Final answer:
The electromechanical delay in muscle contraction is partly due to the time required for the diffusion of calcium, which is integral to the excitation-contraction coupling process.
Step-by-step explanation:
One cause of the electromechanical delay in muscle is the time required for diffusion of calcium. This process is part of the excitation-contraction coupling, which is essential for muscle fibers to contract. When the muscle fiber's membrane is depolarized by an action potential, it triggers the release of calcium ions (Ca++) from the sarcoplasmic reticulum (SR). This calcium release enables the interaction with the troponin-tropomyosin complex, causing a conformational change that exposes the actin-binding sites for myosin attachment. The cross-bridge cycle and subsequent muscle contraction that follows this are dependent on the availability of ATP and the presence of calcium. Therefore, the time it takes for calcium to be released and bind to troponin, facilitating the exposure of actin sites for myosin binding and the power strokes that cause muscle contraction, contributes to the electromechanical delay.