HISTOCHEMICAL AND MORPHOMETRIC CHARACTERISTICS OF THE NORMAL HUMAN VASTUS MEDIALIS LONGUS AND VASTUS MEDIALIS OBLIQUUS MUSCLES

The histochemical and morphometric characteristics of the vastus media lis longus and vastus medialis obliquus muscles were studied and compa red with data on vastus lateralis. Cross-sections of autopsied muscles from 9 healthy men, aged 18-44 y, who had died suddenly were analysed . Data were obtained on proportions, cross-sectional diameter, and on atrophy and hypertrophy factors, of type 1, 2a, 2b, and 2c fibres. The analysis showed that the anatomical differences and the different fun ctional demands placed on vastus medialis longus and vastus medialis o bliquus are also expressed in different proportions and sizes of fibre types in the two muscles. The proportion of type 1 fibres was signifi cantly higher (P < 0.01), and the proportion of 2b fibres was signific antly lower (P < 0.01) in vastus medialis longus than in vastus medial is obliquus. The diameters of type 1 and type 2a fibres were significa ntly smaller (P < 0.01) in vastus medialis longus than in vastus media lis obliquus, although the differences were small. Within muscles a no nrandom arrangement of fibre types existed with the deeper portions of the muscles having more type 1 fibres than the more superficial porti ons. The histochemical and morphometric characteristics of vastus late ralis and vastus medialis obliquus show great similarity, reflecting t he common function of both muscles which is taking part in transverse knee stability. Estimates of the limits of normality of the proportion , diameter, atrophy and hypertrophy factors of type 1, 2a, 2b, and 2c fibres might be useful in obtaining information on how different physi ological and pathological conditions influence the proportion and size of different fibre types. This information could also be helpful in p lanning of specific muscle-training programmes with the purpose of res toring normal muscle function.