EFFECTS OF AGE AND SEX ON INSPIRATORY MUSCLE ACTIVATION PATTERNS DURING EXERCISE

Purpose Characterize the effects of age, sex, and their interaction on inspiratory muscle activation patterns during exercise. Methods Twenty younger (20-30y, n=10 women) and twenty older (60-80y, n=10 women) subjects performed an incremental cycle exercise test. Electromyography of the scalene (EMGsca) and sternocleidomastoid (EMGscm) muscles were measured using skin surface electrodes, while diaphragm electromyography (EMGdi) and esophageal and transdiaphragmatic pressures were measured using an esophageal catheter. Electromyography data were transformed into root-mean-square with a 100ms time constant. Esophageal (PTPes) and diaphragmatic (PTPdi) pressure-time products were used as indices of total inspiratory muscle pressure production and diaphragmatic pressure production, respectively. Results At absolute minute ventilations (V[Combining Dot Above]E), women and older subjects had greater EMGdi than men and younger subjects, respectively (all p0.05). Women had greater EMGsca activity than men at absolute and relative levels of V[Combining Dot Above]E (all p0.05). At absolute and relative levels of V[Combining Dot Above]E, women and older subjects had greater EMGscm than men and younger subjects, respectively (all p0.05). No significant interactions between age and sex were noted (all p>0.05). Conclusion Age and sex significantly affect inspiratory muscle activation patterns during exercise; however, the extent of the effects depends on whether comparisons are made at absolute or relative V[Combining Dot Above]E. Corresponding Author: Yannick Molgat-Seon, PhD, 6108 Thunderbird Blvd, Vancouver, BC, Canada, V6T 1Z3, E-mail: yannick.molgat-seon@hli.ubc.ca. This study was supported by the British Columbia Lung Association (BCLA). YMS, PBD, and AHR were supported by graduate scholarships from the Natural Sciences and Engineering Research Council of Canada (NSERC). PBD and MRS were supported by fellowships from the University of British Columbia and BCLA. JAG was supported by a Scholar Award from the Michael Smith Foundation for Health Research, a New Investigator Award from the Providence Health Care Research Institute and St. Paul's Hospital Foundation, and a Canadian Institutes of Health Research Clinical Rehabilitation New Investigator Award. The funders had no role in the study design, data collection and analysis, or preparation of the manuscript. Conflicts of Interest: YM, PBD, AHR, MRS, LMR, JDR, JAG, and AWS do not have any conflicts of interest to report relevant to this manuscript. The results of the present study do not constitute endorsement by ACSM. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 16 April 2018 © 2018 American College of Sports Medicine

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