Effects of Breath-Hold vs Standard Interval Training on Fitness in Mountaineers

NCT07703839 | Completed

• 1 other identifier: IR.USB.REC.1402.013
• Study Type: interventional
• Target: 24
• Locations: 1 country
• Sites: 1

Brief 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. 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.

Conditions

Healthy Volunteers

Keywords

Voluntary hypoventilation training; Mountaineering; Cardiorespiratory fitness; Interval training; Acclimatization; Aerobic capacity; Pulse oximetry; Breath-Hold Training

Outcome Measures

Primary Outcomes (2)

• 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.

  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.

  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

  Baseline and post-intervention (within 48 hours after the final 8-week training session).

• Diastolic Blood Pressure

  Baseline and post-intervention (within 48 hours after the final 8-week training session).

• Tidal Volume (TV)

  Baseline and post-intervention (within 48 hours after the final 8-week training session).

• Vital Capacity (VC)

  Baseline and post-intervention (within 48 hours after the final 8-week training session).

• Forced Vital Capacity (FVC)

  Baseline and post-intervention (within 48 hours after the final 8-week training session).

Study Arms (2)

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%.

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%.

Behavioral: Progressive Treadmill Interval Training

Interventions

Voluntary Hypoventilation Training BEHAVIORAL

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.

Also known as: VHT; Breath-Hold Training

Controlled-Breathing (CB) Group

Progressive Treadmill Interval Training BEHAVIORAL

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.

Also known as: Interval Training; Treadmill Exercise

Controlled-Breathing (CB) Group; Free-Breathing (FB) Group

Eligibility Criteria

• Age: 25 Years - 35 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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).

You may not qualify if:

• 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.

Sponsors & Collaborators

• Mohammadreza Rezaeipour, MD, PhD: lead
• Mountaineering and Sport Climbing Federation of Sistan and Baluchestan Province: collaborator
• General Directorate of Sports and Youth of Sistan and Baluchestan Province: collaborator

Study Sites (1)

Sport Sciences Department, University of Sistan and Baluchestan

Zahedan, Sistan and Baluchestan, 98135-986, Iran

Location

Study Officials

• Mohammadreza Rezaeipour, MD, PhD

  University of Sistan and Baluchestan

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: NON RANDOMIZED
• Masking: SINGLE
• Who Masked: OUTCOMES ASSESSOR
• Masking Details: Participants and training supervisors were unblinded to the breathing intervention. The technician conducting spirometry assessments was blinded to group allocation.
• Purpose: OTHER
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR INVESTIGATOR
• PI Title: Assoc. Prof. Dr.

Model Details: A two-arm parallel-group design comparing a controlled-breathing interval training group to a free-breathing interval training group.

Study Record Dates

• First Submitted: July 9, 2026
• First Posted: July 14, 2026
• Study Start: September 30, 2023
• Primary Completion: November 30, 2023
• Study Completion: November 30, 2023
• Last Updated: July 20, 2026

Record last verified: 2026-07

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL
• Time Frame: Without end date
• Access Criteria: Available from the corresponding author upon reasonable request.

Locations

IR (1)