and you create a loop you can sustain.
Here are lifestyle takeaways that keep performance tied to real life through art, science, technology, and design.
- Build an artist’s pre swim ritual. Pick one technical image for the day, such as a long body line or calm hand path, then rehearse it briefly before warmup. It keeps your brain quiet and your cue consistent when the set gets hard.
- Use technology as a mirror, not a judge. Track only a few signals that match the zone you trained, such as pace plus perceived effort, and one technique marker. This keeps data helpful instead of overwhelming.1
- Design your week like a clean product sprint. Most days support easy aerobic work, a small number of sessions target high intensity, and recovery is planned, not hoped for. This approach aligns with how many endurance programs manage intensity distribution across seasons.2
When you combine those habits with the paper’s zone definitions, training stops feeling random. Your body gets the right stimulus, your stroke gets the right repetition, and your life does not get consumed by constant guesswork.
FAQ
Do I need lab testing to use this approach
No. The authors highlight that while oxygen, lactate, and heart rate are commonly used, practical constraints exist in standard pools. They also discuss using field-accessible signals like stroke frequency, perceived effort, and heart rate patterns as part of establishing boundaries when full lab data are not available.1
Is middle intensity always bad
No. The paper calls heavy intensity a grey training zone because fatigue can accumulate there, not because it should never be used. The coaching question is whether you have a clear reason for that work and whether your overall intensity distribution supports recovery and technique quality.12
Why include technique metrics in training zones
Because swimming performance depends on technical proficiency as well as conditioning, and the paper adds stroke frequency, stroke length, and coordination timing to its zone descriptions. Other research also supports the idea that the anaerobic threshold can align with technique changes and biophysical transitions in elite swimmers.13
References
1 Fernandes RJ, Carvalho DD, Figueiredo P. Training zones in competitive swimming, a biophysical approach. Frontiers in Sports and Active Living. Two thousand twenty four.
2 Stöggl TL, Sperlich B. The training intensity distribution among well trained and elite endurance athletes. Frontiers in Physiology. Two thousand fifteen.
3 Carvalho DD, Soares S, Zacca R, Sousa J, Marinho DA, Silva AJ, Vilas-Boas JP, Fernandes RJ. Anaerobic threshold biophysical characterisation of the four swimming techniques. International Journal of Sports Medicine. Two thousand twenty.
4 Pla R, Le Meur Y, Aubry A, Toussaint JF, Hellard P. Effects of a period of polarized or threshold training on performance and fatigue in elite swimmers. International Journal of Sports Physiology and Performance. Two thousand nineteen.
5 Pelarigo JG, Greco CC, Denadai BS, and colleagues. Oxygen uptake kinetics and energy system contribution around maximal lactate steady state swimming intensity. PLOS ONE. Two thousand seventeen.
6 Sousa A, Borrani F, Rodríguez FA, Millet GP. Oxygen uptake kinetics is slower in swimming than arm cranking and cycling during heavy intensity. Frontiers in Physiology. Two thousand seventeen.