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Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans.
J Physiol Pharmacol. 2014 Apr; 65(2):217-27.JP

Abstract

In this study we examined the relationship between fast myosin heavy chain (MyHC2) content in the vastus lateralis and the rate of oxygen uptake (VO2) and heart rate (HR) increase during an incremental exercise in 38, young, healthy men. Prior to the exercise test, muscle biopsies were taken in order to evaluate the MyHC composition. It was found that during cycling performed below the lactate threshold (LT), a positive relationship between MyHC2 and the intercept of the oxygen uptake and power output (VO2-PO) relationship existed (r=0.49, P=0.002), despite no correlation between MyHC2 and the slope value of the VO2-PO relationship (r= -0.18, P=0.29). During cycling performed above the LT, MyHC2 correlated positively with the magnitude of the nonlinearity in the VO2-PO relationship; i.e. with the accumulated VO2'excess' (r=0.44, P=0.006) and peak VO2'excess' (r=0.44, P=0.006), as well as with the slope of the HR-PO relationship (r=0.49, P=0.002). We have concluded that a greater MyHC2 content in the vastus lateralis is accompanied by a higher oxygen cost of cycling during exercise performed below the LT. This seems to be related to the higher energy cost of the non-cross-bridge activities in the muscles possessing a greater proportion of MyHC2 content. In the case of heavy-intensity exercise, a higher MyHC2 content in the vastus lateralis is accompanied by greater non-linearity in the VO2-PO relationship, as well as a steeper increase in HR in the function of an increase of PO. This relationship can be explained by greater disturbances in metabolic stability in type II muscle fibres during exercise, resulting in a decrease of muscle mechanical efficiency and greater increase of heart rate at a given power output. Therefore, MyHC composition has an impact on the oxygen cost of cycling both below and above the LT.

Authors+Show Affiliations

Department of Muscle Physiology, Chair of Physiology and Biochemistry, Faculty of Rehabilitation, University School of Physical Education, Cracow, Poland. jerzy.zoladz@awf.krakow.pl.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

24781731

Citation

Majerczak, J, et al. "Myosin Heavy Chain Composition in the Vastus Lateralis Muscle in Relation to Oxygen Uptake and Heart Rate During Cycling in Humans." Journal of Physiology and Pharmacology : an Official Journal of the Polish Physiological Society, vol. 65, no. 2, 2014, pp. 217-27.
Majerczak J, Nieckarz Z, Karasinski J, et al. Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans. J Physiol Pharmacol. 2014;65(2):217-27.
Majerczak, J., Nieckarz, Z., Karasinski, J., & Zoladz, J. A. (2014). Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans. Journal of Physiology and Pharmacology : an Official Journal of the Polish Physiological Society, 65(2), 217-27.
Majerczak J, et al. Myosin Heavy Chain Composition in the Vastus Lateralis Muscle in Relation to Oxygen Uptake and Heart Rate During Cycling in Humans. J Physiol Pharmacol. 2014;65(2):217-27. PubMed PMID: 24781731.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans. AU - Majerczak,J, AU - Nieckarz,Z, AU - Karasinski,J, AU - Zoladz,J A, PY - 2013/10/30/received PY - 2014/02/20/accepted PY - 2014/5/1/entrez PY - 2014/5/2/pubmed PY - 2014/12/17/medline SP - 217 EP - 27 JF - Journal of physiology and pharmacology : an official journal of the Polish Physiological Society JO - J. Physiol. Pharmacol. VL - 65 IS - 2 N2 - In this study we examined the relationship between fast myosin heavy chain (MyHC2) content in the vastus lateralis and the rate of oxygen uptake (VO2) and heart rate (HR) increase during an incremental exercise in 38, young, healthy men. Prior to the exercise test, muscle biopsies were taken in order to evaluate the MyHC composition. It was found that during cycling performed below the lactate threshold (LT), a positive relationship between MyHC2 and the intercept of the oxygen uptake and power output (VO2-PO) relationship existed (r=0.49, P=0.002), despite no correlation between MyHC2 and the slope value of the VO2-PO relationship (r= -0.18, P=0.29). During cycling performed above the LT, MyHC2 correlated positively with the magnitude of the nonlinearity in the VO2-PO relationship; i.e. with the accumulated VO2'excess' (r=0.44, P=0.006) and peak VO2'excess' (r=0.44, P=0.006), as well as with the slope of the HR-PO relationship (r=0.49, P=0.002). We have concluded that a greater MyHC2 content in the vastus lateralis is accompanied by a higher oxygen cost of cycling during exercise performed below the LT. This seems to be related to the higher energy cost of the non-cross-bridge activities in the muscles possessing a greater proportion of MyHC2 content. In the case of heavy-intensity exercise, a higher MyHC2 content in the vastus lateralis is accompanied by greater non-linearity in the VO2-PO relationship, as well as a steeper increase in HR in the function of an increase of PO. This relationship can be explained by greater disturbances in metabolic stability in type II muscle fibres during exercise, resulting in a decrease of muscle mechanical efficiency and greater increase of heart rate at a given power output. Therefore, MyHC composition has an impact on the oxygen cost of cycling both below and above the LT. SN - 1899-1505 UR - https://www.unboundmedicine.com/medline/citation/24781731/Myosin_heavy_chain_composition_in_the_vastus_lateralis_muscle_in_relation_to_oxygen_uptake_and_heart_rate_during_cycling_in_humans_ L2 - http://www.jpp.krakow.pl/journal/archive/04_14/pdf/217_04_14_article.pdf DB - PRIME DP - Unbound Medicine ER -