title: Endurance training decreases the non-linearity in the oxygen uptake-power output relationship in humans.
abstract: In this study, we hypothesized that 5 weeks of cycling endurance training can decrease the magnitude of the non-proportional increase in oxygen uptake (V(O(2))) to power output relationship (V(O(2)) 'excess') at exercise intensities exceeding the lactate threshold (LT). Ten untrained, physically active men performed a bout of incremental cycling exercise until exhaustion before and after training. The mitochondrial DNA copy number, myosin heavy chain composition and content of uncoupling protein 3 and sarcoplasmic reticulum Ca(2+)-ATPases (SERCAs) were analysed in muscle biopsies taken from vastus lateralis before and after training. The training resulted in an enhancement of the power-generating capabilities at maximal oxygen uptake (V(O(2)max)) by ∼7% (P = 0.002) despite there being no changes in V(O(2)max) (P = 0.49). This effect was due to a considerable reduction in the magnitude of the V(O(2)) 'excess' (P < 0.05) above the LT. A decrease in plasma ammonia concentration was found during exercise after training (P < 0.05). A downregulation of SERCA2 in vastus lateralis (P = 0.006) was observed after training. No changes in myosin heavy chain composition, selected electron transport chain proteins, uncoupling protein 3 or the mitochondrial DNA copy number (P > 0.05) were found after training. We conclude that the training-induced increase in power-generating capabilities at V(O(2)max) was due to attenuation of the V(O(2)) 'excess' above the LT. This adaptive response seems to be related to the improvement of muscle metabolic stability, as judged by a lowering of plasma ammonia concentration. The enhancement of muscle metabolic stability after training could be caused by a decrease in ATP usage at a given power output owing to downregulation of SERCA2 pumps.
authors.affiliation: Department of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Krakow, Poland.
authors.forename: Joanna
authors.initials: J
authors.lastname: Majerczak
authors.forename: Michal
authors.initials: M
authors.lastname: Korostynski
authors.forename: Zenon
authors.initials: Z
authors.lastname: Nieckarz
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Szkutnik
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Duda
authors.forename: Jerzy A
authors.initials: JA
authors.lastname: Zoladz
mesh_terms: D000641:Ammonia / Q000097:blood; D001706:Biopsy; D004272:DNA, Mitochondrial / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D007473:Ion Channels / Q000378:metabolism; D007773:Lactates / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D018995:Myosin Heavy Chains / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism; D000071247:Uncoupling Protein 3; D055815:Young Adult
chemical_list: D004272:DNA, Mitochondrial; D007473:Ion Channels; D007773:Lactates; D024101:Mitochondrial Proteins; C000604392:UCP3 protein, human; D000071247:Uncoupling Protein 3; D000641:Ammonia; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D018995:Myosin Heavy Chains; C506946:ATP2A2 protein, human