Which is a true statement about muscle contraction?

Muscle contraction indeed requires energy from ATP. ATP, or adenosine triphosphate, is the primary energy currency of the cell, and its hydrolysis provides the necessary energy for the cross-bridge cycling process in muscle fibers. During contraction, myosin heads on the thick filaments attach to actin on the thin filaments, and the power stroke – which pulls the actin filaments towards the center of the sarcomere – occurs through the energy derived from ATP. Furthermore, ATP is also crucial for detaching the myosin heads from actin, allowing for the next cycle of contraction.

In contrast, muscle contraction is not limited to skeletal muscles; both cardiac and smooth muscles also undergo contractions, hence the statement regarding sole occurrence in skeletal muscle is inaccurate. Additionally, calcium ions play an essential role in muscle contraction as they are necessary for the exposure of binding sites on actin for the myosin heads to attach. Finally, while neurotransmitter release, such as acetylcholine in skeletal muscle, is important for initiating the contraction process, muscle contraction itself is not solely reliant on neurotransmitter release; it also fundamentally requires ATP and calcium ions. Thus, the foundational role of ATP in powering muscle contraction makes the correct statement true.