Freediving for Cyclists: How Apnea Training Boosts VO2max and Breathing Economy

You've spent seasons building your power-to-weight ratio. Your FTP climbs. Your legs are strong. But on a long climb or a race-pace effort in the final kilometres, something breaks down before your legs do — and it's not fitness. It's your breathing system. Research shows it gives out first. And almost no cyclists ever train it.

The respiratory system is the quiet limiting factor in cycling performance. Elite cyclists, coaches, and sports physiologists have long focused on aerobic base, muscular strength, and recovery — but the breathing apparatus itself has been largely ignored as a trainable system. Freediving changes that. Apnea training is, at its core, the most demanding form of inspiratory muscle training available, and the scientific evidence for its transfer to cycling performance is compelling.

This article explains why breathing limits cyclists at threshold, what the research says about training it, and how freediving — including the sessions available in Phuket between training camps — delivers exactly the adaptations that time-trialling and road racing demand.

The Breathing Bottleneck Nobody Talks About

When cyclists bonk on a long climb or blow up on a threshold effort, the narrative is almost always the same: legs. Lactate accumulation. Muscle failure. The legs gave out.

But research tells a different story. A landmark paper by Dempsey et al. (2006), published in Experimental Physiology, found that at VO2max, 85% of trained cyclists show flow-limited breathing — meaning their ventilatory system is operating at its mechanical ceiling before their leg muscles have truly failed. The diaphragm and intercostal muscles reach a state of fatigue that restricts airflow and imposes a ventilatory ceiling on the entire effort. (Dempsey JA et al., 2006)

This means for the majority of cyclists at race pace, the limiting factor is not the quads. It's the breathing muscles. And unlike the legs — which receive months of dedicated interval training — the breathing muscles are almost never directly trained.

The diaphragm fatigues. The intercostals fatigue. The accessory breathing muscles — scalenes, sternocleidomastoid — get recruited to compensate. The whole system becomes mechanically inefficient at exactly the moment when efficiency matters most: the final kilometres of a time trial, the summit of a key climb, the last sprint into a bunch finish.

This is the problem freediving solves.

The Metabolic Cost of Breathing at Threshold

Here's the number that changes how you think about breathing in cycling: at maximal exercise intensity, the respiratory muscles consume 14 to 16% of total cardiac output.

Research by Harms CA et al. (1997), published in the Journal of Applied Physiology, demonstrated this directly by measuring blood flow distribution during maximal cycling exercise. When ventilatory demand was high, the diaphragm and intercostal muscles were diverting nearly one sixth of the heart's entire output away from the working legs. (Harms CA et al., 1997)

Think about what that means practically. Your heart is working at maximum capacity. Your legs are demanding every litre of oxygenated blood available. And 14–16% of that blood is going to your breathing muscles instead. If those muscles were stronger — if they could sustain the same ventilatory output with less energy cost — more of that cardiac output would go to the quadriceps. More blood to the legs means more sustained power output.

This is not a marginal effect. At 250 watts on a climb, 14–16% of cardiac output diverted from the legs represents a meaningful performance ceiling. Cyclists who strengthen their respiratory muscles — through any means — shift that blood flow balance back toward the working muscles.

Freediving is the most direct, most demanding way to strengthen those muscles available outside a laboratory.

What Inspiratory Muscle Training Does

The scientific literature on inspiratory muscle training (IMT) for cyclists is now well established, and the results are consistent.

A study by Romer LM and McConnell AK (2003), published in Medicine & Science in Sports & Exercise, showed that systematic IMT improved cycling time trial performance by 3.8% and significantly reduced perceived exertion at equivalent power outputs. The trained group also showed reduced breathlessness and improved ability to sustain high-power efforts in the late stages of the time trial. (Romer LM & McConnell AK, 2003)

A 3.8% improvement in TT performance is not a minor effect. Over a 40km time trial at an average of 45 minutes, that's roughly 100 seconds — the difference between winning a stage race and finishing second overall.

The mechanism behind this improvement is twofold. First, stronger respiratory muscles require less of the total cardiac output to perform their function, freeing blood for the legs. Second, better breathing mechanics allow more efficient gas exchange per breath, reducing respiratory rate at a given power output and reducing the perceived effort of breathing.

