Healthy VolunteersNCT07703839
Effects of Breath-Hold vs Standard Interval Training on Fitness in Mountaineers
A study testing Voluntary Hypoventilation Training and Progressive Treadmill Interval Training in people with Healthy Volunteers, run by Mohammadreza Rezaeipour, MD, PhD at 1 site in Iran.
Trial summary
This study investigated whether adding structured breath-holds to standard interval training improves cardiorespiratory fitness in recreational mountaineers more than interval training alone. Twenty-four male recreational mountaineers participated in an 8-week progressive treadmill interval training program. Read more about this study
- Who is it for?
- Ages 25 to 35 years, men onlyHealthy volunteers can take part
- Conditions the study is for
- Healthy Volunteers
- What is being tested?
- Voluntary Hypoventilation Training and Progressive Treadmill Interval Training
- Type of treatment
- Lifestyle or therapy programme
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 24 participants
- Where
- 1 siteIran
- Study dates
- 30 Sep 2023to 30 Nov 2023
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 25 to 35 years
- Men only
- Healthy volunteers accepted
- Adult
Who may be able to join
- Male recreational mountaineers aged 25 to 35 years.
- A minimum of 6 months of mountaineering experience with at least 3 sessions per month.
- Willingness to attend at least 85% of the scheduled training sessions.
- Negative responses to all items on the Physical Activity Readiness Questionnaire (PAR-Q).
Who cannot join
- Diagnosed cardiovascular, respiratory, or musculoskeletal disorders.
- Current smoking.
- Use of medications affecting heart rate or blood pressure.
- Prior experience with structured hypoxic or breath-hold training.
Trial locations and contacts
1 site in 1 country.
Iran1 site
Sport Sciences Department, University of Sistan and Baluchestan
Zahedan, Sistan and Baluchestan, 98135-986
About this study
Official title: Effects of Mild Voluntary Hypoventilation During Progressive Interval Training on Cardiorespiratory Fitness in Recreational Mountaineers: A Clinical Trial
This study investigated whether adding structured breath-holds to standard interval training improves cardiorespiratory fitness in recreational mountaineers more than interval training alone. Twenty-four male recreational mountaineers participated in an 8-week progressive treadmill interval training program. Participants were divided into two groups: a controlled-breathing group that performed structured mid-tidal breath-holds during training, and a free-breathing group that maintained unrestricted breathing. The primary outcomes measured were resting heart rate and estimated maximal oxygen uptake, along with secondary measures including blood pressure and pulmonary function indices. The study aimed to determine if this mild voluntary hypoventilation technique provides additional physiological benefits for altitude preparation.
Read the detailed description
Recreational mountaineers often train at low altitudes without access to specialized hypoxic facilities. While intermittent hypoxic training is an established preparation strategy, the required equipment is costly and inaccessible. Voluntary hypoventilation training (VHT), which involves deliberate breath-holds during exercise, has been proposed as a low-cost alternative. However, its efficacy at producing mild desaturation levels suitable for recreational settings had not been established.
This retrospective clinical trial evaluated the effects of mild VHT on cardiorespiratory fitness. Twenty-four male recreational mountaineers completed a progressive 8-week treadmill interval training program (24 sessions, 65-85% heart rate reserve) between September and November 2023. Participants were allocated to either a controlled-breathing (CB) group or a free-breathing (FB) group. The CB group performed structured mid-tidal breath-holds synchronized to an electronic metronome during approximately 25% of the main training phase, targeting a peripheral oxygen saturation (SpO₂) nadir of 92-94%. The FB group completed the identical exercise protocol with unrestricted breathing, maintaining SpO₂ at or above 97%.
Physiological assessments were conducted at baseline and within 48 hours post-intervention. Measurements included resting cardiovascular parameters (heart rate and blood pressure), estimated maximal oxygen uptake (VO₂max) via a modified Bruce treadmill protocol, and comprehensive pulmonary function testing (spirometry). Continuous SpO₂ monitoring was utilized during all training sessions to ensure protocol adherence and participant safety.
