Comparison of peak isometric knee extensor torque in children with and without juvenile rheumatoid arthritis

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Abstract
This study compared peak isometric knee extensor torque in children with juvenile rheumatoid arthritis (JRA) and healthy children. A secondary purpose was to determine the relationship between measures of articular disease severity and peak isometric knee extensor torque. Peak torque was measured with a computerized dynamometer. Twenty-eight children with JRA and 28 children without JRAwere matched for age, sex, and body surface area. Peak isometric knee extensor torque was significantly lower among the children with JRA than their respective control (P < 0.05, paired Student's t-test, one-tailed). There was no relationship between peak torque and measures ofarticular disease severity among the children with JRA. Subjects complained of quadriceps muscle discomfort as a result of the isometric muscle test. One child with JRA complained of increased knee pain and swelling. Peak isometric knee extensor torque appears to be a useful variable for characterizing muscle function deficits in children with JRA. Isometric muscle performance did not correlate with articular disease severity. The results suggest that isometric strengthening programs are indicated for this patient population. We recommend that clinicians monitor patients for joint and muscle symptoms during exercise training sessions.