Skip to main content
  • Meeting abstract
  • Open access
  • Published:

Respiratory mechanics influence VO2max in acute hypoxia in females

Introduction

The magnitude of decrease in maximal oxygen uptake (VO2 max) in hypoxia (H) is more pronounced in male endurance athletes. In these subjects, high pulmonary ventilation (VE) could be beneficial in maintaining VO2 max in H [1]. Because females have smaller chest walls and narrower airways than males, VE during intensive exercise is mechanically limited [2]. Thus, it is hypothesised that in females, respiratory response and mechanics influenced the magnitude of decrease in VO2 max in H relative to males, despite lower VO2 max in females than in males. To test this hypothesis, we studied 22 healthy males and females as they performed an exhaustive cycling test in H and normoxia (N) conditions.

Methods

Twenty-two healthy males (n = 12; VO2 max: 51 (7) ml.kg-1.min-1, age; 21 (2) yr, stature; 172 (3) cm, mass; 66 (6) kg) and females (n = 10; VO2 max = 44 (6) ml.kg-1.min-1, age; 21 (1) yr, stature; 159 (4) cm, mass; 53 (8) kg) performed the incremental cycle exercise test until exhaustion under N (20.9 % O2) and H (15.0 % O2) conditions. During the exercise test, we measured VO2 max and VE max. To mechanically assess the respiratory work, we measured transpulmonary pressure by subtracting mouth pressure from esophageal pressure and calculated work of breathing (WOB) as the integrated area of the Ptp-volume loop.

Results

The percentage decrease in VO2 max in H (% dVO2 max) tended to be larger in females than in males (−16% in males and −21% in females, p < 0.06). VE/VO2 was significantly (p < 0.05) higher in females than males, and it was significantly (p < 0.01) higher in H than in N in both genders. In females only, the % dVO2 max in H was significantly correlated to the extent of change in VE max (r = 0.79, p < 0.05). In comparison with N, WOB/VE in H tended to be lower in males (−13.1%) whereas it was 14.6% higher in females (not significant). Furthermore, in females, the % dVO2 max in H was significantly correlated to WOB/VE in H (r = −0.76, p < 0.05).

Discussion

These results suggest that females have lower ventilatory mechanical efficiency than males, and VE is one of the factors causing this decrease in VO2 max in H. Further, there is a possibility that the oxygen demand at the respiratory muscles greatly increases against the increase in VE in H. Thus, high respiratory muscle work compromises blood flow to the active muscles [3], thereby limiting their peak work rate and VO2 max in H.

Conclusion

Our findings demonstrated that in females, the respiratory muscle work efficiency affected the decrease in VO2 max in H, a decrease which tended to be larger in females than in males, despite the lower VO2 max in females compared with males.

References

  1. Ogawa T, Calbet JA, Honda Y, Fujii N, Nishiyasu T: The effects of breathing a helium-oxygen gas mixture on maximal pulmonary ventilation and maximal oxygen consumption during exercise in acute moderate hypobaric hypoxia. Eur J Appl Physiol. 2010, 110 (4): 853-861. 10.1007/s00421-010-1570-z.

    Article  CAS  PubMed  Google Scholar 

  2. McClaran SR, Harms CA, Pegelow DF, Dempsey JA: Smaller lungs in women affect exercise hyperpnea. J Appl Physiol. 1998, 84 (6): 1872-1881.

    CAS  PubMed  Google Scholar 

  3. Harms CA, Babcock MA, McClaran SR, Pegelow DF, Nickele GA, Nelson WB, et al: Respiratory muscle work compromises leg blood flow during maximal exercise. J Appl Physiol. 1997, 82 (5): 1573-1583.

    CAS  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Takeshi Ogawa.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.

The Creative Commons Public Domain Dedication waiver (https://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Hanamaru, T., Yoshikawa, T., Nishiyasu, T. et al. Respiratory mechanics influence VO2max in acute hypoxia in females. Extrem Physiol Med 4 (Suppl 1), A64 (2015). https://doi.org/10.1186/2046-7648-4-S1-A64

Download citation

  • Published:

  • DOI: https://doi.org/10.1186/2046-7648-4-S1-A64

Keywords