Is there a change in relative muscle fibre composition with age?

Muscle biopsy was taken from the vastus lateralis muscle during surgery of recent fractures of the neck of the femur in 52 patients aged 66-100 years. The percentage of slow twitch (ST) fibres was close to 55% with no significant change with age and no difference between patients with and without clinical diagnoses prior to the fracture. Also subgrouping of fast twitch (FT) fibres showed insignificant changes in this age range. Muscle fibre areas were smaller for FT than for ST fibres. A comparison between proximal and distal sampling site in the muscle did not show any significant difference. Combining these results and previous results from our laboratories no change in relative fibre composition with age could be proven.