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Exercise efficiency impairment in metabolic myopathies - PubMed

  • ️Wed Jan 01 2020

Comparative Study

Exercise efficiency impairment in metabolic myopathies

Jean-Baptiste Noury et al. Sci Rep. 2020.

Abstract

Metabolic myopathies are muscle disorders caused by a biochemical defect of the skeletal muscle energy system resulting in exercise intolerance. The primary aim of this research was to evaluate the oxygen cost (∆V'O2/∆Work-Rate) during incremental exercise in patients with metabolic myopathies as compared with patients with non-metabolic myalgia and healthy subjects. The study groups consisted of eight patients with muscle glycogenoses (one Tarui and seven McArdle diseases), seven patients with a complete and twenty-two patients with a partial myoadenylate deaminase (MAD) deficiency in muscle biopsy, five patients with a respiratory chain deficiency, seventy-three patients with exercise intolerance and normal muscle biopsy (non-metabolic myalgia), and twenty-eight healthy controls. The subjects underwent a cardiopulmonary exercise test (CPX Medgraphics) performed on a bicycle ergometer. Pulmonary V'O2 was measured breath-by-breath throughout the incremental test. The ∆V'O2/∆Work-Rate slope for exercise was determined by linear regression analysis. Lower oxygen consumption (peak percent of predicted, mean ± SD; p < 0.04, one-way ANOVA) was seen in patients with glycogenoses (62.8 ± 10.2%) and respiratory chain defects (70.8 ± 23.3%) compared to patients with non-metabolic myalgia (100.0 ± 15.9%) and control subjects (106.4 ± 23.5%). ∆V'O2/∆Work-Rate slope (mLO2.min-1.W-1) was increased in patients with MAD absent (12.6 ± 1.5), MAD decreased (11.3 ± 1.1), glycogenoses (14.0 ± 2.5), respiratory chain defects (13.1 ± 1.2), and patients with non-metabolic myalgia (11.3 ± 1.3) compared with control subjects (10.2 ± 0.7; p < 0.001, one-way ANOVA). In conclusion, patients with metabolic myopathies display an increased oxygen cost during exercise and therefore can perform less work for a given VO2 consumption during daily life-submaximal exercises.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1

Oxygen consumption plotted against power in representative patients with metabolic myopathies. Subjects performed an incremental work test on an electronically braked bicycle until exhaustion with continuous measurement of oxygen consumption. The relationship between oxygen consumption (V’O2, mL.min−1) and work-rate (WR, watts) was determined from the 2nd minute of the initial 2-min stage until the final stage that elicits peak oxygen uptake. (A) Control subject (male, 34 yrs; ∆V’O2/∆WR = 10.1 mLO2.min−1.W−1, R2 = 0.99). (B) Non-metabolic myalgia patient (male, 24 yrs; ∆V’O2/∆WR = 11.2 mLO2.min−1.W−1, R2 = 0.98). (C) MAD Decreased patient (male, 17 yrs; ∆V’O2/∆WR = 11.7 mLO2.min−1.W−1, R2 = 0.98). (D) MAD Absent patient (male, 16 yrs; ∆V’O2/∆WR = 12.7 mLO2.min−1.W−1, R2 = 0.98). (E) McArdle patient (male, 21 yrs; ∆V’O2/∆WR = 14.5 mLO2.min−1.W−1, R2 = 0.97). (F) Respiratory chain deficiency patient (MELAS; male, 41 yrs; ∆V’O2/∆WR = 13.7 mLO2.min−1.W−1, R2 = 0.97).

Figure 2
Figure 2

Oxygen cost of exercise in metabolic myopathies. Lines indicate the mean values. Data were analyzed using a one-way ANOVA with post hoc Games-Howell test for intergroup analysis. *Significantly different from Control (p < 0.04).

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