title: 31P-magnetic resonance spectroscopy of leg muscle metabolism during exercise in children and adults.
abstract: Gas exchange response to high-intensity exercise differs in children and adults. We hypothesized that these findings are related to a lower anaerobic ATP supply in children. We predicted therefore a maturation of muscle high-energy phosphate metabolism during exercise. To test this hypothesis, we measured calf muscle Pi, phosphocreatine (PCr), and pH with 31P-nuclear magnetic resonance spectroscopy during rest and progressive exercise in 10 children and 8 adults. No differences were found at rest in pH and Pi/PCr between children and adults. Exercise resulted in a greater increase in Pi/PCr (P < 0.001) and decrease in pH (P < 0.0001) in adults than in children. Six adults and five children exhibited a transition from a slow to a faster rate of Pi/PCr increase and pH decrease during exercise. No significant differences were found between the two groups in the initial slow-phase slopes of Pi/PCr and pH as a function of work rate. In contrast, during the fast phase, Pi/PCr increased (slope: adults 23.6 +/- 9.8, children 10.7 +/- 2.5; P < 0.05) and pH decreased (slope: adults -6.0 +/- 1.9, children -3.7 +/- 1.2; P < 0.05) more rapidly in adults than in children. In conclusion, high-intensity exercise results in different kinetics of Pi/PCr and pH between children and adults. These results suggest that children are less able than adults to affect ATP rephosphorylation by anaerobic metabolic pathways during high-intensity exercise.
authors.affiliation: Department of Pediatrics, Harbor-University of California, Medical Center, Los Angeles, Torrance 90509.
authors.forename: S
authors.initials: S
authors.lastname: Zanconato
authors.forename: S
authors.initials: S
authors.lastname: Buchthal
authors.forename: T J
authors.initials: TJ
authors.lastname: Barstow
authors.forename: D M
authors.initials: DM
authors.lastname: Cooper
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000328:Adult; D000375:Aging / Q000378:metabolism*; D000693:Anaerobiosis; D002648:Child; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006019:Glycolysis / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007866:Leg / Q000502:physiology; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009132:Muscles / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D010710:Phosphates / Q000378:metabolism; D010725:Phosphocreatine / Q000378:metabolism
chemical_list: D010710:Phosphates; D010725:Phosphocreatine; D000255:Adenosine Triphosphate