Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise

Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise

Autor Gimenes, Ana Cristina Oliveira Autor UNIFESP Google Scholar
Neder, Jose Alberto Autor UNIFESP Google Scholar
Dal Corso, Simone Autor UNIFESP Google Scholar
Nogueira, Cristiano Rabelo Autor UNIFESP Google Scholar
Nápolis, Lara Maris Autor UNIFESP Google Scholar
Mello, Marco Tulio de Autor UNIFESP Google Scholar
Oliveira, Acary Souza Bulle Autor UNIFESP Google Scholar
Nery, Luiz Eduardo Autor UNIFESP Google Scholar
Instituição Universidade Federal de São Paulo (UNIFESP)
Resumo We determined the response characteristics and functional correlates of the dynamic relationship between the rate (Δ) of oxygen consumption ( <img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1188>O2) and the applied power output (work rate = WR) during ramp-incremental exercise in patients with mitochondrial myopathy (MM). Fourteen patients (7 males, age 35.4 ± 10.8 years) with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years) took a ramp-incremental cycle ergometer test for the determination of the <img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1189>O2 on-exercise mean response time (MRT) and the gas exchange threshold (GET). The Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1190>O2/ΔWR slope was calculated up to GET (S1), above GET (S2) and over the entire linear portion of the response (S T). Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak <img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1191>O2 and muscle performance were lower in patients than controls (P < 0.05). Patients had significantly lower Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1192>O2/ΔWR than controls, especially the S2 component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min-1·W-1, respectively; P < 0.001). There were significant relationships between Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1193>O2/ΔWR (S T) and muscle endurance, MRT-<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1194>O2, GET and peak <img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1195>O2 in MM patients (P < 0.05). In fact, all patients with Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1196>O2/ΔWR below 8 mL·min-1·W-1 had severely reduced peak <img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1197>O2 values (<60% predicted). Moreover, patients with higher cardiopulmonary stresses during exercise (e.g., higher Δ ventilation/carbon dioxide output and Δ heart rate/Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1198>O2) had lower Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1199>O2/ΔWR (P < 0.05). In conclusion, a readily available, effort-independent index of aerobic dysfunction during dynamic exercise (Δ<img border=0 width=11 height=13 src=548_files/image001.gif v:shapes=_x0000_i1200>O2/ΔWR) is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress.
Palavra-chave Muscular diseases
Oxygen consumption
Cardiopulmonary exercise testing
Skeletal muscle
Pathophysiology
Mitochondrial myopathy
Idioma Inglês
Financiador Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Data de publicação 2011-04-01
Publicado em Brazilian Journal of Medical and Biological Research. Associação Brasileira de Divulgação Científica, v. 44, n. 4, p. 354-360, 2011.
ISSN 0100-879X (Sherpa/Romeo, fator de impacto)
Publicador Associação Brasileira de Divulgação Científica
Extensão 354-360
Fonte http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2011000400013
Direito de acesso Acesso aberto Open Access
Tipo Artigo
Web of Science WOS:000289368400013
SciELO S0100-879X2011000400013 (estatísticas na SciELO)
Endereço permanente http://repositorio.unifesp.br/handle/11600/6403

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