title: Reliability of 31P-magnetic resonance spectroscopy during an exhaustive incremental exercise test in children.
abstract: This study examined the reliability of (31)P-magnetic resonance spectroscopy (MRS) to measure parameters of muscle metabolic function in children. On separate days, 14 children (7 boys and 7 girls) completed three knee-extensor incremental tests to exhaustion inside a whole-body scanner (1.5 T, Phillips). The dynamic changes in the ratio of inorganic phosphate to phosphocreatine (Pi/PCr) and intracellular muscle pH were resolved every 30 s. Using plots of Pi/PCr and pH against power output (W), intracellular thresholds (ITs) for each variable were determined using both subjective and objective procedures. The IT(Pi/PCr) and IT(pH) were observed subjectively in 93 and 81% of their respective plots, whereas the objective method identified the IT(Pi/PCr) in 88% of the plots. The IT(pH) was undetectable using the objective method. End exercise (END) END(Pi/PCr), END(pH), IT(Pi/PCr) and IT(pH) were examined using typical error statistics expressed as a % coefficient of variation (CV) across all three exercise tests. The CVs for the power output at the subjectively determined IT(Pi/PCr) and IT(pH) were 10.6 and 10.3%, respectively. Objective identification of the IT(Pi/PCr) had a CV of 16.3%. CVs for END(pH) and END(Pi/PCr) were 0.9 and 50.0%, respectively. MRS provides a valuable window into metabolic changes during exercise in children. During knee-extensor exercise to exhaustion, END(pH) and the subjectively determined IT(Pi/PCr) and IT(pH) demonstrate good reliability and thus stable measures for the future study of developmental metabolism. However, the objectively determined IT(Pi/PCr) and END(Pi/PCr) displayed poor reliability.
authors.affiliation: Children's Health, Exercise Research Centre, St Luke's Campus, University of Exeter, Exeter, UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Barker
authors.forename: Joanne
authors.initials: J
authors.lastname: Welsman
authors.forename: Deborah
authors.initials: D
authors.lastname: Welford
authors.forename: Jonathan
authors.initials: J
authors.lastname: Fulford
authors.forename: Craig
authors.initials: C
authors.lastname: Williams
authors.forename: Neil
authors.initials: N
authors.lastname: Armstrong
mesh_terms: D002648:Child; D005080:Exercise Test; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007717:Knee; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism; D010807:Physical Endurance; D052097:Quadriceps Muscle / Q000378:metabolism; D015203:Reproducibility of Results
chemical_list: D010710:Phosphates; D010725:Phosphocreatine