title: Muscle metabolism during fatiguing isometric quadriceps exercise in adolescents and adults.
abstract: Children and adolescents are less susceptible to muscle fatigue during repeated bouts of high-intensity exercise than adults, but the physiological basis for these differences is not clear. The purpose of the current investigation was to investigate the muscle metabolic responses, using 31-phosphorus magnetic resonance spectroscopy, during fatiguing isometric quadriceps exercise in 13 adolescents (7 females) and 14 adults (8 females). Participants completed 30 maximal voluntary contractions (6-s duration) separated by 6 s of rest. Fatigue was quantified as the relative decrease in force over the test. Fatigue was not significantly different with age (p = 0.20) or sex (p = 0.63). Metabolic perturbation (change in phosphocreatine, inorganic phosphate, and ADP concentrations) was significantly greater in adults compared with adolescents; no sex effects were present. Muscle pH did not differ with age or sex. Phosphocreatine recovery following exercise was not significantly different with age (p = 0.27) or sex (p = 0.97) but a significant interaction effect was present (p = 0.04). Recovery tended to be faster in boys than men but slower in girls than women, though no significant group differences were identified. The results of this study show that at a comparable level of muscle fatigue, the metabolic profile is profoundly different between adolescents and adults.
authors.affiliation: a Children's Health and Exercise Research Centre, Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, St. Luke's Campus, Magdalen Rd., Exeter EX1 2LU, UK.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Willcocks
authors.forename: Jonathan
authors.initials: J
authors.lastname: Fulford
authors.forename: Neil
authors.initials: N
authors.lastname: Armstrong
authors.forename: Alan R
authors.initials: AR
authors.lastname: Barker
authors.forename: Craig A
authors.initials: CA
authors.lastname: Williams
mesh_terms: D000293:Adolescent; D000328:Adult; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D018763:Muscle Fatigue; D052097:Quadriceps Muscle / Q000378:metabolism*