In intact frog semitendinosus muscle up to a sarcomere length of about 3.8 micrometers, resting tension arises from the elastic resistance of the myofibrils rather than connective tissue.
This study challenges the common belief by showing that resting tension in skeletal muscle arises from myofibrils rather than connective tissue.
The tension that develops when relaxed muscles are stretched is the resting (or passive) tension. It has recently been shown that the resting tension of intact skeletal muscle fibers is equivalent to that of mechanically skinned skeletal muscle fibers. Laser diffraction measurements of sarcomere length have now been used to show that the exponential relation between resting tension and sarcomere length for whole frog semitendinosus muscle is similar to that of single fibers. Slack sarcomere lengths and the rates of stress relaxation in these muscles were similar to those in skinned fibers, and sarcomere length remained unchanged during stress relaxation, as in skinned fibers. Thus, in intact semitendinosus muscle of the frog up to a sarcomere length of about 3.8 micrometers, resting tension arises, not in the connective tissue as is commonly thought, but in the elastic resistance of the myofibrils.
Magid et al. (1985) studied Resting tension in skeletal muscle. Whole frog semitendinosus muscle vs. Mechanically skinned skeletal muscle fibers was evaluated on Relation between resting tension and sarcomere length. In intact frog semitendinosus muscle up to a sarcomere length of about 3.8 micrometers, resting tension arises from the elastic resistance of the myofibrils rather than connective tissue.