The main elastic (spring) component within the sarcomere is the endomysium.

In adult humans, a large muscle fibre (one cell) contains around 20 myofibrils.

Skeletal muscle fibres contain hundreds of nuclei and these are located just below the sarcolemma in healthy cells.

Absence of 

the protein

titin makes skeletal muscle fibres more elastic. 

Within a skeletal muscle fibre, each fibril is enveloped

by a sarcolemma membrane.