What is the thick structural protein inside the sarcomere?

During the slow downward motion of this exercise, all of the following muscles act eccentrically EXCEPT?

Which of the following is a macronutrient?

A basketball player at the free throw line during a close game experiences tense muscles, an elevated heart rate, and the butterflies, which type of anxiety do these physical symptoms relate to?

What is released from the sarcoplasmic reticulum into the myofibril, causing tension development in a muscle?