Sex differences in the evolution of net respiratory muscle pressures during incremental exercise
Year: 2020
Type: article
Abstract: The respiratory muscle pressure (P mus ) waveform lends insight into the patterns of net inspiratory v expiratory muscle recruitment under a wide variety of conditions, including mechanical ventilation, spontaneous breathing, and during exercise. On this last point, inspection of the P mus waveform during incremental and constant work rate cycling reveals that inspiratory and expiratory muscle recruitment systematically increase with rising minute ventilations, and that the duration of post‐inspiratory inspiratory activity (PIIA) gradually disappears from low to high levels of respiratory motor output. In recent years, it has become increasingly evident that the work of breathing is systematically higher for women compared with men at a given minute ventilation during exercise. Yet, no study has examined the potential sex differences in the evolution of P mus (and its components; e.g., PIIA) during exercise. Thus, a comprehensive assessment of the P mus waveform during exercise between sexes is warranted. Purpose To compare the evolution of inspiratory and expiratory P mus between men and women during incremental cycling. Methods Thirteen men (21 ± yrs; 181 ± 5 cm; 82 ± 11 kg) and 10 women (21 ± 1 yrs; 165 ± 6 cm; 62 ± 6 kg) visited the laboratory on two separate occasions. The first occasion was used to obtain informed consent and to screen participants for normal pulmonary function (>85% age‐predicted). On the second visit, participants were instrumented with an esophageal balloon catheter to estimate variations in pleural pressure (P pl ). Quasi‐static relaxation curves were obtained to measure chest wall recoil pressure (P cw ). Participants then completed an incremental cycling protocol until volitional exhaustion. P mus was calculated at given minute ventilations during the exercise protocol as follows: P mus = P cw – P pl . Results The peak inspiratory P mus were significantly greater in females compared with men at a given minute ventilation during incremental cycling ( P < 0.05), yet peak expiratory P mus was similar between sexes. The average rates of change (slope) in P mus during inspiration & expiration were significantly faster in females than males at a given minute ventilation ( P < 0.05). Finally, the duration of PIIA (expressed as a fraction of expiratory time) gradually decreased with increasing minute ventilation during exercise ( P < 0.05). This reduction in PIIA was however similar between men and women. Conclusion The primary finding of this study was that the pattern of respiratory muscle recruitment was different between sexes during incremental cycling, insofar as women displayed systematically larger inspiratory P mus , and faster rates of net inspiratory & expiratory pressure‐development compared with men at matched ventilations. However, no differences in PIIA between sexes were observed. Support or Funding Information This research was funded by preliminary data funds provided by Northern Arizona University (JWD). TJC was supported by the Irene Diamond Fund/American Federation for Aging Research Postdoctoral Transition Award during the time of this study.
Source: The FASEB Journal
Institutions: Mayo Clinic, Northern Arizona University
Language: English
Subfield: Complementary and alternative medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W3016570544