Holm P et al. (2004), in a study published in the Scandinavian Journal of Medicine & Science in Sports, found that 10 weeks of IMT combined with endurance training improved VO2max by 5.2% more than endurance training alone. The IMT group achieved the same VO2max gains as the endurance-only group from their cycling — plus an additional 5.2% from the respiratory training component. Adding nothing but breathing work improved the central oxygen uptake variable that defines cycling performance.

How Freediving Is the Most Effective IMT Available

Inspiratory muscle training is most commonly administered via a hand-held device — a Powerbreathe or similar resistive breathing trainer. These devices provide resistance against inhalation, forcing the diaphragm to work harder over repeated breaths. They work. The research shows they work.

Freediving works through an entirely different mechanism — and it's considerably more demanding.

During a breath-hold dive, the diver exhales, fills the lungs fully, and then holds. As the dive progresses, CO2 builds in the blood. The chemoreceptors signal urgency. The diaphragm begins involuntary contractions — the rhythmic spasms familiar to any freediver who has pushed past their comfort zone. These contractions are the diaphragm working against a closed airway, with no flow at all. The resistance experienced by the diaphragm and intercostals during these contractions is orders of magnitude greater than any hand-held IMT device can produce.

Each series of contractions during an apnea is, in effect, a set of maximum-effort diaphragm contractions with full contraction range and complete mechanical resistance. CO2 tables — structured breath-hold protocols with progressively shorter rest periods — create repeated cycles of this stimulus. Over weeks and months of CO2 table training, the diaphragm adapts exactly as any other trained muscle does: it becomes stronger, more fatigue-resistant, and more metabolically efficient.

The carryover to cycling is direct. The same diaphragm that can now sustain 30 consecutive involuntary contractions underwater without succumbing to the urge to breathe can sustain 400 watts on a climb for two additional minutes before fatigue begins to impair function.

Altitude Camp in a Pool: The Hypoxic Adaptation Pathway

There's a second, separate mechanism through which freediving improves cycling performance — one that mirrors the benefits of altitude training without the cost or logistical complexity.

Research by Verges S et al. (2009) on hypoxic training for sea-level performance demonstrated that breath-hold training produces intermittent hypoxia — repeated, brief periods of reduced arterial oxygen saturation — that trigger many of the same physiological adaptations as altitude exposure. These include upregulation of erythropoietin (EPO) production, increased red blood cell synthesis, and enhanced oxygen-carrying capacity of the blood.

Altitude camps cost thousands of dollars, require three to four weeks of time, and involve travel to 2,500–3,500 metres elevation. A CO2 table session in a pool costs nothing beyond pool access and produces a qualitatively similar hypoxic stimulus — less intense per session, but highly repeatable across a training season.

For cyclists who can't afford altitude camps or who need hypoxic stimulation outside of an annual preparation block, regular freediving sessions provide a practical and evidence-based alternative pathway to increased haematocrit and improved oxygen transport.

The Spleen Bonus: Extra Red Blood Cells Without Altitude

Freediving also stimulates a mechanism that altitude training can't replicate: the splenic contraction response.

The spleen stores a reserve of red blood cells — typically 200–300 mL of concentrated erythrocytes — that are released into circulation during repeated breath-hold exercise. Research with trained freedivers consistently shows a 9–10% increase in circulating haemoglobin during dive series, purely from splenic contraction. This is a rapid, acute response that occurs within minutes of beginning breath-hold exercise.

The acute boost is transient. But the cumulative effect of repeatedly triggering splenic contraction across a season of freediving training creates lasting adaptations: the spleen itself enlarges (as observed in diving populations), its storage capacity increases, and the baseline circulating haemoglobin rises slightly over time.

For a cyclist, this means arriving at a key race or training block with measurably more oxygen-carrying red blood cells in circulation — an advantage that requires no pharmaceutical assistance and no altitude logistics. The spleen does the work across the winter pool sessions.

Practical Cycling-Specific Protocol

This protocol is designed for cyclists with no prior freediving experience who want to integrate apnea training into an existing training programme. It requires two pool sessions per week and optional additional breathwork on the bike.

