Breathing training / field note 01

Stronger inhale.
Faster recovery signal.

In the only direct freediver trial, inspiratory muscle training shortened the return to 95% finger SpO2 after a fixed dynamic apnea by 3.08 seconds versus HIIT. More effective first recovery breaths could plausibly improve the immediate post-dive margin, but the trial measured neither blackouts nor actual safety.

VerdictUseful accessory
PriorityAfter core skills
Best fitDynamic + repeat dives

01 / Answer first

Buy it for a specific bottleneck, not for bigger lungs.

It strengthens the diaphragm and accessory inspiratory muscles against a threshold load. That is different from increasing oxygen stores, lung elasticity, CO2 tolerance, equalization skill, or the diving response.

Worth a trial

You feel breathing-muscle fatigue

Most plausible when repeated dynamics, hard finning, surface recovery, or exercise ventilation makes the breathing muscles feel like the weak link.

Low priority

Your target is static or depth

Static apnea is dominated by relaxation, oxygen use, discomfort tolerance, and safety. Depth adds equalization, technique, pressure adaptation, and chest mobility.

Do not infer

Faster recovery proves fewer blackouts

It is a plausible benefit, not a demonstrated outcome. A higher PIMAX or faster finger-SpO2 recovery should never justify pushing a dive. Hypoxic loss of consciousness remains possible after surfacing.

Higher return first
  1. 01 Certified instruction + buddy safety
  2. 02 Relaxation + equalization
  3. 03 Efficient movement + aerobic base
  4. 04 Inspiratory muscle training

02 / Testimonial audit

The improvement is impressive. The headline math is easy to misread.

PIMAX
62to110

+48 cmH2O, or +77% from baseline. The quoted 135% is the final result relative to a predicted reference value, not the training improvement.

PEMAX
70to91

+21 cmH2O, or +30%. PowerBreathe Plus is an inspiratory trainer, so the expiratory change cannot be attributed cleanly to the device.

Interpretation

Real adaptation plus possible test learning

PIMAX and PEMAX are voluntary, coaching-sensitive maneuvers. Standardized lung volume, mouthpiece technique, warm-up, and repeated maximal attempts matter. The ERS notes that peak PIMAX values may appear only after several attempts.

ERS testing statement

03 / What transfers

The strongest freediving result is faster recovery, not a longer dive.

The direct evidence is one small randomized crossover trial. Fifteen trained freedivers completed both four weeks of inspiratory muscle training and four weeks of swimming HIIT, with the order randomized and a two-week gap between them.

15trained freedivers
4weeks per intervention
2 wkwashout between phases
3xsessions per week
-3.08 sSpO2 recovery vs HIIT
Design

Randomized assessor-blinded crossover

Every diver completed both interventions, making each participant their own comparator. The sequence was randomly assigned and concealed. Outcome assessors were blinded, but participants could not be.

Interventions

Matched time, different training

IMT was a home session: seated PowerBreathe work for 20 minutes, three days weekly, reported as 10 minutes at 50% MIP and 10 minutes at 80% MIP. The swimming comparison used the same 20-minute session length and three-session weekly frequency.

Test session

Fixed dynamic apnea, then recovery

Before and after each phase, divers completed spirometry and respiratory-pressure tests, then a bifin dynamic apnea in a 25 m pool with a safety diver. Each person repeated their original test distance across later tests, standardizing the workload rather than retesting maximum distance.

Primary outcome

Time back to 95% finger SpO2

Heart rate, finger SpO2 and end-tidal CO2 were sampled every five seconds during one minute of recovery. The primary endpoint was time to return to 95% SpO2. Secondary outcomes included FEV1, FVC, MIP, MEP, lactate, speed, and self-counted diaphragm contractions.

Swimming HIIT protocolTen continuous 2-minute cycles

The session lasted 20 minutes with active moderate swimming between hard efforts, not passive rest.

1:00 hardRPE about 19 / 20
1:00 moderateRPE about 12 / 20
Repeat x10
Setting
Supervised swimming
Frequency
3 sessions weekly
Duration
4 weeks
Intensity control
Self-rated Borg RPE

What was not specified: the paper does not report a prescribed stroke, distance, pace, heart-rate target, or between-interval stop. RPE 19 represents a near-maximal perceived effort; RPE 12 is a much easier active interval. This makes the physiological intent clear but limits exact replication.

Improved

Inspiratory strength

MIP improved by 16.3 cmH2O during IMT versus 3.3 after HIIT. The between-intervention difference was 13.05 cmH2O (95% CI 0.39 to 25.71; d = 0.73).

Improved

First-second airflow

FEV1 improved relative to HIIT by 0.22 L (95% CI 0.06 to 0.38; d = 0.80). This is a spirometry result, not proof of a bigger usable breath-hold oxygen store.

Not superior

FVC, speed, contractions

No advantage over HIIT appeared for forced vital capacity, swim speed, or reported diaphragm contractions.

Not superior

Heart rate or lactate recovery

Neither intervention beat the other. For SpO2, IMT shortened recovery by 2.71 seconds from its own baseline while HIIT increased it by 0.37 seconds, a between-intervention difference of 3.08 seconds (95% CI 0.43 to 5.72; d = 0.69).

