Hypoxic exposure and air-quality reporting in normobaric hypoxic resistance training: a systematic evidence map and exploratory meta-analysis
- 1College of Physical Education and Health, Guangxi Normal University, Guilin, Guangxi China
Abstract
Background: Normobaric hypoxic resistance training (NHRT) studies describe the hypoxic prescription using the fraction of inspired oxygen (FiO₂) or simulated altitude. However, FiO₂ is an external setting and may not fully represent the hypoxic stimulus experienced during training. Training SpO₂ responses, the hypoxia-delivery method, facility volume, gas flow, ventilation, CO₂, humidity and temperature may affect the exposure environment. These variables are important for interpreting and comparing NHRT studies, but their reporting has not been systematically evaluated.
Methods: This evidence map assessed reporting of hypoxic exposure and air quality in chronic NHRT studies and conducted exploratory meta-analyses when outcomes and data were comparable. The primary evidence map comprised 16 independent chronic NHRT cohorts. Reporting completeness was assessed in this set and repeated in an extended 17-study set that included one additional air-quality reference study. Thirteen independent primary cohorts contributed to at least one exploratory meta-analysis. NHRT-versus-NRT syntheses used random-effects models and Hedges-corrected standardised mean differences.
Results: FiO₂ or simulated altitude was reported relatively well, whereas training SpO₂, CO₂, humidity, temperature, ventilation, space and flow-related variables were underreported. Thirteen independent cohorts contributed to at least one exploratory meta-analysis. Lower-limb maximal strength (7 studies; SMD = 0.07, 95% CI -0.26 to 0.41; I2 = 0%) and lean mass (5 studies; SMD = 0.12, 95% CI -0.25 to 0.49; I2 = 0%) did not show a clear additional advantage of NHRT over NRT. Whole-body body fat percentage showed an unstable numerical direction favouring NHRT (5 studies; SMD = -0.33, 95% CI -0.78 to 0.12; I2 = 23.2%). Local muscle morphology and local muscular endurance outcomes were supported by few studies and should be interpreted as exploratory.
Conclusions: Existing NHRT studies report FiO₂ or simulated altitude relatively well, but actual exposure conditions and internal hypoxic responses remain incompletely described. Exploratory meta-analyses did not show that NHRT was superior to NRT for common outcomes related to strength, body composition or local muscle morphology. Future NHRT studies should report not only FiO₂, but also hypoxia-delivery method, internal oxygenation responses and air-quality control conditions.
Systematic review registration: PROSPERO CRD420261405733.
Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s13102-026-01943-y.
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BibTeX
@article{guan2026hypoxic,
title = {{Hypoxic exposure and air-quality reporting in normobaric hypoxic resistance training: a systematic evidence map and exploratory meta-analysis}},
author = {Zhiyu Guan and Ziwen Wang and Chuangui Mao and Weiguo Liu and Cheng Zhang},
journal = {BMC Sports Science, Medicine and Rehabilitation},
year = {2026},
month = aug,
doi = {10.1186/s13102-026-01943-y},
url = {https://doi.org/10.1186/s13102-026-01943-y},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Hypoxic exposure and air-quality reporting in normobaric hypoxic resistance training: a systematic evidence map and exploratory meta-analysis
AU - Zhiyu Guan
AU - Ziwen Wang
AU - Chuangui Mao
AU - Weiguo Liu
AU - Cheng Zhang
PY - 2026
DA - 2026/08/06
JO - BMC Sports Science, Medicine and Rehabilitation
DO - 10.1186/s13102-026-01943-y
UR - https://doi.org/10.1186/s13102-026-01943-y
AB - Background: Normobaric hypoxic resistance training (NHRT) studies describe the hypoxic prescription using the fraction of inspired oxygen (FiO₂) or simulated altitude. However, FiO₂ is an external setting and may not fully represent the hypoxic stimulus experienced during training. Training SpO₂ responses, the hypoxia-delivery method, facility volume, gas flow, ventilation, CO₂, humidity and temperature may affect the exposure environment. These variables are important for interpreting and comparing NHRT studies, but their reporting has not been systematically evaluated. Methods: This evidence map assessed reporting of hypoxic exposure and air quality in chronic NHRT studies and conducted exploratory meta-analyses when outcomes and data were comparable. The primary evidence map comprised 16 independent chronic NHRT cohorts. Reporting completeness was assessed in this set and repeated in an extended 17-study set that included one additional air-quality reference study. Thirteen independent primary cohorts contributed to at least one exploratory meta-analysis. NHRT-versus-NRT syntheses used random-effects models and Hedges-corrected standardised mean differences. Results: FiO₂ or simulated altitude was reported relatively well, whereas training SpO₂, CO₂, humidity, temperature, ventilation, space and flow-related variables were underreported. Thirteen independent cohorts contributed to at least one exploratory meta-analysis. Lower-limb maximal strength (7 studies; SMD = 0.07, 95% CI -0.26 to 0.41; I2 = 0%) and lean mass (5 studies; SMD = 0.12, 95% CI -0.25 to 0.49; I2 = 0%) did not show a clear additional advantage of NHRT over NRT. Whole-body body fat percentage showed an unstable numerical direction favouring NHRT (5 studies; SMD = -0.33, 95% CI -0.78 to 0.12; I2 = 23.2%). Local muscle morphology and local muscular endurance outcomes were supported by few studies and should be interpreted as exploratory. Conclusions: Existing NHRT studies report FiO₂ or simulated altitude relatively well, but actual exposure conditions and internal hypoxic responses remain incompletely described. Exploratory meta-analyses did not show that NHRT was superior to NRT for common outcomes related to strength, body composition or local muscle morphology. Future NHRT studies should report not only FiO₂, but also hypoxia-delivery method, internal oxygenation responses and air-quality control conditions. Systematic review registration: PROSPERO CRD420261405733. Supplementary Information: The online version contains supplementary material available at https://doi.org/10.1186/s13102-026-01943-y.
SN - 2052-1847
ER -