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Introduction Sarcopenia, the loss of skeletal muscle mass and function with age, is a leading cause of morbidity and mortality. Although the causes are multifactorial, little is known about underlying cellular mechanisms. Identification of histological changes in sarcopenic muscle may provide essential information regarding potential management strategies. The objective of this study was to identify and analyse morphological changes in skeletal muscle fibres in older men.
Methods Vastus lateralis muscle biopsies taken from 95 community dwelling healthy men aged 68-76 (mean age 72) were sectioned and stained for type II fibres. Image analysis was used to determine fibre area, fibre diameter, fibre proportions and number of internalised nuclei. Markers of fibre size and variability termed atrophy factors (AF) and hypertrophy factors (HF) were calculated.
Results Each sample contained a mean (SD) of 115.6 (49.7) fibres, mean fibre counts for type I and type II were, 48.0 (24) and 67.7 (36.9) respectively. Mean fibre area was 6056.0 µm2 (1713.8 µm2) for type I fibres and 4816.1 µm2 (1527.5 µm2) for type II fibres. Mean fibre diameters were 73.4 µm2 (10.3 µm) and 63.1 µm2 (10.5 µm) for type I and type II fibres respectively. An average of 1.6% of type I fibres and 1.8% of type II fibres contained internalised nuclei. Type I fibres had a mean AF of 41.0 (77.8) and HF of 676.3 (508.8). Type II fibres had a mean AF of 147.8 (174.0) and HF of 333.2 (385.3).
Conclusions Observed atrophy of type II fibres suggests a predilection for preferential pathological change in type II fibres. The next steps are to apply the EWGSOP algorithm to the HSS sample to determine the relationship between morphological and pathological changes and sarcopenia. The methodological findings of this study can now be applied to future studies that also include women.