Work of breathing influences muscle sympathetic nerve activity during semi-recumbent cycle exercise.

Autor: Dominelli PB; School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.; Department of Anaesthesiology, Mayo Clinic, Rochester, Minnesota., Katayama K; Research Center of Health, Physical Fitness and Sports, Graduate School of Medicine, Nagoya University, Nagoya, Japan., Vermeulen TD; Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada., Stuckless TJR; Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada., Brown CV; Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada., Foster GE; Centre for Heart, Lung, and Vascular Health, School of Health and Exercise Sciences, University of British Columbia, Kelowna, British Columbia, Canada., Sheel AW; School of Kinesiology, University of British Columbia, Vancouver, British Columbia, Canada.
Jazyk: angličtina
Zdroj: Acta physiologica (Oxford, England) [Acta Physiol (Oxf)] 2019 Apr; Vol. 225 (4), pp. e13212. Date of Electronic Publication: 2018 Nov 25.
DOI: 10.1111/apha.13212
Abstrakt: Reducing the work of breathing during exercise improves locomotor muscle blood flow and reduces diaphragm and locomotor muscle fatigue and is thought to be the result of a sympathetically mediated reflex.
Aim: The aim of this study was to assess muscle sympathetic nerve activity (MSNA) when the work of breathing is experimentally lowered during dynamic exercise.
Methods: Healthy subjects (n = 12; age = 29 ± 9 years) performed semi-recumbent cycling trials at 40%, 60%, and 80% of peak workload. Exercise trials consisted of spontaneous breathing, reduced work of breathing (proportional assist ventilator), followed by further spontaneous breathing (post-ventilator). MSNA was recorded from the median nerve.
Results: There was no difference in work of breathing between PAV and post-PAV at 40% peak work. At 60% peak work, the ventilator significantly (P < 0.05) reduced work of breathing (103 ± 39 vs 144 ± 47 J min -1 ), sympathetic nerve activity (35 ± 5 vs 42 ± 8 burst min -1 ), and V ˙ O 2 (2.4 ± 0.5 vs 2.6 ± 0.5 L min -1 ) without influencing ventilation (86 ± 9 vs 82 ± 10 L min -1 ; P > 0.05), for PAV and post-PAV respectively. During 80% peak work (n = 8), the ventilator significantly (P < 0.05) reduced work of breathing (235 ± 110 vs. 361 ± 150 J min -1 ), MSNA (48 ± 7 vs 54 ± 11 burst min -1 ), and V ˙ O 2 (2.9 ± 0.6 vs 3.2 ± 0.7 L min -1 ) but not ventilation (121 ± 20 vs 123 ± 20 L min -1 ; P > 0.05), for PAV and post-PAV respectively. There was a significant relationship between MSNA and V ˙ O 2 (P < 0.0001) with a significant interaction due to the ventilator (P < 0.05).
Conclusion: Lowering the normally occurring work of breathing during exercise results in commensurate reductions in MSNA. Our findings provide evidence of a sympathetically mediated vasoconstrictor effect emanating from respiratory muscles during exercise.
(© 2018 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.)
Databáze: MEDLINE
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