Document Detail

Lack of importance of respiratory muscle load in ventilatory regulation during heavy exercise in humans.
MedLine Citation:
PMID:  8821150     Owner:  NLM     Status:  MEDLINE    
1. Seven active subjects (24 +/- 1 years; maximal oxygen uptake (VO2,max), 3.77 +/- 0.2 l min-1; mean +/- S.E.M.) performed constant work rate heavy exercise (CWHE, approximately 80% of maximal incremental work rate) to exhaustion on 2 days, one with (unload) and one without (control) respiratory muscle unloading. 2. With unloading, a special device applied flow-proportional mouth pressure assist (positive with inspiratory (I), negative with expiratory (E) flows) throughout each breath. No pressure assist occurred during control CWHE. To confirm unloading, respiratory muscle pressures (Pmus) were derived (n = 5) from measured pleural pressure and chest wall elastic and resistive pressures. 3. Other than minor differences in early exercise, the temporal course of minute ventilation (VE) was similar in both tests as exercise progressed. The fall in estimated mean alveolar CO2 (PA,CO2) throughout CWHE was identical in both tests. There were no significant differences (ANOVA) in VE, tidal volume, frequency, oxygen consumption rate (VO2), heart rate or PA,CO2, between unload and control CWHE, at matched times (at 50% of control duration and at the end of exercise). Unloading reduced Pmus significantly throughout CWHE; at 50% control duration, peak Pmus,I and Pmus,E fell by 24 and 41%, respectively, with unloading, as did mean Pmus,I and Pmus,E (21 and 44%). 4. The lack of any significant changes in VE, PA,CO2 or breathing pattern, despite a marked reduction in respiratory muscle load throughout CWHE, indicates that the load on the respiratory muscles has only a minor role in the regulation of ventilation during heavy exercise. 5. The absence of improvement in CWHE duration (control, 11.4 +/- 1.2 min; unload, 12.6 +/- 2.1 min, n.s.) with unloading implies that respiratory muscle function does not limit endurance exercise performance during cycling in healthy humans.
B Krishnan; T Zintel; C McParland; C G Gallagher
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of physiology     Volume:  490 ( Pt 2)     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  1996 Jan 
Date Detail:
Created Date:  1996-11-06     Completed Date:  1996-11-06     Revised Date:  2009-11-18    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  537-50     Citation Subset:  IM; S    
Department of Medicine, University of Saskatchewan, Saskatoon, Canada.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Carbon Dioxide / physiology
Exercise / physiology*
Heart Rate / physiology
Muscle Fatigue / physiology
Oxygen Consumption
Pulmonary Ventilation / physiology
Respiratory Mechanics / physiology*
Respiratory Muscles / physiology*
Reg. No./Substance:
124-38-9/Carbon Dioxide

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

Previous Document:  Supraspinal factors in human muscle fatigue: evidence for suboptimal output from the motor cortex.
Next Document:  The characteristics and frequency of augmented breaths during CO2-induced hyperpnoea of newborn infa...