Short‐term training alters the control of mitochondrial respiration rate before maximal oxidative ATP synthesis

Abstract

BackgroundThere has not been a study that has directly assessed temporal changes in mitochondrial oxidative capacity and metabolic control as a consequence of short‐term exercise training in vivo.MethodsWe used 31P‐magnetic resonance spectroscopy (31P‐MRS) to examine the effect of short‐term plantar flexion exercise training on phosphocreatine (PCr) recovery kinetics and the control of respiration rate. To this aim, we investigated 12 healthy men experienced with this exercise modality (TRA) and 8 time‐control subjects (TC).ResultsAfter 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 ATP 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 cooperativity 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, we did not observe any systematic variation in any of these variables in the TC.ConclusionThis 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.