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Can J Appl Physiol. 2003 Dec;28(6):888-97.

Fitness as a determinant of the oxygen uptake/work rate slope in healthy children and children with inflammatory myopathy.

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  • 1Dept. of Rehabilitation Medicine, National Institutes of Environmental Health Sciences, National Institutes of Health, 10 Center Dr., Bethesda, MD 20892-1604, USA.


There is evidence that the slope of the change in oxygen uptake accompanying changes in work rate (delta VO2/delta W). during moderate incremental exercise is influenced by fitness (peak VO2). We set out to determine whether delta VO2/delta W was related to fitness in a group of healthy children and in children with juvenile dermatomyositis (JDM), a condition associated with decreased peak VO2. We also hypothesized that delta VO2/delta would be significantly decreased in children with JDM compared to healthy children.


Twelve children (2 boys) with JDM, mean age 11.6 +/- 3.6 yrs, and 20 healthy children (4 boys), mean age 11.3 +/- 2.9 years, performed an incremental exercise test using a cycle ergometer. delta VO2/delta W below the anaerobic threshold was analyzed using linear regression. Correlations between peak VO2 and delta VO2/delta W were calculated, and differences between the JDM and healthy groups were analyzed using independent t-tests.


The delta VO2/delta W was significantly correlated with peak VO2 for children with JDM (r = 0.71, p < 0.01), healthy children (r = 0.53, p < 0.01), and all children combined (r = 0.78, p < 0.001). The delta VO2/delta W (7.4 +/- 1.4 vs. 10.8 +/- 1.2 ml O2.min-1.watt-1) and peak oxygen uptake (VO2peak) (19.2 +/- 5.0 vs. 31.4 +/- 7.2 ml O2.kg-1, min-1) were significantly lower in children with JDM than in healthy children, respectively (all p < or = 0.001).


Fitness is significantly related to delta VO2/delta W in healthy children and those with JDM. Children with JDM have a significantly lower delta VO2/delta W than healthy children. Further study is needed to identify specific factors influencing delta VO2/delta W.

[PubMed - indexed for MEDLINE]
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