Healthy Volunteers
Conditions
Keywords
Voluntary hypoventilation training, Mountaineering, Cardiorespiratory fitness, Interval training, Acclimatization, Aerobic capacity, Pulse oximetry, Breath-Hold Training
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.
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.
Interventions
BEHAVIORALVoluntary Hypoventilation 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.
BEHAVIORALProgressive Treadmill Interval Training
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.
Sponsors
Mohammadreza Rezaeipour, MD, PhD
Mountaineering and Sport Climbing Federation of Sistan and Baluchestan Province
General Directorate of Sports and Youth of Sistan and Baluchestan Province
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
OTHER
Masking
SINGLE (Outcomes Assessor)
Masking description
Participants and training supervisors were unblinded to the breathing intervention. The technician conducting spirometry assessments was blinded to group allocation.
Intervention model description
A two-arm parallel-group design comparing a controlled-breathing interval training group to a free-breathing interval training group.
Eligibility
Sex/Gender
MALE
Age
25 Years to 35 Years
Healthy volunteers
Yes
Inclusion criteria
* 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).
Exclusion criteria
* 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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Resting Heart Rate | 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) | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Systolic Blood Pressure | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Systolic blood pressure (mmHg) measured in triplicate using an automated oscillometric monitor; the average of 3 measurements is retained. |
| Diastolic Blood Pressure | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Diastolic blood pressure (mmHg) measured in triplicate using an automated oscillometric monitor; the average of 3 measurements is retained. |
| Tidal Volume (TV) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Tidal volume (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
| Vital Capacity (VC) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Vital capacity (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
| Forced Vital Capacity (FVC) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Vital capacity (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
| Forced Expiratory Volume in 1 Second (FEV1) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Forced expiratory volume in 1 second (L) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
| Peak Expiratory Flow (PEF) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Peak expiratory flow (L/s) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
| Forced Expiratory Flow at 25-75% of FVC (FEF25-75%) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Forced expiratory flow at 25-75% of FVC (L/s) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
| Maximum Voluntary Ventilation (MVV) | Baseline and post-intervention (within 48 hours after the final 8-week training session). | Maximum voluntary ventilation (L/min) measured via calibrated spirometry; the highest value from three technically acceptable maneuvers is retained. |
Countries
Iran
Contacts
PRINCIPAL_INVESTIGATORMohammadreza Rezaeipour, MD, PhD
University of Sistan and Baluchestan
Outcome results
None listed