What the trial cannot establishUseful signal, narrow question
  • Only 15 divers were analyzed, and the study was powered to detect a large effect on SpO2 recovery.
  • IMT was home-based while HIIT was supervised, and participants knew which intervention they were doing.
  • The fixed swim distance means the study did not test longer dynamic apnea, static time, depth, or competition performance.
  • The primary endpoint used a finger oximeter every five seconds after apnea. Peripheral perfusion and sensor lag limit precision, even though poor-perfusion readings were excluded.
  • The trial compared IMT with active HIIT, not sham IMT or no additional training, and lasted only four weeks per intervention.
DirectnessOne direct trial; no formal certainty grade

You are correct about the reviews: they were not freediving reviews. The 2025 analysis pooled 25 studies and 522 athletes, mostly swimmers and soccer players, and rated that broader evidence low or very low. A 2024 review of 13 studies in 277 mostly elite young swimmers found higher MIP but no change in FEV1 or FVC. These reviews support the general ability to strengthen inspiratory muscles, not transfer to apnea time, distance, depth, or blackout safety. The direct freediving evidence remains limited because it is one small trial with a narrow recovery endpoint.

Freediver crossover trial2025 athlete reviewSwimmer meta-analysis

04 / Transfer map

What it trains, what it might help, and what remains separate.

Direct adaptationInspiratory pressureBreathing-muscle enduranceForceful recovery breaths
Possible transferRepeated dynamicsPost-apnea reoxygenationHard surface swimming
Separate adaptationsCO2 and hypoxia toleranceEqualization and depth techniqueRelaxation and movement economy

05 / Buying guide

For your profile, start with Plus Medium.

Its 23-186 cmH2O range is intended for active to very fit users. Do not start with Heavy: the manufacturer recommends moving to it only after reaching the top of Medium.

Delivered 13 AugustThomann Polska320 zł total

Special Edition Plus Medium: 295 zł plus 25 zł delivery. Shipped 11 August and delivered to Kraków by DHL on 13 August.

View purchased model
Polish medical retailerBioMed24345 zł

Plus Medium, free delivery shown, 1-2 day dispatch and a 24-month warranty.

View offer
EU brand storePOWERbreathe Germanyfrom €53.84

In stock with VAT, shipping extra. Select Medium before ordering and check delivery to Poland.

View offer
ManufacturerPOWERbreathe UK£59.99

Official Plus price across resistance options. Import VAT, shipping or handling may make this less attractive from Poland.

View Medium

Purchase confirmed: Gmail order confirmation reviewed 10 August 2026. Other prices, stock, delivery charges and checkout totals can change. Buy new from a traceable seller because the mouthpiece is personal and hygiene matters.

06 / Practical decision trial

Six weeks. One question: does it improve your diving bottleneck?

This conservative self-test combines the manufacturer's 30-breath structure with loads commonly used in research. A pulmonary physiotherapist can individualize it more precisely.

01

Baseline

Record standardized PIMAX if available, plus one discipline-specific outcome: recovery quality after a fixed dynamic, repeat-dive consistency, or perceived breathing-muscle fatigue.

02

Start

Use Light or Medium resistance, never Heavy as a first model. If PIMAX is measured, begin around 40-50% with clean, full inspirations.

03

Train

Complete 30 resisted breaths once or twice daily, 5-7 days per week. Sit upright. Inhale fast and forcefully; exhale slowly and passively.

04

Progress

Raise resistance slightly only when all 30 breaths are clean and controlled. Do not add endless volume or chase dizziness.

05

Retest

After six weeks, repeat the same measures under the same conditions. Keep it only if the freediving-specific outcome improves meaningfully.

Keep

Clear improvement in repeated dynamics, recovery, or respiratory fatigue with little time cost.

Skip

PIMAX rises but your target discipline and subjective bottleneck do not change.

Device instructions: POWERbreathe Plus user manual

07 / Safety boundary

Training pressure is not permission to push apnea.

Never use the device submerged or during a breath hold.

Keep resistance training separate from apnea. Never hyperventilate. Never conduct in-water apnea alone. A consumer oximeter or a stronger PIMAX is not a blackout warning system.

Stop the session

For chest or rib pain, unusual shortness of breath, marked dizziness, or persistent ear pressure. Do not train through an acute cold, sinusitis, or respiratory infection.

Seek medical guidance first

If you have a history of spontaneous pneumothorax, pulmonary hypertension, large pulmonary bullae, recent abdominal surgery, hernia, significant heart disease, or rib-fracture risk.

Do not use

With a ruptured eardrum, active costochondritis, or the specific severe-asthma and cardiac conditions listed by the manufacturer. Review the full manual rather than relying on this summary.

DAN freediving risk assessmentManufacturer precautions and contraindications

Source standard

Clinical testing guidance, a direct freediver trial, and current safety advice.

  1. European Respiratory Society statement on respiratory muscle testing
  2. Randomized crossover trial in trained breath-hold divers
  3. Systematic review and meta-analysis of respiratory muscle training in athletes
  4. Systematic review and meta-analysis in swimmers
  5. Divers Alert Network freediving risk assessment
  6. POWERbreathe Plus manual
  7. Thomann Polska current Plus Medium offer
  8. BioMed24 current Plus Medium offer
  9. POWERbreathe Germany current range and pricing
  10. POWERbreathe UK Plus Medium product page

Educational resource, not individualized medical clearance or a freediving training plan. Reviewed 10 August 2026.