NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Sympathetic activation in exercise is not dependent on muscle acidosis. Direct evidence from studies in metabolic myopathiesMuscle acidosis has been implicated as a major determinant of reflex sympathetic activation during exercise. To test this hypothesis we studied sympathetic exercise responses in metabolic myopathies in which muscle acidosis is impaired or augmented during exercise. As an index of reflex sympathetic activation to muscle, microneurographic measurements of muscle sympathetic nerve activity (MSNA) were obtained from the peroneal nerve. MSNA was measured during static handgrip exercise at 30% of maximal voluntary contraction force to exhaustion in patients in whom exercise-induced muscle acidosis is absent (seven myophosphorylase deficient patients; MD [McArdle's disease], and one patient with muscle phosphofructokinase deficiency [PFKD]), augmented (one patient with mitochondrial myopathy [MM]), or normal (five healthy controls). Muscle pH was monitored by 31P-magnetic resonance spectroscopy during handgrip exercise in the five control subjects, four MD patients, and the MM and PFKD patients. With handgrip to exhaustion, the increase in MSNA over baseline (bursts per minute [bpm] and total activity [%]) was not impaired in patients with MD (17+/-2 bpm, 124+/-42%) or PFKD (65 bpm, 307%), and was not enhanced in the MM patient (24 bpm, 131%) compared with controls (17+/-4 bpm, 115+/-17%). Post-handgrip ischemia studied in one McArdle patient, caused sustained elevation of MSNA above basal suggesting a chemoreflex activation of MSNA. Handgrip exercise elicited an enhanced drop in muscle pH of 0.51 U in the MM patient compared with the decrease in controls of 0.13+/-0.02 U. In contrast, muscle pH increased with exercise in MD by 0.12+/-0.05 U and in PFKD by 0.01 U. In conclusion, patients with glycogenolytic, glycolytic, and oxidative phosphorylation defects show normal muscle sympathetic nerve responses to static exercise. These findings indicate that muscle acidosis is not a prerequisite for sympathetic activation in exercise.
Document ID
20040172699
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Vissing, J.
(The Copenhagen Muscle Research Center, National University Hospital, Rigshospitalet DK-2100 Copenhagen, Denmark)
Vissing, S. F.
MacLean, D. A.
Saltin, B.
Quistorff, B.
Haller, R. G.
Blomqvist, C. G.
Date Acquired
August 22, 2013
Publication Date
April 15, 1998
Publication Information
Publication: The Journal of clinical investigation
Volume: 101
Issue: 8
ISSN: 0021-9738
Subject Category
Life Sciences (General)
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cardiopulmonary
Non-NASA Center

Available Downloads

There are no available downloads for this record.
No Preview Available