title: Influence of endurance training on muscle [PCr] kinetics during high-intensity exercise.
abstract: We hypothesized that a period of endurance training would result in a speeding of muscle phosphocreatine concentration ([PCr]) kinetics over the fundamental phase of the response and a reduction in the amplitude of the [PCr] slow component during high-intensity exercise. Six male subjects (age 26 +/- 5 yr) completed 5 wk of single-legged knee-extension exercise training with the alternate leg serving as a control. Before and after the intervention period, the subjects completed incremental and high-intensity step exercise tests of 6-min duration with both legs separately inside the bore of a whole-body magnetic resonance spectrometer. The time-to-exhaustion during incremental exercise was not changed in the control leg [preintervention group (PRE): 19.4 +/- 2.3 min vs. postintervention group (POST): 19.4 +/- 1.9 min] but was significantly increased in the trained leg (PRE: 19.6 +/- 1.6 min vs. POST: 22.0 +/- 2.2 min; P < 0.05). During step exercise, there were no significant changes in the control leg, but end-exercise pH and [PCr] were higher after vs. before training. The time constant for the [PCr] kinetics over the fundamental exponential region of the response was not significantly altered in either the control leg (PRE: 40 +/- 13 s vs. POST: 43 +/- 10 s) or the trained leg (PRE: 38 +/- 8 s vs. POST: 40 +/- 12 s). However, the amplitude of the [PCr] slow component was significantly reduced in the trained leg (PRE: 15 +/- 7 vs. POST: 7 +/- 7% change in [PCr]; P < 0.05) with there being no change in the control leg (PRE: 13 +/- 8 vs. POST: 12 +/- 10% change in [PCr]). The attenuation of the [PCr] slow component might be mechanistically linked with enhanced exercise tolerance following endurance training.
authors.affiliation: School of Sport and Health Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK. a.m.jones@exeter.ac.uk
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
authors.forename: Daryl P
authors.initials: DP
authors.lastname: Wilkerson
authors.forename: Nicolas J
authors.initials: NJ
authors.lastname: Berger
authors.forename: Jonathan
authors.initials: J
authors.lastname: Fulford
mesh_terms: D000328:Adult; D000465:Algorithms; D001642:Bicycling; D016552:Ergometry; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D015233:Models, Statistical; D018482:Muscle, Skeletal / Q000737:chemistry / Q000378:metabolism*; D010725:Phosphocreatine / Q000378:metabolism*; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*
chemical_list: D010725:Phosphocreatine