Muscle fibre size and type distribution in thoracic and lumbar regions of erector spinae in healthy subjects without low back pain: normal values and sex differences

Abstract

This study sought to investigate the normal muscle fibre size and type distribution of the human erector spinae, both in thoracic and lumbar regions, in a group of 31 young healthy male (n = 17) and female (n = 14) volunteers. Two percutaneous muscle biopsy samples were obtained under local anaesthesia, from the belly of the left erector spinae, at the levels of the 10th thoracic and 3rd lumbar vertebrae. Samples were prepared for routine histochemistry for the identification of fibre types. Fibre size (cross-sectional area (CSA) and narrow diameter (ND)) was quantified using computerised image analysis. The mean CSA/ND for each fibre type was greater in the thoracic than the lumbar region, but there was no difference between the 2 regions either for percentage type I (i.e. percentage distribution by number), percentage type I area (i.e. relative area of the muscle occupied by type I fibres) or the ratio describing the size of the type I fibre relative to that of the type II. Men had larger fibres than women, for each fibre type and at both sampling sites. In the men, each fibre type was of a similar mean size, whereas in the women the type I fibres were considerably larger than both the type IIA and type IIB fibres, with no difference between the latter two. In both regions of the erector spinae there was no difference between men and women for the proportion (%) of a given fibre type, but the percentage type I fibre area was significantly higher in the women. The erector spinae display muscle fibre characteristics which are clearly very different from those of other skeletal muscles, and which, with their predominance of relatively large type I (slow twitch) fibres, befit their function as postural muscles. Differences between thoracic and lumbar fascicles of the muscle, and between the muscles of men and women, may reflect adaptive responses to differences in function. In assessing the degree of any pathological change in the muscle of patients with low back pain, it seems clear that (1) sex cannot be disregarded and (2) 'atrophied' (using the criteria from other muscles) type II fibres are not necessarily abnormal for the erector spinae, particularly in women.

Les tests de sélection : une course à obstacles vers l’égalité économique des femmes

“…Les femmes possèdent-elles un niveau d'endurance plus élevé que celui des hommes et pour quelles tâches (Speechly, Taylor et Rogers 1996 ;Mannion et autres 1997) ? Jusqu'où les hommes dépassent-ils leurs limites physiques en surestimant leur capacité à lever des poids (Mitai 1984) ?…”

Fatores do trabalho associados à lombalgia não específica, caracterizada no âmbito da resistência da musculatura extensora lombar, entre trabalhadores de enfermagem de Unidades de Terapia Intensiva

“…Assim, durante um levantamento repetitivo, os músculos da coluna fadigada tornam-se menos efetivos na geração de um momento extensor essencial requerido, possibilitando um estresse relativo aos discos intervertebrais e ligamentos e tornando, portanto, as estruturas da coluna susceptíveis à lesão e/ou à dor (MANNION, 1999). Além do mais, a fadiga da musculatura da coluna é acompanhada por uma diminuição do controle do movimento do tronco, por uma alteração na coordenação das atividades musculares e pela perda da estabilidade do tronco (PARNIANPOUR et al, 1988;KENDALL;McCREARY;PROVANCE, 1995 Cabe ressaltar que, segundo Mannion, et al (1997), Mannion, et al (1998), Mannion (1999 e Demoulin et al (2006), o processo de fadiga muscular, notadamente da musculatura extensora da coluna, é diferente entre homens e mulheres, e esta diferença está relacionada a uma variação da morfologia dos tecidos lombares em relação à proporção das fibras tipo 1 e tipo 2 para homens e mulheres. Clark et al (2003) também encontraram em seu estudo diferenças entre homens e mulheres em relação à fadiga da musculatura extensora da coluna lombar, porém para esses autores as diferenças são explicadas devido ao tipo de contração muscular e à quantidade de força gerada.…”

“…De acordo com Mannion et al (1997), Mannion et al (1998) (BORK et al, 1996;SHIMABUKURO et al, 2012). O referido instrumento pode ser um indicativo para comparar a situação encontrada antes e após uma intervenção ergonômica.…”

Nonlinear Analysis of Surface Electromyography

“…Our previous study results indicated that the measurement of back muscle fatigability, especially the erector spinae muscle, indicated that the entropy analysis was a more reliable measure than the power spectral analysis (Sung et al, 2008b). It is well known that the observed EMG signal depends on anatomical factors, such as muscle geometry, subcutaneous fat, gender, and other confounding factors (Lindstrom et al, 1974;Mannion et al, 1997c;Pullman et al, 2000;Roy et al, 1997;Solomonow et al, 1990). As a result, observed quantities from EMG signals show considerable variations even among a group of healthy subjects.…”

“…The myoelectric signals are the instantaneous algebraic summation of all electrical discharges produced by a contraction of the muscle fibers. Muscle fatigue is quantified using surface EMG signals based on the power spectrum which is the Fourier transform of EMG time series (Knowlton et al, 1951;Mannion & Dolan, 1994;Mannion et al, 1997c). Normal electrical source is a muscle membrane potential of approximately -90 mV, and measured EMG potentials range between less than 50 μV and up to 20 to 30 mV, depending on the muscle under observation (Herzog et al, 1987;Nigg et al, 1988).…”