Estimating intrafibrillar and basement membrane contributions to passive elastic modulus in human single muscle fibres

Skeletal muscle passive elastic modulus is an important material property which affects muscle and joint mechanics; yet, it is still poorly understood. Both intrafibrillar (primarily titin) and extrafibrillar (basement membrane) structures are suggested to bear passive tension. Here, we applied the rule of mixtures for a composite material—taking advantage of the fact that intrafibrillar and extrafibrillar area fractions would vary with fibre diameter—and determined that the basement membrane modulus is ~3000 times greater than the intrafibrillar modulus for human skeletal muscle fibres.