VERSAILLES, FRANCE — A Dutch study of 21 adolescents with juvenile idiopathic arthritis found significant impairment in anaerobic fitness when the youngsters were asked to ride a bicycle as fast as they could.
At peak power, girls reached only 53% of the anaerobic fitness predicted for their weight, while boys did only slightly better, at 71%. Both genders also showed moderate impairment in aerobic fitness at peak power: The girls performed at 78% of predicted levels, and the boys performed at 83%.
“Their fitness is about 20% reduced, compared to normal children. … They don't feel at ease with exercise,” researcher Otto Lelieveld, a physical therapist, said in an interview at the annual scientific meeting of the European Pediatric Rheumatology Congress, where he presented the results in a poster.
Nine boys and 12 girls, aged 16–18, took part in the study. On average, 7.6 years had elapsed since the boys were diagnosed, and 8.9 years had elapsed for the girls.
The teenagers were required to perform the Wingate sprint test. Mr. Lelieveld of University Medical Center Groningen (the Netherlands) described this as 5 minutes of steady bicycle riding at low speed, followed by a 30-second sprint at peak power.
Study participants did slightly better in measurements of mean power, both aerobic and anaerobic, during the first part of the test, but still showed moderate impairment. In the measurement of muscle endurance, the boys achieved 78% of the mean anaerobic fitness predicted for their weight; the girls achieved 68%. Mean aerobic fitness reached 83% of prediction for the boys and 78% for the girls.
Based on these results, Mr. Lelieveld and his coinvestigators called for the development of exercise programs with more anaerobic and aerobic training for children with juvenile idiopathic arthritis.
“We know now from adult rheumatology that physical therapists are training at too low a level,” he said.
The children also are afraid to train themselves, he added. “When they are in remission they can have more pain than in the period when they are acute,” he said. “When they start functioning at a higher level, they put more strain on their joints. It is like a vicious circle.”