Age-related changes in human single muscle fibre passive elastic properties are sarcomere length dependent

At short sarcomere lengths (SLs) (1.9 to 2.65 µm) single muscle fibres from old individuals had a greater mean passive modulus than those from young. This resulted in a greater passive stress in the old group at SLs between 2.1 and 3.55 µm. Conversely, at long SLs (i.e. > 3.55 µm) the single fibres from young individuals had a higher passive modulus (not statistically significant) than those from old, resulting in passive stresses that paralleled one another.