- Conditions
- Healthy Volunteers
- Being tested
- Voluntary Hypoventilation Training, Progressive Treadmill Interval Training
- Keywords
- Voluntary hypoventilation training, Mountaineering, Cardiorespiratory fitness, Interval training, Acclimatization, Aerobic capacity, Pulse oximetry, Breath-Hold Training
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Voluntary Hypoventilation TrainingBehavioural
Also called VHT; Breath-Hold Training
A breathing maneuver consisting of structured mid-tidal breath-holds synchronized to an electronic metronome to induce mild voluntary hypoventilation (target SpO₂ nadir 92-94%) during physical exertion.
Progressive Treadmill Interval TrainingBehavioural
Also called Interval Training; Treadmill Exercise
A cardiovascular exercise protocol involving supervised treadmill sessions with progressive increases in intensity (65-85% heart rate reserve) and duration (30-45 minutes) over an 8-week period.
| Study group | Role | What they receive |
|---|---|---|
| Controlled-Breathing (CB) Group | Experimental | Participants completed 24 supervised treadmill interval sessions over 8 weeks (65-85% heart rate reserve). During approximately 25% of the main training phase, participants performed structured mid-tidal breath-holds synchronized to an electronic metronome (progressing from 3-count to 6-count cycles), targeting a peripheral oxygen saturation (SpO₂) nadir of 92-94%. Receives: Behavioral: Voluntary Hypoventilation Training; Behavioral: Progressive Treadmill Interval Training |
| Free-Breathing (FB) Group | Active comparator | Participants completed the identical 24 supervised treadmill interval sessions over 8 weeks (65-85% heart rate reserve) with unrestricted breathing throughout all sessions. Continuous SpO₂ monitoring confirmed values remained at or above 97%. Receives: Behavioral: Progressive Treadmill Interval Training |
What is being measured
The primary outcome is the main question the study is designed to answer.
Resting Heart Rate
Resting heart rate (beats per minute) recorded using a 12-lead electrocardiograph after 10 minutes of seated rest in a quiet, temperature-controlled room. The mean value from the final 2 minutes is used for analysis.
Measured: Baseline (within 48 hours before the first training session) and post-intervention (within 48 hours after the final 8-week training session).
Estimated Maximal Oxygen Uptake (VO2max)
Estimated VO2max (mL·kg-¹·min-¹) determined using a modified Bruce treadmill protocol until volitional exhaustion. It is calculated from total treadmill time (in minutes) using the Foster equation.
Measured: Baseline (within 48 hours before the first training session) and post-intervention (within 48 hours after the final 8-week training session).
Secondary outcomes (9)
Systolic Blood Pressure
Systolic blood pressure (mmHg) measured in triplicate using an automated oscillometric monitor; the average of 3 measurements is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Diastolic Blood Pressure
Diastolic blood pressure (mmHg) measured in triplicate using an automated oscillometric monitor; the average of 3 measurements is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Tidal Volume (TV)
Tidal volume (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Vital Capacity (VC)
Vital capacity (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Forced Vital Capacity (FVC)
Vital capacity (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Forced Expiratory Volume in 1 Second (FEV1)
Forced expiratory volume in 1 second (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Peak Expiratory Flow (PEF)
Peak expiratory flow (L/s) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Forced Expiratory Flow at 25-75% of FVC (FEF25-75%)
Forced expiratory flow at 25-75% of FVC (L/s) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Maximum Voluntary Ventilation (MVV)
Maximum voluntary ventilation (L/min) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained.
Measured: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted14 Jul 2026
- Study start30 Sep 2023
- Primary completion30 Nov 2023
- Study completion30 Nov 2023
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Healthy VolunteersStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Other
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Model description
- A two-arm parallel-group design comparing a controlled-breathing interval training group to a free-breathing interval training group.
