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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

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Majerczak J., Nieckarz Z., Karasinski J., Zoladz J. A.

Journal of Physiology and Pharmacology

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2014

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tom 65

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nr 2

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High content of MyHC II in vastus lateralis is accompanied by higher VO2/power output ratio during moderate intensity cycling performed both at low and at high pedalling rates

100%

Majerczak J., Szkutnik Z., Karasinski J., Duda K., Kolodziejski L., Zoladz J. A.

Journal of Physiology and Pharmacology

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2006

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tom 57

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nr 2

The aim of this study was to examine the relationship between the content of various types of myosin heavy chain isoforms (MyHC) in the vastus lateralis muscle and pulmonary oxygen uptake during moderate power output incremental exercise, performed at low and at high pedalling rates. Twenty one male subjects (mean ± SD) aged 24.1 ± 2.8 years; body mass 72.9 ± 7.2 kg; height 179.1 ± 4.8 cm; BMI 22.69 ± 1.89 kg . m-2; VO2max 50.6 ± 5.3 ml . kg . min-1, participated in this study. On separate days, they performed two incremental exercise tests at 60 rev . min-1 and at 120 rev . min-1, until exhaustion. Gas exchange variables were measured continuously breath by breath. Blood samples were taken for measurements of plasma lactate concentration prior to the exercise test and at the end of each step of the incremental exercise. Muscle biopsies were taken from the vastus lateralis muscle, using Bergström needle, and they were analysed for the content of MyHC I and MyHC II using SDS - PAGE and two groups (n=7, each) were selected: group H with the highest content of MyHC II (60.7 % ± 10.5 %) and group L with the lowest content of MyHC II (27.6 % ± 6.1 %). We have found that during incremental exercise at the power output between 30 - 120 W, performed at 60 rev . min-1, oxygen uptake in the group H was significantly greater than in the group L (ANCOVA, p=0.003, upward shift of the intercept in VO2 / power output relationship). During cycling at the same power output but at 120 rev . min-1, the oxygen uptake was also higher in the group H, when compared to the group L (i.e. upward shift of the intercept in VO2 / power output relationship, ANCOVA, p=0.002). Moreover, the increase in pedalling rate from 60 to 120 rev . min-1 was accompanied by a significantly higher increase of oxygen cost of cycling and by a significantly higher plasma lactate concentration in subjects from group H. We concluded that the muscle mechanical efficiency, expressed by the VO2 / PO ratio, during cycling in the range of power outputs 30 - 120 W, performed at 60 as well as 120 rev . min-1, is significantly lower in the individuals with the highest content of MyHC II, when compared to the individuals with the lowest content of MyHC II in the vastus lateralis.

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Human muscle fatigue: the significance of muscle fibre type variability studied using a micro-dissection approach

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Sargeant A. J., de Haan A.

Journal of Physiology and Pharmacology. Supplement

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2006

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tom 57

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nr 10

During human locomotion the ability to generate and sustain mechanical power output is dependent on the organised variability in contractile and metabolic properties of the muscle fibres that comprise the active muscles. In studies of human exercise we have used a micro-dissection technique to obtain fragments of single muscle fibres from needle biopsies before and after exercise. Each fibre fragment is divided into two parts. One part is used to characterize the fibre type in respect of the heavy chain myosin isoform expressed. The other part of the fragment is analysed for high energy phosphate concentrations. Fibres are classified on the basis of expressing either type I, type IIA, or type IIX myosin heavy chain isoforms. It should be noted however that in the type II population many fibres co-express both IIA and the IIX isoforms and we therefore characterize these fibres on the basis of the degree of co-expression. We have used this technique to examine the time course of high energy phosphate concentration and fatigue in different fibre populations during exercise. The progressive reduction of power during maximal sprint efforts may be interpreted as the cumulative effect of metabolic depletion in successive fibre type populations from IIX to IIXa to IIAx to IIA to I. One important application of the micro-dissection technique is that PCr content may also be used as a very sensitive metabolic marker for fibre type recruitment during very short duration concentric, isometric and eccentric exercise.

Ograniczanie wyników

2 Journal of Physiology and Pharmacology

1 Journal of Physiology and Pharmacology. Supplement

2 Karasinski J.

2 Majerczak J.

2 Zoladz J. A.

1 Duda K.

1 Kolodziejski L.

1 Nieckarz Z.

1 Sargeant A. J.

1 Szkutnik Z.

1 de Haan A.

1 2014

2 2006

Myosin heavy chain composition in the vastus lateralis muscle in relation to oxygen uptake and heart rate during cycling in humans

High content of MyHC II in vastus lateralis is accompanied by higher VO2/power output ratio during moderate intensity cycling performed both at low and at high pedalling rates

Human muscle fatigue: the significance of muscle fibre type variability studied using a micro-dissection approach