Metabolic myopathies: Functional evaluation by analysis of oxygen uptake kinetics

Bruno Grassi, Simone Porcelli, Mauro Marzorati, Francesca Lanfranconi, Paola Vago, Claudio Marconi, Lucia Morandi

Research output: Contribution to journalArticlepeer-review


PURPOSE: The aim was to identify additional noninvasive tools allowing to detect and to quantify the metabolic impairment in patients with mitochondrial myopathies (MM) or McArdle's disease (McA). METHODS: Kinetics of adjustment of pulmonary oxygen uptake (V̇O2 kinetics) during transitions to constant-load moderate-intensity cycle ergometer exercise were determined on 15 MM, 8 McA, 21 patients with signs and/or symptoms of metabolic myopathy but a negative biopsy ("patient controls"; P-CTRL), and 22 healthy untrained controls (CTRL). RESULTS: V̇O2 kinetics were slower in MM and in McA versus P-CTRL and CTRL, slower in McA versus MM, and not significantly different between P-CTRL and CTRL. The time constants (τ) of the monoexponential function describing the V̇O2 kinetics were (X̄ ± SE) 59.2 ± 8.5 s in MM, 87.6 ± 16.4 s in McA, 36.9 ± 3.1 s in P-CTRL, and 35.4 ± 1.9 s in CTRL. In a subgroup of the patients (eight MM and seven McA), τ of V̇O2 kinetics were negatively correlated with two variables determined in a previous study (Grassi B, Marzorati M, Lanfranconi F, et al. Impaired oxygen extraction in metabolic myopathies: detection and quantification by near-infrared spectroscopy. Muscle Nerve. 2007;35:510-20): a) a muscle oxygenation index, obtained by near-infrared spectroscopy, estimating the peak capacity of skeletal muscle fractional O2 extraction; and b) V̇O2 peak. CONCLUSIONS: In MM and McA patients, analysis of pulmonary V̇O2 kinetics during moderate-intensity exercise allows to identify and to quantify, noninvasively, the impairment of skeletal muscle oxidative metabolism. In these patients, the slower V̇O2 kinetics can be considered a marker of the impaired exercise tolerance. The present data could be useful for clinicians who need an objective, quantitative, and longitudinal evaluation of the impairment to be used in the follow-up of these patients as well as in the assessment of therapeutic interventions.

Original languageEnglish
Pages (from-to)2120-2127
Number of pages8
JournalMedicine and Science in Sports and Exercise
Issue number12
Publication statusPublished - Dec 2009


  • Gas exchange kinetics
  • Mitochondrial myopathy
  • Myophosphorylase deficiency
  • Near-infrared spectroscopy
  • Oxidative metabolism

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation


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