Weeks 1–2: Foundations

• 2× pool sessions per week (45–60 minutes each)
• Static apnea: establish baseline max hold; focus on diaphragmatic breathe-up mechanics
• CO2 table introduction: 6 rounds at 50% of max hold with progressively shorter rest periods
• On the bike: begin nose-breathing during Zone 2 efforts to build CO2 tolerance
• No open water yet; buddy protocol mandatory in pool

Weeks 3–4: CO2 Adaptation

• CO2 tables: 8 rounds, shorter rest intervals
• Add dynamic apnea (25m lengths, fully relaxed pace) for whole-body oxygen efficiency
• On the bike: add 5-minute nose-breathing intervals during easy spinning at threshold heart rate
• Monitor perceived exertion at given power outputs — most cyclists notice a change in weeks 3–4

Weeks 5–6: Integration

• 1× pool session + 1× open water session (if in Phuket: Racha Yai, Kata Noi)
• CO2 tables continue 1× per week as maintenance
• Pre-ride breathwork: 3 static apneas of 30–45 seconds before key sessions for splenic activation
• Post-ride breathwork: 4-7-8 breathing (inhale 4, hold 7, exhale 8) for parasympathetic recovery

Expected timeline for cyclists:

• 4 weeks: Breathing feels less demanding at threshold; nose-breathing during Zone 2 becomes easy
• 8 weeks: Perceived exertion at the same power output measurably reduced; diaphragmatic breathing automatic under effort
• 12 weeks: Time trial performance improvement detectable; late-climb power retention improved

The Professional Peloton Is Already Using This

This is not a fringe concept. In the professional peloton, breath-hold training has been quietly appearing in preparation cycles for several years. Teams operating at the World Tour level now employ specialists who integrate breathwork protocols alongside altitude camps and power testing.

The comparison to altitude preparation is instructive. A traditional altitude camp involves three to four weeks at 2,500–3,000 metres, a sharp disruption to training load, travel costs, and the need to carefully time the return to sea level before competition. A freediving-based hypoxic protocol involves two pool sessions per week, costs a fraction of the logistical investment, and can be run continuously throughout the off-season and into the preparation block without interruption to road training.

The adaptations are not identical — altitude camp produces more dramatic haematological changes per unit of time. But the freediving protocol is sustainable, repeatable, injury-free, and cumulative across an entire season. Over a full training year, the aggregate hypoxic stimulus from consistent pool sessions is not negligible.

For amateur and masters cyclists who can't take three weeks at altitude, the pool-based protocol is effectively the only practical route to comparable adaptations.

Phuket: Training Camp + Freediving Combined

Phuket is one of Southeast Asia's most popular cycling training destinations during the European winter. The roads around Rawai, Chalong, and the hills of the island interior offer quality riding in warm conditions at a fraction of the cost of a European training camp.

What most cycling visitors don't know is that Phuket also offers world-class freediving access within minutes of the main riding routes. Racha Yai Island — 30–40 minutes by speedboat from Rawai — provides some of the clearest warm water in the region at depths suitable for beginners through advanced freedivers.

The optimal integration model for a cycling camp: replace one easy spin per week with a freediving session. The aerobic load is similar. The recovery cost is low. The respiratory muscle stimulus, CO2 tolerance adaptations, and hypoxic training effects accumulate across the camp block. By the time cyclists return to Europe or their home training environment, they're carrying adaptations that months of conventional training could not have produced alone.

If you're planning a cycling training camp in Phuket and want to add a structured freediving component, our Trial Freediving Lesson is the natural entry point — it covers the fundamentals of safe breath-hold training in a single session. For a more complete protocol, the Wave 1 Freediving Course provides the full foundation you need to run CO2 tables independently. Contact us to discuss scheduling around your cycling camp.

Summary

The breathing system is the most undertrained performance variable in competitive cycling. At VO2max, 85% of cyclists are ventilatory-limited before their legs fail. The respiratory muscles consume 14–16% of cardiac output at maximal effort — blood that could be going to the quads. And IMT consistently produces 3–5% performance improvements that are entirely additional to gains from cycling training itself.

Freediving is the most demanding, most full form of IMT available. It trains inspiratory muscle strength, CO2 tolerance, hypoxic adaptation, and the mental ability to sustain effort through discomfort — all in a single modality. For cyclists who want to find performance gains that conventional training has already maxed out, the pool is the next frontier.

Train the breathing system. The legs will follow.