- Masking
- Single blind
- Who is masked
- Outcomes assessor
- Enrolment
- 24 participants (actual)
Sponsor and investigators
- Lead sponsor
- Mohammadreza Rezaeipour, MD, PhD
- Sponsor type
- University, hospital or other
- Collaborators
- Mountaineering and Sport Climbing Federation of Sistan and Baluchestan Province, General Directorate of Sports and Youth of Sistan and Baluchestan Province
- Responsible party
- Sponsor-investigator, Mohammadreza Rezaeipour, MD, PhD, University of Sistan and Baluchestan
- Investigators
- Mohammadreza Rezaeipour, MD, PhD, Principal investigator, University of Sistan and Baluchestan
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07703839
- Sponsor's protocol ID
- IR.USB.REC.1402.013
- Status last verified
- Jul 2026
- First submitted
- 9 Jul 2026
- Last updated
- 20 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Yes: The de-identified dataset and full study protocol are available from the corresponding author upon reasonable request.
Study at a glance
From the registry record, last updated by the sponsor on 20 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Effects of Mild Voluntary Hypoventilation During Progressive Interval Training on Cardiorespiratory Fitness in Recreational Mountaineers: A Clinical Trial
- ClinicalTrials.gov ID
- NCT07703839
- Acronym / sponsor ID
- IR.USB.REC.1402.013
- Conditions
- Healthy Volunteers
- Keywords
- Voluntary hypoventilation training, Mountaineering, Cardiorespiratory fitness, Interval training, Acclimatization, Aerobic capacity, Pulse oximetry, Breath-Hold Training
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 24 participants (actual)
- Lead sponsor
- Mohammadreza Rezaeipour, MD, PhDUniversity, hospital or other
- Collaborators
- Mountaineering and Sport Climbing Federation of Sistan and Baluchestan Province, General Directorate of Sports and Youth of Sistan and Baluchestan Province
- Study start
- 30 Sep 2023 (actual)
- Primary completion
- 30 Nov 2023 (actual)
- Study completion
- 30 Nov 2023 (actual)
- First posted
- 14 Jul 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This study investigated whether adding structured breath-holds to standard interval training improves cardiorespiratory fitness in recreational mountaineers more than interval training alone. Twenty-four male recreational mountaineers participated in an 8-week progressive treadmill interval training program. Participants were divided into two groups: a controlled-breathing group that performed structured mid-tidal breath-holds during training, and a free-breathing group that maintained unrestricted breathing. The primary outcomes measured were resting heart rate and estimated maximal oxygen uptake, along with secondary measures including blood pressure and pulmonary function indices. The study aimed to determine if this mild voluntary hypoventilation technique provides additional physiological benefits for altitude preparation.
Detailed description
Recreational mountaineers often train at low altitudes without access to specialized hypoxic facilities. While intermittent hypoxic training is an established preparation strategy, the required equipment is costly and inaccessible. Voluntary hypoventilation training (VHT), which involves deliberate breath-holds during exercise, has been proposed as a low-cost alternative. However, its efficacy at producing mild desaturation levels suitable for recreational settings had not been established.
This retrospective clinical trial evaluated the effects of mild VHT on cardiorespiratory fitness. Twenty-four male recreational mountaineers completed a progressive 8-week treadmill interval training program (24 sessions, 65-85% heart rate reserve) between September and November 2023. Participants were allocated to either a controlled-breathing (CB) group or a free-breathing (FB) group. The CB group performed structured mid-tidal breath-holds synchronized to an electronic metronome during approximately 25% of the main training phase, targeting a peripheral oxygen saturation (SpO₂) nadir of 92-94%. The FB group completed the identical exercise protocol with unrestricted breathing, maintaining SpO₂ at or above 97%.
Physiological assessments were conducted at baseline and within 48 hours post-intervention. Measurements included resting cardiovascular parameters (heart rate and blood pressure), estimated maximal oxygen uptake (VO₂max) via a modified Bruce treadmill protocol, and comprehensive pulmonary function testing (spirometry). Continuous SpO₂ monitoring was utilized during all training sessions to ensure protocol adherence and participant safety.
