title: Short-term training alters the control of mitochondrial respiration rate before maximal oxidative ATP synthesis.
abstract: OBJECTIVE
  Short-term exercise training may induce metabolic and performance adaptations before any changes in mitochondrial enzyme potential. However, there has not been a study that has directly assessed changes in mitochondrial oxidative capacity or metabolic control as a consequence of such training in vivo. Therefore, we used (31) P-magnetic resonance spectroscopy ((31) P-MRS) to examine the effect of short-term plantar flexion exercise training on phosphocreatine (PCr) recovery kinetics and the control of respiration rate.
  
  
  METHODS
  To this aim, we investigated 12 healthy men, experienced with this exercise modality (TRA), and 7 time-control subjects (TC).
  
  
  RESULTS
  After 5 days of training, maximum work rate during incremental plantar flexion exercise was significantly improved (P < 0.01). During the recovery period, the maximal rate of oxidative adenosine triphosphate synthesis (PRE: 28 ± 13 mm min(-1) ; POST: 26 ± 15 mm min(-1) ) and the PCr recovery time constant (PRE: 31 ± 19 s; POST: 29 ± 16) were not significantly altered. In contrast, the Hill coefficient (nH ) describing the co-operativity between respiration rate and ADP was significantly increased in TRA (PRE: nH = 2.7 ± 1.4; POST: nH = 3.4 ± 1.9, P < 0.05). Meanwhile, there were no systematic variations in any of these variables in TC.
  
  
  CONCLUSIONS
  This study reveals that 5 days of training induces rapid adaptation in the allosteric control of respiration rate by ADP before any substantial improvement in muscle oxidative capacity occurs.
authors.affiliation: Department of Medicine, Division of Geriatrics, University of Utah, Salt Lake City, UT, USA.
authors.forename: G
authors.initials: G
authors.lastname: Layec
authors.forename: L J
authors.initials: LJ
authors.lastname: Haseler
authors.forename: J
authors.initials: J
authors.lastname: Hoff
authors.forename: C R
authors.initials: CR
authors.lastname: Hart
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Le Fur
authors.forename: E-K
authors.initials: EK
authors.lastname: Jeong
authors.forename: R S
authors.initials: RS
authors.lastname: Richardson
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000293:Adolescent; D000328:Adult; D015444:Exercise / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008928:Mitochondria / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology*; D055815:Young Adult
chemical_list: D000255:Adenosine Triphosphate
keywords: 31P-MRS; exercise training; metabolic control; mitochondrial function; skeletal muscle energetics