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Muscle Metabolic Responses During Dynamic In-Magnet Exercise Testing: A Pilot Study in Children with an Idiopathic
Marco van Brussel1, Joep W M van Oorschot2, Joep P J Schmitz3
1Division of Pediatrics, Child Development and Exercise Center, Wilhelmina Children's Hospital, University Medical Center Utrecht, Rm KB.02.056.0, P.O. Box 85090, NL-3508 AB Utrecht, The Netherlands.
Insights
In-magnet bicycling with phosphorus magnetic resonance spectroscopy ((31)P MRS) effectively assesses quadriceps muscle metabolism in children with juvenile dermatomyositis (JDM). This method reveals similar muscle energy patterns between JDM patients and controls.
Area of Science:
- Pediatric Rheumatology
- Musculoskeletal Physiology
- Biomedical Imaging
Background:
- Juvenile dermatomyositis (JDM) is a rare autoimmune disease affecting children, causing muscle inflammation.
- Assessing muscle metabolism in JDM patients is crucial for monitoring disease activity and treatment efficacy.
- Phosphorus magnetic resonance spectroscopy ((31)P MRS) offers a non-invasive method to evaluate muscle energetics.
Purpose of the Study:
- To evaluate the clinical utility of supine in-magnet bicycling combined with (31)P MRS.
- To assess quadriceps muscle metabolism in children with JDM in remission.
- To compare muscle metabolism between JDM patients and healthy controls.
Main Methods:
- Maximal supine bicycling tests performed using a magnetic resonance-compatible ergometer.
- Cardiopulmonary performance assessed during the first test.
- (31)P MRS used during the second test to determine quadriceps energy and acid/base balance.
Main Results:
- No significant differences in cardiopulmonary performance between JDM patients and controls.
- Similar quadriceps phosphocreatine and pH time courses observed, except in one patient with postexercise pain.
- This patient showed faster phosphocreatine depletion and acidification, but a twofold faster mitochondrial ATP synthesis rate.
Conclusions:
- In-magnet cycle ergometry with (31)P MRS is clinically useful for assessing muscle energetics in pediatric inflammatory myopathies.
- This technique can help monitor muscle energetic patterns in JDM patients.
- The study demonstrates the feasibility of using this combined approach in pediatric research.
Rationale And Objectives:
The clinical utility of supine in-magnet bicycling in combination with phosphorus magnetic resonance spectroscopy ((31)P MRS) to evaluate quadriceps muscle metabolism was examined in four children with juvenile dermatomyositis (JDM) in remission and healthy age- and gender-matched controls.
Materials And Methods:
Two identical maximal supine bicycling tests were performed using a magnetic resonance-compatible ergometer. During the first test, cardiopulmonary performance was established in the exercise laboratory. During the second test, quadriceps energy balance and acid/base balance during incremental exercise and phosphocreatine recovery were determined using (31)P MRS.
Results:
During the first test, no significant differences were found between patients with JDM and their healthy peers regarding cardiopulmonary performance. The outcomes of the first test indicate that both groups attained maximal performance. During the second test, quadriceps phosphocreatine and pH time courses were similar in all but one patient experiencing idiopathic postexercise pain. This patient demonstrated faster phosphocreatine depletion and acidification during exercise, yet postexercise mitochondrial adenosine triphosphate synthesis rate measured by phosphocreatine recovery kinetics was approximately twofold faster than control (time constant 23 seconds vs 43 ± 7 seconds, respectively).
Conclusions:
These results highlight the utility of in-magnet cycle ergometry in combination with (31)P MRS to assess and monitor muscle energetic patterns in pediatric patients with inflammatory myopathies.
