Functional and structural changes after disuse of human muscle – first study to quantify disuse muscle atrophy at fibre level in humans

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Clinical Science and Molecular Medicine (1977) 52, 337-342. Functional and structural changes after disuse of human muscle – Authors: ANTHONY J SARGEANT,* C. T. M. DAVIES,* R. H. T. EDWARDS, C. MAUNDER AND A. YOUNG *Medical Research Council Environmental Physiology Unit, London School of Hygiene and Tropical Medicine, University of London, and Jerry Lewis Muscle Research Centre, Royal Postgraduate Medical School, Hammersmith Hospital, London

Summary

1. Seven patients who had suffered unilateral leg fracture were studied after removal of immobilizing plaster casts.

2. Leg volume measured anthropometrically was reduced by 12% in the injured leg (5.68 f 1.05 litres) compared with the uninjured (6.43 f 0.87 litres). Associated with this loss was a similar reduction in the net maximum oxygen uptake achieved in one-leg cycling, from 1.89 k 0.21 l/min in the uninjured leg to 1.57+0.18 l/min in the injured.

3. Measured by a percutaneous needle biopsy technique, a reduction of 42% was found in the cross-sectional area of the muscle fibres sampled from the vastus lateralis of the injured compared with the uninjured leg.

4. Staining for myosin adenosine triphosphatase activity showed that both type I and I1 fibres were affected, being reduced respectively from 3410 to 1840 pm2 and from 3810 to 2390 pm2 cross-sectional area.

5. Possible reasons and implications are discussed for the discrepancy between the magnitude of the difference observed in the gross measurement of leg function (maximum oxygen uptake) and structure (leg volume) as compared with the cellular level (cross-sectional fibre area).

 

Correspondence: Dr A. J. Sargeant, MRC Environmental Physiology Unit, London School of Hygiene and Tropical Medicine, University of London, Keppel Street (Gower Street), London WClE 7HT.

Introduction

Atrophy of the affected limb and loss of muscle power follows bone fracture and subsequent immobilization. Years of experience have enabled the rehabilitation professions to develop empirical programmes to reverse these changes. However, the efficacy of such programmes may be further improved if we can increase our understanding of the atrophic response to disuse in human muscle. Recent studies showed that 15 weeks immobilization in a long-leg plaster cast after fracture reduced the fat-free volume of the affected leg by 12%, which was accompanied by a similar fall in the maximum oxygen uptake ( ~oz,,,,=.) achieved with oneleg pedalling (Davies & Sargeant, 1975a,b). However, it was not known how far these changes in gross structure and function were reflected at a cellular level within the affected muscles. Since the work of pedalling is performed mainly by the leg extensors (A. J. Sargeant & C. T. M. Davies, unpublished work) needle biopsy was used (Edwards, Maunder, Lewis & Pearse, 1973) to study fibre atrophy in the quadriceps femoris muscle and to compare this with measurements of the gross leg volume and maximal oxygen uptake of patients recovering from unilateral leg fracture.

http://www.clinsci.org/content/ppclinsci/52/4/337.full.pdf

Structural and functional determinants of human muscle power – Review by Anthony J Sargeant

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Experimental PhysiologyExperimental Physiology

Abstract

Measurements of human power need to be interpreted in relation to the movement frequency, since that will determine the velocity of contraction of the active muscle and hence the power available according to the power–velocity relationship. Techniques are described which enable movement frequency to be kept constant during human exercise under different conditions. Combined with microdissection and analysis of muscle fibre fragments from needle biopsies obtained pre- and postexercise we have been able ‘to take the muscle apart’, having measured the power output, including the effect of fatigue, under conditions of constant movement frequency. We have shown that fatigue may be the consequence of a metabolic challenge to a relatively small population of fast fatigue-sensitive fibres, as indicated by [ATP] depletion to ∼30% of resting values in those fibres expressing myosin heavy chain isoform IIX after just 10 s of maximal dynamic exercise. Since these same fibres will have a high maximal velocity of contraction, they also make a disproportionate contribution to power output in relation to their number, especially at faster movement rates. The microdissection technique can also be used to measure phosphocreatine concentration ([PCr]), which is an exquisitely sensitive indicator of muscle fibre activity; thus, in just seven brief maximal contractions [PCr] is depleted to levels < 50% of rest in all muscle fibre types. The technique has been applied to study exercise at different intensities, and to compare recruitment in lengthening, shortening and isometric contractions, thus yielding new information on patterns of recruitment, energy turnover and efficiency.

The Physiology and Pathophysiology of Exercise Tolerance edited by Jürgen M. Steinacker, Susan A. Ward

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The Physiology and Pathophysiology of Exercise Tolerance

Jürgen M. Steinacker, ‎Susan A. Ward – 2012 – ‎Medical

Bauer, J., A.C.H.J. Rademaker, J.A. Zoladz, and A.J. Sargeant. Is reduced mechanical efficiency at high pedalling rate due to less optimally directed leg forces

 

https://books.google.co.uk/books?id=bLbeBwAAQBAJ&pg=PA251&lpg=PA251&dq=aj+sargeant&source=bl&ots=4jgoyKK-FN&sig=WCdsa7zr-2npWXKCXQrydu6gSZA&hl=en&sa=X&ved=0ahUKEwj46PT9pMnTAhXIDMAKHXUzCTkQ6AEIVjAJ#v=onepage&q=aj%20sargeant&f=false

The Great Repeal Bill – a nonsense name

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Professor Anthony J Sargeant comments : Actually the Bill is an “incorporation” of all existing EU laws and regulations into UK law. The Bill is repealing nothing except the jurisdiction of the EU and European Courts. Apart from necessary technical changes about the naming of authorities who will arbitrate when there are disputes nothing will be different.

EU workers’ rights as they exist today will become UK workers’ rights, EU environmental laws will become UK environmental laws and so on and so forth. Of course at some time in the future it is possible that a democratically elected UK government may seek to improve upon existing, that is previously EU, laws in the interests of the UK – but that will be a decision of just that, a democratically elected UK government.

The Bill should more correctly referred to as ‘The Great Incorporation Bill’ designed as it is to incorporate EU laws and regulations into UK law.