Study design
- Primary purpose
- Other
- Allocation
- Non-randomised
- Intervention model
- Parallel groups
- Masking
- Single blind (outcomes assessor)
- Number of arms
- 2
- Model description
- A two-arm parallel-group design comparing a controlled-breathing interval training group to a free-breathing interval training group.
| Arm | Type | Receives |
|---|---|---|
| Controlled-Breathing (CB) Group | Experimental | Behavioral: Voluntary Hypoventilation Training, Behavioral: Progressive Treadmill Interval TrainingParticipants completed 24 supervised treadmill interval sessions over 8 weeks (65-85% heart rate reserve). During approximately 25% of the main training phase, participants performed structured mid-tidal breath-holds synchronized to an electronic metronome (progressing from 3-count to 6-count cycles), targeting a peripheral oxygen saturation (SpO₂) nadir of 92-94%. |
| Free-Breathing (FB) Group | Active comparator | Behavioral: Progressive Treadmill Interval TrainingParticipants completed the identical 24 supervised treadmill interval sessions over 8 weeks (65-85% heart rate reserve) with unrestricted breathing throughout all sessions. Continuous SpO₂ monitoring confirmed values remained at or above 97%. |
Who may qualify
- Ages
- 25 to 35 years
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult
Key inclusion criteria (4 listed)
- Male recreational mountaineers aged 25 to 35 years.
- A minimum of 6 months of mountaineering experience with at least 3 sessions per month.
- Willingness to attend at least 85% of the scheduled training sessions.
- Negative responses to all items on the Physical Activity Readiness Questionnaire (PAR-Q).
Key exclusion criteria (4 listed)
- Diagnosed cardiovascular, respiratory, or musculoskeletal disorders.
- Current smoking.
- Use of medications affecting heart rate or blood pressure.
- Prior experience with structured hypoxic or breath-hold training.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Voluntary Hypoventilation TrainingAlso: VHT; Breath-Hold TrainingA breathing maneuver consisting of structured mid-tidal breath-holds synchronized to an electronic metronome to induce mild voluntary hypoventilation (target SpO₂ nadir 92-94%) during physical exertion. | Behavioural | Controlled-Breathing (CB) Group |
| Progressive Treadmill Interval TrainingAlso: Interval Training; Treadmill ExerciseA cardiovascular exercise protocol involving supervised treadmill sessions with progressive increases in intensity (65-85% heart rate reserve) and duration (30-45 minutes) over an 8-week period. | Behavioural | Controlled-Breathing (CB) Group, Free-Breathing (FB) Group |
Primary outcome
Resting Heart Rate
Time frame: Baseline (within 48 hours before the first training session) and post-intervention (within 48 hours after the final 8-week training session).
Resting heart rate (beats per minute) recorded using a 12-lead electrocardiograph after 10 minutes of seated rest in a quiet, temperature-controlled room. The mean value from the final 2 minutes is used for analysis.
Estimated Maximal Oxygen Uptake (VO2max)
Time frame: Baseline (within 48 hours before the first training session) and post-intervention (within 48 hours after the final 8-week training session).
Estimated VO2max (mL·kg-¹·min-¹) determined using a modified Bruce treadmill protocol until volitional exhaustion. It is calculated from total treadmill time (in minutes) using the Foster equation.
9 secondary outcomes
Systolic Blood Pressure
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Diastolic Blood Pressure
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Tidal Volume (TV)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Vital Capacity (VC)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Forced Vital Capacity (FVC)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Forced Expiratory Volume in 1 Second (FEV1)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Peak Expiratory Flow (PEF)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Forced Expiratory Flow at 25-75% of FVC (FEF25-75%)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Maximum Voluntary Ventilation (MVV)
Time frame: Baseline and post-intervention (within 48 hours after the final 8-week training session).
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 20 Jul 2026.
- Individual participant dataSharing planned: Yes. The de-identified dataset and full study protocol are available from the corresponding author upon reasonable request.
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Screening Protocol
Pain
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Mohammadreza Rezaeipour, MD, PhD principal investigator
University of Sistan and Baluchestan
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Voluntary Hypoventilation Training and Progressive Treadmill Interval Training in people with Healthy Volunteers, run by Mohammadreza Rezaeipour, MD, PhD at 1 site in Iran.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 20 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Iran. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Resting Heart Rate (time frame: Baseline (within 48 hours before the first training session) and post-intervention (within 48 hours after the final 8-week training session).). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 20 Jul 2026.